Reduced integrity of the left arcuate fasciculus is specifically associated with auditory verbal hallucinations in schizophrenia

Abstract

BACKGROUND: Schizophrenia patients with auditory verbal hallucinations (AVH) have reduced structural integrity in the left arcuate fasciculus (AFL) compared to healthy controls. However, it is neither known whether these changes are specific to AVH, as opposed to hallucinations or schizophrenia per se, nor how radial and/or axial diffusivity are altered. This study aimed to test the hypothesis that reductions to the structural integrity of the AFL are specifically associated with AVH in schizophrenia. METHOD: Diffusion tensor imaging scans and clinical data were obtained from the Australian Schizophrenia Research Bank for 39 schizophrenia patients with lifetime AVH (18 current, 21 remitted), 74 schizophrenia patients with no lifetime AVH (40 with lifetime hallucinations in other modalities, 34 no lifetime hallucinations) and 40 healthy controls. RESULTS: Fractional anisotropy was significantly reduced in the AFL of patients with lifetime AVH compared to both healthy controls (Cohen's d=1.24) and patients without lifetime AVH (d=.72), including compared to the specific subsets of patients without AVH who either had hallucinations in other modalities (d=.69) or no history of any hallucinations (d=.73). Radial, but not axial, diffusivity was significantly increased in patients with lifetime AVH compared to both healthy controls (d=.89) and patients without lifetime AVH (d=.39). Evidence was found for a non-linear relation between fractional anisotropy in the AFL and state AVH. CONCLUSION: Reduced integrity of the AFL is specifically associated with AVH, as opposed to schizophrenia in general or hallucinations in other modalities. Increased radial diffusivity suggests dysmyelination or demyelination of the AFL may play a role in AVH.