Visual stimuli were generated by a portable VSG 2/5 (CRS, Cambridge Research Systems) housed on a laptop (DELL) and controlled by Matlab programs, they were displayed on a gamma-corrected CRT monitor (MODEL) driven at a resolution of 1024X600 pixels, with a refresh rate of 120 Hz. Observers' head was stabilized with a chinrest placed at a distance of 57 centimeters from the monitor, participants viewed the visual stimuli through CRS FE-Shuttering Goggles that were fastened to the chinrest. The goggles were synchronized with the monitor refresh rate through the VSG 2/5 and occluded alternatively the two lenses at each frame allowing dichoptic viewing.

Visual stimuli were achromatic orthogonal (horizontal and vertical) Gabor patches (size 2°, spatial frequency 2 cpd, contrast 75%) presented on a uniform average grey background (luminance 37 cd/m2 ) in central vision, with a black fixation point and a black common squared frame (size 2.5°). Observers reported verbally their visual perception and responses were recorded through the computer keyboard manipulated by the experimenter.

Occlusion therapy was achieved by sticking a Bartenger 0.4 filter on the spectacle lens of the fellow eye. Since the optical features of the Bartenger foils are not homogeneous and often differ from the labeled density designation (Perez, Archer, & Artal, 2010), each filter was first controlled by the experimenter for the correct level of blur by measuring Snellen acuity through it and was then applied on the appropriate spectacle lens.

## *Task and Procedures*

To make the setup and the task appealing for children, we covered the monitor with a black cloth with yellow stars pinned on it and we stuck some cartoon characters on the monitor in order to make it look like a sort of "magic box". A picture of the setup is reported in Figure 4.1. We invented a story, that we told to the children showing a Power Point presentation, about a magic competition and we asked the children to be the referees of the context, telling them that the magic tricks could only be seen through the goggles. Children were very keen to perform the task, some of them even enthusiastic. They were trained to report verbally whether the "stripes" (Gabor patches) on the monitor were "standing up" (vertical) or "lying down" (horizontal). The experimenter held the appropriate key of the computer keyboard ac-

cording to the visual perception reported by the observer. Children were motivated to perform accurately the task because at the end of each 3-minutes experimental block they were asked to judge which of the characters had won the magic context (one was associated with the horizontal, the other with the vertical orientation). The orientation presented to each eye was swapped at every session as well as the orientation associated with a particular character, in order to reduce the possibility of response bias in favour of one or the other orientation.

During the first training session binocular rivalry was simulated by presenting the same orientation to both eyes and changing it at random intervals mimicking the dynamics of binocular rivalry. During the training session the experimenter could check the accuracy of the child and ended the trial when the observer reported the visual orientation precisely. Children that were not able to perform the task were discarded and did not take part to the binocular rivalry experiment.

After the training session a short (90 seconds) binocular rivalry session was recorded to determine the quality of binocular rivalry for the different children. Observers that did not show binocular rivalry (either not alternating at all or fusing the two visual images reporting to perceive a plaid) were discarded. None of the observers that we considered for analysis reported periods of patchy rivalry. Binocular rivalry was measured before the placement of the Bartenger foil on the lens of the fellow eye (baseline measurements) and at different time intervals following the onset of the occlusion therapy: 120 minutes, 30 days, 60 days, 150 days. 2x180 seconds experimental blocks were recorded for each interval.

#### Figure 4.1. Experimental Setup

Two pictures of the child-friendly experimental setup are shown.  The monitor was covered with a black cloth and yellow stars and a "sorcer Mickey Mouse" cartoon was stuck in correspondence of the visual stimulus. Children were asked to help Mickey Mouse in judging the magic context and were told that the goggles were especially constructed to show magic tricks.

## **4.2.2. Preliminary results**

The outcome of the occlusion therapy is shown in Table 4.1, where visual acuity of the two eyes is reported for the different time intervals tested. All children showed an improvement of visual acuity of the amblyopic eye, improvement that, for some children, was virtually complete two months after the beginning of the treatment and stabilized 5 months after. If binocular rivalry dynamics were governed by the same neural mechanisms underlying the recovery of amblyopia we would expect to observe an initially strong perceptual bias in favour of the fellow eye (that we will define as the *deprived eye* because it is the one that will undergo the patching procedure) and a subsequent reduction of the bias, with balance between the eyes being restored with recovered acuity of the amblyopic (*non-deprived*) eye.

Table 4.1. Participants' age and visual acuity in the two eyes.

The table reports the date of births of the five children tested and the visual acuity of the right and left eyes (RE and LE) measured using Snellen tables. All children show an improvement of visual acuity of the amblyopic eye following occlusion therapy. The improvement is already important 1 month after the onset of the treatment.

