| Popis: |
Electrical stimulation of the supraorbital branch of the human facial nerve resulted in an oligosynaptic ipsilateral reflex (R1) and a polysynaptic bilateral late reflex (R2) of the orbicularis oculi muscle. Former studies had already reported different reaction patterns of R1 and R2 during mental tasks as well as during low-frequency stimulation. The present study was concerned with the possible difference in habituation of R1 and R2 under conditions with and without a mental task. The habituation paradigm was as follows: Ten control stimuli were presented at 1-min intervals. Identical stimuli were then given during a 30-min session at one of the following frequencies: 1/3.75 sec, 1/7.5 sec, 1/15 sec, 1/30 sec, and 1/60 sec, during which time subjects either had a continuous rest or performed a mental task. At the end of this session, the stimulation frequency changed to 1/3.75 sec. R1 increased during a mental task, whereas R2 was reduced. It was further concluded that R1 underwent more sensitization influences, as R2 showed more habituation, and that this divergence was due to differences in central neural pathways. |
