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Regulation of circadian period in humans was thought to differ from that of other species, with the period of the activity rhythm reported to range from 13 to 65 hours (median 25.2 hours) and the period of the body temperature rhythm reported to average 25 hours in adulthood, and to shorten with age. However, those observations were based on studies of(More)
The authors present here mathematical models in which levels of subjective alertness and cognitive throughput are predicted by three components that interact with one another in a nonlinear manner. These components are (1) a homeostatic component (H) that falls in a sigmoidal manner during wake and rises in a saturating exponential manner at a rate that is(More)
The visibility of a 1 degree, 200-msec flash on a large yellow field was measured as a function of the intensity of a coincident pedestal flash (a flash that was the same in both temporal intervals of a two-alternative forced-choice trial). The various flashes were incremental (+Lum) or decremental (-Lum) yellow luminance flashes or green (+Chr) or red(More)
Ocular exposure to early morning room light can significantly advance the timing of the human circadian pacemaker. The resetting response to such light has a non-linear relationship to illuminance. The dose-response relationship of the human circadian pacemaker to late evening light of dim to moderate intensity has not been well established. Twenty-three(More)
The response of the human circadian pacemaker to light was measured in 45 resetting trials. Each trial consisted of an initial endogenous circadian phase assessment, a three-cycle stimulus which included 5 hours of bright light per cycle, and a final phase assessment. The stimulus induced strong (type 0) resetting, with responses highly dependent on the(More)
1. The human luminance (LUM) mechanism detects rapid flicker and motion, responding to a linear sum of contrast signals, L' and M', from the long-wave (L) and middle-wave (M) cones. The red-green mechanism detects hue variations, responding to a linear difference of L' and M' contrast signals. 2. The two detection mechanisms were isolated to assess how(More)
Eisner and MacLeod [J. opt. Soc. Am. 71, 705-718 (1981)] showed that intense green and red chromatic adapting fields may suppress respectively the M and L cone input to the luminance mechanism by a factor considerably greater than Weber's law. We obtained evidence for such chromatic suppression by measuring complete detection contours for different ratios(More)
Detection contours were measured in L and M cone contrast coordinates for foveal flashes of 200 msec duration and 2.3, 5, 10 and 15 min arc diameter on a bright yellow field. The test flash consisted of simultaneous incremental and decremental red and green lights in various amplitude ratios. At all sizes, the most sensitive detection mechanism was not a(More)
A general model is developed to account for all kinds of periodic breathing (PB) resulting from instability in respiratory control: in normals during sleep and on acute exposure to high altitude, in sleeping infants, and in patients with cardiovascular or neurologic lesions. It is found that in almost every case the ventilatory oscillation is mediated(More)