Mainstream Use of EPDs in Buildings: Lessons Learned from Europe

*Naeem Adibi, Marjan Mousavi, Ricardo Méndez Escobar, Manon Glachant and Aliasghar Adibi*

#### **Abstract**

Life cycle assessment (LCA) has been used widely by building sector to assess the environmental impacts of products, new buildings, and renovations. Environmental product declarations (EPDs) based on LCA are developed for products in different EU countries. In addition, product environmental footprint (PEF) initiated by European Commission aims to provides benchmarking for products based on LCA. Although EPDs are well developed in the Europe, their use is challenging. First challenge for mainstream implementation is lack of knowledge of different key actors to use EPDs. Awareness rising, training, and simplification is needed for the key actors. The second issue is lack of equal opportunity for companies to develop their EPDs. The cost of EPDs for small and medium-sized companies is a real barrier. Finally, EPDs are developed as information for building assessment to be used at building level for B2B and B2C communication. Therefore, EPDs require new mechanisms in a decision-making and benchmarking context at product or at application level. At building level, simplified approaches are needed to converge EPDs to the buildings. The aim of this contribution is to highlight the use of EPD in European context and discuss challenges for a wider application of the EPD worldwide.

**Keywords:** mainstream, building, EPD, LCA, decision-making

#### **1. Introduction**

Buildings account for 40% of primary energy consumption and 36% of Greenhouse Gas emissions across Europe. Decreasing the environmental impacts of buildings is key to realize EU 2020 objectives of 20% reduction of GHG and energy consumption while using 20% renewable energy [1].

Sustainable buildings are the fabric of sustainable lifestyle. While building sector understands the importance of energy efficiency, the environmental impacts of the building products and elements remained less known. For an energy-efficient house, embodied energy in the construction represents approximately 75 years of heating in equivalent energy. To assess environmental impacts of a building, it is necessary to consider the overall building lifecycle [2].

Buildings have also influence on the vision of sustainability of a region. Energy efficiency in a sector is well understood by the industry and the public sector,

but impact of product and materials are less known. The goal of sustainbility can only be achieved if the entire life cycle of the building is considered. All construction stakeholders should be involved to improve buildings overall environmental performance.

 Building sector has already developed some intitatives based on life cycle approaches to improve and harmonize the communication of the environmental performance of products. The notion of life cycle thinking depends on the region and the size of the company. While large enterprises can invest resources in implementing life cycle thinking tools, smaller organizations find more problems. Lack of awareness about life cycle aproaches avoid actors to obtain the benefits by creation of shared value and reinforcement of links between stakeholders [2].

#### **2. Life cycle approaches for building**

#### **2.1 Life cycle thinking**

 In selecting the most environment friendly product, some questions are frequently asked: Is there a proper approach to select the best product? How to find the product with the best ecological performance? What are the impacts of different products in terms of global warming potential (greenhouse gases), human health effects, ecosystem biodiversity losses, and depletion of resources? What is the best approach to make an intelligent choice? Given the importance of products and materials in context of sustainable buildings, it is important to make a wise choice among available solutions. Decision-making needs to be based on objective information and approaches.

The following two main issues are important for selecting the most environment friendly products:

Life cycle assessment (LCA) is used by sustainability experts in many different fields which includes the two previous points in the basis of the study. LCA is based on the principles of sustainable development and it has already been demonstrated its efficiency in providing a systematic environmental assessment approach of products, product system, and processes.

The effectiveness of LCA methods depend on the very fact that they contemplate all life cycle stages of a product, from the extraction of raw materials to the end-of-life (recycling, etc.) through an assessment covering completely different impact categories climate change, human health, ecosystems, and resources. Using life cycle approaches also give economic value to companies, who are adopting life cycle thinking practices to optimize their activities [4].

*Mainstream Use of EPDs in Buildings: Lessons Learned from Europe DOI: http://dx.doi.org/10.5772/intechopen.87836*

 As an example, environmental performance of insulation products can be easily misunderstood if the study is focused only on the use phase, where the energy savings are highlighted. The material used and the manufacturing processes, as well as the location of the manufacturing plant and the recyclability of the product must be considered to make a holistic overview of the impacts of an isolation product. The assessment can be used to identify hotspots of a product or to compare different products in a decision-making context.

Along the different life cycle stages, resources from the environment are used and transformed to develop a product, causing some impacts on the environment. Using LCA is possible to assess the environmental performance of a product and compare different products. Comparison is only representative when the study has been made under certain conditions. International and national standards have been implemented to make the comparison possible, providing general requirements and guidelines to carry out and structure the document of the study (see **Figure 2**).

The first step to do an LCA is defining the goal and scope of the LCA. The product system understudy and system boundary are determined to define processes, materials, emissions, products, and by-products included in the study. Subsequently, the data requirements, assumptions, and limitations are explained. This first step will shape the study. In the life cycle inventory (LCI), all the data used in the study

**Figure 2.**  *Phase of an LCA, from the international standard ISO 14040 [5].*

are gathered and shown, such as inputs (material and energy resources and products) and outputs (emissions to the environment, products and by-products). These data are used in the life cycle impact assessment to provide the impacts classified in different impact categories (climate change, acidification, eutrophication, etc.). At the end of the study, the results are interpreted considering the scope, the data used and the calculation method for the assessment previously described.

LCA can be applied to all types of products. Building sector has already implemented to study the environmental impacts of different products used in the construction of buildings. The construction industry is one of leading sectors in the use of LCA. LCA has been used to assess the environmental impacts of construction products and buildings. Life cycle approaches have been adopted by different building actors involved aware of the benefits of minimizing the environmental impacts. Different standards have been developed to facilitate environmental assessment based on LCA (ISO 14040 and ISO 14044) and more specifically for Type III environmental declarations [ISO 14025: 2006 the LCAbased mechanism, more commonly known as environmental product declarations (EPD)]. The first European leading national standards regarding EPDs of building products were the French NF P01–010 and the Dutch Standard NEN 8006 both established in 2004 for the environmental declaration of building products.

 Third-party verified environmental product declarations (EPDs) based on LCA are developed in the European context. EPDs are available for a wide range of products and product systems in different EU countries. The environmental declarations can be used in the context of decision-making and they are also used nowadays in the study of potential impacts of new buildings and renovation. In some countries, EPDs are related to benchmarking approach at product or building level (e.g., shadow cost approach in Netherlands permitting monetarization of impacts). The standardization of the method allows the comparison between products or systems with the same function. EPDs are standardized internationally by ISO 14025 and, at European level, by the norm EN-15804:2012. They serve as reference for national standards.

The building sector is currently implementing CEN/TC 350: EN 15804 [6] and EN 15978 [7]. One of the outcomes of the work of CEN/TC350 "Sustainability of construction works" is the development of voluntary horizontal standardized methods for the assessment of the sustainability aspects of new and existing construction works, and for the environmental product declaration of construction products.

The most relevant elements in this context are:

The work of CEN TC350 focuses on construction products (in EN 15804) and buildings (in EN 15978). EN 15804 provides a structure to ensure that all EPDs of construction products are derived, verified, and presented in a harmonized way. EPDs are organized in modules covering different life cycle stages. Some modules are mandatory (depending on the scope of the study—cradle to gate/cradle to gate with option/cradle to grave); others are optional (such as module D). An important methodological aspect is that indicators are declared in the individual modules to

*Mainstream Use of EPDs in Buildings: Lessons Learned from Europe DOI: http://dx.doi.org/10.5772/intechopen.87836*

**Figure 3.**

*Pathway to develop an environmental product declarations and use them in the building assessment [3].*

enable the user of the EPD to aggregate information from different EPDs at the building level as illustrated in **Figure 3**.

#### **3. Use of EPD for building products in Europe**

More than 5000 verified EN 15804 EPDs are published and available in different European countries in 2019. The EPDs are published in different national databases in different EU countries. Some of these national databases are illustrated in **Figure 4**.

Different national bodies provide all the requirements and the platform to realize and register an EPD in their respective national databases. All the products found in a building are classified in different categories with specific rules to carry out an environmental assessment, compiled in product category rules (PCRs). The procedure to obtain an EPD includes contact the national body, carry out an LCA following the PCRs, redaction of the EPD following the PCRs, verification by an authorized verification, and submitting all the documents requested to the national body. Once the EPD is available, the product environmental impact assessment is valid for 5 years and the impacts must be recalculated after that period in order to preserve the certificate.

