Symposium: Fast dynamic encoding of the sound landscape: regularities, deviance and categories
Thursday, Sep 10, 2015
Evoked gamma band and microsaccadic responses indicate fast deviance detection and sound categorization
1Cognitive and Biological Psychology, University of Leipzig, Leipzig, Germany
2Experimental and Biological Psychology, University of Potsdam, Potsdam, Germany
A key function of predictive processing is the fast deviance detection and stimulus categorization in complex and dynamic environments in order to quickly adapt behavior. With an audio-visual symbol-to-sound matching and with an auditory oddball paradigm we aimed to benchmark how fast auditory deviance detection and sound categorization can be performed using EEG and eye-movements. In the symbol-to-sound matching paradigm participants are presented with visual patterns predicting corresponding sound patterns and asked to detect incongruent symbol-sound pairs. We found an enhanced evoked gamma-band response to congruent compared to incongruent symbol-sound pairs peaking 42 ms after sound onset presumably reflecting the successful matching of expectation and sensory input. Furthermore, we observed a sharp increase in rightward saccades at 118 ms presumably indicating the overt allocation of visual attention to the subsequent visual symbol. A congruent-incongruent categorization was, thus, established already 80-100 ms after sound onset. These findings were corroborated by microsaccade rates measured in the active and passive oddball paradigm. In the three-tone oddball paradigm a significant difference between microsaccade rates in target vs. standard and target vs. distractor trials was observed 120 ms after sound onset. In the passive oddball paradigm saccade inhibition in response to novel but not to standard sounds was observed as early as 65-80 ms. Our results demonstrate that predictive processing allows the fast detection of a violation of the expected input 40-60 ms and sound categorization as early as 80-100 ms after sound onset. This is considerably faster than assumed previously on the basis of electrophysiological data.