The proportion of time spent by the observers seeing the stimulus presented to the deprived (fellow) eye for the different time intervals recorded is reported in Figure 4.2. The dashed line represents perfect balance between the two eyes (with dominance proportion being 50%). In the baseline measurements, surprisingly, all but one observer showed balanced rivalrous perception, despite anisometropia. We chose visual stimuli having an optimal spatial frequency (2 cycles per degree of visual angle), that should be well visible even for the amblyopic eye, the blur caused by amblyopia, in fact, principally affects high spatial frequencies. Nevertheless, this result indicates that the dynamics of binocular rivalry are not affected by the weakening of the signal from the amblyopic eye provoked by the pathology, suggesting that binocular rivalry engages different neural mechanisms.

Equally surprising is the result that the occlusion of the fellow eye disrupted the initial balance, with visual perception during binocular rivalry being biased in favour of the deprived (fellow) eye. The measurements recorded 2 hours after the onset of the occlusion therapy confirm our previous findings obtained with adult normal observers undergoing monocular patching (Lunghi, Burr, & Morrone, 2011). Interestingly, the bias in favour of the fellow (deprived) eye is maximum 30 days following the onset of the treatment, with the deprived eye dominating competition with the non-deprived (amblyopic) eye 80% of the time, despite the recovered acuity of the amblyopic eye compared to the baseline measurements. 60 days after eye-patching, the recovery of the amblyopic eye is almost complete and balance between the two eyes during binocular rivalry is restored, balance that is confirmed in measurements recorded 150 days after the onset of occlusion therapy.

Figure 4.2. Proportion of Dominance in favour of the deprived eye.

The proportion of time spent seeing the visual stimulus presented to the deprived (fellow) eye is plotted as a function of time elapsed from the onset of the occlusion therapy (temporal units on the x scale are arbitrary). The dashed line represents perfect balance between the eyes. The small hollow symbols stand for individual observers' performance, while the full black stars are the average (error bars represent s.e.m). Despite anisometropia, the baseline measurements show a balanced visual perception during binocular rivalry. Following monocular patching with Bartenger 0.4 filters, visual perception is biased in favour of the deprived eye, the bias is already present 2 hours following patching and is maximum 30 days after. 60 days following the beginning of treatment, balance between the eyes is re-established and reinforced 150 days after, when the amblyopic eye has virtually completely recovered (see Table 3.4.1).

## **4.2.3. Discussion**

The data presented above are still preliminary and incomplete, and much more work needs to be done, but nevertheless, they show an interesting trend: the dynamics of binocular rivalry recorded before and during occlusion therapy seem to be unrelated with the visual loss provoked by amblyopia and the subsequent recovery of visual acuity during the treatment. Before the onset of the therapy, in fact, all observers tested had an important anisometropia between the eyes, with visual acuity being perfect in the fellow eye and impaired in the amblyopic eye. Nevertheless, surprisingly, observers' perception during binocular rivalry was balanced, with only one child showing a strong perceptual bias in favour of the fellow eye.

During occlusion therapy visual acuity of the amblyopic eye improved and was virtually recovered two months following the beginning of the treatment. Interestingly, during the first month of treatment, that is when plasticity is maximum and the amblyopic eye rapidly improves visual acuity, the initial perceptual balance between the eyes was disrupted and visual perception during binocular rivalry was strongly biased in favour of the fellow (deprived) eye, that dominated 80% of the time over the amblyopic (non-deprived) eye. The initial perceptual balance between the eyes was then re-established two months following the onset of the treatment and reconfirmed five months after, when visual acuity of the amblyopic eye was stabilized and neural-plasticity probably lowered.

The marked dissociation between the strength of the visual signals (diminished by amblyopia and then recovered during the treatment) and visual perception during binocular rivalry suggests that different neural mechanisms underlie the two phenomena. Binocular rivalry is a peculiar case of bistable vision that engages competition between the monocular inputs and the neural representation of the rivalring visual stimuli at different stages of neural processing (for review see: Tong, Meng, & Blake, 2006). Importantly, binocular rivalry also engages strong adaptation and reciprocal inhibition between the eyes (for review see: Alais, 2012) and is in principle sensitive to the level of intracortical inhibition of the visual cortex.

Balance between intracortical inhibition and excitation at the level of the visual cortex is crucial for experience-dependent plasticity. As discussed in the introduction (3.1), the development of GABA-ergic inhibition is one of the most relevant factors provoking the closure of the critical period in mammals (Fagiolini & Hensch, 2000), and plasticity in adult animals can be restored by decreasing pharmacologically the levels of intracortical inhibition (Harauzov et al., 2010; Maya Vetencourt et al., 2008). Finally, GABA-ergic neurons are the only cells in the visual cortex retaining some form of experience-dependent plasticity (Hendry & Jones, 1986; Lee et al., 2006). If experience-dependent plasticity driven by the occlusion therapy causes some changes in intracortical inhibition (probably lowering the level of GABA-ergic inhibition), the perceptual changes observed in binocular rivalry are likely to reflect the timecourse of neural plasticity during the treatment of amblyopia.

