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The neural basis of social cognition in health and neuropsychological disorders

Book - Dissertation

Facial expressions are important for nonverbal communication and can display personal emotions and indicate an individual's intention within a social situation. The expression of emotion is known to enhance retention of facial identity. Relative little is known about the underlying neuropsychology and the link between emotional and social memory, an interaction known to be of pivotal importance for an individual's social interactions. The human brain has been found to possess multiple neuronal networks involved in managing the complex process of social interaction. This doctoral thesis includes a literature study and five research studies that are conducted in order to investigate the neural basis of social cognition. The first objective was to provide a better understanding of both facial and emotion recognition in subjects with different neurodegenerative disorders. The second objective was to explore the neural substrate of social and emotional memory. The third objective was to investigate the link between neurobiology and personality (brain-trait association). In addition, the role of the amygdala as possible key structure relevant for social cognition was studied and discussed. Chapter one is dedicated to a general introduction. In chapter two, the results are discussed of a systematic literature review to obtain a comprehensive overview of the current knowledge and the impact of neurodegeneration in the form of Frontotemporal Dementia (FTD) and Alzheimer's disease (AD) on facial expression recognition and the differential impact of FTD versus AD. The qualitative syntheses revealed that in both FTD and AD overall emotion recognition was most frequently impaired. The results of the meta-analyse support the general hypothesis, that FTD is characterized by impaired emotion recognition, in comparison to AD and healthy controls. In addition, AD patients perform significantly worse on the non-emotional control task. In the third chapter, we studied in more detail the impact of neurodegeneration in bvFTD on not only facial expression recognition but also on moral reasoning abnormalities. Our study revealed a more utilitarian response on low-conflict personal moral dilemmas in bvFTD and these responses were found to be associated with facial emotion recognition. At the neural level, abnormal moral cognition in bvFTD is related to structural integrity of the medial prefrontal cortex and functional characteristics of the anterior insula. The present findings provide a common basis for emotion recognition and moral reasoning and link them with areas in the default mode and salience network. In chapter four, we tested the predictive coding hypothesis for repetition suppression (RS) during social memory processing by investigating the interaction between RS and differences due to memory in category-selective cortex (FFA, pSTS, PPA, and RSC) and the amygdala. The results revealed that absolute RS during encoding interacts with probability of future remembrance in face-selective cortex, an opposite correlation was observed in the amygdala. The findings also reveal an association between adapter response and RS, both for short long-term (48h) intervals. Furthermore, we clinically validated the findings in developmental prosopagnosia, which shows consistent effects that are also associated with behavioural deficits. These combined findings are challenging for predictive coding models of visual memory and are more compatible with adapter-related and familiarity accounts. Chapter four emphasizes the importance of eye movements during face recognition (Supplementary Information), therefore, in chapter five we observed eye-scanning patterns for social and emotional memory. The results revealed enhanced memory for angry faces for young adults compared to older adults, consistent with the socioemotional selectivity theory. This effect was associated with a shorter fixation duration for angry faces compared to neutral faces in the older adults group. Furthermore, the results revealed that total fixation duration also was a strong predictor for face memory performance. To further improve our understanding of the 'social brain' we investigated the Brain-Trait association chapters six and seven. The results revealed a significant specific positive correlation between a region in the left thalamic pulvinar and 'novelty seeking', driven by the subscale impulsiveness. We further observed opposing associations in males and females between temperament brain associations, emphasizing the importance of the acknowledgement of the role of sex on structural neurobiology of personality. The results support the general hypothesis that individual personality differences reflect the structural differences observed in the brain. This doctoral thesis highlights that including social cognitive deficits, as emotion recognition, in neuropsychological criteria may improve the differential diagnosis of neurodegenerative disorders. The results further support the adapter-related and familiarity accounts of social memory, which was absent in developmental prosopagnosia. The main findings of this doctoral thesis are more in line with the psychological construction theory stating that the amygdala is involved in several aspects of emotion processing, including social processing. This leaves the question about the actual role of the amygdala in social cognition open for future study. In an extensive discussion, we elaborate on future prospects in early diagnosis and understanding disease onset and progression of different neuropsychological disorders.
Publication year:2022