Abstract
Impaired analysis of signal conflict and congruence may contribute to diverse socio-emotional symptoms in frontotemporal dementias, however the underlying mechanisms have not been defined. Here we addressed this issue in patients with behavioural variant frontotemporal dementia (bvFTD; n = 19) and semantic dementia (SD; n = 10) relative to healthy older individuals (n = 20). We created auditory scenes in which semantic and emotional congruity of constituent sounds were independently probed; associated tasks controlled for auditory perceptual similarity, scene parsing and semantic competence. Neuroanatomical correlates of auditory congruity processing were assessed using voxel-based morphometry. Relative to healthy controls, both the bvFTD and SD groups had impaired semantic and emotional congruity processing (after taking auditory control task performance into account) and reduced affective integration of sounds into scenes. Grey matter correlates of auditory semantic congruity processing were identified in distributed regions encompassing prefrontal, parieto-temporal and insular areas and correlates of auditory emotional congruity in partly overlapping temporal, insular and striatal regions. Our findings suggest that decoding of auditory signal relatedness may probe a generic cognitive mechanism and neural architecture underpinning frontotemporal dementia syndromes.
Highlights
Natural sensory environments or scenes often convey a cacophonous mixture of signals
Overall pleasantness ratings of individual sounds did not differ significantly for either patient group versus healthy controls (bvFTD, β =0.08 [95% confidence interval (CI) -0.33 to 0.45, p>0.05]; semantic dementia (SD), β =0.44 [95% CI -0.10 to 1.00, p>0.05]) nor between patient groups (β =0.36 [95% CI -0.22 to 0.88, p>0.05]); inspection of individual sound pleasantness ratings suggests that affective valuation of particular constituent sounds was similar between participant groups; this factor is unlikely to have driven any group differences in the affective processing of sounds combined as scenes
We have shown that patients with behavioural variant frontotemporal dementia (bvFTD) and SD have impaired processing of semantic and emotional congruence in auditory scenes relative to healthy older individuals
Summary
Natural sensory environments or scenes often convey a cacophonous mixture of signals. Successful decoding of such scenes depends on resolution of the sensory mixture to enable a coherent behavioural and emotional response. Competing or conflicting signals present an important challenge to this enterprise. Accurate determination of signal similarities and congruence is essential to establish regularities in the environment that can guide future adaptive behaviours. Analysis of signal ‘relatedness’ (conflict versus congruence) and conflict resolution are integral to complex decision making and emotional responses, in social contexts
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