Changes of middle latency somatosensory evoked potentials (SEPs) and alpha rythmicity associated with oculomotor processes

Objectives: To evaluate median nerve somatosensory evoked potentials (SEPs) and α waves during different eye conditions. Methods: Median SEPs and occipital electroencephalographs (EEG) were recorded in 6 eye conditions: eye-closed (EC), goggle (G), goggle+saccade (GS), saccade (S), eye-opened (EO) and pursuit (P), in 8 normal adults. Subjects saccaded their eyes reacting to auditory cues to watch a diode on the right or left side alternatively during the S condition, or imitated the same saccadic eye-movement as that in the S condition during the GS condition. In the P condition, subjects traced a small circle moving on a computer screen. Results: Compared with the EC and G conditions, N30 (P25-N30 or P14-N30) amplitudes in C4′ were significantly larger and the mean amplitude and power of the α band was significantly attenuated in the other 4 conditions. The amplitude and power of the α band differed significantly between the GS and S conditions, whereas N30 amplitudes were similar between the two conditions. N30-P45 or P45-N60 amplitudes in C4′ were significantly larger in the P condition than in other conditions. Conclusions: Present findings suggest that different neural mechanisms cause α blocking and the modification of middle latency SEPs associated with oculomotor control.