The cyclic alternating pattern (abbreviated CAP) is a pattern of two long-lasting alternate

electroencephalogram Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex ...

(EEG) patterns that occur in

sleep Sleep is a sedentary state of mind and body. It is characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and reduced interactions with surroundings. It is distinguished from wakefulness by a de ...

. It is a pattern of spontaneous cortical activity which is ongoing and occurs in the absence of sensory

stimulation Stimulation is the encouragement of development or the cause of activity generally. For example, "The press provides stimulation of political discourse." An interesting or fun activity can be described as "stimulating", regardless of its physica ...

. It is the reorganization of the sleeping brain challenged by the modification of environmental conditions and it is characterized by periodic abnormal electrocortical activity that recurs with a frequency of up to one minute. It is considered "the EEG marker of unstable sleep". CAP does not occur during

rapid eye movement sleep Rapid eye movement sleep (REM sleep or REMS) is a unique phase of sleep in mammals and birds, characterized by random rapid movement of the eyes, accompanied by low muscle tone throughout the body, and the propensity of the sleeper to dream viv ...

(REM). In Lennox-Gastaut syndrome, CAP modulates the occurrence of clinical

seizures An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or neural oscillation, synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much o ...

and generalized

epileptic Epilepsy is a group of non-communicable neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrical ...

discharges by means of a gate-control mechanism. CAP is a marker of sleep instability and it is found during

non-rapid eye movement sleep Non-rapid eye movement sleep (NREM), also known as quiescent sleep, is, collectively, sleep stages 1–3, previously known as stages 1–4. Rapid eye movement sleep (REM) is not included. There are distinct electroencephalographic and other char ...

(NREM). CAP is organized into sequences of successive cycles composed of two phases, A and B. Phase A involves phasic events, in other words, not continuous. Phase A subtypes of CAP allow adaptive adjustments of ongoing states to internal and external inputs. Phase B refers to background rhythm during CAP. Furthermore, CAP involves cerebral activities and is influenced by autonomic and

motor functions Motor control is the regulation of movement in organisms that possess a nervous system. Motor control includes reflexes as well as directed movement. To control movement, the nervous system must integrate multimodal sensory information (both f ...

. Interaction between CAP and neurovegetative fluctuations and motor events determine the

pathophysiology Pathophysiology ( physiopathology) – a convergence of pathology with physiology – is the study of the disordered physiological processes that cause, result from, or are otherwise associated with a disease or injury. Pathology is the ...

of several

sleep disorders A sleep disorder, or somnipathy, is a medical disorder of an individual's sleep patterns. Some sleep disorders are severe enough to interfere with normal physical, mental, social and emotional functioning. Polysomnography and actigraphy are test ...

and the effect of medication on

continuous positive airway pressure Continuous positive airway pressure (CPAP) is a form of positive airway pressure (PAP) ventilation in which a constant level of pressure greater than atmospheric pressure is continuously applied to the upper respiratory tract of a person. The ap ...

(CPAP) treatment which is used to treat

obstructive sleep apnea Obstructive sleep apnea (OSA) is the most common sleep-related breathing disorder and is characterized by recurrent episodes of complete or partial obstruction of the upper airway leading to reduced or absent breathing during sleep. These episod ...

(OSA). CAP is a marker of NREM instability and is also the "master clock" that accompanies the stage transitions maintained in sleep phases, noted in both the EEG and by autonomic functions through regular fluctuations. CAP is decreased in

narcolepsy Narcolepsy is a long-term neurological disorder that involves a decreased ability to regulate sleep–wake cycles. Symptoms often include periods of excessive daytime sleepiness and brief involuntary sleep episodes. About 70% of those affec ...

multiple system atrophy Multiple system atrophy (MSA) is a rare neurodegenerative disorder characterized by autonomic dysfunction, tremors, slow movement, muscle rigidity, and postural instability (collectively known as parkinsonism) and ataxia. This is caused by progr ...

, in certain cases of

drug administration A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy (pharmacotherapy) is an important part of the medical field and rel ...

, with CPAP treatment for OSA, and during night-time recovery sleep after prolonged sleep deprivation. There is a relationship present between CAP and arousals that allows for adjustments of vigilance during sleep. If there is a failure in this relationship during sleep, sleep disorders may develop. Rechtschaffen and Kales developed the standard criteria for sleep staging in 1968. In 1992, the AASM defined arousals as markers of sleep disruption, which is harmful for sleep. According to Boselli, et al., in 1998 it was noted that spontaneous arousals are natural in sleep and increase over life.

References

Sleep physiology Electroencephalography Sleep medicine {{Neuroscience-stub