Electrical stimulation of the pontine omnipause area inhibits eye blink.

BACKGROUND

Single-unit recordings of pontine omnipause neurons (OPN) in the monkey have shown that these neurons cease firing for saccades in all directions. OPNs are located in pontine nucleus raphe' interpositus and are known to inhibit a variety of target neurons, including saccadic burst neurons. Recently, a single-unit investigation of these same OPNs revealed that they pause for blinks as well as saccades. Electrical microstimulation of the OPN area has been shown to inhibit saccadic eye movements in all directions. The present study is designed to determine if OPN area microstimulation inhibits blinks as well as saccades.

METHODS

Two rhesus monkeys were trained to track visual targets for a reward. Eye and lid position were measured using the electromagnetic search coil technique. The pontine OPN area was located using single-unit recording and microstimulation techniques. OPN stimulation was delivered just before and during the presentation of air puffs to elicit blinks.

RESULTS

OPN are microstimulation inhibited air puff-induced blinks as well as saccades. The threshold current for inhibiting blinks was generally slightly higher than for inhibiting saccades.

CONCLUSIONS

Although OPN area stimulation inhibits blinks as well as saccades, the mechanisms for inhibiting these behaviors appears to be different. OPNs are known to inhibit saccadic burst neurons, but there is no evidence that these neurons inhibit orbicularis oculi motoneurons which burst for blinks. Moreover, the temporal pattern of OPN activity makes it unlikely that they directly suppress blinks. The OPN region appears to be important for eye retraction during blinks and may be associated with other pontine areas which control blinks.