neural engineering neural engineering neural engineering (also known as neuroengineering) is a discipline within biomedical engineering that uses engineering techniques to understand, repair, replace, or enhance neural systems. neural engineers are uniquely qualified to solve design problems at the interface of living neural tissue and non-living constructs (hetling, 2008). overview the field of neural engineering draws on the fields of computational neuroscience, experimental neuroscience, neurology, electrical engineering and signal processing of living neural tissue, and encompasses elements from robotics, cybernetics, computer engineering, neural tissue engineering, materials science, and nanotechnology. prominent goals in the field include restoration and augmentation of human function via direct interactions between the nervous system and artificial devices. much current research is focused on understanding the coding and processing of information in the sensory and motor systems, quantifying how this processing is altered in the pathological state, and how it can be manipulated through interactions with artificial devices including brain–computer interfaces and neuroprosthetics. other research concentrates more on investigation by experimentation, including the use of neural implants connected with external technology. neurohydrodynamics is a division of neural engineering that focuses on hydrodynamics of the neurological system. history as neural engineering is a relatively new field, information and research relating to it is comparatively limited, although this is changing rapidly. the first journals specifically devoted to neural engineering, the journal of neural engineering and the journal of neuroengineering and rehabilitation both emerged in 2004. international conferences on neural engineering have been held by the ieee since 2003, from 29 april until 2 may 2009 in antalya, turkey 4th conference on neural engineering, the 5th international ieee embs conference on neural engineering in april/may 2011 in cancún, mexico, and the 6th conference in san diego, california in november 2013. the 7th conference was held in april 2015 in montpellier. the 8th conference was held in may 2017 in shanghai. fundamentals the fundamentals behind neuroengineering involve the relationship of neurons, neural networks, and nervous system functions to quantifiable models to aid the development of devices that could interpret and control signals and produce purposeful responses. neuroscience messages that the body uses to influence thoughts, senses, movements, and survival are directed by nerve impulses transmitted across brain tissue and to the rest of the body. neurons are the basic functional unit of the nervous system and are highly specialized cells that are capable of sending these signals that operate high and low level functions needed for survival and quality of life. neurons have special electro-chemical properties that allow them to process information and then transmit that information to other cells. neuronal activity is dependent upon neural membrane potential and the changes that occur along and across it. a constant voltage, known as the membrane potential, is normally maintained by certain concentrations of specific ions across neuronal membranes. disruptions or variations in this voltage create an imbalance, or polarization, across the membrane. depolarization of the membrane past its threshold potential generates an action potential, which is the main source of signal transmission, known as neurotransmission of the nervous system. an action potential results in a cascade of ion flux down and across an axonal membrane, creating an effective voltage spike train or "electrical signal" which can transmit further electrical changes in other cells. signals can be generated by electrical, chemical, magnetic, optical, and other forms of stimuli that influence the flow of charges, and thus voltage levels across neural membranes (he 2005). engineering engineers employ quantitative tools that can be used for understanding and interacting with complex neural systems. methods of studying and generating chemical, electrical, magnetic, and optical signals responsible for extracellular field potentials and synaptic transmission in neural tissue aid researchers in the modulation of neural system activity (babb et al. 2008). to understand properties of neural system activity, engineers use signal processing techniques and computational modeling (eliasmith & anderson 2003). to process these signals, neural engineers must translate the voltages across neural membranes into corresponding code, a process known as neural coding. neural coding studies on how the brain encodes simple commands in the form of central pattern generators (cpgs), movement vectors, the cerebellar internal model, and somatotopic maps to understand movement and sensory phenomena. decoding of these signals in the realm of neuroscience is the process by which neurons understand the voltages that have been transmitted to them. transformations involve the mechanisms that signals of a certain form get interpreted and then translated into another form. engineers look to mathematically model these transformations (eliasmith & anderson 2003). there are a variety of methods being used to record these voltage signals. these can be intracellular or extracellular. extracellular methods involve single-unit recordings, extracellular field potentials, and amperometry; more recently, multielectrode arrays have been used to record and mimic signals. scope neuromechanics neuromechanics is the coupling of neurobiology, biomechanics, sensation and perception, and robotics (edwards 2010). researchers are using advanced techniques and models to study the mechanical properties of neural tissues and their effects on the tissues' ability to withstand and generate force and movements as well as their vulnerability to traumatic loading (laplaca & prado 2010). this area of research focuses on translating the transformations of information among the neuromuscular and skeletal systems to develop functions and governing rules relating to operation and organization of these systems (nishikawa et al. 2007). neuromechanics can be simulated by connecting computational models of neural circuits to models of animal bodies situated in virtual physical worlds (edwards 2010). experimental analysis of biomechanics including the kinematics and dynamics of movements, the process and patterns of motor and sensory feedback during movement processes, and the circuit and synaptic organization of the brain responsible for motor control are all currently being researched to understand the complexity of animal movement. dr. michelle laplaca's lab at georgia institute of technology is involved in the study of mechanical stretch of cell cultures, shear deformation of planar cell cultures, and shear deformation of 3d cell containing matrices. understanding of these processes is followed by development of functioning models capable of characterizing these systems under closed loop conditions with specially defined parameters. the study of neuromechanics is aimed at improving treatments for physiological