Optokinetic nystagmus as an assessment of visual attention to divided stimuli

Attentional resources are finite and decline with age. We measured subjects' abilities to generate optokinetic nystagmus (OKN), to suppress it with fixation and to continue to suppress it when fixating while simultaneously paying covert attention to a feature of the optokinetic (OK) stimulus. During fixation with a red laser spot, OKN was almost fully suppressed. When subjects suppressed the OKN while simultaneously paying covert attention to a feature of the OK stimulus, suppression of the OKN was less well suppressed. The active OKN was vigorous. Age affected only the divided attention task, perhaps reflecting a diminution in resources of attention with age. The neural pathways serving attention and those serving eye movements appear to be closely related. We suggest the test presented here represents an objective measurement of the ability to divide attention, and that it has the potential to be developed for much more widespread, possibly clinical, use.