Simple somatosensory event related potentials and brain oscillatory responses

Aim: The aim of this study was to investigate oscillatory brain responses (delta, theta, alpha, beta) to non-painful tactile stimuli in oddball paradigm via electrophysiological methods.Methods: The measurements were performed with eighteen subjects (21.39+/-2.75 ages; 12 male). One type of tactile stimuli was applied to the two fingers on the right hand. The target (25%) stimuli were presented on index finger and nontarget stimuli (75%) were presented on middle finger randomly. Subjects counted the target stimuli mentally. The electroencephalogram (EEG) was recorded from 64 channels. Primarily 14 electrodes (F3,F4,FZ,CZ,C3,C4,T7,T8,P3,P4,P7,P8,O1,O2) were analyzed. The repeated measures ANOVA test was used for statistical analysis. In four frequency bands for each electrode location, beside the differences between responses to target and non-target stimuli, topological distribution of responses to target stimuli were evaluated.Results: When responses to target and non-target stimuli were compared, delta responses to target stimuli were significantly higher than nontarget stimuli at 11 eletrode locations ((Fz,F3,F4,Cz,C3,T7,P3,P4,P7,P8,O2); for each location, p<0.05). Theta responses to both stimuli for each electrode location were similar and consistent and had high amplitude. Alpha responses to both stimuli had higher amplitude at the frontal region and there was no significant difference between responses to both stimuli. In beta frequency band, responses to both stimuli were highly distributed on the scalp.When topographical distribution of the responses to target stimuli were evaluated; in all frequency bands, the central responses had the highest amplitude. The responses of the frontal and parietal regions followed the central region. When we compared left and right hemisphere topographically the delta responses of left central, frontal and temporal regions were higher than the contralateral ones (p<0.05).Conclusion: The result of the thesis indicated that oscillatory responses to target and non-target stimuli were observed at all scalp?s regions and were highly differentiable in some frequency bands. Selectively distributed responses elicited by simple stimuli supports the theory of ?whole-brain-work?. Results of this study may serve as a roadmap for future physiological and clinical applications.