Stimulus-elicited behavior in rapid eye movement sleep without atonia

Area of Science:

• Neuroscience
• Sleep Science
• Animal Behavior

Background:

• Alert wakefulness (W) and rapid eye movement sleep (REM) share brain activity patterns.
• REM sleep is characterized by reduced sensory responsiveness and postural muscle atonia.
• Pontine tegmental lesions induce REM without atonia (REM-A), releasing motor behaviors.

Purpose of the Study:

• To investigate the impact of REM without atonia (REM-A) on sensory responsiveness and motor reflexes.
• To compare behavioral and neurophysiological measures during wakefulness, REM, REM-A, and non-REM (NREM) sleep.
• To elucidate the relationship between brain activity similarity and motor inhibition during REM sleep.

Main Methods:

• Studied acoustic startle reflex (ASR), orienting response (OR), and ponto-geniculo-occipital waves (PGOE) in 9 cats.
• Elicited responses using auditory stimuli (tones) across different sleep-wake states (W, REM, REM-A, NREM).
• Compared responses in cats with pontine tegmental lesions (REM-A) versus normal cats.

Main Results:

• Orienting responses (OR) were observed during wakefulness (W) and REM-A, most pronounced with complex spontaneous behaviors.
• Acoustic startle reflexes (ASR) occurred in W, NREM, and REM-A states in lesioned cats, but rarely in NREM and REM of normal cats.
• Ponto-geniculo-occipital waves (PGOE) exhibited similar characteristics in both lesioned and normal cats.

Conclusions:

• The study highlights that REM sleep closely resembles wakefulness when motoneuronal inhibition is absent (REM-A).
• REM-A facilitates motor behaviors and alters sensory processing, suggesting a crucial role for atonia in normal REM sleep.
• Findings underscore the importance of motor inhibition in differentiating REM sleep from wakefulness despite similar brain activity.