A tale of two hemispheres: Contrasting socioemotional dysfunction in right- versus left-lateralised semantic dementia

Abstract

OBJECTIVESemantic dementia, a subtype of frontotemporal lobar degeneration, is characterised by cross-modal loss of conceptual knowledge attributable to progressive degeneration of the left anterior temporal lobe. Much less is known regarding the clinical presentation of SD patients with predominantly right-lateralised atrophy. Recent reports emphasise marked socioemotional and behavioural disturbances in such cases. Given the importance of the right anterior temporal lobes in social cognition, we hypothesised that socioemotional functioning would be disproportionately affected in right versus left-lateralised SD cases.METHODSWe assessed well-characterised cases of predominantly right (n=10) and left (n=12) SD and 20 matched healthy controls on tests of emotion processing and interpersonal functioning.RESULTSRight SD cases showed disproportionate difficulties in the recognition of positive and negative facial emotions, specifically happiness and anger, compared with left SD cases. Deficits in anger recognition persisted in right SD despite covarying for facial and semantic processing. On a contextually rich task of emotion recognition using multimodal videos, no subgroup differences were evident. Finally, empathic concern was rated as significantly lower by caregivers of right versus left SD cases. Overall, the extent of socioemotional disturbance was associated with the degree of behavioural changes in SD.CONCLUSIONOur results reveal considerable overlap in the extent to which socioemotional processes are disrupted in left and right-lateralised cases of SD. Notably, however, right SD cases show disproportionate deficits for recognition of facial emotions and the capacity for empathic concern, supporting a specialised role for the right anterior temporal lobes in mediating these cognitive functions.

Differentiating between right-lateralised semantic dementia and behavioural-variant frontotemporal dementia: an examination of clinical characteristics and emotion processing

“…Our results indicate that the atypical (right-lateralised) presentation of SD is associated with marked alterations in complex emotion processing, at a similar level to that seen in bvFTD, which concords with the significant behavioural and interpersonal disturbances observed clinically in right SD and bvFTD 7 15. Notably, our results highlighted a subtle differentiation in emotion processing profiles; when determining if two faces expressed the same emotion, only patients with bvFTD were impaired, whereas when selecting a specific emotion from a series of distractor emotions, both groups showed comparable impairments.…”

“…Replication of our results in a larger patient cohort with neuropathological data is important for future studies. Further, it will be important to explore the potential differences in complex social cognitive processes such as interpersonal functioning and emotion reactivity, in which deficits have been previously documented in bvFTD15 and right SD7 separately. Consideration of additional socioemotional domains, such as theory of mind, may prove particularly insightful, given mounting evidence implicating the right anterior temporal lobe in this aspect of social cognition 16 35.…”

“…Emotion processing dysfunction is well documented in right SD2 7 and bvFTD,13 however, direct comparisons between these syndromes are scant. Of relevance here, recent studies suggest that aspects of socioemotional processing are differentially affected in bvFTD compared with the non-fluent variant of PPA,14 suggesting that different profiles may also exist between bvFTD and right SD.…”

Do I know you? Examining face and object memory in frontotemporal dementia

“…Clinically, right SD is often characterised by a change in behaviour and personality, with reports of prosopagnosia also common Josephs et al, 2009;Kamminga et al, in press;Snowden et al, 2004;Thompson et al, 2004). Although few studies have systematically examined episodic memory performance in right SD, some evidence suggests that non-verbal episodic memory and spatial navigation is compromised in this phenotype (Chan et al, 2009;Irish et al, 2013).…”

P2‐241: Focal Temporal Pole Atrophy and Network Degeneration in Semantic Variant Primary Progressive Aphasia

“…Additionally, some patients with semantic dementia ($30%) present initially with greater atrophy in the right anterior temporal lobe, and these patients often have greater social-emotional deficits along with prosopagnosia (Chan et al, 2009;Hodges et al, 2010;Irish et al, 2013). Patient-specific neurodevelopmental factors likely contribute to the selective vulnerability of neural regions and networks to progressive degeneration (Rogalski et al, 2008;Spreng et al, 2010;Miller et al, 2013), and may account for some of the variability observed in the atrophy patterns of patients with svPPA.…”