EPDs are used inside building assessment softwares, enabling the assessment, and Eco design of the buildings. The adoption of EPDs depends on various factors and actors. Project owners, project managers, building products manufacturers, and end-of-life collectors have more influence on the building value-chain than the rest of the stakeholders in the building industry. The planning and design phase of the building are the most influencing hotspots in the environmental performance of the building. The impacts from manufacturing, construction, use, and end-of-life depend directly on the design of the building.

**Figure 4.**  *Example of European EPD databases [3].*

They can use LCA methods to select more environment friendly products and force the adoption of life cycle thinking in the rest of the supply chain.

#### **4. Mainstream use of EPDs in buildings**

 EPDs are one of the main examples of how to use LCA in buildings. These initiatives amplify the development of strategies aligned with the objectives of reducing the carbon emissions in Europe. At the same time, LCM is not yet an established approach for the majority of building stakeholders. A studied carried out in France, Portugal, and Belgium showed that life cycle approaches are only implemented by half of building sector companies in their environmental strategy [7]. Only 21% of the participants in the study were using tools or systems to manage the environmental impacts. It is stated that building companies in Northern France use life cycle management tools and resources more than in other regions.

 The difficulty to understand LCA and EPDs, their content, and value have avoided the mainstream use of EPDs. Lack of homogenization of EPD in different countries has been also an issue for companies to invest on EPDs given that the certificate is only valid for one country for 5 years. There are also initiatives to homogenize and simplify EPDs among European countries. Also several efforts have been made in order to implement life cycle thinking in the building sector at region level, such as LCiP Project [8] or the creation of platforms where different stakeholders have access to training or LCM tools. In this way, small and medium-sized enterprises (SMEs), with a lack of financial capacity or human resources to implement life cycle approaches in the business, can receive help from regional or national platforms who gather key actors and base the strategy in some key LCM concepts [9]. Although EPDs are well developed in the European context, their use is limited and challenging. Several challenges are identified in the use of EPDs.

#### **4.1 Lack of knowledge and training of key actors**

First major issue is the complexity of EPDs and lack of knowledge of different key actors involved in the supply chain of the building to use EPDs. Although LCA and EPDs are used in building and construction sectors, there is a need to raise awareness regarding the applications of EPDs to public authorities and project owners and providing training of EPDs for those who are involved in design and manufacturing. For example, in France, our major challenge is to train real estate owners: public and private on the use of EPDs. Missing regulation is another barrier to use EPDs in wider context.

#### **4.2 Missing EPDs for products**

Tools and actions to support LCM integration need to be adapted to different sectors to make them as relevant as possible to SMEs and reduce the cost of EPDs. The second major issue is the lack of equal opportunity for different companies and products to use EPDs. Availability of EPDs is still very limited. As a consequence of the cost, small and medium-sized companies are developing less EPDs. The missing EPDs for the companies with limited resources are a discriminatory aspect. Therefore, it is required to financially support small companies to create EPDs to avoid discrimination in accessing data.

#### **4.3 Difficulty in use of EPD for decision-making context**

 No CEN standards are provided for benchmark systems that aim to inform consumers and businesses about the environmental performance of construction products and assemblies in the consumer market. The benchmarking is based on the use of a functional unit with a cradle-to-grave scope and the use of environmental product declarations (EPD) drawn up in accordance with EN 15804. Intended users are stakeholders setting up benchmark systems to make benchmarking possible for their product group.

Based on EN 15804 and EN 15978, EPDs are developed as information for building assessment to be used only at building level for B2B and B2C communication. Therefore, the information provided at a product level (or even at an application level) cannot be used in a context of decision-making and benchmarking. Therefore, it is required to facilitate the decision-making process for B2B and B2C. For instance, at a product level (or application level), development of tools or a proper method for normalizing and weighting of environmental impacts would help facilitating the decision-making process.

At building level, the mechanism to converge EPDs to the building needs to be further assessed. Simplified tools are crucial to mainstream the use of EPDs at this level. At a building level, the ongoing integration of BIM with EPDs would facilitate the decision-making process for B2B.

#### **5. Conclusion**

The building and construction industry in Europe are one of the leading sectors in developing and implementing EPDs based on LCA. LCA has been used to assess the environmental impacts of construction products and buildings. Meanwhile, use of EPDs in decision-making context to reduce the environmental impacts in building sector is limited. The challenges and barriers for mainstream use of EPDs in the context of decision-making in construction sector is highlighted in this chapter.

The adoption of these methods by SME and non-organized group of building materials and products is less frequent and rely on the development of the region in terms of life cycle management. The lack of awareness in the public procurement and the main actors of the building supply chain (like project owners) slow down the implementation and mainstream use of EPDs. More investment for easier and more adapted tools and methods for both consumers and businesses are needed to facilitate the sustainability decision-making context.

In this context, the efforts and actions are ongoing at European level (both by institutions and businesses) to mainstream the use of LCM in building sector. As an example, ongoing initiatives like level(s) [10] project are an example of implementation of EPDs in construction decision-making. Level(s) aims to increase the understanding of how buildings impact the environment. Level(s) shows how to reduce environmental impact and can prepare users for more challenging performance assessment schemes and tools [10].

Regions and regional authorities in Europe are playing a significant role in this direction. North of France is one of these regions [2]. A variety of actors from supply and demand sides of the building sector are engaged in the implementation of the action plan to mainstream the use of LCM in North of France. Life cycle management is now systematically adopted in most regional development projects in this region. The work has shown that active participation by regional

government and by various authorities and institutions in the region is a key success factor in fostering a life cycle management approach. Active participation and support by industry federations and trade associations is also vital as smaller companies—a strong feature of the building sector—rely heavily on their advice and guidance.

### **Author details**

 Naeem Adibi1 \*, Marjan Mousavi2 , Ricardo Méndez Escobar1 , Manon Glachant1 and Aliasghar Adibi3

\*Address all correspondence to<EMAIL_ADDRESS>
© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Mainstream Use of EPDs in Buildings: Lessons Learned from Europe DOI: http://dx.doi.org/10.5772/intechopen.87836*

#### **References**

[1] European Commission. The Energy Performance of Buildings Directive. Context. 2010

[2] Adibi N, Darul M, Pasquet VD, Christelle Traisnel C. Life cycle management for regional development in France: Example of building sector. In: Life Cycle Approaches to Sustainable Regional Development. New York: Routledge; 2016. p. 362. ISBN:<PHONE_NUMBER>223. DOI: https://doi. org/10.4324/9781315674223

[3] WeLOOP—Life Cycle Assessment [Internet]. 2019. Available from: http:// weloop.org/fr/ [Accessed: April 17, 2019]

 [4] UNEPLife cycle management. How business uses it to decrease footprint, create opportunities and make value chains more sustainable. Life Cycle Assessment: Theory and Practice. 2009;**1**:519-544. Available from: http:// hdl.handle.net/20.500.11822/7921

[5] ISO. ISO 14040: Environmental management—Life cycle assessment— Principles and framework. Environmental Management. 2006;**3**:28. Available from: http://www.iso.org/iso/ catalogue\_detail?csnumber=37456

[6] CEN/TC350. EN 15804+A1. Sustainability of Construction Works— Environmental Product Declarations— Core Rules for the Product Category of Construction Products. Brussels, Belgium: European Committee for Standardization; 2014

[7] CEN/TC350. EN 15978: Sustainability of Construction Works—Assessment of Environmental Performance of Buildings—Calculation Method. Brussels, Belgium: European Committee for Standardization; 2012. p. 61

[8] Pasquet V, Roy A, Adibi N, Coppée S, Echard P, Rocha C, et al. Life Cycle in Practice—Capacity building aiming European SME's. Conference Proceedings of the 17th European Roundtable on Sustainable Consumption and Production - ERSCP 2014, Portorož, Slovenia; 2015. p. 11

