The Cyclic Alternating Pattern as a Physiologic Component of Normal NREM Sleep

Abstract

Summary: The cyclic alternating pattern (CAP) is a long-lasting periodic activity consisting of two alternate electroencephalogram (EEG) patterns. This variation in EEG is closely related to fluctuations in the level of arousal that characterize two different functional states in the arousal control mechanism. We studied 20 sleep records of 10 healthy subjects to see if CAP appears under physiologic conditions. During NREM sleep, CAP corresponded to a periodic succession of spontaneous phasic phenomena recurring within every stage, i.e., intermittent alpha rhythm, K-complex sequences, and reactive slow wave sequences. The following analyses were performed. Each EEG specific alternating pattern, defined as a cycle, was subdivided into two phases depending on the arousal response to stimulation. Average cycle length, average duration of each phase, and average ratio phase/cycle were calculated. CAP rate defined as (CAP time/Sleep time) was calculated for total sleep time (TST), (CAP time/TST); for NREM sleep, (CAP time/Total NREM); and for each NREM sleep stage. CAP is the EEG translation of the reorganization of the sleeping brain challenged by the modification of environmental conditions.

Sleep Abnormalities in Chronic Fatigue Syndrome/Myalgic Encephalomyelitis: A Review

“…Cyclic alternating pattern (CAP) is an EEG-derived measure of sleep instability, which is reflected as periodic EEG activity during NREM sleep. 68,69 In contrast, periods of Non-CAP are indicative of consolidated sleep. CAP is somewhat distinct from typically measured arousals from sleep, both as a phenomenon and in terms of how they are scored.…”

Infraslow oscillations modulate excitability and interictal epileptic activity in the human cortex during sleep

“…In addition to these relatively fast EEG oscillations, some studies have demonstrated infraslow fluctuations in, for instance, neuronal population activity (2-5), EEG power (5-9), discrete sleep events (arousals, spindles, K complexes) (9)(10)(11)(12), as well as in the occurrence of epileptic events (4,11,13). These observations have raised the possibility that the human cortex may generate infraslow oscillations (ISOs) underlying such fluctuations.…”

Baroreflex Buffering of Sympathetic Activation During Sleep

“…[5][6][7] Studies investigating sleep structure have led to the identification of a natural electroencephalographic arousal rhythm within the non-REM sleep stages, related to transient lightenings of sleep depth, known as the cyclic alternating pattern (CAP). 8,9 CAP corresponds to a prolonged oscillation of the arousal level, whereas the complementary condition, non-CAP (NCAP), is closely related to a degree of stability in sleep depth. 8,9 Functionally, CAP translates a condition of sustained arousal instability; however, the arousal swings that characterize CAP sequences are not driven by any motor or respiratory disturbances and are associated with variations of autonomic activity.…”

“…8,9 Functionally, CAP translates a condition of sustained arousal instability; however, the arousal swings that characterize CAP sequences are not driven by any motor or respiratory disturbances and are associated with variations of autonomic activity. 8,9 Spectral analysis studies reported an increase in the low-frequency (LF) and a decrease in the high-frequency (HF) component of heart rate variability (HRV) during CAP compared with non-CAP sequences, 10,11 suggesting the occurrence of nighttime periods of relative sympathetic activation even during phases, like non-REM sleep, characterized by an increase in the background level of parasympathetic activity. These findings would indicate that surges of sympathetic activity may occur not only during REM.…”