Neuroesthetics

Neuroesthetics (or neuroaesthetics) is a relatively recent sub-discipline of empirical aesthetics. Empirical aesthetics takes a scientific approach to the study of aesthetic perceptions of art and music. Neuroesthetics received its formal definition in 2002 as the scientific study of the neural bases for the contemplation and creation of a work of art. Neuroesthetics uses the techniques of neuroscience in order to explain and understand the aesthetic experiences at the neurological level. The topic attracts scholars from many disciplines including neuroscientists, art historians, artists, and psychologists.

Overview
Neuroesthetics is an attempt to combine neurological research with aesthetics by investigating the experience of beauty and appreciation of art on the level of brain functions and mental states. The recently developed field seeks the neural correlates of artistic judgment and artistic creation. It is widely accepted that visual aesthetics, namingly the capacity of assigning different degrees of beauty to certain forms, colors, or movements, is a human trait acquired after the divergence of human and age lineages. The theory of art can be broken down into distinct components. The logic of art is often discussed in terms of whether it is guided by a set of universal laws or principles. Additionally, the evolutionary rationale for the formation and characteristics of these principles are sought. Tying in the human experience, the determination of specific brain circuitry involved can help pinpoint the origin of the human response through the use of brain imaging in experimentation.

Approaches of Study
Researchers who have been prominent in the field combine principles from perceptual psychology, evolutionary biology, neurological deficits and functional brain anatomy in order to address the evolutionary meaning of beauty that may be the essence of art. It is felt that neuroscience is a very promising path for the search for the quantified evaluation of art.

With the aim of discovering general rules about aesthetics, one approach is the observation of subjects viewing art and the exploration of the mechanics of vision. This popular approach was championed by the prominent neuroscientist Semir Zeki. It is proposed that pleasing sensations are derived from the repeated activation of neurons due to primitive visual stimuli such as horizontal and vertical lines. In addition to the generation of theories to explain this, such as Ramachandran's set of laws, it is important to use neuroscience to determine and understand the neurological mechanisms involved.

The link between specific brain areas and artistic activity is of great importance to the field of neuroesthetics. This can be applied both to the ability to create and interpret art. A common approach to uncover the neural mechanisms is through the study of individuals, specifically artists, with neural disorders such as savant syndrome or some form of traumatic injury. The analysis of art created by these patients provide valuable insights to the brain areas responsible for capturing the essence of art.

The aesthetic enjoyment of individuals can be investigated using brain imaging experiments. When subjects are confronted with images of a particular level of aesthetics, the specific brain areas that are activated can be identified. It is argued that the sense of beauty and aesthetic judgment presupposes a change in the activation of the brain's reward system.

A crucial aspect of research lies in whether aesthetic judgment can be thought of as a bottom-up process driven by neural primitives or as a top-down process with high level cognition. Neurologists have had success researching primitives. However, there is a need to define higher level abstract philosophical concepts objectively with neural correlates. It is suggested that aesthetic experience is a function of the interaction between top-down, intentional orientation of attention and the bottom-up perceptual facilitation of image construction. In other words, because untrained persons automatically apply the object-identification habit to viewing artworks, top-down control to reduce this habit may be necessary to engage aesthetic perception. This suggests that artists would show different levels of activation that non-artists.

Aesthetic responses to different types of art and techniques has recently been explored. Cubism is the most radical departure from Western forms of art, with the proposed purpose of forcing the viewer to discover less unstable elements of the object to be represented. It eliminates interferences such as lighting and perspective angle to capture objects as they really are. This may be compared to how the brain maintains an object's identity despite varying conditions. Modern, representational, and impressionistic art has also been studied for the purpose of explaining visual processing systems. Yet aesthetic judgments exists in all domains, not just art.

Theories of Pioneers
=== Semir Zeki's Laws of the Visual Brain  ===

Semir Zeki is a professor of Neuroesthetics at the University College of London. He sees the viewing of art as an example of the variability of the brain. Thus a neurological approach to the source of this variability may explain particular subjective experiences as well as the ranges of abilities to create and experience art. Zeki theorizes that artists unconsciously use techniques to create visual art to study the brain. Zeki suggests that "...the artist is in a sense, a neuroscientist, exploring the potentials and capacities of the brain, though with different tools. How such creations can arouse aesthetic experiences can only be fully understood in neural terms. Such an understanding is now well within our reach."  He proposes two supreme laws of the visual brain.

Constancy
Despite the changes that occur when processing visual stimuli (distance, viewing angle, illumination, etc.), the brain has the unique ability to retain knowledge of constant and essential properties of an object and discard irrelevant dynamic properties. This applies not only to the ability to always see a banana as the color yellow but also the recognition of faces at varying angles. Much of this neural functioning has been attributed to the visual areas of the brain specifically the V1 cortex and specialized groups of cells which fire for a specific orientation stimulus.