[9] Adibi N, Pasquet V, Roy A, Salamon A, Bricout J, Darul M, et al. Mainstreaming the use of life cycle management in small and medium sized enterprises using a sector based and regional approach. In: Sonnemann G, Margni M, editors. Life Cycle Management. LCA Compendium – The Complete World of Life Cycle Assessment. Dordrecht: Springer; 2015. pp. 79-90. Print ISBN: 978-94-017-7220-4. Online ISBN: 978-94-017-7221-1. https://doi. org/10.1007/978-94-017-7221-1\_7

[10] Level(s) Building Sustainability Performance [Internet]. 2019. Available from: http://ec.europa.eu/environment/ eussd/buildings.htm [Accessed: March 10, 2019]

**147**

**Chapter 12**

**Abstract**

Proposals

that would eliminate architectural problems.

architectural arrangements, sustainability

**1. Introduction**

**Keywords:** wheelchair sporters, sports halls, disabled people, disability,

It is quite difficult to make a common definition of disability that can be adopted

by everyone. In the Declaration of Rights of Disabled People being accepted by General Council of United Nations, disabled people have been defined as: "Those who cannot realize the works, which a normal person is required to do in his personal or social life, due to a lack in their physical or spiritual skills originating as a result of deficiencies being hereditary or occurring later on in their lives" [1]. If we would like to generalize disability, we could define it as deficiency or incapability in the skills or movements that would be had by a healthy individual. Depending on the situation of deficiency in these skills or movements, disability can be divided

Problems Experienced by

Wheelchair Sporters in Sports

Halls and Sustainable Solution

*Eylem Çelik, Zekeriya Çelik, Hüseyin Yılmaz Aruntaş,*

*Şefik Taş, Kübra Altunkaynak and Arzuhan Burcu Gültekin*

Purpose of this chapter is to attract attention to the problems faced by wheelchair sporters in sports halls and to present some proposals for the elimination of these problems. Regularly made sports create positive development and changes in a person regardless of whether the individual has disability or not. Many of the limited number of sports options for physically disabled individuals can be made in sports halls. Here it is focused on sports halls where sports such as volleyball, basketball, and handball a field football, being among the sports that can be played by wheelchair sporters are being done. Features of sports halls have been tried to be explained in order for these sports to be done in a comfortable and easy way by disabled individuals. Arrangements that will be made in sports halls for wheelchair sporters will both increase participation in sports and improve the life quality of sporters as well. While these arrangements are planned, primary criterion should enable the sporter to realize all his activities in sports hall without requiring the help of anyone.  In the notification, certain solution proposals have been made

#### **Chapter 12**


**3. Formation and structure of the metal clusters in zeolite framework**

#### **3.1 Progress**

Already in the years 1970s, the high temperature hydrogen reduction of Ag ion to metallic silver in zeolite Y was known but it was only in 1978 when Kellerman and Texter reported the first optical measurements [32]. By measuring the Shuster-Kubelka-Munk re-emission function and fluorescence of a vacuum dehydrated sample of silver clusters they presented and characterized for the very first time the excited electronic state of monodispersed atoms as well as optical absorption of collaterally produced clusters and particles. They assigned the broad absorption peaking at 3.3 eV to "intrazeolitic silver particles". The results triggered a large interest among scientist. Three years later Gellens *et al* reported the formation of the so called "color centers" in Ag-A zeolites, as a result of the reduction of Ag+ ions upon dehydration. The authors assigned the process to the formation of linear Ag3 2+ clusters with Ag0 located inside the sodalite cage opposite the framework D4R and in between two Ag+ cations located at the D6R [33]. It was then believed that the yellow color is due to isolated cluster whereas the observed red color was associated to the formation of two or more interacting Ag3 2+ clusters in the sodalite cage to a maximum of four.

As stated above, the silicon-to-aluminum ratio is an important parameter of zeolite as this determines the number of exchangeable cations. In 1984, Johnson *and al*. detected distinct species following the reaction of sodium-exchanged zeolite Y with sodium, potassium, or rubidium vapor in dehydrated samples of zeolite Y [34]. Upon exposure to high concentrations of metal vapor he obtained stable ionic clusters (Na4 3+, K4 3+ and Rb4 3+) characteristic of small metallic particles located inside the zeolite cavities. Also interesting is that the researchers observed cluster species Ag6 q+ (q = 1, 3, 5) in which an unpaired electron is trapped at a cluster of six equivalent silver cations. In the same year ESR measurements on silver particles in zeolite A proved that during the reduction of silver-loaded zeolite A certain stages of cluster formation can be followed and detected the presence of Ag6 x+ and Ag8 y+ clusters which fit in the sodalite cage [35]. Two years later, Wang and Herron succeeded in encapsulation of CdS and PbS in zeolite Y matrix and indicated that zeolites can be thought as providing a solid solvent for this type of clusters [36]. Impressive work since, through simple experiments, they showed that their optical properties were dependent on size and state of aggregation, a property well-known already for metal particles. A fascinating conclusion was drawn: due to the fact that the transition from clusters to aggregates is not continuous but abrupt they suggested that aggregation inside the zeolite is a percolative process.

The first important review on the structure and chemistry of silver clusters in zeolites has been published by Sun and Self and the reader is encouraged to read

this excellent work which inspired many scientists [9]. The spectroscopy and light induced processes of silver clusters in zeolites have been incipiently discussed by Chen *et al*. [37] For the first time they looked at photostimulated luminescence of silver-exchanged zeolite-Y. Once irradiated with 254 nm wavelength, the photoluminescence intensity of silver atoms centered at 505 nm decreases and a new absorption band shows up around 840 nm. By photostimulation of this absorption band, the fluorescence of silver atoms is observed and the photoluminescence intensity of silver atoms increases slightly. These phenomena were considered to be caused by the charge transfer between the zeolite framework and the entrapped silver atoms. The photostimulated luminescence of silver clusters encapsulated in zeolite-Y was caused by the recombination of luminescence centers with electrons released from their traps by photo- stimulation. Charge transfer from the framework oxygens to silver cations was also reported by Seff and Kim based on a color change from brick-red to yellow [38].

Following the pioneering work presented above, small metal particles started to attract the real interest of scientists due to their peculiar optical, electronic and catalytic activity that change from bulk properties to molecular-like properties once the size decreases under a certain range. For instance, a change in the electronic properties from a band structure to molecular orbitals levels was common for isolated species of a few atoms particle. Such change was almost invariable of the nature of the constituent atoms. Of a particular interest was to control the size and coordination because these would allow fine-tuning of electronic and luminescent properties of the clusters. However, to achieve that, a deep understanding of the electronic state was much desired. Based on such understanding the revealed structure-to-function relationship could finally open perspectives for practical applications.

The exact structure of metal clusters stabilized be the zeolite matrix remained under debate for a long time. Gellens et al. investigated the electronic properties of silver clusters using extended Hűckel framework [39]. They calculated isolated Ag3 molecules in linear or nearly linear geometries and a strong similarity with the electronic spectrum of yellow Ag clusters were found. The proposed model for Ag3 encaged in the zeolite framework appeared to be weakly interacting with the zeolite lattice. Very interesting is that the scientists suggest the occurrence of an electron transfer of approximately two electrons from the cluster toward the zeolite framework increasing the charge density on the Si/Al model.

Until 1990s, simple structures as dimers and trimers of alkali-metal elements or noble metals were only experimentally investigated with UV–VIS and IR spectroscopy, Raman, ESR and EXAFS techniques [40–42]. These experiments indicated various shapes such as linear, bent or triangular structure and even interconversions between such structures were proposed. Precise studies of the effect of cluster shape, structure and interactions with the zeolite environment have been rather limited mainly due to a combination of instrumentation and techniques used. Other difficulties were found due to a distribution of particle size or problems with high mobility of precursors. Zeolite X and Y have been utilized as scaffolds to restrict and stabilize metal agglomeration. In such matrices, for instance, geometric models based on EXAFS experimental results revealed the formation of Pd2, Pd3 and Pd4 clusters occupying adequate positions of the sodalite cages [43]. This showed again a "molecular" cluster elegantly stabilized in an open-framework zeolite. Texter *et al* encountered similar difficulties when investigated the formation of charged silver clusters of activated dehydration of zeolite A [44]. The nuclearity of these clusters formed in the sodalite unit was uncertain, believed to be between 6 and 14 while the dominant cluster had an absorption band centered at 2.72 eV and a higher band at 3.8 eV. Closely, more details about the cluster nuclearity and interactions

#### *Zeolites as Scaffolds for Metal Nanoclusters DOI: http://dx.doi.org/10.5772/intechopen.96876*

with the framework have been brought via far-infrared experiments [45]. The cage vibrational mode characteristic for Ag0 atoms isolated in zeolite Y has been identified at 89 cm−1 while silver-silver stretching modes were identified for zeolites A and Y encapsulated Agn q+ clusters with n = 2, 3 and 6. Via IR spectroscopy the presence of silver microcrystals located on the external surface of zeolite has been also demonstrated. Although important steps have been made, the structure of the metal cluster remains largely uncertain and very few have succeeded in providing strong evidences. Spectroscopic experiments, although widely qualitative, remain the basis in identifying a cluster species. Generally, larger clusters give rise to lower optical bandgap and inconsistencies in assignment of these bands were sometimes observed in literature.

