When intense adapting lights are turned off, the pupil of the turtle, Pseudemys scripta elegans, enlarges. The recovery functions for pupillary dilation have different time constants that are defined by red- and green-sensitive cones and rods as they are affected by prior light adaptation and time in the dark. Pupillary area related to dilation responds over at least a three- to four-fold range. Following white-light adaptation, the course of pupil dilation in the dark shows a three-legged curve of differing time constants. With spectral-light adaptations, the contributions of separate classes of photoreceptors can be isolated. Red- and green-sensitive cones contribute shorter time constants of 3.31 and 3.65 min to prior white-light adaptation—4.81 and 4.18 min to prior spectral-light adaptations. Rods contribute a much longer time constant of 6.69 min to prior white-light adaptation—7.60 min to prior spectral-light adaptation. The ratios are in keeping with the flash sensitivities of photoreceptors in this same animal, as well as with psychophysical visual threshold mechanisms of color sensitivity.

The aim of the present study is to analyze how well physiological measures of sleepiness derived from pupillography and the Multiple Sleep Latency Test correlate with a subjective measure, the Stanford Sleepiness Scale (SSS) score. The results are based on data from 12 healthy participants, who underwent these tests every 2 hr from 7:00 a.m. until 11:00 p.m. Sleep latencies were correlated with four different variables derived from pupillography and the SSS score. The results indicate that the physiologically based variables correspond very well. This is reflected by similar patterns of time-of-day variations, a good agreement at the group level, and correlations at the individual level, whereas the SSS shows a quite different pattern of variation. The two physiological measures of sleepiness seem to reflect the same aspect of the level of tonic central nervous activation, which is not correlated with the subjective feeling of sleepiness.

Cognitive impairment in schizophrenia may be related to reduced availability of information-processing resources (resource limitations hypothesis). An abnormally accelerated age-related decline in processing resource availability may also occur in older patients with schizophrenia (neurodegeneration hypothesis). To test these hypotheses, pupillary responses were recorded as an index of processing resource availability during performance of the span of apprehension (SOA) task in 33 middle-aged and older patients with schizophrenia and 37 age-comparable nonpsychiatric participants. Consistent with the resource-limitations hypothesis, the patients with schizophrenia showed impaired detection accuracy and abnormally small pupillary responses (reduced resource allocation) only in the higher processing load SOA conditions. This pattern of results suggests that the patients depleted their available processing resources at lower processing loads than the nonpsychiatric participants. Consistent with the neurodegeneration hypothesis, cross-sectional analyses showed abnormally accelerated rates of age-related decline in SOA performance and pupillary responses in the patients with schizophrenia relative to age-comparable normal participants. (JINS, 2000, 6, 30–43.)