Altered corollary discharge in the auditory cortex could reflect louder inner voice experience in patients with verbal hallucinations, a pilot fMRI study

Introduction: Wide range of evidence associates auditory verbal hallucinations (AVH) with frontotemporal corollary discharge deficit. AVH likely reflect altered experiences of the inner voice and are phenomenologically diverse. The aspects of hallucinations (and related inner voice experiences) that could be explained by this deficit remain unclear. To address this important subject, we examined the temporal cortex activity during two tasks with and without corollary discharge. Methods: We carried out an event-related BOLD fMRI study to examine temporal cortex activity in seven patients and eight healthy controls during two tasks with and without corollary discharge: reading aloud and hearing, respectively. Data were denoised by removing independent components related to head movement and subsequently processed using finite impulse response basis function to address hemodynamic response variations. To mitigate the small sample size, final analyses were carried out using permutation-based analysis of variance. Results: There was a significant group interaction in the Read relative to Hear condition during the early poststimulus stage in the left Heschl's Gyrus (p < 0.01, corrected for multiple comparisons, at peak voxel [-72,53,41]). This effect was driven by a higher activity in the Read relative to the Hear condition in the same area in the patients (p < 0.02, corrected). Conclusions: Our results are consistent with prior literature indicating abnormal frontotemporal disconnection in participants with hallucinations. The functional repercussions of this deficit were limited to the primary auditory cortex in early post -stimulus stage, which suggests louder experience of the inner voice in patients and could account for the loudness of their hallucinations.