A first attempt to establish the structure of the model Ag clusters in zeolite sample was made in 2004 by employing a combination of steady-state spectroscopy and K-edge XANES/EXAFS analyses [46]. The absorption spectra showed bands at 255 and 305 nm and from Ag K-edge EXAFS results, the structure of the cluster was presumably identified as Ag4 2+. The coordination number 3.3 and the Ag-Ag distance of 2.7 Å suggest that the cluster consisted of 3 or 4 Ag atoms. The amount of the clusters increases with the Ag/Al ratio of Ag zeolites. Further spectroscopic investigations on very small particles Ag2S and PbS in zeolite A showed photoluminescence in the visible range and lifetimes as long as 300 μs and these properties were shown to be strongly dependent on co-cations [47]. A broad investigation has been carried out for Li<sup>+</sup> , Na+ , K+ , Rb+ , Cs+ , Mg2+, Ca2+, and Sr2+. Interestingly, the unusual long luminescence lifetime has been interpreted as excitation energy transfer between Ag2S and Ag4S2, a concept that comes often forward in literature.


**Abstract**

Homology modeling is one of the key discoveries that led to a rapid paradigm shift in the field of computational biology. Homology modeling obtains the three dimensional structure of a target protein based on the similarity between template and target sequences and this technique proves to be efficient when it comes to studying membrane proteins that are hard to crystallize like GPCR as it provides a higher degree of understanding of receptor-ligand interaction. We get profound insights on structurally unsolved, yet clinically important drug targeting proteins through single or multiple template modeling. The advantages of homology modeling studies are often used to overcome various problems in crystallizing GPCR proteins that are involved in major disease-related pathways, thus paving way to more structural insights via in silico models when there is a lack of experimentally solved structures. Owing to their pharmaceutical significance, structural analysis of various GPCR proteins using techniques like homology modeling is of utmost importance.

**Keywords:** membrane protein, bovine rhodopsin, template-based modeling, GPCR-EXP, GPCRdb

### **1. Introduction**

The comparative modeling of proteins, more popularly known as homology modeling among the research community, is a computational procedure that constructs three dimensional atomic resolution structure of a 'target' protein, the structure of it is unknown. A new structure for the target protein is modeled using its own amino acid sequence and a known experimental structure of a homologous protein as a template based upon which the model is constructed. This template-based modeling technique became a plausible computational technique because of the fact that evolutionary related proteins share a similar structure [1]. This undeniable truth led to the famous outbreak of using homology modeling to determine the three dimensional structure of proteins whose structures were otherwise difficult to solve.

One such family of protein that poses a great challenge to study is membrane proteins due to their partially flexibility and lack of stability. The surface of membrane proteins is also comparatively hydrophobic and can only be extracted from the cell membrane with detergents which cause challenges at many levels, including expression, solubilization, purification, crystallization, data collection and structure solution. **Figure 1** shows the total number of membrane protein structures deposited in PDB as of August 2020 and this data was derived from the mpstruc database [2]. There are 2037 published reports of membrane protein structures in this database. It is also very clear that the number of available membrane protein structures is very less compared to the expected exponential growth in the number of available structures [3]. Though approximately 25% of all proteins are membrane proteins, there are less solved structures available due to the difficulty in crystallizing membrane proteins.

Many advances are being made in developing novel methods that can help in solving and studying the structure of membrane proteins in a high-throughput manner. The key to overcome the membrane protein structural biology is the underlying fact that they are structurally homologous to proteins which are evolutionarily related to them. This kindled the structural biologists to try a large number of targets and homologs of each target so that at least a few proteins will show progress through all the steps associated with their structural studies. This is where computational techniques like homology modeling came to the aid of structural biologists in helping solve the structures of membrane proteins by obtaining the three dimensional structure of a target protein based on the similarity between template and target sequences. One arena of such membrane protein structural biology research that has proved to be promising is the G-protein-coupled receptors (GPCRs) which are the largest family of membrane proteins.

The GPCRs constitute a diverse family of proteins in mammalian genomes [4]. The first GPCR for which structure was determined was Rhodopsin, a prototypical class A GPCR. The GPCRs are categorized into five major classes based on their

#### **Figure 1.**

*The number of membrane protein structures deposited each year since the first structure was solved as given by the mpstruc database. The number of structures available is considerably low compared to the expected number of membrane protein structures (red line).*

**57**

studies of GPCRs.

*Importance of Homology Modeling for Predicting the Structures of GPCRs*

sequences as well as on their known or suspected functions in vertebrate: rhodopsin (family A), secretin (family B), glutamate (family C), adhesion and Frizzled/Taste2 [5]. The actual estimate of GPCRs in human genome is still being analyzed. The presence of seven transmembrane (7-TM) spanning α-helical segments separated by alternating intracellular and extracellular loop regions is one of the characteristic features in the structure of GPCRs. They also possess an extracellular N-terminus and an intracellular C-terminus which paved way for GPCRs to be also known as the 7-TM receptors or the heptahelical receptors. The tertiary structure of the GPCR resembles a barrel, with the seven transmembrane helices forming a cavity within the plasma membrane that serves as a ligand-binding domain. With its unique structure, the GPCRs serve many important roles in the human body. Hence the structure function correlation of GPCRs is a vital area of research even today.

The crystal structure of protein plays a pivot role in determining the functional importance of a protein. However membrane proteins are difficult to crystallize. Being a membrane protein, the GPCR structural studies have complexity because of low protein expression level in native tissues and heterologous systems. The poor protein stability and multiple conformational states of the receptors also are major hurdles in the GPCR structural studies. GPCRs have also been notoriously difficult to crystallize owing to their intrinsic flexibility and the above mentioned reasons [6]. For such special cases, homology modeling aids in developing three dimensional models of such proteins. This has been possible through the understanding about the structure of GPCRs facilitated by homology modeling. Since many of these receptors lack experimentally solved structures, in silico methods like homology modeling were applied to gain insights. Template structure with high homology was used for modeling the structures to gain more advance insights on their function. Approximately one-fifth of the total GPCRs structure are solved whereas the remaining GPCR structures can be predicted by homology modeling. Three dimensional model building with the help of template helps us to predict protein structural and functional domains which further aids in drug discovery. .This chapter deals with the contribution of homology modeling to the structural

**2. The importance and multifaceted functionality of GPCRs**

from the perspective of advanced structural research.

The importance of G-protein coupled receptors (GPCRs) in the fields of biology,

medicine and pharmaceutical studies have been extensively studied, well established and properly documented [7]. Due to its significance in playing a crucial role in various normal and pathological processes, GPCRs have become a major field of advanced research and a promising focus for drug discovery processes. The GPCRs have an extensive medical significance owing to their position and function within the human cell spanning the whole cell's plasma membrane. By this way it bridges the extra- and an intracellular environment which enables the GPCRs to act as signal transducers wherein it acclaims a direct mechanism for the transduction of extracellular messages into intracellular responses. In this way and together with their transmitters and effectors, GPCR systems function to modulate a broad spectrum of cellular phenomena dictated by the needs of the tissues and organs they serve. The gradient of GPCR distribution across vast majority of the body's organs and tissues and its primary role as signal transducers like converting transduce extracellular stimuli into intracellular signals at cellular levels makes it fascinating molecules

Other fascinating roles of GPCRs include modulation of neuronal firing, regulation of ion transport across the plasma membrane and within intracellular

*DOI: http://dx.doi.org/10.5772/intechopen.94402*

#### *Importance of Homology Modeling for Predicting the Structures of GPCRs DOI: http://dx.doi.org/10.5772/intechopen.94402*

*Homology Molecular Modeling - Perspectives and Applications*

to the difficulty in crystallizing membrane proteins.

