Saccades in pursuit eye tracking reflect motor attention processes.

A dysfunction of pursuit eye tracking in psychiatric patients has been well documented, but its cause has not. Recent speculation implicates a pathological disinhibition of saccades in these patients. However, great variability in tracking performance was found among nine normal subjects, and tracking quality improved in each when asked to perform a simple analysis of the tracking target: saccade counts and amplitudes decreased, as did a root-mean-square (RMS) error measure of overall tracking performance. This improvement was as great at the end as at the beginning of the analysis condition, suggesting that the improvement is not due to increased attention to a novel task, but rather is the preferred mode of tracking automatically, while attending to target analysis. The anticipatory, purposive saccades produced in attending to the act of tracking thus can be studied as involuntary attention effects reflecting frontal lobe function, and used for diagnostic classification of attentional dysfunction.