Even though our data are still preliminary and the interpretation speculative so far, the correlation between visual acuity recovery and the perceptual bias in favour of the fellow eye that we observed is striking and suggests that binocular rivalry could be an useful non-invasive tool to monitor the efficiency and timecourse of occlusion therapy for amblyopia and maybe predict its outcome.

## **Chapter 5 General Conclusions**

In this work we have revealed some unexpected properties of the early visual cortex. We have challenged the view that considers primary sensory areas as being exclusively dedicated to unisensory processing by showing that touch can interact with vision during binocular rivalry at early stages of visual analysis, probably already in V1. Our results have further challenged the notion of neuroplasticity being restricted to a sensitive period early in life by demonstrating that a brief period of monocular deprivation in adult observers provokes important perceptual effects that results in unbalancing visual perception during binocular rivalry in favour of the deprived eye with an effect being measurable for a period of time exceeding the duration of deprivation.

We propose that using binocular rivalry as psychophysical method to investigate these aspects of visual perception is the crucial factor that allowed the discovery of these important properties of early visual cortices. Binocular rivalry, in fact is a peculiar visual phenomenon presenting unique characteristics that can be used to unmask subtle behavioural effects. For example, the intrinsic ambiguity of visual rivalrous perception can help in unmasking signals from other sensory modalities, that are normally concealed by a strong and reliable visual input, without needing to weaken visual stimulation by degrading the visual stimuli. In addition, since binocular rivalry requires the interaction between monocular signals, it is resolved at the cortical level, that is the first stage of neural processing in which the monocular signals are integrated. Using binocular rivalry therefore ensures that the cortical origin of the neural processes that are investigated.

One of the most stryking features of binocular rivalry is the dissociation between constant physical stimulation and alternating visual perception: albeit two different visual stimuli are contemporaneously displayed on the retinae, only one of them is consciously perceived at a time, the other being suppressed from visual awareness. While the neural signal associated with the dominant visual stimulus is processed by a complex hierarchy of cerebral areas, starting from primary visual cortex and reaching object-sensitive areas in the infero-temporal cortex, the neural trace of the suppressed visual stimulus is not treacable outside of V1 or V2. Factors interfering with the suppressed visual signals are therefore extremely likely to reflect neural interactions occurring at these early stages of visual processing. This aspect of binocular rivalry importantly revealed the early interaction between vision and touch that we found.

Binocular rivalry engages strong competition between the monocular signals and is therefore a sensitive probe for measuring the relative strength of the signal associated with each eye. Other psychophysical methods, in fact, involve collaborative rather than competitive interactions between the eyes. Binocular rivalry is a unique method to separately track the strength of the monocular signals in a context in which they compete with each other. This is the property of binocular rivalry that was crucial for revealing the effects of monocular deprivation on adult visual perception, for competition between the monocular signals is one of the important factors underlying neuroplastic changes in the visual cortex.

Moreover, visual competition during binocular rivalry is thought to be driven by reciprocal inhibition between the monocular signals. Binocular rivalry could therefore be used as a sensitive method for indirectly evaluate the balance between intracortical inhibition and excitation, the dynamics of binocular rivalry being regulated by inhibitory processes. Balance between inhibition and excitation at the cortical level is crucial for neuroplasticity, for either increasing excitation or decreasing intracortical inhibition restores neuroplasticity in the visual cortex of adult animals and critical periods depends on the development and maturation of GABAergic inhibition. This characteristic is probably the reason why we have shown that binocular rivalry can be efficiently used as a non-invasive tool to monitor neuroplastic changes in the visual cortex of amblyopic children during the recovery of visual acuity in the amblyopic eye caused by the occlusion of the fellow eye.

In conclusion, taking advantage of the peculiar features of binocular rivalry detailed above, we have been able to reveal novel properties of early visual cortex such as residual plasticity and early cross-modal processing.

Taken together, our results have important implications for understanding the consequences of sensory loss on the adult visual system, suggesting that the recruitment of primary visual cortex for the processing of information from other sensory modalities observed in blind patients occurs by unmasking pre-existing connections from those modalities to the primary visual cortex, rather than in creating them exnovo.

Finally, our deprivation studies also show that the adult visual cortex retains a higher degree of residual experience-dependent plasticity than previously thoutght. These results strongly suggest that the first response of the adult visual system to deprivation is a compensatory homeostatic boost of neural activity, probably occurring through up-regulation of contrast gain control mechanisms, as a first attempt to compensate for the impoverished incoming information provoked by visual deprivation.