(GPCRs) which are the largest family of membrane proteins.

from the cell membrane with detergents which cause challenges at many levels, including expression, solubilization, purification, crystallization, data collection and structure solution. **Figure 1** shows the total number of membrane protein structures deposited in PDB as of August 2020 and this data was derived from the mpstruc database [2]. There are 2037 published reports of membrane protein structures in this database. It is also very clear that the number of available membrane protein structures is very less compared to the expected exponential growth in the number of available structures [3]. Though approximately 25% of all proteins are membrane proteins, there are less solved structures available due

Many advances are being made in developing novel methods that can help in solving and studying the structure of membrane proteins in a high-throughput manner. The key to overcome the membrane protein structural biology is the underlying fact that they are structurally homologous to proteins which are evolutionarily related to them. This kindled the structural biologists to try a large number of targets and homologs of each target so that at least a few proteins will show progress through all the steps associated with their structural studies. This is where computational techniques like homology modeling came to the aid of structural biologists in helping solve the structures of membrane proteins by obtaining the three dimensional structure of a target protein based on the similarity between template and target sequences. One arena of such membrane protein structural biology research that has proved to be promising is the G-protein-coupled receptors

The GPCRs constitute a diverse family of proteins in mammalian genomes [4]. The first GPCR for which structure was determined was Rhodopsin, a prototypical class A GPCR. The GPCRs are categorized into five major classes based on their

*The number of membrane protein structures deposited each year since the first structure was solved as given by the mpstruc database. The number of structures available is considerably low compared to the expected number*

**56**

**Figure 1.**

*of membrane protein structures (red line).*

sequences as well as on their known or suspected functions in vertebrate: rhodopsin (family A), secretin (family B), glutamate (family C), adhesion and Frizzled/Taste2 [5]. The actual estimate of GPCRs in human genome is still being analyzed. The presence of seven transmembrane (7-TM) spanning α-helical segments separated by alternating intracellular and extracellular loop regions is one of the characteristic features in the structure of GPCRs. They also possess an extracellular N-terminus and an intracellular C-terminus which paved way for GPCRs to be also known as the 7-TM receptors or the heptahelical receptors. The tertiary structure of the GPCR resembles a barrel, with the seven transmembrane helices forming a cavity within the plasma membrane that serves as a ligand-binding domain. With its unique structure, the GPCRs serve many important roles in the human body. Hence the structure function correlation of GPCRs is a vital area of research even today.

The crystal structure of protein plays a pivot role in determining the functional importance of a protein. However membrane proteins are difficult to crystallize. Being a membrane protein, the GPCR structural studies have complexity because of low protein expression level in native tissues and heterologous systems. The poor protein stability and multiple conformational states of the receptors also are major hurdles in the GPCR structural studies. GPCRs have also been notoriously difficult to crystallize owing to their intrinsic flexibility and the above mentioned reasons [6]. For such special cases, homology modeling aids in developing three dimensional models of such proteins. This has been possible through the understanding about the structure of GPCRs facilitated by homology modeling. Since many of these receptors lack experimentally solved structures, in silico methods like homology modeling were applied to gain insights. Template structure with high homology was used for modeling the structures to gain more advance insights on their function. Approximately one-fifth of the total GPCRs structure are solved whereas the remaining GPCR structures can be predicted by homology modeling. Three dimensional model building with the help of template helps us to predict protein structural and functional domains which further aids in drug discovery.

.This chapter deals with the contribution of homology modeling to the structural studies of GPCRs.


**5. Conclusions**

This study suggests that the PNI condition may have a positive e ffect on sports training. However, there are limitations to this study. We conducted the experiments on 10 elite swimmers, but it is necessary to expand the sample size in order to generalize this study. It is thus necessary that future studies be conducted with more participants. In addition, although this study conducted the experiment twice in an environment in which the athletes were randomly switched, it is recognized that emotions may change depending on the condition of the athlete on that day. Therefore, it is suggested that conducting a longitudinal experiment on the same participants might shed more accurate findings on the matter.

**Author Contributions:** Conceptualization, G.H. and H.M.; methodology, G.H., H.M., and T.T.; investigation, M.M., H.F., and T.T.; writing—original draft preparation, G.H.; writing—review and editing, H.M. and T.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Sharp Corporation.

**Conflicts of Interest:** This study was funded by Sharp Corporation. M.M. and H.F. are employees of Sharp Corporation.


**5.1 Cryptococcosis**

*Cryptococcus neoformans* (*Cn*) is a facultative intracellular fungal pathogen and can propagate inside the host macrophages during many stages of experimental and human infections [136, 137]. *Cryptococcus* is a soil fungus that causes lifethreatening meningitis in immunocompromised patients [138, 139]. *Cryptococcus* is an encapsulated pathogenic yeast composed primarily of glucuronoxylomannan (GXM). This polysaccharide helps the fungus play a defensive and offensive role during pathogenesis. It protects the fungus against phagocytosis and promoting intracellular pathogenesis through the cytotoxic release of polysaccharides into macrophage vacuoles [136]. *Cryptococcus* rarely causes clinically visible infections in healthy hosts, but it can be present in latency and persistence inside macrophages *Superoxide Dismutase: A Key Enzyme for the Survival of Intracellular Pathogens in Host DOI: http://dx.doi.org/10.5772/intechopen.100322*

[61, 62]. *C. neoformans var. gattii* predominantly infects individuals having a normal immune response, whereas var. grubii and neoformans are common in immunocompromised individuals. *C. neoformans var. gattii* hinders macrophage phagocytic response, whereas the other two varieties are readily killed by ROS released by phagocytic cells [140, 141].

*C. neoformans* is resistance to ROS mediated oxidative killing of macrophage by inducing the SOD activity and might be playing an important role in virulence of this fungus. Exogenous supplementation of SOD significantly controlled the bacterial growth by inducing human neutrophil function, suggesting that SOD plays a protective role during *C. neoformans* infection [63]. *Cryptococcus neoformans* var. *gattii* contains two types of SODs such as copper, zinc-depend SOD (SOD1) and Mn-dependent (SOD2) isoenzymes [142]. Both SOD1 and SOD2 are intracellular SODs, and deletion of their encoding genes reduces the fungal virulence in vivo model of infection. Furthermore, the mutant fungus also increases sensitivity to pharmacologically-induced intracellular oxidative stress [143]. The sod1 mutant *C. neoformans* was shown three characteristic features 1) highly sensitivity toward oxidative killing by human polymorphonuclear (PMN) cells and by the redox cycling agent menadione. 2) The sod1 mutant was markedly attenuated in virulence when raising the infection in mice, and it also showed significantly susceptibility to in vitro killing by human neutrophils. 3) SOD1 deletion also appeared to be defects in the expression of a number of virulence factors such as laccase, urease, and phospholipase. Complementation of the sod1 gene mutant *C. neoformans* with SOD1 protein regained the virulence factor and menadione resistance. Hence, the antioxidant function of SOD1 is critical for the pathogenesis of the fungus during intracellular survival [60, 141, 144].

#### **5.2 Histoplasmosis**

*Histoplasma capsulatum* is an intracellular fungal pathogen structurally similar to yeast cells. *H. capsulatum* successfully infect host cells like neutrophils and macrophages. *H. capsulatum* is prevalent in the Midwestern United States and Latin America. Macrophages efficiently phagocytize the *Histoplasma* cells, but they failed to kill the fungus despite having ample ROS production. *Histoplasma* cells counter the ROS-mediated oxidative stress of the host by three proteins that are possibly involved in defending *Histoplasma* from ROS. sod1 and sod3 gene deficient *Histoplasma* strains shown the spatial specificity of the SOD1 and SOD3 superoxide dismutases for internal and external (i.e., host-derived) superoxide, respectively. SOD-3 is the primary source of extracellular SODs, and its expression is significantly enriched in the pathogenic phase of fungus cells. *Histoplasma* SOD-3 offers higher resistance of fungus against the phagocytic killing of host cells leading to increased capacity to cause disease in immunocompetent hosts. In *in vivo* studies, sod-3 gene deficient *Histoplasma* strains were shown the attenuation in virulence in mice. Furthermore, restoration of ∆sod3 mutant *Histoplasma* virulence in mice unable to produce superoxide radicals conclusively proves that SOD3 functions in the detoxification of superoxide generated by the host. SOD-3 also prevents the superoxide-dependent killing of *Histoplasma* yeast cells. The host to control the infection of *Histoplasma* requires ROS production. Hence, SOD-3 is a central virulence factor of *Histoplasma* and help to fungus survives under oxidative stress produced by host phagocytic cells during infection [64].


