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Eye movements of hyperactive and normal boys were compared on a visual pursuit task in three experiments. In the first series of tests, irregular pursuit occurred more often in hyperactive than in normal boys. Hyperactive boys made more saccadic movements, their average saccades were larger, and they looked away from the pursuit path more frequently than the normal boys. In a second series of tests three years later, the differences between normal and hyperactive boys still existed. In a third set of experiments the effects of an attention task, different stimulus velocities and stimulant medication were studied in another group of control and hyperactive boys. With or without the attention task, hyperactive boys not receiving stimulant medication made more saccades than normal boys. Differences were greatest at lower target velocities and decreased at higher stimulus velocities. Differences between hyperactive and normal boys disappeared when the former received both stimulant medication and the attention task. The findings were the same in the two groups of hyperactive boys: they had more saccades superimposed on ocular pursuit than did normal boys. Differences between the groups may be related to their relative ability to attend to the target. The differences are of a magnitude that might make them useful as an adjunct for diagnosis of hyperactivity or for evaluating the effects of treatment.

We investigated the development of oculomotor activity in zebrafish embryos and larvae of ages 48-96 hrs postfertilization (hpf). The optokinetic response (OKR: smooth tracking movements evoked by a rotating striped drum) improved steadily after its onset at 73 hpf, and by 96 hpf had a achieved a gain (eye velocity/drum velocity) of 0.9, comparable to adult performance. Reset movements (the fast phase of optokinetic nystagmus) developed over 75-81 hpf. The vestibuloocular reflex (VOR: compensatory eye movements evoked by passive rotation of the head) developed over 74-81 hpf, and the associated reset movements, over 76-81 hpf. The VOR was qualitatively normal in dark-reared fish, which excludes an essential role for visual experience in its early development. Spontaneous saccadic movements (the fast shift of eye position) appeared between 81 and 96 hpf, and at 96 hpf had maximum velocities that were comparable to adults. These results are compared to, and found to be incompatible with, two earlier ideas of motor development: behavioral "differentiation" and "encephalization."

Previously we have measured rapid-velocity vergence responses to targets at different distances that provided no disparity or accommodative stimulation. To evaluate the possibility that this rapid-velocity vergence occurs during saccades, the latencies of eye movement between two long dim luminous rods were compared under two conditions. Rapid-velocity vergence with an average latency of approximately 300 ms was elicited when subjects alternately viewed horizontal rods at distances of 38 and 78 cm, and with a vertical separation of 5.2 degrees. Horizontal saccades with a comparable latency were measured when the rods were equidistant and oriented vertically. The correlation between the mean latencies of vergence and saccadic movements was 0.97, suggesting that the two movements occurred together. In a second experiment vergence responses were measured when the subject looked between a bright vertical line on a screen at 76 cm and a second pair of lines (vertically displaced between 0.15 degrees and 3 degrees) with crossed disparity to simulate a target at 38 cm. Slow-velocity vergence often occurred alone when the vertical separation between targets was small; rapid-velocity vergence intruded when the separation between the targets was larger. The results can be accounted for if proximity and disparity stimulation act through a single vergence controller, the output of which produces slow- or rapid-velocity vergence depending upon whether the saccadic system is concurrently active.

1. Eye movements were measured in monkeys trained for visual tracking. 2. In response to periodic square wave target movements, monkeys do not show a significant reduction in the latency of saccadic movements. 3. Under similar conditions, human beings subconsciously reduce their latency and after several cycles are in step with the target. 4. In response to sinusoidal targets, monkeys show a latency or phase lag which increases monotonically with frequency starting at 0·3 c/s. Human beings can remain in phase with the target at frequencies up to 1·0 c/s. 5. Hence, monkeys do not exhibit the human predictive tracking response.