## **References**

#### premio tesi di dottorato

#### anno 2007

Bracardi M., *La Materia e lo Spirito. Mario Ridolfi nel paesaggio umbro*

#### anno 2008

Bemporad F., *Folding and Aggregation Studies in the Acylphosphatase-Like Family*

Buono A., *Esercito, istituzioni, territorio. Alloggiamenti militari e «case Herme» nello Stato di Milano (secoli XVI e XVII)*

Castenasi S., *La finanza di progetto tra interesse pubblico e interessi privati*

Colica G., *Use of Microorganisms in the Removal of Pollutants from the Wastewater*

Gabbiani C., *Proteins as Possible Targets for Antitumor Metal Complexes: Biophysical Studies of their Interactions*

#### anno 2009

Decorosi F., *Studio di ceppi batterici per il biorisanamento di suoli contaminati da Cr(VI)*

Pace R., *Identità e diritti delle donne. Per una cittadinanza di genere nella formazione*

Vignolini S., *Sub-Wavelength Probing and Modification of Complex Photonic Structures*

#### anno 2010

Fedi M., *«Tuo lumine». L'accademia dei Risvegliati e lo spettacolo a Pistoia tra Sei e Settecento*

Fondi M., *Bioinformatics of genome evolution: from ancestral to modern metabolism. Phylogenomics and comparative genomics to understand microbial evolution*

Marino E., *An Integrated Nonlinear Wind-Waves Model for Offshore Wind Turbines*

Orsi V., *Crisi e Rigenerazione nella valle dell'Alto Khabur (Siria). La produzione ceramica nel passaggio dal Bronzo Antico al Bronzo Medio*

Polito C., *Molecular imaging in Parkinson's disease*

Romano R., *Smart Skin Envelope. Integrazione architettonica di tecnologie dinamiche e innovative per il risparmio energetico*

#### anno 2011

Acciaioli S., *Il* trompe-l'*œil letterario, ovvero il sorriso ironico nell'opera di Wilhelm Hauff*

Bernacchioni C., *Sfingolipidi bioattivi e loro ruolo nell'azione biologica di fattori di crescita e citochine*

Fabbri N., *Bragg spectroscopy of quantum gases: Exploring physics in one dimension*

Gordillo Hervás R., *La construcción religiosa de la Hélade imperial: El Panhelenion*

Mugelli C., *Indipendenza e professionalità del giudice in Cina*

Pollastri S., *Il ruolo di TAF12B e UVR3 nel ciclo circadiano dei vegetali*

Salizzoni E., *Paesaggi Protetti. Laboratori di sperimentazione per il paesaggio costiero euro-mediterraneo*

#### anno 2012

Bondì D., *Filosofia e storiografia nel dibattito anglo-americano sulla svolta linguistica*

Petrucci F., Petri Candidi Decembrii *Epistolarum iuvenilium libri octo.* A cura di Federico Petrucci

Ramalli A., *Development of novel ultrasound techniques for imaging and elastography. From simulation to real-time implementation*

#### anno 2013

Bacci M., *Coarse-grained molecular dynamics and continuum models for the transport of protein molecules*

Brancasi I., *Architettura e Illuminismo. Filosofia e progetti di città nel tardo Settecento francese*

Cucinotta E., *Produzione poetica e storia nella prassi e nella teoria greca di età classica*

Locatelli M., *Mid infrared digital holography and terahertz imaging*

Muniz Miranda F., *Modelling of spectroscopic and structural properties using molecular dynamics*

Pellegrini L., *Circostanze del reato: trasformazioni in atto e prospettive di riforma*


**4. Photoprotective behaviors**

Acute UVR exposure has deleterious effects on the skin, and contributes to the cumulative effects of lifetime UV exposure. Cellular damage and DNA mutations caused by UVR, if not repaired, can accumulate in the skin and contribute to skin aging and increase skin cancer risk. Melanomas typically develop in areas of the skin that are occasionally exposed to sunlight, while non-melanomas tend to develop in areas of the skin that are frequently exposed to sunlight [19]. Therefore, it is important to protect all areas of skin from UVR by practicing a combination of photoprotective behaviors. The most common form of sun protection that comes to mind is sunscreen, but it is not the only method. Comprehensive sun protection programs endorsed by healthcare professionals include the use of broad spectrum sunscreen, wearing protective clothing, staying in the shade and limiting sun exposure especially at times of peak intensity (10am-2pm), and avoiding indoor tanning devices [8, 9, 24]. Sand, water, and snow reflect UV rays, so protective measures should be taken seriously when in these environments[19]. These core photoprotective methods should be followed by all people regardless of skin color and FST, and especially followed by susceptible populations. However, only 60.6% of adults surveyed in the United States in 2010 reported that they usually or always follow at least one photoprotective behavior when spending time outdoors [25].