Neurofeedback treatment is particularly indicated in ADHD patients who show excessive EEG slowing in the superior frontal cortex or the midline central cortex (i.e. the first two subtypes) The most relevant neurological EEG correlate in these ADHD cases is usually assumed in the place where the highest ratio of theta/beta activity or lowest *fb* is seen, so that placement of the electrode between Cz and Fz is the best for training. We followed two consecutive treatment protocols. (1) Training to increase the SMR EEG rhythm (11 - 13 Hz) and at the same time, starting to inhibit (decrease) slow activity in the theta range (4 - 8 Hz); this approach is primarily used for the hyperactive component of ADHD. (2) Training to focus attention aiming at increasing higher beta activity (16 - 20 Hz), while training for decreasing the slow activity continued. The training is performed with 40 sessions, 60 min duration per session, one per week. To obtain stress diminishing, before neurofeedback we

Practically all neurofeedback interventions can be roughly reduced to the need of mastering flexibility in increasing or decreasing the general mental activation, i.e. mental arousal (which is somehow coupled with metabolic activity). Thereby, in practice, whenever a certain band is trained, the other bands are affected too (it may even appear that e.g. "…the changes that occurred as a result of stimulating in the alpha frequency were not in alpha but were in beta…"(Lubar 1997). Therefore, the introduced brain rate *f*b could be employed as a complementary biofeedback parameter, characterizing the whole EEG spectrum (as distinct from e.g. theta-beta ratio). The rationale is that, according to the mentioned empirical results, the EEG frequency shifts are related to mental activation / deactivation, as the main

Using brain rate as a neurofeedback parameter for a group of ADHD children (N=50 mean age 11.11 years) Pop-Jordanova et al. (2005 and 2008) obtained the shifting of the spectrum from under-arousal to normal mental arousal, and it corresponded to improved attention and cognition as well as better school performance. Thereby obtained change of brain rate (i.e. arousal level) appeared to be more realistic in respect to the changes of psychological state of children than the drastic reduction of theta/beta ratio, which appeared to be even halved.

If we introduce brain rate as a general indicator of mental arousal in ADHD example, we can see that the first two subtypes are correlated with lower brain rate, (underarousal-UA) the third subtype with higher brain rate (overarousal-OA), while the four subtype is related to excess of alpha activity and "normal" arousal state. In the first three subtypes of ADHD

the protocol for UA and OA is clear, while for the "normal" arousal it is not.

illustrating functional cortical interactions.

use peripheral biofeedback for all children.

defined (Kropotov, 2009).

objective of the treatment.

biofeedback are related to both sympathetic and parasympathetic arousal (Andreassi 2000; Mangina 1996).

Treatment by EDR biofeedback is generally based on training patients in strategies for lowering arousal and maintaining a healthful sympathetic/parasympathetic tone. Consequently, EDR biofeedback modality is a first choice for introvert persons, where high inner arousal is a typical finding and biofeedback training is supposed to lower sympathetic activity. Changes in electrodemal activity can be reliably detected within one second of stimulus presentation, often following a single event. It is important to know that electrodermal conductance precede any other signals related to neuroimaging such a positron emission tomography (PET), blood oxygen level-dependent functional magnetic resonance (BOLD), single photon emission computerized tomography (SPECT) etc. In other words, the changes of electroderamal activity can be registered before the changes obtained by the other neuroimaging techniques.

Neurofeedback (NF) i.e. EEG biofeedback refers to a specific operant-conditioning paradigm where an individual learns how to influence the electrical activity (frequency, amplitude or synchronization) of his brain. It involves teaching skills through the rewarding experience of inducing EEG changes reflected in a perceivable signal (light or sound). Neurofeedback has been shown to be particularly useful in reference to pathologies characterized by dysfunctional regulation of cortical arousal, such as epilepsy and attention deficit hyperactivity disorder (Lubar 1991, 1997; Birbaumer 1999; Mann et al. 1992; Monastra 2001; Pop-Jordanova et al 2005). Our team also used EEG biofeedback in anorectic girls (Pop-Jordanova 2000, 2003), posttraumatic stress disorder - PTSD (Pop-Jordanova 2004), headaches (Pop-Jordanova 2008), as well as for optimal school (Pop-Jordanova, Cakalaroska, 2008) and music performance (Markovska-Simoska et al. 2008).

As we explained previously, the application of spectral analysis to EEG shows that in some brain dysfunctions the EEG amplitude in certain frequency bands significantly differs from the EEG amplitude of healthy subjects. For example, a relatively large group of children with ADHD reveals an excess of the theta/beta ratio i.e. decrease of *fb* in central – frontal leads. This EEG abnormality is associated with hypo activation of frontal lobes. Neurofeedback provides a best tool for correcting such deviations from normality.

Neurofeedback is based on three scientific facts. First, EEG parameters reflect brain dysfunction in a particular disease (in the case of specific subgroup of ADHD children this means the corresponding changes of theta beta ratio and of *fb*). Second, subject can voluntarily change the state of his/her brain so that changes can be associated with increasing or decreasing the relevant parameter. Third, the brain can memorize this new state and keep it for longer time not only in lab conditions but also in other environments, such as school, home etc.

For applying neurofeedback therapy, QEEG evaluation of each patient is needed. In our studies the QEEG is obtained by standard MITSAR EEG recordings (21 electrodes), with the administration of standardized tests: eyes-open (EO), eyes-closed (EC), visual continuous performance (VCPT), auditory continuous performance (ACPT), reading test and math test. EEG data are analyzed for frequency content using the fast Fourier transformation. Statistical analysis compares subject's data with a normative database corrected for time-ofday variations. Data are also evaluated for percentage change across states and compared

biofeedback are related to both sympathetic and parasympathetic arousal (Andreassi 2000;

Treatment by EDR biofeedback is generally based on training patients in strategies for lowering arousal and maintaining a healthful sympathetic/parasympathetic tone. Consequently, EDR biofeedback modality is a first choice for introvert persons, where high inner arousal is a typical finding and biofeedback training is supposed to lower sympathetic activity. Changes in electrodemal activity can be reliably detected within one second of stimulus presentation, often following a single event. It is important to know that electrodermal conductance precede any other signals related to neuroimaging such a positron emission tomography (PET), blood oxygen level-dependent functional magnetic resonance (BOLD), single photon emission computerized tomography (SPECT) etc. In other words, the changes of electroderamal activity can be registered before the changes obtained

Neurofeedback (NF) i.e. EEG biofeedback refers to a specific operant-conditioning paradigm where an individual learns how to influence the electrical activity (frequency, amplitude or synchronization) of his brain. It involves teaching skills through the rewarding experience of inducing EEG changes reflected in a perceivable signal (light or sound). Neurofeedback has been shown to be particularly useful in reference to pathologies characterized by dysfunctional regulation of cortical arousal, such as epilepsy and attention deficit hyperactivity disorder (Lubar 1991, 1997; Birbaumer 1999; Mann et al. 1992; Monastra 2001; Pop-Jordanova et al 2005). Our team also used EEG biofeedback in anorectic girls (Pop-Jordanova 2000, 2003), posttraumatic stress disorder - PTSD (Pop-Jordanova 2004), headaches (Pop-Jordanova 2008), as well as for optimal school (Pop-Jordanova, Cakalaroska,

As we explained previously, the application of spectral analysis to EEG shows that in some brain dysfunctions the EEG amplitude in certain frequency bands significantly differs from the EEG amplitude of healthy subjects. For example, a relatively large group of children with ADHD reveals an excess of the theta/beta ratio i.e. decrease of *fb* in central – frontal leads. This EEG abnormality is associated with hypo activation of frontal lobes.

