Howard P. Roffwarg

Spontaneous Middle Ear Muscle Activity in Man: A Rapid Eye Movement Sleep Phenomenon

Changes in compliance of the tympanic membrane have been detected in normal human sleep, presumably due to spontaneous contraction of the stapedius and tensor tympani muscles of the middle ear. In the waking state, these muscles generally respond to loud sound (middle ear reflex). Middle ear muscle activity typically erupts before or at the onset of rapid eye movement (REM) sleep and persists throughout the REM period in a discontinuous pattern resembling that exhibited by rapid eye movements. Approximately 80 percent of all nocturnal middle ear muscle activity is contained in REM sleep. Half of the remaining 20 percent occurs in the 10-minute intervals just prior to the onset of REM sleep. Middle ear muscle activity is often associated with other phasic events such as momentary enhancement of electromyogram inhibition, apnea, and K complexes. Rapid eye movements and middle ear muscle activity, though significantly correlated in REM sleep, are not always simultaneous.

REM sleep inhibition by light in the albino rat

Abstract Two groups of rats were maintained on a 12 hr light-12 hr darkness (L12-D12) schedule. One was subjected to continuous light and the other to continuous darkness for 3 weeks and then returned to the original schedule. Rats placed in continuous light, initially showed a marked decrement in both rapid eye movement sleep (REMS) and slow wave sleep (SWS) time. A dissociation developed later between the sleep stages; REMS time remained below baseline but SWS time increased above it. In recovery (L12-D12), a temporary increase of REMS time above baseline was observed. During the first 2 weeks of continuous darkness REMS time increased 30% and REMS/total sleep (%-REMS) increased 17%. Both measures returned to baseline during the third week of darkness. In recovery (L12-D12), REMS decreased 37% and %-REMS decreased 18%. Changes in SWS time paralleled those in REMS time in direction but were proportionately smaller relative to baseline values. It is proposed that light stimulation inhibits REMS in the rat whereas darkness is the preferred and, whenever possible, the utilized condition for elaboration of REMS. Rats housed under long-term exposure to L12-D12 schedules develop and maintain a chronic REMS debt though daily REMS values return to normal. Prolonged darkness seems to be necessary for a complete REMS rebound. The possibility that light inhibits SWS as well as REMS is also considered. The effects of the lighting environment on the stages of sleep are interpreted within the larger context of the rats life style.

Ontogenesis of ponto-geniculo-occipital activity in the lateral geniculate nucleus of the kitten.

Abstract In the adult cat, just before the onset of and throughout paradoxical sleep, sharp, monophasic waves appear in the pontine reticular formation, and are transmitted to the lateral geniculate nucleus and occipital cortex. This report describes a study of the appearance and maturation of these ponto-geniculo-occipital weves, or PGO “spikes,” in the lateral geniculate nucleus of the developing kitten. Thirty-nine implantations of the lateral geniculate nucleus were carried out in 34 kittens (ages 8–75 days). Electrodes were also placed for the recording of electrocorticograms, neck muscle activity, and eye movements. Despite the high proportion of paradoxical sleep, and the copious amount of peripheral phasic activity in the neonatal kitten, no PGO activity was found prior to Day 15. The average age of emergence of the activity was Day 21. The PGO waves, at initial appearance, were low in frequency as well as amplitude. However, during a 3- to 6-day sequence, the spikes increased in both frequency and amplitude, and an association developed progressively with the increasingly well-defined periods of paradoxical sleep. Adult PGO spike frequencies were reached by Day 35, though the temporal characteristics of their discharge continued to change for several weeks thereafter. The 3-week postbirth latency to the first appearance of the PGO spikes, as well as the ensuing rise in their recorded frequency and amplitude, seem to be basic characteristics of PGO development. Further, the ontogenesis of spontaneous PGO activity in the lateral geniculate nucleus of the kitten during paradoxical sleep parallels the pace of maturation of the sleep-wake pattern and of the neuroanatomical and neurochemical pathways that function in the mediation of the stages of sleep.

