Cortical beta EEG oscillations related to changes in muscle tone activity during sleep in spider monkey (Ateles geoffroyi)

Background The physiological mechanisms that allow for sleeping in a vertical position, which is primordial for arboreal primates, have not been studied yet. Methods A non‐invasive polysomnographic study of 6 spider monkeys (Ateles geoffroyi) was conducted. The relative beta power of the motor cortex and its linear relation with muscle tone in the facial mentalis muscle and the abductor caudae medialis muscle of the tail during wakefulness and sleep stages were calculated. Results A strong negative linear relationship (r = −.8, P = .03) was found between the relative power of the beta2 band in the left motor cortex and abductor caudae medialis muscle tone during delta sleep. Conclusions The left motor cortex, through beta2 band activity, interacts with abductor caudae medialis muscle tonicity during delta sleep. This interaction takes part in the mechanisms that regulate the sleep postures.