Detecting phasic lapses in alertness using pupillometric measures.

Small, nonreflexive pupillary changes are robust physiological indicators of cognitive activity. In the present paper, we examined whether measures of pupillary changes could be used to detect phasic lapses in alertness during a vigilance task. A polynomial curve-fitting method for quantifying parameters from single task-evoked pupillary responses (TEPRs) is described. The TEPR parameters associated with long latency responses (indicating low alertness) were compared to the TEPR parameters associated with normal latency responses (indicating an alert state) within a multilevel modeling framework. Three parameters, pupil diameter, linear pupil dilation rate and curvilinear pupil dilation rate, significantly differed between the long latency and normal latency response types. The results provide preliminary evidence that these parameters would be useful neurocognitive markers of operator state in a bio-behavioral alertness monitoring system.

Cognition, blinks, eye-movements, and pupillary movements during performance of a running memory task.

INTRODUCTION: Blinks, saccades, and pupil diameter changes are studied for their application as tools to unobtrusively monitor aspects of performance. METHODS: Subjects performed a running memory task for a 60-min period. To evaluate changes in the relationship of blinks to saccades as a function of time on task, the ratio of blinks occurring with and without saccade was calculated for the second following stimulus termination plus the last 0.2 s of stimulus presentation, and also the second preceding stimulus onset plus the initial 0.2 s of stimulus presentation. Changes in pupil diameter following blinks with and without saccades were measured at the beginning, middle, and late in the experiment. RESULTS: Blink frequency increased during both periods as a function of time on task (p < 0.0001). The ratio of blinks concurrent with saccades during the post-stimulus period increased as a function of time on task (p < 0.0001). Pupil diameter increased following blink termination (p < 0.05), regardless of time on task, blink duration, or the presence of a saccade during the blink. CONCLUSION: Our results suggest that the increase in blinking associated with saccades as a function of time on task, and the pupillary dilation following a blink are associated with aspects of information processing. These results provide a framework for future studies assessing higher-order cognitive function in operational environments based on measurements of blink, pupil, and saccades.