Wearing protective clothing means that the clothing should be a physical barrier to sunlight, and should cover as much of the body as possible. Protective clothing includes wearing long pants or a long skirt, and long sleeves. Hats that shade the face, neck and ears are part of protective clothing. Most men wear a baseball cap for protection, but these caps do not shade the face, neck, and ears as well as a wide-brimmed hat that offers more coverage [25]. Sunglasses also fall under protective clothing as they protect the eyes and areas around the eyes from UVR and reduce the risk of developing ocular melanoma. The best protec‐ tion against solar UVR would be obtained by through a combination of protective cloth‐ ing and sunscreen [26].

regions with light-skinned populations such as Australia, Switzerland, and Ireland [2], and that the highest registered incidence of melanoma is found in Australia (Geller et.al, 2012). There is a 20 times greater incidence of malignant melanoma in Caucasians than in African-Americans in the United States [19]. One reason for this difference is that darkly pigmented skin responds to UVR differently than light pigmented skin. In African-Americans, DNA damage is not prominent below the epidermis, and damaged skin cells are more likely to undergo apoptosis. It is believed that the melanin in more highly pigmented individuals provides a higher level of protection than in light skinned individuals. By absorbing UV light, melanin is protective, but it is not enough to give 100% protection, so more highly pigmented

people are still prone to UV-induced skin damage and can still get skin cancer [23].

number sunburns experienced during childhood and adolescence [6, 17].

**4. Photoprotective behaviors**

214 Highlights in Skin Cancer

The effects of UV damage on the skin are cumulative. The total number of severe sunburn incidences and lifetime dose of UVR are important factors to consider when determining skin cancer susceptibility. Outdoor workers have a greater risk of developing SCC than indoor workers because their skin experiences chronic irradiation with solar UV. Spending long periods of time outdoors for recreational purposes is associated with increased risk of melanoma [17]. Major risk factors for developing melanoma are the number of nevi and

Acute UVR exposure has deleterious effects on the skin, and contributes to the cumulative effects of lifetime UV exposure. Cellular damage and DNA mutations caused by UVR, if not repaired, can accumulate in the skin and contribute to skin aging and increase skin cancer risk. Melanomas typically develop in areas of the skin that are occasionally exposed to sunlight, while non-melanomas tend to develop in areas of the skin that are frequently exposed to sunlight [19]. Therefore, it is important to protect all areas of skin from UVR by practicing a combination of photoprotective behaviors. The most common form of sun protection that comes to mind is sunscreen, but it is not the only method. Comprehensive sun protection programs endorsed by healthcare professionals include the use of broad spectrum sunscreen, wearing protective clothing, staying in the shade and limiting sun exposure especially at times of peak intensity (10am-2pm), and avoiding indoor tanning devices [8, 9, 24]. Sand, water, and snow reflect UV rays, so protective measures should be taken seriously when in these environments[19]. These core photoprotective methods should be followed by all people regardless of skin color and FST, and especially followed by susceptible populations. However, only 60.6% of adults surveyed in the United States in 2010 reported that they usually or always

follow at least one photoprotective behavior when spending time outdoors [25].

Wearing protective clothing means that the clothing should be a physical barrier to sunlight, and should cover as much of the body as possible. Protective clothing includes wearing long pants or a long skirt, and long sleeves. Hats that shade the face, neck and ears are part of protective clothing. Most men wear a baseball cap for protection, but these caps do not shade the face, neck, and ears as well as a wide-brimmed hat that offers more coverage

Consumers are advised to select sunscreens that offer broad spectrum (UVA and UVB) protection with a sun protective factor (SPF) of 15 or greater by the United States Food and Drug Administration (FDA) [1]. Sunscreens are applied directly onto the skin and they reduce UVR penetration by reflection or absorption [9]. Broad spectrum sunscreens can protect against UV-induced erythema and immunosuppression [21]. Sunscreen use is a method of chemoprevention, meaning it can suppress or prevent the progression of premalignant skin lesions into cancer [19]. Sunscreen with SPF of 15 or greater reduces skin cancer risk, and prevents both melanoma and non-melanoma skin cancers [24]. The amount of protection is related to the SPF level and the amount of sunscreen applied. Lower SPF sunscreens are less effective, especially when applied inadequately, than higher SPF sunscreens [27].

Consistent daily application of sunscreen is especially recommended for individuals who are more susceptible to developing melanoma [19]. Consistent long-term daily application of broad spectrum sunscreen to the head and arms was shown to decrease the incidence of malignant melanoma compared to discretionary sunscreen use in a randomized controlled prospective study of Australians [28]. Fewer melanocytic nevi develop on Caucasian children who routinely used SPF 30 broad spectrum sunscreen when going outdoors for more than 30 minutes than children who do not use sunscreen [29]. Sunscreen itself is safe and does not increase the risk of skin cancer. Meta-analysis of 11 case-control studies did not find an association between sunscreen use and increased risk of developing melanoma [30]. Some studies have reported an association between topical sunscreen use and melanoma, but this relationship is probably connected to inappropriate and compensatory use of sunscreen.

