A high-field fMRI study of auditory mismatch processing in healthy volunteers: implications for auditory sensory memory dysfunction in schizophrenia

Smaller mismatch negativity (MMN) amplitude is one of the most reliable ERP findings in studies comparing patients with schizophrenia and healthy volunteers. Several fMRI studies have examined analogous BOLD responses using similar stimulus presentation methods (e.g. Schall et al., NeuroImage, 2003). Whilst all studies reported activation in the superior temporal plane, only a subset reported activation in lateral frontal cortical regions. The present study used a variant of the usual MMN duration deviant design to elicit mismatch-related activation using a 4T MRI scanner. Data were obtained from 12 healthy volunteers, (six male). Subjects watched a silent movie whilst they were presented with auditory stimuli (1000Hz, 90dB tones, SOA = 500ms) that varied in stimulus duration (standards: 50ms; deviants: 100ms). Three runs were presented, each comprising 111 volumes of whole brain EPI data (36 4mm-thick axial slices, TR=3000, TE=30, FOV=230x230mm, 64X64 matrix). Each run comprised a randomised series of short blocks, which were comprised of 4, 8 or 16 standards followed by either another standard or a longer duration deviant. Data were analysed using SPM2, using an event-related design. A contrast of BOLD responses elicited by deviants versus the terminal standards across the three conditions showed significant activation in a network that included the left and right superior frontal cortex, superior temporal cortex and right posterior cingulate. We also found a linear increase in BOLD activation for deviants preceded by 4, 8 or 16 standards in areas in the superior temporal and anterior cingulate gyri. Results will be discussed in relation to convergent data supporting the role of the frontal cortex in mismatch perception and involuntary orienting of attention