The semantic representation of social groups and its neural substrate

Neuropsychological studies described brain damaged patients with a deficit at recognizing exemplars from some semantic categories while being still able to recognize exemplars from other categories, and vice versa. This evidence suggested that categories such as animals, plants, artifacts and conspecifics might be independently organized in the brain. Several theories tried to explain the category specificity, and proposed that concepts are represented in the brain according to the modality of their features, on the relevance of a domain for survival or on the degree of inter-correlation between features. Perhaps one limitation on investigation on how categories are represented in the brain has to do with the poor characterization of the concept about conspecifics often limited to famous and familiar persons as unique entities, and as such not very comparable with the other categories of stimuli. Recent findings suggested that even the knowledge about categories of conspecifics defined as social groups might well be represented independently of other categories.In the current thesis I investigated whether social group knowledge is indeed represented independently of other categories, consistently with previous findings, and the eventual neural substrates of such knowledge. In two different studies, I tested the knowledge of patients with brain tumors and neurodegenerative diseases about social groups, animate and inanimate entities. Correlating patients\u2019 behavioural performance with structural MRI data, I found that the lesion of a left-lateralized set of areas was selectively associated with the impairment in naming social group pictures. Specifically, inferior frontal gyrus, insula and anterior temporal cortex were associated with social group processing in both the studies. Since these areas were reported to be involved in emotional processing, In a third study with healthy individuals, I tested whether one of the above brain regions, within the opercular part of inferior frontal gyrus, might be involved in processing social groups per se or in processing the valence of stimuli. Results revealed that this area was involved in the processing of negative stimuli and suggested that the semantic impairment in processing social groups might be related to the intrinsic emotional value of this category of stimuli. This pattern of findings suggests that human conceptual knowledge is associated with modality-specific processing areas, and that social group representation might interacts with emotional features

Is the representation about social groups distinct from that of other concepts? A neuropsychological study

Traditionally neuropsychological observations have constrained the view that semantic knowledge is organized in categories: animals, plants or tools (Warrington & Shallice, 1984; Caramazza & Shelton, 1998; Tyler & Moss, 2001). Recently it has suggested that social groups, defined as categories of individuals that share category-relevant characteristics and/or features (Mason & Macrae, 2004),could have a representation of their own. Rumiati et al. (2014) documented double dissociations on word sorting tasks between living things, non-living things and social groups in patients with primary dementia. Consistently with this neuropsychological finding, a neuroimaging study showed that, relatively to non-social concepts, concepts about social groups activated the medial prefrontal cortex, posterior cingulate, and the temporo-parietal junction (Contreras et al., 2012). In the present study we tested whether social groups, such as “Muslims” or “fat people”, are represented independently of the other concepts and, if so, what are their brain correlates. Twenty-nine patients with temporal and frontal brain tumors, either in the left or right hemisphere, and 19 healthy controls matched for age and education (all p> .05) were tested on three tasks (picture naming, word-to-picture-matching, and picture sorting) using stimuli that belonged to three categories: living things (animals and plants, N=15), non-living things (artifacts, N=15) and social groups (N=15). The stimuli belonging to the three categories were matched for letter length and frequency (all p> .05). Results showed that left-brain tumor patients (lBTP) were found to be worse than both healthy controls (HC) and right-brain tumor patients (rBTP) on naming non-living things (p<.05) and social groups (p<.01). lBTP performed significantly worse on naming non-living things than living things and social groups, while rBTP performed as well as healthy controls. Moreover lBTP made significantly more semantic errors and circumlocutions only with social groups category than rBTP who, in turn, made more visual errors. All the patients performed at ceiling level on both the word-to-picture-matching and picture sorting tasks. Voxel-based lesion-symptom mapping (VLSM) revealed that lesions involving the left inferior frontal gyrus led to a selective impairment in naming living things, lesions of the inferior temporal cortex led to a selective impairment in naming non-living things, and lesions of the area between the left inferior and middle frontal gyri led to a selective deficit in naming social groups. Thus the lesion analysis confirms that the social groups are represented independently of other concepts. Moreover, the brain regions, that when damaged give rise to a deficit in naming social groups, are comparable to those found activated in imaging findings dealing with social stereotypes

The Neural Signatures of Shame, Embarrassment, and Guilt: A Voxel-Based Meta-Analysis on Functional Neuroimaging Studies

Self-conscious emotions, such as shame and guilt, play a fundamental role in regulating moral behaviour and in promoting the welfare of society. Despite their relevance, the neural bases of these emotions are uncertain. In the present meta-analysis, we performed a systematic literature review in order to single out functional neuroimaging studies on healthy individuals specifically investigating the neural substrates of shame, embarrassment, and guilt. Seventeen studies investigating the neural correlates of shame/embarrassment and seventeen studies investigating guilt brain representation met our inclusion criteria. The analyses revealed that both guilt and shame/embarrassment were associated with the activation of the left anterior insula, involved in emotional awareness processing and arousal. Guilt-specific areas were located within the left temporo-parietal junction, which is thought to be involved in social cognitive processes. Moreover, specific activations for shame/embarrassment involved areas related to social pain (dorsal anterior cingulate and thalamus) and behavioural inhibition (premotor cortex) networks. This pattern of results might reflect the distinct action tendencies associated with the two emotions

Impaired processing of conspecifics in Parkinson's disease

Experimental evidence indicates that the inferior frontal gyrus (IFG) processes emotional/affective features crucial to elaborate knowledge about social groups and that knowledge of social concepts is stored in the anterior temporal lobe (ATL). We investigated whether knowledge about social groups is impaired in Parkinson's disease (PD), in which dysfunctional connectivity between IFG and ATL has been demonstrated. PD patients (N = 20) and healthy controls (HC, N = 16) were given a lexical decision task in a semantic priming paradigm: the prime-targets included 144 words and 144 pseudowords, each preceded by three types of prime ("animals," "things," "persons"). Out of these 288 prime-targets, forty-eight were congruent (same category) and 96 incongruent (different category). Out of 48 congruent prime-targets, 24 denoted social items and 24 nonsocial items. Thus, four types of trials were obtained: congruent social; congruent nonsocial; incongruent social; incongruent nonsocial. Congruent target-words were recognized better than incongruent target-words by all groups. The semantic priming effect was preserved in PD; however, accuracy was significantly lower in PD than in HC in social items. No difference emerged between the two groups in nonsocial items. Impaired processing of words denoting social groups in PD may be due to impairment in accessing the affective/emotional features that characterize conceptual knowledge of social groups, for the functional disconnection between the IFG and the ATL

The neural network associated with lexical-semantic knowledge about social groups.

A person can be appraised as an individual or as a member of a social group. In the present study we tested whether the knowledge about social groups is represented independently of the living and non-living things. Patients with frontal and temporal lobe tumors involving either the left or the right hemisphere performed three tasks - picture naming, word-to-picture matching and picture sorting - tapping the lexical semantic knowledge of living things, non-living things and social groups. Both behavioral and voxel-based lesion-symptom mapping (VLSM) analyses suggested that social groups might be represented differently from other categories. VLSM analysis carried out on naming errors revealed that left-lateralized lesions in the inferior frontal gyrus, amygdala, insula and basal ganglia were associated with the lexical-semantic processing of social groups. These findings indicate that the social group representation may rely on areas associated with affective processing