TY - JOUR
T1 - A comparison of head-unrestrained and head-restrained pursuit
T2 - Influence of eye position and target velocity on latency
AU - Wellenius, Gregory A.
AU - Cullen, Kathleen E.
N1 - Funding Information:
This study was supported by the Medical Research Council of Canada (MRC) and by the Natural Science and Engineering Research Council of Canada (NSERC)
PY - 2000
Y1 - 2000
N2 - Horizontal step-ramp target trajectories were used to study the initiation of head-unrestrained and head-restrained pursuit in the monkey. In a first series of experiments, initial target position (0°, 5°, or 30°, contraversive to the direction of pursuit), fixation duration, target velocity (20°, 40°, 60° and 80°/s), and target direction were randomized in order to minimize predictive responses. Animals pursued the target either with their eyes alone (head-restrained: HR condition) or with a combination of eye and head movements (head-unrestrained: HU condition). Head motion onset consistently lagged pursuit onset (i.e., eye motion) by 50 ms or more in the HU condition, and was influenced by target velocity as well as by initial target position. Pursuit onset latencies did not vary systematically as a function of target velocity in either the HR or HU conditions. However, pursuit initiation latencies tended to be longer in the HU condition as compared to the HR condition when target motion started from the most contraversive position. A second series of experiments revealed that this difference in HR and HU pursuit onset latencies could be explained by the effects of initial eye-in-head position; more contraversive initial eye positions yielded shorter pursuit latencies in both conditions, and the monkeys generally moved their head towards the target in the HU condition, resulting in smaller eye-in-head eccentricities. Furthermore, we found that initial gaze and head positions had little or no effect on pursuit latencies. We conclude that the latency for pursuit initiation is similar irrespective of whether an animal is head-restrained or head-unrestrained, when initial eye position is held constant.
AB - Horizontal step-ramp target trajectories were used to study the initiation of head-unrestrained and head-restrained pursuit in the monkey. In a first series of experiments, initial target position (0°, 5°, or 30°, contraversive to the direction of pursuit), fixation duration, target velocity (20°, 40°, 60° and 80°/s), and target direction were randomized in order to minimize predictive responses. Animals pursued the target either with their eyes alone (head-restrained: HR condition) or with a combination of eye and head movements (head-unrestrained: HU condition). Head motion onset consistently lagged pursuit onset (i.e., eye motion) by 50 ms or more in the HU condition, and was influenced by target velocity as well as by initial target position. Pursuit onset latencies did not vary systematically as a function of target velocity in either the HR or HU conditions. However, pursuit initiation latencies tended to be longer in the HU condition as compared to the HR condition when target motion started from the most contraversive position. A second series of experiments revealed that this difference in HR and HU pursuit onset latencies could be explained by the effects of initial eye-in-head position; more contraversive initial eye positions yielded shorter pursuit latencies in both conditions, and the monkeys generally moved their head towards the target in the HU condition, resulting in smaller eye-in-head eccentricities. Furthermore, we found that initial gaze and head positions had little or no effect on pursuit latencies. We conclude that the latency for pursuit initiation is similar irrespective of whether an animal is head-restrained or head-unrestrained, when initial eye position is held constant.
KW - Eye movements
KW - Eye position
KW - Gaze
KW - Head movements
KW - Pursuit
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U2 - 10.1007/s002210000369
DO - 10.1007/s002210000369
M3 - Article
C2 - 10968215
AN - SCOPUS:0033923081
SN - 0014-4819
VL - 133
SP - 139
EP - 155
JO - Experimental Brain Research
JF - Experimental Brain Research
IS - 2
ER -