Comparatively, a work of art captures the essence of an object. The creation of art itself may be modeled off of this primitive neural function. The process of painting for example involves distilling an object down to represent it as it really is, which differs from the way the eyes see it. Zeki also tried to represent the Platonic Ideal and the Hegalian Concept through the statement: forms do not have an existence without a brain and the ability for stored memory, referring to how artists such as Monet could paint without knowing what the objects in order to capture their true form.

Abstraction
This process refers to the hierarchical coordination where a general representation can be applied to many particulars, allowing the brain to efficiently process visual stimuli. The ability to abstract may have evolved as a necessity due to the limitations of memory. In a way, art externalizes the functions of abstraction in the brain. The process of abstraction is unknown to cognitive neurobiologist. However, Zeki proposes an interesting question of whether there is a significant difference in the pattern of brain activity when viewing abstract art as opposed to representational art.

Ramachandran's Eight Laws of Artistic Experience
Vilayanur S. Ramachandran and his fellow researchers including William Hirstein, developed a popular theory of human artistic experience and the neural mechanisms that mediate it. They propose a set of heuristics that artists either consciously or unconsciously utilize to optimally stimulate the visual ares of the brain. These laws combine to develop underlying high order concepts of the human artistic experience. Although not all encompassing as there are undoubtedly many other principles of artistic experience, they provide a framework for understanding aspects of visual art, aesthetics and design. Testing of these principles quantitatively can provide future evidence for specific areas of the brain responsible for aesthetic appeal.

Peak Shift Principle
This psychological phenomenon is typically known for its application in animal discrimination learning. In the peak shift effect, animals sometimes respond more strongly to exaggerated versions of the training stimuli. For instance, a rat is trained to discriminate a square from a rectangle by being rewarded for recognizing the rectangle. The rat will respond more frequently to the object for which it is being rewarded to the point that a rat will respond to rectangle that is longer and skinner with a higher frequency than the original of which is was trained. This is called a super stimulus. The fact that the rat is responding more to a 'super' rectangle implies that it is learning a rule.

This effect can be applied to human pattern recognition and aesthetic preference. Artists attempt to capture the very essence of something in order to evoke a direct emotional response. In other words, they try to make a 'super' rectangle to get the viewer to have a higher frequency response. To capture the essence of something, an artist amplifies the differences of that object, or what makes it unique, to highlight the essential features and reduce redundant information. This process mimics what the visual areas of the brain have evolved to do and more powerfully activates the same neural mechanisms that were originally activated by the original object.

Artists deliberately exaggerate shading, highlights, illumination, etc to an extent that would never occur in a real image to produce a caricature. However, at some times many artists may be unconsciously producing heightened activity in the specific areas of the brain in a manner that is not obvious to the conscious mind. Currently, it is unknown how the visual pathways account for this.

Isolation
Isolating a single visual cue helps the organism allocate attention to the output of a single module thereby allowing it to more effectively enjoy the peak shift along the dimensions represented in that module. In other words, there is a need to isolate the desired visual form before that aspect is amplified. This is why an outline drawing or sketch is sometimes more effective as art than an original color photograph. For example, a cartoonist may exaggerate certain facial features which are unique to the character and remove other forms which it shares such as skin tones. This efficiency prevents non-unique features from detracting from the image. This is why one can predict that an outline drawing would be more aesthetically pleasing than a color photograph.

The viewers attention is drawn towards this single area allowing one's attention to be focused on this source of information. Enhancements introduced by the artist more carefully noted resulting in the amplification of limbic system activation and reinforcement.

Grouping
Perceptual grouping to delineate a figure from the background may be enjoyable. The source of the pleasure may have come about because of the evolutionary necessity to give organisms an incentive to uncover objects, such as predators, from noisy environments. For example, when viewing ink blots, the visual system segments the scene to defeat camouflage and link a subset of splotches together. This may be accomplished most effectively if limbic reinforcement is fed back to early vision at every stage of visual processing leading up to the discovery of the object. The key idea is that due to the limited attentional resources, constant feedback facilitates processing of features at earlier stages due to the discovery of a clue which produces limbic activation to draw one's attention to important features. Though not spontaneous, this reinforcement is the source of the pleasant sensation. The discovery of the object itself results in a pleasant 'aha' revelation causing the organism to hold onto the image.

An artist can make use of this phenomenon by teasing the system. This allows for temporary binding to be communicated by a signal to the limbic system for reinforcement which is a source of the aesthetic experience.