Neurofeedback is based on three scientific facts. First, EEG parameters reflect brain dysfunction in a particular disease (in the case of specific subgroup of ADHD children this means the corresponding changes of theta beta ratio and of *fb*). Second, subject can voluntarily change the state of his/her brain so that changes can be associated with increasing or decreasing the relevant parameter. Third, the brain can memorize this new state and keep it for longer time not only in lab conditions but also in other environments,

For applying neurofeedback therapy, QEEG evaluation of each patient is needed. In our studies the QEEG is obtained by standard MITSAR EEG recordings (21 electrodes), with the administration of standardized tests: eyes-open (EO), eyes-closed (EC), visual continuous performance (VCPT), auditory continuous performance (ACPT), reading test and math test. EEG data are analyzed for frequency content using the fast Fourier transformation. Statistical analysis compares subject's data with a normative database corrected for time-ofday variations. Data are also evaluated for percentage change across states and compared

Neurofeedback provides a best tool for correcting such deviations from normality.

Mangina 1996).

by the other neuroimaging techniques.

such as school, home etc.

2008) and music performance (Markovska-Simoska et al. 2008).

with a normative database for state modulation. The obtained topographic maps show covariance between all sites at relevant frequencies compared with a normative database, illustrating functional cortical interactions.

Many studies of QEEG for the ADHD group confirmed an increased theta activity predominantly in frontal regions, and a decreased beta activity in comparison to normal children (Mann et al 1992). In this context increased theta/beta ratio is reported as a typical finding in ADHD children (Lubar 1991; Monastra et al. 2001; Muller, 2006). So, the typical ADHD finding can be underarousal. As we said previously, the recent cluster analysis identified several subgroups of ADHD based on different EEG topographies. As a consequence, manly four distinct subgroups of ADHD with regard to electrophysiology are defined (Kropotov, 2009).

Neurofeedback treatment is particularly indicated in ADHD patients who show excessive EEG slowing in the superior frontal cortex or the midline central cortex (i.e. the first two subtypes) The most relevant neurological EEG correlate in these ADHD cases is usually assumed in the place where the highest ratio of theta/beta activity or lowest *fb* is seen, so that placement of the electrode between Cz and Fz is the best for training. We followed two consecutive treatment protocols. (1) Training to increase the SMR EEG rhythm (11 - 13 Hz) and at the same time, starting to inhibit (decrease) slow activity in the theta range (4 - 8 Hz); this approach is primarily used for the hyperactive component of ADHD. (2) Training to focus attention aiming at increasing higher beta activity (16 - 20 Hz), while training for decreasing the slow activity continued. The training is performed with 40 sessions, 60 min duration per session, one per week. To obtain stress diminishing, before neurofeedback we use peripheral biofeedback for all children.

Practically all neurofeedback interventions can be roughly reduced to the need of mastering flexibility in increasing or decreasing the general mental activation, i.e. mental arousal (which is somehow coupled with metabolic activity). Thereby, in practice, whenever a certain band is trained, the other bands are affected too (it may even appear that e.g. "…the changes that occurred as a result of stimulating in the alpha frequency were not in alpha but were in beta…"(Lubar 1997). Therefore, the introduced brain rate *f*b could be employed as a complementary biofeedback parameter, characterizing the whole EEG spectrum (as distinct from e.g. theta-beta ratio). The rationale is that, according to the mentioned empirical results, the EEG frequency shifts are related to mental activation / deactivation, as the main objective of the treatment.

Using brain rate as a neurofeedback parameter for a group of ADHD children (N=50 mean age 11.11 years) Pop-Jordanova et al. (2005 and 2008) obtained the shifting of the spectrum from under-arousal to normal mental arousal, and it corresponded to improved attention and cognition as well as better school performance. Thereby obtained change of brain rate (i.e. arousal level) appeared to be more realistic in respect to the changes of psychological state of children than the drastic reduction of theta/beta ratio, which appeared to be even halved.

If we introduce brain rate as a general indicator of mental arousal in ADHD example, we can see that the first two subtypes are correlated with lower brain rate, (underarousal-UA) the third subtype with higher brain rate (overarousal-OA), while the four subtype is related to excess of alpha activity and "normal" arousal state. In the first three subtypes of ADHD the protocol for UA and OA is clear, while for the "normal" arousal it is not.

Amen, DG. (1997) Brain SPECT imaging: Implication for EEG biofeedback. Keynote address

Amen DG, Hanks C, Prunella J. (2008) Preliminary evidence differentiating ADHD using brain SPECT imaging in older patients, *J Psychoactive Drugs*. 40(2):139-46. Andreassi, JL. (2000) Psychophysiology. Human behavior and physiological response. LEA,

Anokhin, AP, Heath AC, Myers E. (2006) Genetic and environmental influences on frontal

Barkley, R. (1990) Attention Deficit Hyperactivity Disorder: A Handbook for Diagnosis and

Berg, A. (1948) A simple objective technique for measuring flexibility in thinking, *J. Gen.*

Birbaumer, N, Roberts LE, Lutzenbrger W, Rockstroh B, Elbert T. (1999) Area-specific self-

Crosbie J, Schachar R. Deficient inhibition as a marker for familial ADHD. *Am J Psychiatry*.

Culbert, TC, Kajander RL, Reaney JB. (1996) Biofeedback with children and adolescent: clinical observations and patient perspectives. *J Dev Pediatr* 17(5):342–350 Demerzieva, A. (2011) EEG spectra power characteristics of Attention Deficit Hyperactivity

Gottesman I I. and Shields J., (1972) Schizophrenia and Genetics: A Twin Study Vantage

Kaniusas, E, Varoneckas G, Alonderis A, Podlipsky A. (2007) Heart rate variability and EEG

Lubar JF. (1991) Discourse on development on EEG diagnostics and biofeedback treatment for attention deficit/hyperactivity disorders. *Biofeedback Self-Regul* 16: 201–225 Lubar JF. (1997) Neurocortical dynamics: Implications for understanding the role of 388

Mann, C., Lubar J., Zimmerman A., Miller C., and Muenchen R. (1992) Quantitative analysis

Mangina CA, Beuzeron-Mangina JH. (1996) Direct electrical stimulation of specific human brain structures and bilateral electrodermal activity. *Int J Psychophysiol* 22:1–8 Markovska-Simoska S, Pop-Jordanova N, Georgiev D. (2008) Simultaneous EEG and EMG

Markovska-Simoska S., Pop-Jordanova N. (2011) Quantitative EEG Spectrum-weighted

Monastra VJ, Lubar JF, Linden M. (2001) The development of quantitative

disorder: reliability and validity studies. *Neuropsychology* 15(1):136–144

Kropotov, J. (2009) Quantitative EEG, ERP's and neurotherapy. Elsevier, Amsterdam

Point. Personality and Psychopathology Series, New York and London, Academic

during sleep using spectrum-weighted frequencies – a case study, COST B27.

neurofeedback and related techniques for the enhancement of attention. *Appl*

of EEG in boys with attention-deficit/hyperactivity disorder: A controlled study

Frequency (Brain Rate) Distribution in Adults with ADHD, *CNS spectr* 16 (5): 579-587

electroencephalographic scanning process for attention deficit-hyperactivity

regulation of slow cortical potential on the sagittal midline and its effects on

EEG asymmetry: A twin study. *Biol. Psychol*. 71 (3): 289-295

behavior. *Electroencephalogr Clin Neurophysiol* 84:352–361

Boucsein, W. (1992) Electrodermal activity. Plenum, New York.

Disorder in childhood, *Epilepsija:* 124-136

*Psychophysiol Biofeedback* 22(2):111–126

with clinical implications. *Paediatric Neurology*, 8: 30-36

biofeedback for peak performance in musician. *Prilozi* 1:239–253

presented at 28th annual meeting of the Association for Applied Psychophysiology

**8. References**

London.

*Psychol.* 39: 15-22

2001; 158:1884-1890.

EU/ESF, Brussels.

Press.

and Biofeedback, San Diego, CA.

Treatment, Guilford Press, New York

The detailed analysis of QEEG after the neurofeedback training with brain rate as a parameter could detect which bands have been most changed. For instance, in some cases shifting the brain rate to higher values could result in increasing high alpha or beta frequencies; in other, the same change can appear due to diminishing the power of theta or delta bands. As a result, the QEEG comparison before and after the brain rate training can be informative for assessing the individual spectrum band sensitivity.

