The relationship of sensory processing and NMDA was also evaluated in a double-blind, randomized ketamine challenge experiment [12▪]. Eight healthy controls were tested on a self-monitoring task in which auditory feedback was experimentally modified during two functional MRI (fMRI) sessions. The auditory feedback was modified by a decrease in pitch of either the individual’s own or someone else’s voice. This experiment was intended to study higher level cognitive processing, for example, discerning self versus other in the context of auditory hallucinations, and the primary hypothesis was that ketamine would lead to increased misattribution of voice source, and increased lateral temporal activation. Individuals made more external misattribution errors during the ketamine infusion than placebo, and moreover, as hypothesized by the investigators, ketamine-induced misattributions were associated with relative increases in left superior temporal cortex and Heschel’s gyrus. Of note, the superior temporal gyrus is also important in basic sensory (pitch) processing, and, in addition to deficits in higher order cognitive processing, this study also supports the importance of sensory regions in schizophrenia.
