Extraocular muscle activity, rapid eye movements and the development of active and quiet sleep

] indicate that sleep bout durations exhibit an exponential distribution, whereas wake bout durations exhibit a power-law distribution. Moreover, it was found that wake bout distributions, but not sleep bout distributions, exhibit scale invariance across mammals of different body sizes. Here we test the generalizability of these findings by examining the distributions of sleep and wake bout durations in infant rats between 2 and 21 days of age. In agreement with Lo et al., we find that sleep bout durations exhibit exponential distributions at all ages examined. In contrast, however, wake bout durations also exhibit exponential distributions at the younger ages, with a clear power-law distribution only emerging at the older ages. Further analyses failed to find substantial evidence either of short-or long-term correlations in the data, thus suggesting that the durations of current sleep and wake bouts evolve through time without memory of the durations of preceding bouts. These findings further support the notion that bouts of sleep and wakefulness are regulated independently. Moreover, in light of recent evidence that developmental changes in sleep and wake bouts can be attributed in part to increasing forebrain influences, these findings suggest the possibility of identifying specific neural circuits that modulate the changing complexity of sleep and wake dynamics during development.atonia ͉ renewal process ͉ Markov process ͉ development A s members of a diurnal species, adult humans experience sleep as a prolonged period of rest during the night; however, sleep actually occurs as a series of discrete bouts interrupted by bouts of wakefulness. What is perhaps most striking during the first several months after birth, when circadian influences on behavioral state are not well established, is the brevity of these bouts of sleep and wakefulness (1). In newborn rats at 2 days of age (P2), these cycles are astonishingly rapid: The average bout lengths of nuchal muscle atonia (indicative of sleep) and high nuchal muscle tone (indicative of wakefulness) are only 15 s and 5 s, respectively (2). Over the next week, bout lengths increase significantly as forebrain mechanisms exert increasing modulatory control over brainstem mechanisms controlling sleep and wakefulness (2).Recently, Lo et al. (3) analyzed the distributions of sleep and wake bouts in human adults. They found that, whereas sleep bouts exhibited an exponential distribution [such that the frequency distribution f(t) of bout durations of duration t was proportional to e (Ϫt/) , where is the characteristic time scale], wake bouts exhibited a power-law distribution [such that f(t) Ϸ t Ϫ␣ , where ␣ is a characteristic power-law exponent]. In a subsequent report (4), these findings were extended to cats, rats, and mice. From this comparative analysis, Lo and colleagues found that the exponential time scale for sleep bout durations increased with body size, thus possibly implicating a constitutional variable (e.g., metabolic rate) in the regulation of sleep bout...

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“…5. Bipolar stainless steel hook electrodes were implanted bilaterally into the nuchal muscle and secured with collodion.…”

Section: Methodsmentioning

confidence: 99%

Dynamics of sleep-wake cyclicity in developing rats

Blumberg

Seelke

Lowen

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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143

154

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“…Startles, occurring at a rate of approximately 1-2 per min in infant rats, are easily distinguished from other infantile behaviors, such as the more frequent myoclonic twitching that characterizes active sleep (de Vries et al, 1982;Gramsbergen et al, 1970;Roodenburg et al, 1991;Seelke et al, 2005). The neural basis of startles remains unknown, although the simultaneous activation of multiple muscle groups that characterizes a startle suggests a supraspinal source of initiation (O'Donovan, 1999).…”

mentioning

confidence: 99%

On the co‐occurrence of startles and hippocampal sharp waves in newborn rats

Karlsson¹,

Mohns²,

Prisco³

et al. 2006

Hippocampus

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Hippocampal sharp waves (SPWs) are among the earliest neural population patterns observed in infant mammals. Similarly, startles are among the earliest behavioral events observed. Here we provide evidence indicating that these two events are linked mechanistically soon after birth in freely moving and head-fixed 1-4-day-old rats. EMG electrodes and intrahippocampal silicon depth electrodes were used to detect the presence of startles and SPWs, respectively. In intact pups, the majority of sharp waves were preceded by startles (average latency: 161 ms). When the hippocampal formation was surgically separated from the brainstem, however, sharp waves and startles still occurred, but now independently. In addition, unrelated to startles or SPWs, gamma oscillations were detected in several subjects, as were neocortical "spindles" that propagated passively into the hippocampus. The co-occurrence of sharp waves and startles provides the opportunity for Hebbian changes in synaptic efficacy and, thus, is poised to contribute to the assembly of neural circuits early in development.

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“…Between birth and eye opening (P12), when the extraocular muscles are still immature (Spencer and Porter, 2006), the extraocular motoneuron population grows with a decrease in their input resistances (Carrascal et al, 2006;2009). Later, functional maturation occurs in parallel in the synaptic circuitry, extraocular motoneurons, and extraocular muscles (Seelke et al, 2005;Carrascal et al, 2011) to reach adult levels by P21 (Carrascal et al, 2006;Nieto-Gonzalez et al, 2007, Carrascal et al, 2009). …”

Section: Ocular Motor Neurons In the Vor Pathwaymentioning

confidence: 96%