Mechanisms of generation of mismatch negativity and their role in the recognition of brief auditory stimuli.

The endogenous components of auditory evoked potentials were studied in the human brain, arising in conditions of voluntary and involuntary attention. Variation of the duration of acoustic stimuli led to a situation in which the generation of mismatch negativity was blocked. The recognition of acoustic stimuli was compared in conditions in which passive perception of the deviant signal in some cases evoked mismatch negativity and in others did not. This demonstrated the following: 1) stimuli not evoking mismatch negativity in the classical "oddball" paradigm can be recognized efficiently; 2) recognition of stimuli evoking mismatch negativity (in conditions of passive perception) occurs with a significantly shorter response time. The difference in the present experiments was 49-51 msec. There was also an increase in the proportion of correct responses to the deviant stimulus (to 92%). Thus, if the experimental conditions allow the mechanism generating mismatch negativity to trigger, then the response time to the actively perceived stimulus decreases. These results are evidence that the mechanisms of involuntary attention contribute to the active perception of acoustic stimuli.

[Mechanisms of generation of mismatch negativity and their role in discrimination of short acoustical stimuli]. / Mekhanizmy generatsii negativnosti rassoglasovaniia i ikh rol' pri raspoznavanii akusticheskikh stimulov korotkoi dlitel'nosti.

The effect of stimulus duration on the mismatch negativity in the auditory event-related potentials was used to study the role of mismatch negativity (MMN) in discrimination of short acoustical stimuli. We compared discrimination of different short acoustical stimuli in active variant of "odd ball" paradigm. It was shown that it is possible to discriminate between standard and deviant acoustical stimuli which do not produce MMN in passive condition. It makes possible to estimate behavioural significance of MMN in active discrimination task. If the MMN had not been recorded in passive condition, that leads to an increase of reaction time in active paradigm approximately by 50 ms.