Contrast
Extracting contrast involves eliminating redundant information and focusing attention. Cells in the retina, the lateral ginculate body or relay station in the brain, and in the visual cortex respond predominantly to step changes in luminance rather than homogeneous surface colors. Smooth gradients are much harder for the visual system to detect rather than segmented divisions of shades resulting in easily detectable edges. Contrasts due to the formation of edges may be pleasing to the eye. The importance of the visual neuron's varying responses to the orientation and presence of edges has previously been proven by David H. Hubel and Torsten Wiesel. This may hold evolutionary significance since regions of contrast are information rich requiring reinforcement and the allocation of attention. In contrast to the principle of grouping, contrasting features are typically in close proximity eliminating the need to link distant, but similar features.

Perceptual Problem Solving
Tied to the detection of contrast and grouping is the concept that discovery of an object after a struggle is more pleasing than one which is instantaneously obvious. The mechanism ensures that the struggle is reinforcing so that the viewer continues to look until the discovery. From a survival point of view, this may be important for the continued search for predators. Ramachrandran suggests for the same reason that a model whose hips and breasts are about to be revealed is more provocative than one who is already completely naked. A meaning that is implied is more alluring than one that is explicit.

The Generic Viewpoint
The visual system dislikes interpretations which rely on a unique vantage point. Rather it accepts the visual interpretation for which there is an infinite set of viewpoints that could produce the class of retinal images. For example in a landscape image, it will interpret that an object in the foreground is overlapping an object in the background instead of assuming that the background figure has a piece missing. In theory, if an artist is trying to please the eye, they should avoid such coincidences. However, in certain applications, the violation of this principle can also produce a pleasing effect.

Visual Metaphors
Ramachandran defines a metaphor as a mental tunnel between two concepts that appear grossly dissimilar on the surface, but instead share a deeper connection. Similar to the effects of perceptual problem solving, grasping an analogy is rewarding. It enables the viewer to highlight crucial aspects that the two objects share. Although it is unsure whether the reason for this mechanism is for effective communication or purely cognitive, the discovery of similarities between superficially dissimilar events leads to activation of the limbic system to create a rewarding process.

Support for this view is highlighted by the symptoms of Capgras delusion, where sufferers experience reduced facial recognition due to impairments in the connections from the inferotemporal cortex to the amygdala, which is responsible for emotions. The result is that a person no longer experiences the warm fuzzy feeling when presented with a familiar face. A person's 'glow' is lost through what is suggested as due to the lack of limbic activation.

Symmetry
The aesthetic appeal of symmetry is easily understandable. Biologically it is important during the detection of a predator, location of prey, and the choosing of a mate as all of these tend to display symmetry in nature. It complements other principles relating to the discovering of information rich objects. Additionally, evolutionary biologists suggest that the predisposition towards symmetry is because biologically, asymmetry is associated with infection and disease, which can lead to poor mate selection.

Areas of the Brain Linked to the Processing of Visual Aesthetics
Aesthetic perception relies heavily on the processing by the visual centers in the brain such as the V1 cortex. Signals from V1 are distributed to various specialized areas of the brain. There is no single area where all specialized visual circuitry connect, reducing the chances of determining a single neural center responsible for aesthetics, rather a neural network is more likely. Therefore, the visual brain consists of several parallel multistage processing systems, each specialized in a given task such as color or motion. Functional specializations of the visual brain are already known.

Physiological phenomenon can explain several aspects of art appreciation. Different extrastriate areas of the visual cortex may have evolved to extract correlations of different visual features. The discovery and linking of various visual stimuli is facilitated and reinforced by direct connections from these areas to limbic structures. Additionally, art my be most appealing if it produces heightened activity in a single dimension rather than redundant activation of multiple modules, restricted by the allocation of attentional resources. In experimentation to determine specific areas, many researchers allow the viewer to decide the aesthetic appeal prior the use of imaging techniques to account for the varying perceptions of beauty. When individuals contemplate the aesthetic appeal, different neural processes are engaged than when pragmatically viewing an image. However, processes of object identification and aesthetic judgment are involved simultaneously in the overall perception of aesthetics.

Prefrontal Cortex
The prefrontal cortex is previously known for its roles in the perception of colored objects, decision making, and memory. Recent studies have also linked it to the conscious aesthetic experience because it is activated during aesthetic tasks such as determining the appeal of a visual stimuli. This may be because a judgment is needed, requiring visiospatial memory. In a study performed by Zeki and Kawabata, it was found that the orbito-frontal cortex (OFC) is involved in the judgment of whether a painting is beautiful or not. There is high activation in this region when a person views paintings which they consider beautiful. Surprisingly, when a person views a painting which they consider ugly, no separate structures are activated. Therefore, it is proposed that changes in the intensity of activation in the orbito-frontal cortex correlate with the determination of beauty (higher activation) or ugliness (lower activation). Additionally, the medial OFC has been found to respond aesthetics in terms of the context of which it is presented, such as text or other descriptions about the artwork. The current evidence linking the OFC to attributed hedonistic values across gustatory, olfactory, and visual modalities, suggests that the OFC is a common center for the assessment of a stimulus's value. The perception of aesthetics for these areas must be due to the activation of the brain's reward system with a certain intensity.

