Abstract
Auditory working memory impairments feature prominently in schizophrenia. However, the existence of altered and perhaps compensatory neural dynamics, sub-serving auditory working memory, remains largely unexplored. We compared the dynamics of induced high gamma power (iHGP) across cortex in humans during speech-sound working memory in individuals with schizophrenia (SZ) and healthy comparison subjects (HC) using magnetoencephalography (MEG). SZ showed similar task performance to HC while utilizing different brain regions. During encoding of speech sounds, SZ lacked the correlation of iHGP with task performance in posterior superior temporal gyrus (STGp) that was observed in healthy subjects. Instead, SZ recruited the visual word form area (VWFA) during both stimulus encoding and response preparation. Importantly, VWFA activity during encoding correlated with the magnitude of SZ hallucinations, task performance and an independent measure of verbal working memory. These findings suggest that VWFA plasticity is harnessed to compensate for STGp dysfunction in schizophrenia patients with hallucinations.
Highlights
Auditory working memory impairments feature prominently in schizophrenia
We have previously shown that when healthy subjects engage in an auditory speech reproduction task, induced high gamma power fluctuates across the dorsal speech stream in a spatially and temporally choreographed manner that correlates with performance[35]
We present evidence here of compensatory activation of the Visual Word Form Area (VWFA) in the left ventral visual stream during auditory working memory in patients with schizophrenia
Summary
Auditory working memory impairments feature prominently in schizophrenia. the existence of altered and perhaps compensatory neural dynamics, sub-serving auditory working memory, remains largely unexplored. VWFA activity during encoding correlated with the magnitude of SZ hallucinations, task performance and an independent measure of verbal working memory These findings suggest that VWFA plasticity is harnessed to compensate for STGp dysfunction in schizophrenia patients with hallucinations. Auditory hallucinations are associated with structural and functional abnormalities in temporal cortex/planum temporale[6,22,23,24,25,26,27,28] Despite these widely reported impairments in speech-sound representation that appear fundamental to the disease process, many patients with schizophrenia spectrum disorders perform at or above the level of matched healthy controls on auditory and language tasks, raising the possibility that compensatory pathways may have developed[29]. We hypothesized that in addition to dysfunctional activation patterns we would find evidence of facilitatory processes that may reflect compensation for underlying disease-related pathology in audio-motor speech areas
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