The development of unit activity in the lateral geniculate nucleus of the kitten

Abstract The spontaneous unit activity in the lateral geniculate nucleus of 15 kittens has been analyzed in terms of the sleep-wake state. Lateral geniculate units in animals ranging from 2 days to 5 weeks of age were recorded under chronic conditions by means of a hydraulically movable glass micropipet. During the first postnatal month, the mean frequency of firing increased progressively in the awake state and in paradoxical sleep but was not modified in quiet or slow wave sleep. However, as early as the third postnatal week, the pattern of modulation of the frequency of unit discharge in response to changes in state reached an organization close to that seen in the adult cat. The most dramatic alteration in the cellular discharge configuration was represented by the introduction of the “burst-pause” pattern in slow wave sleep. Serial interspike interval distributions demonstrated the appearance of this pattern at the end of the second week. The organization of unit firing in the 1-month-old animal was qualitatively similar to that in the adult, though quantitatively less intense. The pattern of development of unit firing is discussed in light of the appearance of other important developmental features such as cortical synchronization, ponto-geniculo-occipital spikes, and maturation of certain monamine-containing cells in the central nervous system. Some structural and neurochemical factors in development are mentioned that may be responsible for the ontogenetic organization of unit discharges in the lateral geniculate nucleus.

EFFECTS OF GOGGLE-ALTERED COLOR PERCEPTION ON SLEEP'

This study was designed to examine the effects of long-term perceptual alterations in color and illumination, which have been associated with changes in dream content, on physiological parameters of sleep. Subsequent to a period of sleep standardization, 3 Ss slept 4 or 5 baseline nights in the lab immediately followed by 4 or 5 experimental nights. Sleep was monitored polygtaphically. During all waking time on the experimental days, Ss wore goggles equipped with No. 29 Wratten color filters which screen all light save the red band. Ss were required to continue normal daily routines The variables assessed were: total minutes of REM sleep (REMS) and of NREMS stages 1, 2 and 3/4; latencies to initial stage 3/4 and to REMS, and the intensity of REMS. No variable showed a statistically significant difference between baseline and goggle conditions in any single S or in the group. Statistical power analysis did not indicate that the failure to achieve significance could be meaningfully attributed to the number of Ss. We conclude that significant perceptual readjustments in terms of color, illumination and peripheral vision, though strongly affecting dream content, do not result in measurable changes in the basic physiological parameters of sleep.

Ontogeny of luteinizing hormone and testosterone secretion

Abstract Plasma luteinizing hormone (LH) and testosterone (T) were measured by radioimmunoassay in 9 pubertal boys and 9 sexually mature adult men at 20 min intervals for 24 h. Polygraphic monitoring of sleep was also carried out to precisely identify sleep onset, wakefulness and specific sleep stages. In all 9 pubertal boys, plasma LH showed the characteristic augmentation of secretion synchronous with sleep. This increased LH secretory activity was effective in stimulating increased T secretion during sleep that resulted in uniformly higher mean T concentrations during sleep compared with waking. Plasma LH and T were also measured in 3 of these pubertal boys during acute inversion of the sleep wake cycle. The results showed that plasma LH and T were now augmented during the reversed daytime sleep period; the mean LH and T concentrations were significantly higher than during nocturnal waking. Measurement of LH and T in the 9 adult men showed episodic secretion of both hormones during waking and sleep periods with no consistent augmentation of either hormone during sleep.

ONTOGENY OF LUTEINIZING HORMONE AND TESTOSTERONE SECRETION

Plasma luteinizing hormone (LH) and testosterone (T) were measured by radioimmunoassay in 9 pubertal boys and 9 sexually mature adult men at 20 min intervals for 24 h. Polygraphic monitoring of sleep was also carried out to precisely identify sleep onset, wakefulness and specific sleep stages. In all 9 pubertal boys, plasma LH showed the characteristic augmentation of secretion synchronous with sleep. This increased LH secretory activity was effective in stimulating increased T secretion during sleep that resulted in uniformly higher mean T concentrations during sleep compared with waking. Plasma LH and T were also measured in 3 of these pubertal boys during acute inversion of the sleep wake cycle. The results showed that plasma LH and T were now augmented during the reversed daytime sleep period; the mean LH and T concentrations were significantly higher than during nocturnal waking. Measurement of LH and T in the 9 adult men showed episodic secretion of both hormones during waking and sleep periods with no consistent augmentation of either hormone during sleep.