The Amygdala and the Relevance Detection Theory of Autism: An Evolutionary Perspective

In the last few decades, there has been increasing interest in the role of the amygdala in psychiatric disorders and in particular its contribution to the socio-emotional impairments in autism spectrum disorders (ASDs). Given that the amygdala is a component structure of the social brain, several theoretical explanations compatible with amygdala dysfunction have been proposed to account for socio-emotional impairments in ASDs, including abnormal eye contact, gaze monitoring, face processing, mental state understanding and empathy. Nevertheless, many theoretical accounts, based on the Amygdala Theory of Autism, fail to elucidate the complex pattern of impairments observed in this population, which extends beyond the social domain. As posited by the Relevance Detector theory (Sander, Grafman and Zalla, 2003), the human amygdala is a critical component of a brain circuit involved in the appraisal of self-relevant events that include, but are not restricted to, social stimuli. Here, we propose that the behavioral and social-emotional features of ASDs may be better understood in terms of a disruption in a ‘Relevance Detector Network’ affecting the processing of stimuli that are relevant for the organism’s self-regulating functions. In the present review, we will first summarize the main literature supporting the involvement of the amygdala in socio-emotional disturbances in ASDs. Next, we will present a revised version of the amygdala Relevance Detector hypothesis and we will show that this theoretical framework can provide a better understanding of the heterogeneity of the impairments and symptomatology of ASDs. Finally, we will discuss some predictions of our model, and suggest new directions in the investigation of the role of the amygdala within the more generally disrupted cortical connectivity framework as a model of neural organization of the autistic brain. <br/

Don’t be too strict with yourself! Rigid negative self-representation in healthy subjects mimics the neurocognitive profile of depression for autobiographical memory.

Autobiographical memory (AM) comprises representation of specific (episodic) and generic personal information (semantic). Depression is characterized by a shift from episodic to semantic AM retrieval (overgeneralization). Theoretical models have proposed that this effect could be linked to reduced executive resources. Moreover, overgeneral memories, accompanied by a negativity bias in depression, lead to a pervasive negative self-representation. Even in non clinical populations executive functions and AM specificity are closely linked, and overgeneral memories could result in depressive emotional responses. We made the hypothesis that healthy subjects showing a rigid negative self-image would mimic the neurocognitive profile of patients. We measured executive functions and the self-image in young healthy subjects, and recorded their brain activity, by means of fMRI, while they retrieved episodic AMs. We report that a more rigid negative self-image corresponds to lower executive functions and less vivid specific memories. Moreover, higher negative self-image is accompanied by attenuated activity in the left ventrolateral prefrontal and in the anterior cingulate cortex, that have been repeatedly shown to exhibit altered functionality in depression. Activity in these regions, on the contrary, positively correlates with executive and memories performances, in agreement with their role in executive functions and AM retrieval. We claim that rigid negative self-image could represent a marker or a vulnerability trait of depression that is linked to reduced executive functions efficiency and to episodic AM decline. Our results are encouraging for psychotherapeutic approaches promoting cognitive flexibility in depression and other psychiatric disorders

Episodic memory and self-reference via semantic autobiographical memory: insights from an fMRI study in younger and older adults

International audienceSelf-referential processing relies mainly on the medial prefrontal cortex (MPFC) and enhances memory encoding (i.e., Self-Reference Effect, SRE) as it improves the accuracy and richness of remembering in both young and older adults. However, studies on age-related changes in the neural correlates of the SRE on the subjective (i.e., autonoetic consciousness) and the objective (i.e., source memory) qualitative features of episodic memory are lacking. In the present fMRI study, we compared the effects of a self-related (semantic autobiographical memory task) and a non self-related (general semantic memory task) encoding condition on subsequent episodic memory retrieval. We investigated encoding-related activity during each condition in two groups of 19 younger and 16 older adults. Behaviorally, the SRE improved subjective memory performance in both groups but objective memory only in young adults. At the neural level, a direct comparison between self-related and non self-related conditions revealed that SRE mainly activated the cortical midline system, especially the MPFC, in both groups. Additionally, in older adults and regardless of the condition, greater activity was found in a fronto-parietal network. Overall, correlations were noted between source memory performance and activity in the MPFC (irrespective of age) and visual areas (mediated by age). Thus, the present findings expand evidence of the role of the MPFC in self-referential processing in the context of source memory benefit in both young and older adults using incidental encoding via semantic autobiographical memory. However, our finding suggests that its role is less effective in aging