The effect of epoch length and smoothing on infant sleep and waking state architecture for term infants at 42 to 46 weeks postconceptional age.

STUDY OBJECTIVES: Epoch lengths from 20 seconds to 1 minute, and smoothing strategies from zero to three minutes are encountered in the infant sleep and waking literature. The present study systematically examined the impact of various epoch lengths and smoothing strategies on infant sleep state architecture. DESIGN: Overnight polysomnographic recordings were visually assessed by epoch as wake or as each of four sleep state parameters: electroencephalographic patterns, respiration, body movement, and eye movement. From these findings, sleep and waking states were assigned for each of six combinations of epoch length (30-second or 1-minute) and smoothing window length (none, 3-epoch, or 5-epoch). SETTING: N/A. PARTICIPANTS: Subjects were 91 term infants, 42-46 weeks postconceptional age, from the Collaborative Home Infant Monitoring Evaluation (CHIME) study. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: A greater epoch length resulted in more active and less quiet sleep as a percentage of total study; however, the size of the smoothing window did not affect the percentage of sleep/waking states. In general, the greater the epoch length and the greater the smoothing window length, the fewer the number of, the greater the mean duration of, and the greater the longest continuous episode of sleep/waking states. Analysis of significant interactions indicated that a 1-minute epoch length relative to a 30-second epoch length resulted in increasingly longer episodes of quiet and especially active sleep with a greater smoothing window length. CONCLUSIONS: Smoothing strategy significantly altered sleep state architecture in infants and may explain part of the variability in infant sleep state findings between laboratories.

The prediction of hue and saturation for non-spectral lights.

The Jameson and Hurvich opponent-colors model of hue and saturation was tested for spectral and non-spectral lights. Four observers described the color of lights by scaling hue and saturation. The lights ranged from 440 to 640 nm and consisted of five purities: 1.0, 0.80, 0.60, 0.40 and 0.20. Admixtures of monochromatic and a xenon-white light yielded the different colorimetric purities. For each subject, chromatic response functions were measured by the method of hue cancellation at each purity, and an achromatic response function was measured by the method of heterochromatic flicker photometry for spectral lights. Chromatic response functions measured for a particular purity and the achromatic response function were used to predict hue and saturation for that purity. The model successfully predicted hue at each level of purity, but failed to predict precisely the Abney effect. The model made relatively poor predictions of saturation, tending to overestimate short-wave lights and underestimate long-wave lights. An additional experiment found that stimulus parameters that favor rod contribution weaken the model's predictions of saturation, while stimulus parameters that do not favor rod contribution improve the model's predictions of saturation.

Black spectral responsivity.

Six subjects induced blackness within a circular broadband field by increasing the radiance of a surrounding monochromomatic annulus, which varied in wavelength. Between the central field and the annulus was a thin dark ring. Half of the subjects were instructed to increase the radiance of the annulus until the central field just turned black, and the other half were instructed to increase the radiance of the annulus until the contour between the central field and the dark ring disappeared. Spectral luminous efficiency functions measured by the methods of heterochromatic flicker photometry (HFP) and brightness matching (HBM) were determined for each subject and compared with the subject's blackness-induction functions. The hypothesis that the contour-disappearance instruction would yield blackness-induction curves best fitted by flicker photometric functions and that the absolute-blackness instruction would yield blackness-induction curves best fitted by HBM functions was not confirmed. There was only one subject for whom the spectral efficiency of blackness was represented better by HFP than by HBM. There was one subject for whom blackness spectral efficiency was fitted better by HBM than by HFP. For the remaining four subjects, there was no difference in fits.