Additionally, the prefrontal dorsalateral cortex (PDC) is selectively activated only by stimuli considered beautiful whereas prefrontal activity as a whole is activated during the judgment of both pleasing and unpleasing stimuli. The prefrontal cortex may be generally activated for directing the attention of the cognitive and perceptual mechanisms towards aesthetic perception in viewers untrained in visual arts. In other words, related directly to a person viewing art from an aesthetic perception due to the top-down control of their cognition. The lateral prefrontal cortex is shown to be linked to higher order self-referential procession and the evaluation of internally generated information. The left lateral PFC, Brodmann area 10, may be involved in maintaining attention on the execution of internally generated goals associated with approaching art from an aesthetic orientation. As previously mentioned, directing of attention towards aesthetics may have evolutionary significance.

Additional Areas
Emotions play a large role in aesthetic processing. Experiments designed specifically to force the subjects to view the artwork subjectively (by inquiring of its aesthetic appeal) rather than simply with the visual systems, revealed a higher activation in the brain's emotional circuitry. Results from these experiments revealed high activation in the bilateral insula which can be attributed to the emotional experience of viewing art. This correlates with other known emotional roles of the insula. However, the correlation between the insula's varying states of activation and positive or negative emotions in this context is unknown. The emotional view of art can be contrasted with perception related to object recognition when pragmatically viewing art. The right fusiform gyrus has been revealed to show activation to visual stimuli such as faces and representational art. This holds importance in the field because as Ramachandran also speculated, object recognition and the search for meaning can evoke a pleasant emotional response. The motor cortex was also shown to be involved in aesthetic perception. However, it displayed opposite trends of activation from the OFC. It may be a common correlate for the perception of emotionally charged stimuli despite its previously known roles. Several other areas of the brain were shown to be slightly activated during certain studies such as the anterior cingulate cortex, previously known for its involvement in the feeling of romance, and the left parietal cortex, whose purpose may be to direct spacial attention.

Different artistic styles may also be processed differently by the brain. In a study between filtered forms of abstract and representation art, the bilateral occipital gyri, left cingulate sulcus, and bilateral fusiform gyrus showed increased activation with increased preference when viewing art. However, activation in the bilateral occipital gyri may be caused by the large processing requirements placed on the visual system when viewing high levels of visual detail in artwork such as representational paintings. Several areas of the brain have been shown to respond particularly to forms representational art perhaps due to the brain's ability to make object associations and other functions relating to attention and memory. This form of stimuli leads to increased activation in the left frontal lobe and bilaterally in the parietal and limbic lobes. Also, the left superior parietal lobule, Brodmann's area 7, has been shown to play a role in active image construction during the viewing of art specifically containing indeterminate forms such as soft edge paintings. Bottom up processes such as edge detection and the exploration of visual stimuli are engaged during this type of aesthetic perception. These roles are consistent with previously known parietal lobe responsibilities in spatial cognition and visual imagery.

Criticism
There are several objections to researchers attempts to reduce aesthetic experience to a set of physical or neurological laws. It is questionable whether the theories can capture the evocativeness or originality of individual works of art. Experiments performed may not account for these theories directly. Also, current experimentation measures a person's verbal response to how they feel about art which is often selectively filtered. Ramachandran suggests the use of galvanic skin response to quantify the judgment associated viewing aesthetics. Overall, it can be argued that there is lack of proportion between the narrow approach to art taken by researchers versus the grand claims they make for their theories.

Future Directions & Related Fields
Since 2005 the notion of bridging brain science and the visual arts has blossomed into a field of increasing international interest. In his 2008 book, Neuroarthistory: from Aristotle and Pliny to Baxandall and Zeki, Professor John Onians of the University of East Anglia positions himself in the forefront of the field of neural scientific biased art historical research. Contemporary artists like Mark S. Smith (William Campbell Gallery, USA) and others have developed extensive bodies of work mapping the convergence of brain science and painting. Smith's work explores fundamental visual analogies between neural function and self-expression in abstract art. The past decade has also seen a corresponding growth in the aesthetics of music studied from neuroscientific approaches, with musician and cognitive neuroscientist Daniel Levitin of McGill University playing a dominant role. Psychological and social approaches to art help provide other theories of experience.

Steady advances in neuroimaging tools such as functional magnetic resonance imaging and in genetic analysis have contributed to advances in neuroesthetic knowledge. New experimental designs will account for the neural basis of aesthetic experience and creativity. Additional research on visual processing disorders effecting the perception of aesthetics such as savant syndrome and dementia may provide other valuable insights.