S. Ron et al., SACCADE VESTIBULOOCULAR REFLEX COOPERATION AND EYE HEAD UNCOUPLING DURING ORIENTATION TO FLASHED TARGET, Journal of physiology, 464, 1993, pp. 595-611
1. Eye-head co-ordination in the horizontal plane was studied in four
human subjects using two successive flashes in the same direction, eit
her increasing in eccentricity (IE), or decreasing in eccentricity (DE
). 2. Results showed that for both conditions, head movements preceded
eye movements and were typically longer or followed by a slow gaze mo
vement. This slow movement was due to a vestibulo-ocular reflex gain o
f less than one. Gaze accuracy was achieved by small head movement adj
ustments. 3. Gaze movement to an IE stimulus had a staircase pattern,
and to a DE stimulus, a pulse-step pattern or one gaze saccade to the
final flash eccentricity. 4. In some cases, however, in response to a
DE stimulus, the eye and head movements were directed to different dis
placements (dissociation); i.e. the head movement started towards the
first flash eccentricity with a concomitant eye saccade to the second
flash eccentricity. When this occurred, gaze movement did not resemble
a pulse-step pattern. 5. It is suggested that non-visually orienting
gaze is driven mainly by head movement. Eye and head movements can be
either tightly coupled or dissociated, depending on the stimulus patte
rn.