Objectives: We aimed to investigate morphometric correlates of auditory hallucinations in bipolar disorder (BD) by comparing cortical thickness and cortical surface area in bipolar disorder patients with (BD+) and without (BD-) a lifetime history of auditory hallucinations. Based on previous findings in schizophrenia patients, we hypothesized that the cortex would be thinner in the auditory cortex in BD+ compared to BD-.
Methods: Bipolar disorder spectrum (n = 157) patients and healthy controls (n = 279) underwent 1.5T magnetic resonance imaging (MRI) scanning. Hypothesis-driven analyses of cortical thickness and surface area in regions of the auditory cortex (Heschl's gyrus [HG], planum temporale and superior temporal gyrus) were conducted comparing BD+ (n = 49) and BD- (n = 108) using linear regression models, covaried for age and sex. Furthermore, we explored vertex-wise group differences in thickness and surface area across the whole cerebral cortex.
Results: Hypothesis-driven analyses:BD+ had significantly thicker cortex in the left HG compared to BD- (B = 0.128, P = .0046). The finding was not explained by duration of illness, global functioning, bipolar subtype, IQ or use of antipsychotic, antidepressant or antiepileptic medication, or by lithium. Exploratory analyses: A small region of thicker cortex in BD+ compared to BD- was seen in the left superior parietal lobule (false discovery rate <0.05). There were no significant group differences in cortical surface area.
Conclusion: A lifetime history of auditory hallucinations in BD was associated with cortical thickness alterations in both the left HG and the superior parietal lobule. Contrary to our hypothesis, BD+ showed thicker, rather than thinner cortex compared to BD-. Replications in independent samples are needed.
Keywords: auditory cortex; freesurfer; magnetic resonance imaging; psychosis; superior parietal lobule; surface area.
© 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.