### **7. Conclusions**

The frontal regions are most likely to show deviations from normal development in the case of ADHD, with disturbed thalamo-cortical and septal-hippocampal pathways, altogether named as executive system.

Application of spectral analysis to EEG shows that the EEG amplitude in certain frequency bands significantly differs from the EEG amplitude of healthy subjects. For example, a relatively large group of children with ADHD reveals an excess of the theta/beta ratio i.e. decrease of brain rate in central – frontal leads. This EEG abnormality is mostly associated with under activation of frontal lobes.

For the exact diagnosis of ADHD, it is recommendable QEEG to be combined with DSM-IV (or ICD-10) behavioral based approach.

There are four main endophenotypes in ADHD population: I subtype (abnormal increase of delta-theta frequency range centrally or centrally-frontally), II subtype (abnormal increase of frontal midline theta rhythm), III subtype (abnormal increase of beta activity frontally), and IV subtype (excess of alpha activities at posterior, central, or frontal leads). Thereby, we consider the second subtype as a subgroup of the first subtype.

The dysfunction of the executive system can be evaluated by event related potentials (ERP's) as well. Children with ADHD showed significant presence of the perseverative mistakes and difficulties in the mental flexibility. The results obtained for visual cognitive performance test (VCPT) showed significantly higher ommission and commission errors, lower reaction time (RT) as well as higher variation of time reaction (var RT) compared to the tests norms.

Distribution of brain rate values for sagittal and lateral topographies reflects the arousal levels in the corresponding conditions. There is a positive correlation between brain rate values and the QEEG spectra subtypes.

Neurofeedback provides a tool for correcting deviations from normality, especially for the subtypes I, II and III. For obtaining better therapeutic results, before neurofeedback, the use of peripheral biofeedback (such as electrodermal activity) aiming to obtain stabilization of sympathetic/parasympathetic system is recommended for all patients.

Brain rate can be used as a multiband biofeedback parameter in mediating the under arousal or over arousal states, complementary to few-band parameters and the skin conduction

Follow-up research is needed in order to determine more precisely the specificity and sensitivity of QEEG and brain rate approach related to neurophysical substrates of ADHD.

#### **8. References**

266 Current Directions in ADHD and Its Treatment

The detailed analysis of QEEG after the neurofeedback training with brain rate as a parameter could detect which bands have been most changed. For instance, in some cases shifting the brain rate to higher values could result in increasing high alpha or beta frequencies; in other, the same change can appear due to diminishing the power of theta or delta bands. As a result, the QEEG comparison before and after the brain rate training can

The frontal regions are most likely to show deviations from normal development in the case of ADHD, with disturbed thalamo-cortical and septal-hippocampal pathways, altogether

Application of spectral analysis to EEG shows that the EEG amplitude in certain frequency bands significantly differs from the EEG amplitude of healthy subjects. For example, a relatively large group of children with ADHD reveals an excess of the theta/beta ratio i.e. decrease of brain rate in central – frontal leads. This EEG abnormality is mostly associated

For the exact diagnosis of ADHD, it is recommendable QEEG to be combined with DSM-IV

There are four main endophenotypes in ADHD population: I subtype (abnormal increase of delta-theta frequency range centrally or centrally-frontally), II subtype (abnormal increase of frontal midline theta rhythm), III subtype (abnormal increase of beta activity frontally), and IV subtype (excess of alpha activities at posterior, central, or frontal leads). Thereby, we

The dysfunction of the executive system can be evaluated by event related potentials (ERP's) as well. Children with ADHD showed significant presence of the perseverative mistakes and difficulties in the mental flexibility. The results obtained for visual cognitive performance test (VCPT) showed significantly higher ommission and commission errors, lower reaction time (RT) as well as higher variation of time reaction (var RT) compared to

Distribution of brain rate values for sagittal and lateral topographies reflects the arousal levels in the corresponding conditions. There is a positive correlation between brain rate

Neurofeedback provides a tool for correcting deviations from normality, especially for the subtypes I, II and III. For obtaining better therapeutic results, before neurofeedback, the use of peripheral biofeedback (such as electrodermal activity) aiming to obtain stabilization of

Brain rate can be used as a multiband biofeedback parameter in mediating the under arousal or over arousal states, complementary to few-band parameters and the skin conduction

Follow-up research is needed in order to determine more precisely the specificity and sensitivity of QEEG and brain rate approach related to neurophysical substrates of

be informative for assessing the individual spectrum band sensitivity.

consider the second subtype as a subgroup of the first subtype.

sympathetic/parasympathetic system is recommended for all patients.

**7. Conclusions**

the tests norms.

ADHD.

named as executive system.

with under activation of frontal lobes.

(or ICD-10) behavioral based approach.

values and the QEEG spectra subtypes.

**14**

*Iran*

Mohammad Ali Nazari *University of Tabriz, Tabriz,*

**EEG Findings in ADHD and the Application**

**of EEG Biofeedback in Treatment of ADHD**

As defined in the 4th edition of Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1994), Attention deficit hyperactivity disorder (ADHD) is characterized by a persistent pattern of inattention, hyperactivity, and impulsiveness, though it can present with or without hyperactivity. ADHD is the most common childhood mental health disorder, with an estimated prevalence of 7% to 10% in boys and 3% in girls aged 4-11 years (Sgrok et al., 2000). This disorder substantially affects the individual's normal cognitive and behavioral functioning. For example, children with ADHD can have a great deal of difficulty focusing on lessons presented by their teachers and remembering how to do their homework. They may often be easily distracted whereby they pay attention

The numerous studies support a model that defines ADHD as an inherited disorder whose core symptoms are founded in neuroanatomic, neurochemical, and neurophysiologic abnormalities of the brain (Monastra, 2005). Deficits associated with ADHD support a hypothesis that anatomical and biochemical abnormalities of the prefrontal cortex constitute the physical basis of this disorder (Barkley, 1997). In this line, neurodiagnostic procedures (e.g., positron emission tomography [PET], single photon emission tomography [SPECT] and magnetic resonance imaging [MRI]) studies have provided evidence of the neurological basis of ADHD (Boutros, et al., 2009). Nevertheless, new theories on the pathogenesis of psychopathological phenomena conceptualize as a consequence of the failure to integrate the activity of different brains' areas (Boutros et al., 2009). It needs techniques tapping the dynamics of complex interaction over time among cerebral regions involved in the

Electrophysiological techniques enable monitoring brain processing in real time, providing the best methods to describe the time course of brain electrical activities. Growth of this field came from the newer and quantifiable techniques such as quantitative electroencephalography (QEEG). QEEG methods provide a set of non-invasive tools that are capable of quantitatively assessing resting and evoked activity of the brain with sensitivity and temporal resolution

QEEG studies have explored brainwave profile in children with ADHD, compared to normal children. These brainwaves could be trained via operant conditioning (called EEG

superior to those of any other imaging methods (Hughes & John, 1999).

**1. Introduction**

to other things than what they should.

integration of cognitive processing.


*4.8. Immunohistochemistry*

Hemispheres previously fixed in paraformaldehyde were cryoprotected in 20% sucrose/PBS and embedded in gelatin. Then, sequential coronal brain sections (8 μm thick) near the midstriatum (Bregma 1.00) and SN (Bregma −3.20) were obtained by cryostat sectioning and mounted on SuperFrost-Plus glass slides (Thermo Fisher Scientific). Afterward, sections were incubated in warm PBS at 37 ◦C for 15 min, followed by two washes in PBS, to remove gelatin.  Subsequentially, to stain dopaminergic neurons, sections were incubated with primary rabbit polyclonal antityrosine hydroxylase (TH) antibody (#ab112; Abcam, Cambridge, UK, 1:700), overnight at 4 ◦C. After several washes with PBS, anti-TH primary antibody was detected with diluted (1:200) Alexa Fluor 488 (anti-rabbit) conjugated secondary antibody (Invitrogen— Thermo Fisher Scientific) for 2 h at room temperature. After extensive rinsing, sections were counterstained with Hoechst 33258 (Sigma-Aldrich) and mounted on Mowiol 4-88 (Sigma-Aldrich).