Poster #: 16
Topic: Clinical applications (incl. consciousness)
Wednesday, Sep 9, 2015
Complex pattern MMN to extra identical tones in schizophrenia
1Psychiatry, University of Pittsbirgh, Pittsburgh, PA, United States
Mismatch negativity (MMN) to simple stimulus parameter deviants is robustly reduced in schizophrenia. Stimulus-specific adaptation (SSA) models argue MMN is an epiphenomenal sensory effect because neurons adapt to repetitive tones. Hence deviant afferent activity is processed by non-adapted neurons, and MMN does not reflect deviation from a memory trace of past stimuli or a predictive model of stimulus patterns. The present experiment explored whether SSA was necessary to elicit MMN, and whether true novelty detection MMN was reduced in schizophrenia.
A single tone complex pattern paradigm used the Gestalt principle of proximity to form implicit groups of 5 stimuli (330 ms SOA, 800 ms ITI). Pattern models predict MMN will be elicited by an occasional 6th tone. SSA models predict no MMN, as the same tone would necessarily activate adapted neurons. Subjects passively underwent a pitch-deviant and duration-deviant simple MMN task and extra tone complex MMN task while actively watching a silent movie.
Simple MMN at FCz was significantly reduced in patients for pitch deviants (p<.05), and for duration deviants (p<.05). Analysis of activity to the complex pattern deviant revealed a large late MMN-like deviance-related negativity between 320 - 470 ms. This response was significantly reduced in schizophrenia (p <.01).
Simple MMN is reduced in schizophrenia. The complex pattern MMN occurs later, and is reduced in schizophrenia. True novelty detection as reflected in complex MMN is impaired in schizophrenia, and cannot reflect deficient SSA.