Aims/Background:
The aim of this study was to apply established psychoacoustic and functional magnetic resonance imaging (fMRI) techniques to examine the neuroanatomical basis of auditory temporal processing deficits in schizophrenia. Previously, we showed reduced sensitivity to auditory temporal stimulation using fMRI and psychoacoustic responses to variations in sinusoidally amplitude-modulated noise (SAM). The present study extends these previous findings by examining the extent to which reduced sensitivity to SAM stimulation reflects anatomically specific changes in auditory cortical activity.
Methods:
Eighteen individuals meeting diagnostic criteria for schizophrenia and 18 controls participated in separate psychoacoustic and fMRI sessions. Region-of-interest analyses were conducted using cytoachitec-turally defined anatomical probability maps of primary and secondary auditory cortex. Parametric modulation of auditory BOLD responses was performed using each individual's psychoacoustic SAM detection thresholds for bandpass noise stimuli (0–6 kHz) for 7 SAM rates (4, 8, 16, 32, 64, 128 and 256 Hz).
Results:
ROI-based analyses showed that BOLD responses to SAM stimulation were primarily confined to increased activity in transverse temporal gyrus and planum temporal. Analysis of individual sensitivity to SAM rate showed that BOLD responses in anterior-lateral auditory regions showed a significant quadratic function of SAM thresholds. Further, reduced BOLD activity in schizophrenia was evidenced as reduced auditory responses in the same anterior-lateral regions.
Conclusions:
The results suggest that reductions in sensitivity to auditory temporal stimulation in schizophrenia may reflect changes in cytoarchitecturally distinct regions of primary auditory cortex (te1.2). These findings are discussed in terms of the possible neural mechanisms underlying auditory temporal processing deficits in schizophrenia.
