Mental-task instructions and optokinetic nystagmus to the left and right

The frequency of elicited optokinetic nystagmus (OKN) in both directions was studied in subjects instructed to perform mental tasks thought to be asociated primarily with either the right or left hemisphere or a combination of both. A negative relationship between OKN frequency and right-hemisphere activity was more strongly confirmed than the alternative hypotheses that OKN frequency would be negatively related to the total amount of inner processing or to the amount of visualization required by a task. A significantly higher frequency of OKN was elicited (in nonmyopic subjects) when the stripes were moving in the direction contralateral to the hemisphere presumably involved in the instructed mental task. Subjects showing higher rates of right lateral eye shift (in an interview situation) made greater adjustments in OKN frequency according to the nature of the mental task.