Sarah Mosko

Induced acetylcholinesterase-rich layer in rat dentate gyrus following entorhinal lesions

Abstract Unilateral lesions were placed in the entorhinal cortex of rats and the hippocampal formation examined histochemically for the localization of acetylcholinesterase. On the lesioned side, an intense band of acetylcholinesterase developed in the molecular layer of the dentate gyrus exactly where the entorhinal fibers normally terminate. This layer develops over a period of 30–40 days and is eliminated by septal lesions, which cause the disappearance of the normal bands of acetylcholinesterase. The suggestion is made that the sprouting of acetylcholinesterase containing septal terminals occurs under these conditions.

Self-reported depressive symptomatology, mood ratings, and treatment outcome in sleep disorders patients

Based on self-rating questionnaire evaluation of symptoms of major affective disorder, 67% of patients who presented to a major sleep disorders center reported an episode of depression within the previous 5 years, and 26% described themselves as depressed at presentation. Furthermore, patients with sleep apnea, narcolepsy, or sleep-related periodic leg movements all averaged high rates of self-reported depressive symptomatology, which suggests that sleep disorders should be considered in the differential diagnosis of affective disorders, and vice versa. Change scores on the Profile of Mood States were obtained for four subgroups of patients who were undergoing conventional treatment. Significant improvement in scores was observed in obstructive sleep apneics treated surgically and in patients with sleep-related periodic leg movements placed on clonazepam, but not in narcoleptics placed on a stimulant or in insomniacs with chronic use of sedative-hypnotic drugs who were withdrawn from sleep medications. Differential improvement in POMS scores after treatment for different sleep disorders could mean that the relationship to mood disturbance differs for different sleep disorders.

Sleep Apnea and Sleep‐related Periodic Leg Movements in Community Resident Seniors

The elderly have a high incidence of sleep complaints. A high incidence of sleep apnea (SA) and sleep‐related periodic leg movements (PLMs) is also suspected. The relationship between the incidence and severity of SA and PLMs and sleep complaints has not, however, been determined in terms of symptomatology and physiologic abnormality. In a group of 46 community resident seniors (60 to 95 years old), the incidence of SA and PLMs was correlated with subjective sleep‐wake complaints. Sixty‐one percent of subjects had SA and/or PLMs. Apneas/hypopneas were associated with an average oxygen desaturation of less than 5% and an average change in heart rate of less than 10 beats per minute. While subjects with SA or PLMs had clear evidence of objective sleep disturbance, only one quarter of them admitted to any subjective sleep complaints or daytime sleepiness. Furthermore, severity of SA or PLMs failed to predict sleep‐wake complaints, and vice versa. This study confirms that typically mild SA and PLMs are widespread in the elderly but tend not to be manifested in sleep‐wake complaints and probably go untreated as a result. Further research is needed to determine any long‐term medical significance.

Experimental studies of infant-parent co-sleeping: mutual physiological and behavioral influences and their relevance to SIDS (sudden infant death syndrome)

We hypothesize that maternal sensory exchanges, likely involving a combination of heat, sound, gas, smells, movement, and touch, induce important physiological changes, especially in the healthy infants arousal patterns, body temperature, and sleep architecture as defined by standard physiological measures. We summarize the results of two preliminary physiological studies, and some early data from a third, in which mothers and infants are monitored using standard polysomnographic techniques as they sleep in the same bed, and then in adjacent rooms. Our data suggest that infant-parent co-sleeping alters the infants sleep experience as, for example, the characteristics of arousals, the frequency and duration of nursing, infant sleep position and the number of maternal inspections. For example, while sleeping in the same bed, mothers nurse their infants three times more frequently than they do while their infants sleep in an adjacent room. These preliminary data demonstrate significant differences between routine co-sleeping and solitary sleeping environments. This work underscores the importance of studying infant sleep as it unfolds in the co-sleeping environment, the environment within which it evolved over at least 5 million years of human evolution. Should our preliminary findings be confirmed in future studies they will provide a beginning point for considering additional, possibly unconventional ways of helping to reduce SIDS risks.

