Electrophysiological Assessment of Auditory Stimulus-Specific Plasticity in Schizophrenia

Background

Disrupted neuroplasticity may be an important aspect of the neural basis of schizophrenia. We used event-related brain potentials (ERPs) to assay neuroplasticity after auditory conditioning in chronic schizophrenia patients (SZ) and matched healthy control subjects (HC).

Methods

Subjects (15 HC, 14 SZ) performed an auditory oddball task during electroencephalogram recording before and after auditory tetanic stimulation (Pre/Post Blocks). Each oddball block consisted of 1000-Hz and 1500-Hz standards and 400-Hz targets. During tetanic conditioning, 1000-Hz tones were presented at 11 Hz for 2.4 min. We analyzed the standard trials, comparing the ERPs evoked by the tetanized stimuli (1000 Hz tones: TS+) and untetanized stimuli (1500 Hz tones: TS–) in the Post Blocks with ERPs from the Pre Blocks (averaged into Baseline ERPs).

Results

In Post Block 1 in HC, TS+ tones evoked a negative shift (60–350 msec) at right temporal electrodes relative to Baseline. No pre-/post-tetanus effects were found in SZ. In Post Block 2 in HC, TS+ tones evoked a positive shift (200–300 msec) at bilateral frontal electrodes. In SZ, TS+ tones evoked a positive shift (100–400 msec) at right frontotemporal electrodes. No pre-/post-tetanus effects were found in either subject group for the TS– tones. The right temporal Post Block 1 and 2 effects were correlated in SZ, suggesting a trade-off in the expression of these effects.

Conclusions

These results suggest that stimulus-specific auditory neuroplasticity is abnormal in schizophrenia. The electrophysiologic assessment of stimulus-specific plasticity may yield novel targets for drug treatment in schizophrenia.

Key Words:  Auditory processing , ERP , event-related brain potential , NMDA receptor , plasticity , schizophrenia