The compensation hypothesis is that people tend to wear less protective clothing and/or prolong the amount of time spent in the sun when they use higher SPF sunscreens. This compensatory behavior actually defeats the purpose of using sunscreen, and it increases risk of skin cancer because the risk of sunburn is increased [1, 17, 24]. In an observational study of European sunbathers, it was found that the duration of time spent sunbathing was up to 25% longer for those who used SPF 30 than those who used SPF 10 [31]. Sunscreen is meant to be used as an adjunct to other methods of photoprotection and not to extend the amount of intentional sun exposure time. Consumers generally have a false sense of security when wearing high SPF sunscreens, especially those of SPF of 50 and greater, and they often forgo other methods of photoprotection, such as wearing protective clothing. Interestingly, the consumers who wear sunscreen and spend more time sunbathing are generally those who are more sensitive to UVR. This likely explains why the incidence of melanoma continues to increase despite more people wearing sunscreen [26].

Another behavior that compromises the effectiveness of sunscreen is inadequate sunscreen application thickness. Sunscreen accumulates in fissures on the skin, so it is necessary to apply enough product to fill in the fissures and to fully cover epidermal ridges [32]. Most consumers apply sunscreen below the standard thickness used for the international SPF test, which is 2 mg/cm2 [1]. Consumers apply between 0.5 and 1.2 mg/cm2 sunscreen and consequently do not receive the expected amount of sun protection. The actual SPF of the sunscreen can be decreased by 20-50% compared to the rated SPF when it is applied improperly [19, 27, 32]. The reduction of actual SPF as a function of application thickness was recently demonstrated during a study in which Chinese women applied SPF 4,15, 30, or 55 sunscreen at 0.5, 1, 1.5, or 2 mg/cm2 . The actual SPF was calculated for each individual after exposure to solar simulated UVR. It was determined that at the standard application thickness of 2 mg/cm2 the observed SPF was similar to the rated SPF. However, as application thickness decreased there was an observed linear decrease in actual SPF for SPF 4 and 15 sunscreens, and an exponential decrease in the actual SPF for the SPF 30 and 55 sunscreens [27]. Inadequate application of lower SPF sunscreens may put consumers at greater risk of sunburn and skin cancer than inadequate application of higher SPF sunscreens.

been in a tanning bed [19]. The age at which people start using indoor tanning technolo‐ gies is a risk factor for developing skin cancer as well. The lifetime risk of developing melanoma is 75% higher in people who first use indoor tanning beds before the age of 35 [35]. Younger people have a greater tendency to use indoor tanning devices, possibly because of the social perception that having a tan is attractive. More people between the ages of 18-24 used indoor tanning devices than people over the age of 25 in 2010. In both age groups, females exposed themselves to artificial UVR to obtain a tan more than males did. Most of these adults were non-Hispanic whites [25]. The high skin cancer risk associated with indoor tanning coupled with the addictiveness of the behavior has caused many states in the U.S. to pass laws restricting the use of indoor tanning devices by minors in 2012 [19].

Skin Cancer Prevention Strategies http://dx.doi.org/10.5772/55241 217

Consumers should be aware of their skin's reaction to sunlight when they are outdoors, and take appropriate action when noticing adverse reactions to sun exposure. Regardless of sunscreen application and whether sun exposure is intentional or unintentional, if the skin becomes red (indicative of cellular damage) and uncomfortable at any time it is prudent to immediately find shade and put on protective clothing [26]. Parents should be vigilant of signs of redness in their childrens' skin as well. Infants and children should be kept in the shade out of direct sunlight [2]. Self-examination of skin for suspicious growths and nevi is also recom‐

Chemoprevention is the use of natural or synthetic agents to prevent or reverse the develop‐ ment of cancer [21]. Sunscreen use is considered a form of chemoprevention because it contains compounds, such as avobenzone and octyl salicylate, that inhibit UVR from damaging the skin. Supplementation of sunscreens with various phytochemicals and antioxidants has been shown to improve the function of sunscreens in preventing photodamage [13]. Oral intake of certain vitamins, antioxidants, and plant extracts can provide systemic protection as well.

A diet rich in fruits and vegetables has generally been associated with lowering the risk of a variety of diseases and cancers, including skin cancer. Regular consumption of fruits and vegetables was associated with a decreased risk of SCC in a dietary study of 1360 adults in Nambour, Australia. In this study it was also found that a diet high in meat and fat was positively associated with the development of SCC but not BCC [36]. Fruits and vegeta‐ bles contain bioactive phytochemicals, such as flavonoids, polyphenols and carotenoids. These compounds can boost antioxidant and immune system defenses in the body, including in the skin [37]. Carotenoids and flavonoids naturally protect plants from solar UVR, and consumption of these phytochemicals can provide systemic photoprotection for humans [8]. Polyphenols from tea have been shown to protect against UVB-induced contact sensitization, inflammation, carcinogen-induced cancer of the skin, lung, and esophagus in

mended for early detection of skin cancer [2, 17].

rodent models [37].

