International Journal of Computer Science Issues

More than a traditional journal...

The functional properties and topographic distribution of eventrelated potential (ERP) components elicited by simultaneously music sound and picture discrimination were investigated. Simultaneous audio-visual stimulus in the oddball paradigm was used to re-examine the MMN occurrence in auditory, visual and audiovisual modalities. This study was designed to investigate whether task-related processing of visual and auditory features was independent or task-related processing in one modality might influence the processing of the other. The grand-average deviant-related components producing deviant-related negativities (DRNs) divided into and early DRN1 around 100- 200 ms and late DRN2 around 200-300 ms. Two ERP components were found: MMN associated with DRN1, and N2b associated with DRN2. MMN and N2b were more negative when a stimulus was a target, showing the selection negativity effect. Feature-specific effects on component amplitude or topography varied by component. ANOVA shows that the interaction between electrode site and modality of MMN amplitudes at 100- 200 ms was statistically significant. The difference waves with 100-200 ms latency at the anterior sites were markedly different to the posterior sites. In visual modality, there was no MMN elicitation in the posterior sites compared to the auditory and audiovisual modalities. The emergence of posterior negativity (MMN) in the present study is thus not to be attributed to visual discrimination process. These data provide topographic evidence that ERP components in the 100-300 ms time domain can be differentiated on the basis to proceeding of specific stimuli features, and reflect neurophysiologically distinct auditory and visual pathways in the human cortex.