health problems which includes optimization of prostheses design, restoration of movement post injury, and design and control of mobile robots. by studying structures in 3d hydrogels, researchers can identify new models of nerve cell mechanoproperties. for example, laplaca et al. developed a new model showing that strain may play a role in cell culture (laplaca et al. 2005). neuromodulation neuromodulation aims to treat disease or injury by employing medical device technologies that would enhance or suppress activity of the nervous system with the delivery of pharmaceutical agents, electrical signals, or other forms of energy stimulus to re-establish balance in impaired regions of the brain. researchers in this field face the challenge of linking advances in understanding neural signals to advancements in technologies delivering and analyzing these signals with increased sensitivity, biocompatibility, and viability in closed loops schemes in the brain such that new treatments and clinical applications can be created to treat those with neural damage of various kinds. neuromodulator devices can correct nervous system dysfunction related to parkinson's disease, dystonia, tremor, tourette's, chronic pain, ocd, severe depression, and eventually epilepsy. neuromodulation is appealing as treatment for varying defects because it focuses in on treating highly specific regions of the brain only, contrasting that of systemic treatments that can have side effects on the body. neuromodulator stimulators such as microelectrode arrays can stimulate and record brain function and with further improvements are meant to become adjustable and responsive delivery devices for drugs and other stimuli. neural regrowth and repair neural engineering and rehabilitation applies neuroscience and engineering to investigating peripheral and central nervous system function and to finding clinical solutions to problems created by brain damage or malfunction. engineering applied to neuroregeneration focuses on engineering devices and materials that facilitate the growth of neurons for specific applications such as the regeneration of peripheral nerve injury, the regeneration of the spinal cord tissue for spinal cord injury, and the regeneration of retinal tissue. genetic engineering and tissue engineering are areas developing scaffolds for spinal cord to regrow across thus helping neurological problems (schmidt & leach 2003). research and applications research focused on neural engineering utilizes devices to study how the nervous system functions and malfunctions (schmidt & leach 2003). neural imaging neuroimaging techniques are used to investigate the activity of neural networks, as well as the structure and function of the brain. neuroimaging technologies include functional magnetic resonance imaging (fmri), magnetic resonance imaging (mri), positron emission tomography (pet) and computed axial tomography (cat) scans. functional neuroimaging studies are interested in which areas of the brain perform specific tasks. fmri measures hemodynamic activity that is closely linked to neural activity. it is used to map metabolic responses in specific regions of the brain to a given task or stimulus. pet, ct scanners, and electroencephalography (eeg) are currently being improved and used for similar purposes. neural networks scientists can use experimental observations of neuronal systems and theoretical and computational models of these systems to create neural networks with the hopes of modeling neural systems in as realistic a manner as possible. neural networks can be used for analyses to help design further neurotechnological devices. specifically, researchers handle analytical or finite element modeling to determine nervous system control of movements and apply these techniques to help patients with brain injuries or disorders. artificial neural networks can be built from theoretical and computational models and implemented on computers from theoretically devices equations or experimental results of observed behavior of neuronal systems. models might represent ion concentration dynamics, channel kinetics, synaptic transmission, single neuron computation, oxygen metabolism, or application of dynamic system theory (laplaca et al. 2005). liquid-based template assembly was used to engineer 3d neural networks from neuron-seeded microcarrier beads. neural interfaces neural interfaces are a major element used for studying neural systems and enhancing or replacing neuronal function with engineered devices. engineers are challenged with developing electrodes that can selectively record from associated electronic circuits to collect information about the nervous system activity and to stimulate specified regions of neural tissue to restore function or sensation of that tissue (cullen et al. 2011). the materials used for these devices must match the mechanical properties of neural tissue in which they are placed and the damage must be assessed. neural interfacing involves temporary regeneration of biomaterial scaffolds or chronic electrodes and must manage the body's response to foreign materials. microelectrode arrays are recent advances that can be used to study neural networks (cullen & pfister 2011). optical neural interfaces involve optical recordings and optogenetics, making certain brain cells sensitive to light in order to modulate their activity. fiber optics can be implanted in the brain to stimulate or silence targeted neurons using light, as well as record photon activity—a proxy of neural activity— instead of using electrodes. two-photon excitation microscopy can study living neuronal networks and the communicatory events among neurons. brain–computer interfaces brain–computer interfaces seek to directly communicate with human nervous system to monitor and stimulate neural circuits as well as diagnose and treat intrinsic neurological dysfunction. deep brain stimulation is a significant advance in this field that is especially effective in treating movement disorders such as parkinson's disease with high frequency stimulation of neural tissue to suppress tremors (lega et al. 2011). microsystems neural microsystems can be developed to interpret and deliver electrical, chemical, magnetic, and optical signals to neural tissue. they can detect variations in membrane potential and measure electrical properties such as spike population, amplitude, or rate by using electrodes, or by assessment of chemical concentrations, fluorescence light intensity, or magnetic field potential. the goal of these systems is to deliver signals that would influence neuronal tissue potential and thus stimulate the brain tissue to evoke a desired response (he 2005). microelectrode arrays microelectrode arrays are specific tools used to detect the sharp changes in voltage in the extracellular environments that occur from propagation of an action potential down an axon. dr. mark allen and dr. laplaca have microfabricated 3d electrodes out of cytocompatible materials such as su-8 and sla polymers which have led to the development of in vitro and in vivo microelectrode systems with the characteristics of high compliance and flexibility to minimize tissue disruption.