Nicotine and the hallucinating brain: effects on mismatch negativity (MMN) in schizophrenia

Elevated smoking rates have been noted in schizophrenia, and it has been hypothetically attributed to nicotine's ameliorating abnormal brain processes in this illness. There is some preliminary evidence that nicotine may alter pre-attentive auditory change detection, as indexed by the EEG-derived mismatch negativity (MMN), but no previous study has examined what role auditory verbal hallucinations (AVH) may have on these effects. The objective of this study was to examine MMN-indexed acoustic change detection in schizophrenia (SZ) following nicotine administration and elucidate its association with AVH. Using a modified multi-feature paradigm, MMNs to duration, frequency and intensity deviants were recorded in 12 schizophrenia outpatients (SZ) with persistent AVHs following nicotine (6mg) and placebo administration. Electrical activity was recorded from 32 scalp electrodes; MMN amplitudes and latencies for each deviant were compared between treatments and were correlated with trait (PSYRATS) and state measures of AVH severity and Positive and Negative Syndrome Scale (PANSS) ratings. Nicotine administration resulted in a shortened latency for intensity MMN. Additionally, nicotine-related change in MMN amplitude was correlated with nicotine-related change in subjective measures of hallucinatory state. In summary, nicotine did not affect MMN amplitudes in schizophrenia patients with persistent AVHs, however this study reports accelerated auditory change detection to intensity deviants with nicotine in this group. Additionally, nicotine appeared to induce a generalized activation of the auditory cortex in schizophrenia, resulting in a concurrent increase in intensity MMN amplitude and subjective clarity of AVHs.