**phytochemicals, and vitamin supplementation**

**5. Chemoprevention with topical and dietary antioxidants,**

To compensate for inadequate application thickness, the American Academy of Dermatol‐ ogy recommends using a minimum of SPF 30 sunscreen, which is higher than the FDA's recommendation of 15. High SPF sunscreen should especially be used when going outdoors on days when the UV index is predicted to be high and there is greater risk of overexpo‐ sure. Spending even 45 minutes outdoors unprotected on a day of moderate UV index value can cause skin damage [33]. One application of sunscreen may not be enough if an individual stays outdoors for long periods of time and/or is involved in activities that cause the skin to perspire or get wet.

Proper use of sunscreen includes reapplication every two hours, and more frequently when sweating, swimming, or towel drying [24]. It is important to reapply sunscreen because the active components may become unstable and lose activity during exposure to sunlight [27]. The FDA does not currently require a photostability test for sunscreens [1]. The duration of water resistance is limited, so water resistant sunscreens need to be reapplied frequently when swimming or sweating [24]. It is required by USFDA monograph that the duration of water resistance (40 or 80 minutes) be indicated on the label to instruct consumers about when they should reapply the sunscreen [1]. Spray on sunscreen is thought to be less effective than traditional sunscreens because it is not rubbed directly onto the skin. The FDA is currently investigating the effectiveness of spray on sunscreens, and is performing inhalation safety testing as well [24].

Indoor tanning is a popular alternative to natural tanning because it can be done at any time of the year, but it is actually very dangerous because the skin is intentionally exposed to intense UVR repeatedly over short periods of time. Tanning bulbs emit predominantly UVA, which is known to cause high levels of oxidative stress in the skin and contribute to greater risk of melanoma [26]. They also emit a small amount of UVB that primarily damages the DNA in skin cells during indoor tanning sessions. Artificial UVR from indoor tanning equipment is considered to be carcinogenic along with solar UVR, yet approximate‐ ly 28 million people expose themselves to it annually in the United States [34].The likelihood of developing SCC is 2.5 times greater for people who use tanning beds, and the likeli‐ hood of developing BCC is 1.5 times greater [35].  The age at which people start using indoor tanning technolo‐ gies is a risk factor for developing skin cancer as well. The lifetime risk of developing melanoma is 75% higher in people who first use indoor tanning beds before the age of 35 [35]. Younger people have a greater tendency to use indoor tanning devices, possibly because of the social perception that having a tan is attractive. More people between the ages of 18-24 used indoor tanning devices than people over the age of 25 in 2010. In both age groups, females exposed themselves to artificial UVR to obtain a tan more than males did. Most of these adults were non-Hispanic whites [25]. The high skin cancer risk associated with indoor tanning coupled with the addictiveness of the behavior has caused many states in the U.S. to pass laws restricting the use of indoor tanning devices by minors in 2012 [19].

mg/cm2 [1]. Consumers apply between 0.5 and 1.2 mg/cm2

application of higher SPF sunscreens.

the skin to perspire or get wet.

testing as well [24].

2 mg/cm2

216 Highlights in Skin Cancer

receive the expected amount of sun protection. The actual SPF of the sunscreen can be decreased by 20-50% compared to the rated SPF when it is applied improperly [19, 27, 32]. The reduction of actual SPF as a function of application thickness was recently demonstrated during a study in which Chinese women applied SPF 4,15, 30, or 55 sunscreen at 0.5, 1, 1.5, or

SPF was similar to the rated SPF. However, as application thickness decreased there was an observed linear decrease in actual SPF for SPF 4 and 15 sunscreens, and an exponential decrease in the actual SPF for the SPF 30 and 55 sunscreens [27]. Inadequate application of lower SPF sunscreens may put consumers at greater risk of sunburn and skin cancer than inadequate

To compensate for inadequate application thickness, the American Academy of Dermatol‐ ogy recommends using a minimum of SPF 30 sunscreen, which is higher than the FDA's recommendation of 15. High SPF sunscreen should especially be used when going outdoors on days when the UV index is predicted to be high and there is greater risk of overexpo‐ sure. Spending even 45 minutes outdoors unprotected on a day of moderate UV index value can cause skin damage [33]. One application of sunscreen may not be enough if an individual stays outdoors for long periods of time and/or is involved in activities that cause

