Poster B53, Sunday, March 26, 8:00 – 10:00 am, Pacific Concourse
Abnormal brain network activity underlying internal speech in schizophrenia
Nicole Sanford1,2, Todd Woodward1,2; 1University of British Columbia, 2BC Children's Hospital Research Institute
Introduction: Functional brain networks underlying internal thought have been implicated in schizophrenia, and particularly auditory hallucinations. However, comparing networks between different studies is imprecise. The present functional magnetic resonance imaging (fMRI) study used a multivariate approach to investigate task-correlated networks common to working memory and language tasks. We expected schizophrenia patients to exhibit abnormal brain activity underlying internal speech and rehearsal. Methods: Chronic schizophrenia patients, bipolar disorder patients, and healthy controls completed one of two tasks: (1) a thought-generation task (TGT), involving listening to or internally generating a definition, or (2) a working memory task (WM), involving remembering a letter string over a four-second delay or no delay. Constrained principal component analysis and mixed-model ANOVA were used to extract task-correlated networks and investigate effects of group, condition, and post-stimulus time. Results: Five networks were extracted. One included activations in dorsal anterior cingulate, insula, Broca’s area, and visual cortex, which responded during the delay phase of WM and thought generation in TGT. This network was inactive when effortful inner speech was not required. Recently-hallucinating schizophrenia patients exhibited hyper-suppression of this network between trials in TGT. Conclusions: Hyper-suppression of an internal speech-related network in hallucinating patients could reflect a neurological distinction between controlled internal speech and spontaneous hallucinatory voices, with the latter suppressing the former during reduced cognitive demand. A clinical implication is the possibility of diminishing hallucinations by strengthening this network through cognitive training. Consolidating studies allowed a direct evaluation of spatial and temporal replication of networks underlying the two tasks.
Topic Area: EXECUTIVE PROCESSES: Working memory