The role of the rostral prefrontal cortex in the context of the aesthetic experience

The evaluation of visual art involves sensory, emotional and cognitive processes that lead to an aesthetic judgement or an aesthetic emotion (e.g. beauty). Aesthetic experiences are multisensory processes that undergo a variety of stages. Early processes occur in the visual and sensory cortices, and are central to object identification that may be no different from visual experiences of everyday objects. Later processing stages are related to complex human thought consisting of emotion and cognition that involve areas such as the orbitofrontal cortex, hippocampus and prefrontal cortex (PFC). The later stages are concerned with the comprehension and meaningful analysis of the artwork that contribute to the formation of an aesthetic judgement or emotion.This thesis aims to investigate affective evaluations and their interactions with cognitive processes during the later processing stages of the aesthetic experience in the rostral prefrontal cortex (rPFC). The role of the rPFC will be explored using functional near-infrared spectroscopy (fNIRS) with reference to existing frameworks. Specifically: hemispheric asymmetry in the processing of emotional stimuli, the Gateway Hypothesis and the Default Mode Network will be explored.Experimental WorkA database of sixty images was created in an online survey (chapter 3) at the beginning of the experimental programme. Images were rated online (N = 1028) for complexity, comprehension, novelty, activation, attraction and valence providing stimuli that could be systematically manipulated according to their psychological properties in the experimental studies.The first hypothesis (is the rPFC involved in early perceptual processes such as complexity during aesthetic experience? ) was addressed in a pilot study (chapter 4) and repeated in the first experimental study (chapter 5). Both cognitive (high/low complexity) and emotional (positive/negative valence) aspects of the images were manipulated. Images were shown for sixty second and analysed in three time periods (early, middle and late) each consisting of twenty seconds. The results showed an interaction between valence and time with positive images yielding greater activation in the early period and negative images in the late period. This highlighted the importance of long exposure times to capture the aesthetic experience.The second hypothesis (is the rPFC involved in implicit memory formation such as the comprehension of an image during aesthetic experience) was investigated in chapter 6 where the levels of comprehension (high/low) and postive/negative valence associated with the viewed image were manipulated. An interaction between comprehension and valence was found with respect to rPFC activity. Positive easy to comprehend images and negative difficult to comprehend images yielded greater rPFC oxygenation. These findings indicated that the experience of pleasure in positive artworks and increased cognitive effort during the resolution of uncertainty or threat in negative artworks is related to rPFC activation.The third hypothesis (is the rPFC involved in prospective memory during aesthetic experience? ) was investigated in chapter 7 where positive and negative artworks were shown under two conditions. Condition one asked participants to introspect about their emotions and condition two to direct their attention to features in the image through a spot-the-difference task. A main effect of emotion was found, but no interaction or effect for condition. Greater rPFC activation was found during the contemplation of positive images. This may be attributed to pleasantness experienced in relation to these images.The last question (is the rPFC involved in self-referential processing and is this important to aesthetic experience? ) was investigated in chapter 8 where participants viewed negative and positive images under two viewing conditions. Condition one asked participants to introspect about their own emotions (Self) and condition two about the artist’s emotions at the time of painting (Other). The other-condition resulted in overall greater rPFC activation indicating that participants found it more challenging to think of another’s emotions. An interaction showed greater rPFC activation for positive images in the self -condition and greater activation for negative images in the other-condition. This may have been the result of a positive bias and the detection of self-relevance in positive images and the analysis of threat or uncertainty in negative images.ConclusionsThis thesis used a cognitive model of the aesthetic experience as a framework to understand the interaction between emotional and cognitive processes in the formation of an aesthetic judgement or emotion. No evidence for asymmetrical processing of emotional stimuli, or the Gateway Hypothesis was found. The research reported here indicates that the rPFC has an important role during the later processing stages of the aesthetic experience. Viewing negative visual art activated rPFC when the images were difficult to comprehend and when participants thought about the artist’s feelings. Positive emotions, on the other hand, activated rPFC when the images were easy to comprehend and when participants thought about their own feelings. The contemplation of visual art was continuously associated with medial rPFC activation, indicating that the rPFC has a key role in self-relevant processing of visual art. The rPFC may aid personal value judgements of visual art (e.g. this artwork means xyz to me) because this area of the brain mediates the interaction between self-relevance, autobiographical memories and continuously changing emotional states.