Pursuit differs from the vestibulo-ocular reflex, which only occurs during movements of the head and serves to stabilize gaze on a stationary object.
[2] During oculomotor experiments, it is often important to ensure that no saccades occurred when the subject was supposed to be smoothly pursuing a target.
Researchers are able to discard portions of eye movement recordings that contain saccades, in order to analyze the two components separately.
Saccadic eye movements differ from the smooth pursuit component by their very high initial acceleration and deceleration, and peak velocity.
Signals from the retina ascend through the lateral geniculate nucleus and activate neurons in primary visual cortex.
[5] Recent evidence suggests that the superior colliculus also responds during smooth pursuit eye movement.
Open-loop pursuit is the visual system's first response to a moving object we want to track and typically lasts ~100 ms.
[14] Under conditions in which there is no visual stimulation (in total darkness), we can still perform smooth pursuit eye movements with the help of a proprioceptive motion signal (e.g. your moving finger).
[16] Although we can clearly separate smooth pursuit from the vestibulo-ocular reflex, we can not always draw a clear separation between smooth pursuit and other tracking eye movements like the slow phase of the optokinetic nystagmus and the ocular following response (OFR), discovered in 1986 by Miles, Kawano, and Optican,[17] which is a transient ocular tracking response to full-field motion.
This impairment is correlated with less activation in areas known to play a role in pursuit, such as the frontal eye field.
[20] However, other studies have shown that people with schizophrenia show relatively normal pursuit, compared to controls, when tracking objects that move unexpectedly.
[21] This study speculates that smooth pursuit deficits in schizophrenia are a function of the patients' inability to store motion vectors.
Children with autism show reduced velocity of smooth pursuit compared to controls during ongoing tracking.
People with post traumatic stress disorder, with secondary psychotic symptoms, show pursuit deficits.
[24] "Lack of Smooth Pursuit" is a scorable clue on the NHTSA's standardized field sobriety tests.
Drugs causing lack of smooth pursuit include depressants, some inhalants, and dissociative anesthetics (such as phencyclidine or ketamine).