To understand the pathology of auditory verbal hallucination (AVH), we investigated 3 MRI indices: generalized fractional anisotropy (GFA) using diffusion spectrum imaging in the auditory radiation, gray matter volume (GMV) using T1-weighted images in Heschl’s gyrus (i.e., auditory cortex) and BOLD contrast estimates using task-fMRI in the auditory cortex. The BOLD relative to the GFA was significantly greater in controls than in patients with schizophrenia who had AVH. The GMV relative to the GFA also tended to show greater values in controls than in patients. An unregulated auditory sensation attributed to a dysfunction in the cortex might eventually encompass AVH.
Auditory verbal hallucination (AVH) is a devastating symptom of schizophrenia. We investigated alterations in the auditory system in AVH using 3 types of MRI technologies: diffusion spectrum imaging (DSI) for the auditory radiation (AR), T1-weighted image for gray matter volumes (GMV) in Heschl’s gyrus and fMRI for the estimations of functional activity in the auditory cortex (i.e., Heschl’s gyrus). Two hypotheses, which were mutually exclusive, were possible. One was a “fiber-first” hypothesis, supposing that an impairment in the AR would cause a reduction in the GMV in Heschl’s gyrus, and then result in aberrant activity in the auditory cortex. Previous studies appeared to support this hypothesis1-3. However, an opposite hypothesis was also possible, supposing that the dysfunction in the auditory cortex with a reduction of the GMV and the activity would cause a failure to control the AR, inducing AVH (“cortex-first” hypothesis).
[Subjects]
Four patients with schizophrenia who had AVH (age 25-54) (diagnosed with DSM-V) and age- and gender-matched 8 controls (age 25-51) participated in this study. The severity of patients’ AVH was measured using PSYRATS-J. The total scores ranged from 28 to 32 (out of 44 points).
[Imaging and Analysis]
We used 3-T MRI with a 32-ch head coil (GE Healthcare).
DSI was conducted using the following parameters: 56 axial slices interleaved, TR 8000, TE minimum, slice thickness 2.5 mm, FOV 200, 80 x 80, max b-value 4000 sec/mm and 102 directions (half sphere). We computed generalized fractional anisotropy (GFA) in the whole brain. An LDDMM algorithm generated a group template to transform the individual brains to the template brain and to extract fiber tracts4-5. In the auditory radiation, 25 out of 100 steps of the GFA adjacent to Heschl’s gyrus were averaged and used as the index of diffusion anisotropy.
T1-weighted images were taken by parameters of: 170 sagittal slices, TR 8.2, TE 3.2, FA 12, TI 450, slice thickness 1 mm, FOV 256 and 256 x 256. Images underwent segmentation into gray matter and other structures using a DARTEL algorithm in SPM12. Voxel values of normalized, modulated and smoothed gray matter images within Heschl’s gyrus were averaged to use as the index of GMV.
Two task-fMRI runs in a block design were conducted by the following parameters: 45 axial-coronal slices interleaved, TR 2000, TE 22, FA 90, slice thickness 3 mm, FOV 192, 64 x 64 and 136 volumes. Eight task and 9 fixation blocks occurred alternately (total 272 sec). One run conducted a narration listening task, whereas the other run conducted a button press task to auditory cues. We included both tasks into a design matrix using SPM12. Averages of contrast estimates (task greater than fixation) extracted from Heschl’s gyri were used as the index of activity (BOLD).
[Statistics]
We performed a 2-way ANOVA for each index (between factor: schizophrenia/controls, within factor: left/right). We employed generalized omega square to estimate the effect size (ES).