Proper use of sunscreen includes reapplication every two hours, and more frequently when sweating, swimming, or towel drying [24]. It is important to reapply sunscreen because the active components may become unstable and lose activity during exposure to sunlight [27]. The FDA does not currently require a photostability test for sunscreens [1]. The duration of water resistance is limited, so water resistant sunscreens need to be reapplied frequently when swimming or sweating [24]. It is required by USFDA monograph that the duration of water resistance (40 or 80 minutes) be indicated on the label to instruct consumers about when they should reapply the sunscreen [1]. Spray on sunscreen is thought to be less effective than traditional sunscreens because it is not rubbed directly onto the skin. The FDA is currently investigating the effectiveness of spray on sunscreens, and is performing inhalation safety

Indoor tanning is a popular alternative to natural tanning because it can be done at any time of the year, but it is actually very dangerous because the skin is intentionally exposed to intense UVR repeatedly over short periods of time. Tanning bulbs emit predominantly UVA, which is known to cause high levels of oxidative stress in the skin and contribute to greater risk of melanoma [26]. They also emit a small amount of UVB that primarily damages the DNA in skin cells during indoor tanning sessions. Artificial UVR from indoor tanning equipment is considered to be carcinogenic along with solar UVR, yet approximate‐ ly 28 million people expose themselves to it annually in the United States [34].The likelihood of developing SCC is 2.5 times greater for people who use tanning beds, and the likeli‐ hood of developing BCC is 1.5 times greater [35].  It was determined that at the standard application thickness of 2 mg/cm2

. The actual SPF was calculated for each individual after exposure to solar simulated

sunscreen and consequently do not

the observed

Consumers should be aware of their skin's reaction to sunlight when they are outdoors, and take appropriate action when noticing adverse reactions to sun exposure. Regardless of sunscreen application and whether sun exposure is intentional or unintentional, if the skin becomes red (indicative of cellular damage) and uncomfortable at any time it is prudent to immediately find shade and put on protective clothing [26]. Parents should be vigilant of signs of redness in their childrens' skin as well. Infants and children should be kept in the shade out of direct sunlight [2]. Self-examination of skin for suspicious growths and nevi is also recom‐ mended for early detection of skin cancer [2, 17].


Perspective Chapter: Optimal Analysis for the Correlation between Vibration and Temperature through an Intelligent Sensor/Transducer Based in Amorphous Nanostructures to Measure Vibrating Surfaces Temperature

*Jesús Alan Calderón Chavarri, Julio César Tafur Sotelo, Eliseo Benjamín Barriga Gamarra, John Hugo Lozano Jáuregui, Dante Jim Randal Gallo Torres, Rodrigo Alonso Urbizagástegui Tena, Jaime Eduardo Zeña Delgado and Christian Enrique Gózar Pastor*


**Appendix A**

Subgroups of WHS chosen for climate communication recognition scheme *Climate Footprints of Heritage Tourism* (some sites are included in more than one subgroup):

### (a) **Carbon Footprint Analysis**

### (b) **Sites with Narrative Potential**

### (c) **Sites Pursuing Sustainability Practices**

### (d) **Sites Most Impacted by Climate Change (Current and Projected)**


**4.5. GLUT4 signalling and cell biology**

GLUT4 contains unique sorting motifs at its N-terminus (FQQI) and C-terminus (dileucine) are critical for its capability to traffic between specific intracellular compartments and translocate to theplasma membrane in response todifferent stimuli.Insulin andexercise are able to rapidly and acutely stimulate GLUT4 translocation to the plasma membrane and thereby influence glucose uptake in muscle and adipose tissue via distinct signalling mechanisms. Activation of the insulin receptor (IR) leads to its autophosphorylation and subsequent signalling through the insulin receptor substrate proteins (IRS) and recruitment of PI 3-kinase catalyzes the formation of phosphatidylinositol (3,4,5)-3-phosphate (PIP3). PIP3 itself activates the protein kinase Akt via two intermediate protein kinases, PDK1 andRictor/ mTOR. Akt2 ratherthan the Akt1 or Akt3 isoforms appears to control GLUT4 trafficking. With the identification of the Akt substrates TBC1D4 (AS160), and more recently TBC1D1, two GTPase activating proteins have been identified that appearto bridge the gap between insulin-signalling and trafficking events. For TBC1D4 the substrate is the rab GTPase rab10 which has been shown to be required for insulin-stimulated translocation of GLUT4 vesicles to the plasma membrane.

Exercise has also been shown to induce TBC1D4 phosphorylation but apparently via a distinct PI3-kinase independent mechanism that requires activation of AMPK. However, simultaneous disruption of AMPK and Akt failed to completely inhibit contraction-induced AS160 phos‐ phorylation hinting towards alternative signalling events leading to GLUT4 translocation. A PI 3-kinase-independent pathway has been proposed that involves the adaptor molecules APS and CAP that bind to the insulin receptor and recruit c-Cbl. C-Cbl signals to the guanine nucleotide exchange factor C3G which activates the small GTP binding protein TC10. How‐ ever, recent data indicated a rather minor contribution for this pathway in insulin mediated GLUT4 translocation.

## *4.5.1. GLUT4 physiology*