EEG alpha rhythm, ocular activity and basal skin resistance.

Most hypotheses about the origin of the occipital alpha rhythm stress the specific influence of ocular activity.In this study, the influence of eye-movement frequency and extreme upward deviation of the eyeballs (enlarging the corneo-retinal potential) on occipital alpha activity and basal skin resistance is investigated. Eye-movement frequency did not significantly influence alpha activity and basal skin resistance. On the other hand, extreme upward deviation of the eyeball resulted in alpha activity enhancement and BSR increase. A white noise stimulus, given while the eyeballs were in an extreme upward position lead to a significant decrease in both alpha activity and BSR. However, the influence of the white noise condition was relatively larger on BSR than on alpha activity.The results of this study lead to the hypothesis that the extreme deviation of the eyeballs effects occipital alpha activity in two different ways; one is a direct influence from the eyes, along a low conductance pathway to the occipital region, according to Ennever; secondly, it is proposed that, during the extreme upward deviation of the eyeballs, inhibitory impulses from extra-ocular muscle receptors are sent down to the reticular formation leading to alpha activity increase (e.g. cortical arousal decrease).