A comparative study of auditory and visual event related coherences

Abstract

The analysis of evoked and event related EEG Coherence gives important information on EEG changes in long distance connections in brain areas upon application of sensory/cognitive stimulations. The comparison of evoked/event related coherences of healthy subjects versus coherences in neuropsychiatric patients could be a new emerging method to understand brain pathologies. At the first step analyzes of evoked/event related coherences in healthy subjects are needed. The present study aims to fulfill this gap in the literature. 27 healthy subjects were included in this study. Simple visual and auditory stimulation and visual /auditory oddball paradigms were presented to the subjects during EEG recording. The coherence was analyzed for delta (1-3.5 Hz), theta (4-7.8 Hz), alpha (8-13.7 Hz), beta (14.6-30 Hz) and gamma (30-48 Hz) frequency ranges for (F3P3, F4-P4, F3-T7, F4-T8, F3-TP7, F4-TP8, F3-O1, F4-O2, C3-O1, C4-O2) electrode pairs. The repeated measures of ANOVA were used for statistical analysis. Event related delta, theta, alpha target coherence values were higher in the range of 25% -70% than the event related delta, theta, alpha non-target coherence values and as well evoked coherence values in both auditory and visual paradigms (pb0.05). No significant differences were recorded between target-nontarget and evoked coherence values in beta and gamma frequency ranges (pb0.05). Furthermore, evoked and event related coherence values in response to visual stimuli were higher than the evoked and event related coherence values in response to auditory stimuli (pb0.05). The results showed the existence of separate sensory and cognitive networks that are activated either on sensory or cognitive stimulation. These results may, in turn, serve in future to accomplish a more differentiated analysis in neuropsychiatric patients.