Evolution and the sudden infant death syndrome (SIDS)

This paper extends the evolutionary and developmental research model for SIDS presented in previous articles (McKenna 1990a, 1990b). Data from variety of fields were used to show why we should expect human infants to be physiologically responsive in a beneficial way to parental contact, one form of which is parent-infant co-sleeping. It was suggested that on-going sensory exchanges (touch, movement, smell, temperature, etc.) between co-sleeping parent-infant pairs might diminish the chances of an infantile cardiac-respiratory crisis (such as those suspected to occur in some SIDS cases).In this article we review recent epidemiological data and sleep research findings on SIDS to show how they relate to evolutionary and cross-cultural perspectives. Results of a preliminary study of the co-sleeping behavior of mother-infant pairs indicate that, with respect to sleep, arousal, and respiratory patterns, co-sleeping mother-infant pairs affect each other in potentially important ways. We suggest specifically that co-sleeping may shorten periods of consolidated sleep among young infants by causing them to arouse more frequently. Moreover, we suggest that partner-induced arousals might help the infant to confront sleep crises more competently. In the long run, these arousals might prevent the premature emergence of prolonged (adultlike) sleep bouts from which some infants have difficulty arousing—especially during a breathing pause or apnea.

Sleep and arousal, synchrony and independence, among mothers and infants sleeping apart and together (same bed): an experiment in evolutionary medicine

Although solitary sleeping in infancy is a very recent custom, limited to Western industrialized societies, and most contemporary people practice parent‐infant co‐sleeping, virtually all laboratory research on sleep in human infants assumes that solitary infant sleep is the normal and desirable environment. We have used evolutionary and developmental data to challenge this view. We suggest that co‐sleeping provides a sensory‐rich environment which is the more appropriate environment in which to study infant sleep. In addition, two preliminary, in‐laboratory, polygraphic investigations of mother‐infant co‐sleeping are reported in normal infants, within the peak age range for sudden infant death syndrome (SIDS). Five mother‐infant pairs co‐slept one night in the first study; in the second, three additional pairs slept separately for two nights and co‐slept the third consecutive night. The results suggest that co‐sleeping is associated with enhanced infant arousals and striking temporal overlap (synchronicity) in infant and maternal arousals, and that, possibly as a result, co‐sleeping mothers and infants spend more time in the same sleep stage or awake condition. The implications of the hypothesis and preliminary results for research on the normal development of infant sleep and on SIDS are discussed.

Parent-infant cosleeping: The appropriate context for the study of infant sleep and implications for sudden infant death syndrome (SIDS) research

Nearly all laboratory research on human infant sleep assumes that solitary sleeping is the normal and desirable environment. Yet solitary sleeping in infancy is a very recent custom limited to Western industrialized societies, and most of the worlds peoples still practice parent-infant cosleeping. A hypothesis is presented that cosleeping provides a sensory-rich environment which is the more appropriate environment in which to study normal infant sleep. In addition, two preliminary, in-laboratory, polygraphic investigations of mother-infant cosleeping are reported in normal infants within the peak age range for sudden infant death syndrome (SIDS). Five mother-infant pairs coslept for 1 night in the first study; in the second, three additional pairs slept separately for 2 nights and coslept the third consecutive night. The results suggest that cosleeping is associated with enhanced infant arousals and striking temporal overlap in infant and maternal arousals. Infant sleep also showed subtle alterations with cosleeping, as manifested in increased overlap with corresponding maternal sleep stages and decreased amount of Stage 3–4. These are the first in-laboratory investigations of parent-infant cosleeping. The implications of the hypothesis and preliminary results for research on the normal development of infant sleep and on SIDS are discussed.

