Arousal mechanisms related to posture and locomotion: 1. Descending modulation.
Much of the controversy surrounding the induction of locomotion following stimulation of mesopontine sites, including the pedunculopontine nucleus (PPN), appears based on procedural differences, including stimulus onset, delay preceding stepping, and frequency of stimuli. The results reviewed in this chapter address these issues and provide novel information suggesting that descending projections from the PPN may exert a frequency-dependent effect. Stimulation at approximately 60 Hz (which induces prolonged tonic firing) may exercise a "push" towards locomotion (activation of pontine interneurons) as well as a "pull" away from decreased muscle tone (inhibiting giant pontine reticulospinal cells). Higher frequencies of stimulation (> 100 Hz, which induces phasic burst-like activity) may "push" towards decreases in muscle tone, including the atonia of rapid eye movement sleep (activating giant pontine reticulospinal cells).
Garcia-Rill
Edgar
E
Department of Anatomy and Neurobiology, University of Arkansas Medical Sciences, Little Rock, AR 72205, USA. garciarilledgar@uams.edu
Homma
Yutaka
Y
Skinner
Robert D
RD
D000818:Animals; D001143:Arousal / Q000502:physiology*; D004525:Efferent Pathways / Q000502:physiology; D009043:Motor Activity / Q000502:physiology*; D011187:Posture / Q000502:physiology*