Neville Longbottom x Severus snape smut

Fourth part

The scientific attempts to map specific emotions onto underlying neural substrates dates back to the first half of the 20th century. Functional MRI experiments have revealed that the anterior insula in the brain is particularly active when experiencing disgust, when being exposed to offensive tastes, and when viewing facial expressions of disgust.[35] The research has supported that there are independent neural systems in the brain, each handling a specific basic emotion.[6] Specifically, f-MRI studies have provided evidence for the activation of the insula in disgust recognition, as well as visceral changes in disgust reactions such as the feeling of nausea.[6] The importance of disgust recognition and the visceral reaction of "feeling disgusted" is evident when considering the survival of organisms, and the evolutionary benefit of avoiding contamination.[6]

Insula
Edit

The insula of the left side, exposed by removing the opercula. From Henry Gray, Warren Harmon Lewis (1918). Anatomy of the Human Body. Fig. 731
The insula (or insular cortex), is the main neural structure involved in the emotion of disgust.[6][30][36] The insula has been shown by several studies to be the main neural correlate of the feeling of disgust both in humans and in macaque monkeys. The insula is activated by unpleasant tastes, smells, and the visual recognition of disgust in conspecific organisms.[6]

The anterior insula is an olfactory and gustatory center that controls visceral sensations and the related autonomic responses.[6] It also receives visual information from the anterior portion of the ventral superior temporal cortex, where cells have been found to respond to the sight of faces.[37]

The posterior insula is characterized by connections with auditory, somatosensory, and premotor areas, and is not related to the olfactory or gustatory modalities.[6]

The fact that the insula is necessary for our ability to feel and recognize the emotion of disgust is further supported by neuropsychological studies. Both Calder (2000) and Adolphs (2003) showed that lesions on the anterior insula lead to deficits in the experience of disgust and recognizing facial expressions of disgust in others.[36][38] The patients also reported having reduced sensations of disgust themselves. Furthermore, electrical stimulation of the anterior insula conducted during neurosurgery triggered nausea, the feeling of wanting to throw up and uneasiness in the stomach. Finally, electrically stimulating the anterior insula through implanted electrodes produced sensations in the throat and mouth that were "difficult to stand".[6] These findings demonstrate the role of the insula in transforming unpleasant sensory input into physiological reactions, and the associated feeling of disgust.[6]

Studies have demonstrated that the insula is activated by disgusting stimuli, and that observing someone else's facial expression of disgust seems to automatically retrieve a neural representation of disgust.[6][39] Furthermore, these findings emphasize the role of the insula in feelings of disgust.

One particular neuropsychological study focused on patient NK who was diagnosed with a left hemisphere infarction involving the insula, internal capsule, putamen and globus pallidus. NK's neural damage included the insula and putamen and it was found that NK's overall response to disgust-inducing stimuli was significantly lower than that of controls.[36] The patient showed a reduction in disgust-response on eight categories including food, animals, body products, envelope violation and death.[36] Moreover, NK incorrectly categorized disgust facial expressions as anger. The results of this study support the idea that NK had damage to a system involved in recognizing social signals of disgust, due to a damaged insula caused by neurodegeneration.[36]