Maternal proximity and infant CO2 environment during bedsharing and possible implications for SIDS research

Sudden infant death syndrome (SIDS) is the leading cause of human infant mortality after the neonatal period in Western countries. Recently, child care practices have been shown to be important in determining infant vulnerability to SIDS. However, very little is known about the impact of parent-infant cosleeping on infant sleep physiology and behavior and SIDS risk. This reflects the failure of Western societal research paradigms to appreciate the human infants evolutionary history of cosleeping, the recency of the emergence of solitary infant sleeping as a practice and the fact that parent-infant cosleeping is still the preferred sleeping arrangement for the majority of contemporary societies. Incorporating current hypotheses on the mechanisms of SIDS, we have hypothesized that the comparatively sensory-rich cosleeping environment might be protective against SIDS in some contexts. As a first step to characterize cosleeping environments, this investigation is aimed at assessing, in routinely bedsharing mothers and infants, their relative sleeping positions and the potential for sleeping in close face-to face proximity and for infant exposure to increased environmental CO2 produced by maternal respiration. The latter is important in that breathing elevated levels of CO2 can have diverse effects, ranging from respiratory stimulation at low levels to suffocation at very high levels. Two related laboratory studies were performed. In the first, all-night videotapes of 12 healthy, routinely bedsharing mother-infant pairs were analyzed for sleeping positions and time spent in face-to-face orientation and distances separating their faces. Infants were 11-15 wk old. Mothers predominantly positioned themselves on their sides facing their infants, with the infants placed either supine or on their sides. Mothers and infants slept oriented face-to-face for 64 +/- 27% (S.D.) of non-movement time, with distance less than 20 cm commonly separating their faces. In the second study, concentrations of CO2 in air were measured in six young women at distances of up to 21 cm from their nares. Peak expiratory CO2 concentrations remained above 1.0% at distances up to 9 cm and above 0.5% at 18 cm. Both baseline and peak CO2 levels were further increased at all distances when measured within a partial air pocket created to simulate a bedding environment sometimes seen during bedsharing. We conclude that during bedsharing there is potential for 1) a high degree of face-to-face orientation and close proximity and consequently 2) increased environmental CO2, as a result of maternal respiration, to non-lethal levels that might stimulate infant respiration. The close proximity would also maximize the sensory impact of the mother on the infant through other modalities. We also suggest that bedsharing may minimize prone infant positioning, a known risk factor for SIDS.

Normal brain stem auditory evoked potentials recorded in sleep apneics during waking and as a function of arterial oxygen saturation during sleep

Brain stem auditory evoked potentials (BAEPs) can be utilized as an index of neuronal dysfunction at the level of the brain stem. These waves are known to be independent of level of arousal. In the present study, BAEPs (waves I-V) to monaural click stimulation were recorded during daytime waking and as a function of arterial oxygen saturation during nocturnal sleep in 6 subjects with obstructive sleep apnea syndrome. Normal conduction times were recorded in all 6 subjects during daytime waking. In addition, BAEPs remained stable in every case during sleep-related apneas when averaged over intervals of arterial oxygen saturation as low as 45-70% in one subject. Our data indicate that (1) the repetitive oxygen desaturation experienced during sleep in apneics had neither acute nor chronic, measurable effects on neurons which subserve the BAEP, and (2) a brain stem abnormality involving the structures which subserve the BAEP does not underly obstructive sleep apnea.

Neonatal ablation of the suprachiasmatic nucleus. Effects on the development of the pituitary-gonadal axis in the female rat.

Ablation of the suprachiasmatic nucleus (SCN) at 2 days of age, prior to the formation of the retinohypothalamic projection, produces a permanent state of constant vaginal estrus in the postpubertal female rat. Although such lesions do not alter the onset of puberty in sighted rats, they do compensate for the delay in vaginal opening induced by neonatal binding. The ovaries of sighted and blinded SCN-lesion rats are small and polyfollicular and the pituitaries of blinded SCN-lesion rats are abnormally large. Sampling of plasma in the morning and afternoon for up to 12 consecutive days in sighted SCN-lesion rats reveals continuously low luteinizing hormone levels. This constellation of endocrine alterations does not correlate with damage to any structures outside the SCN. Since the organization of the rodent estrous cycle is circadian, these results emphasize further the importance of the SCN in circadian rhythm generation. The necessity of an intact SCN for the development of normal, cyclic reproductive function implies that sparing or recovery of function does not occur.