title: Positive feedback in a brainstem tactile sensorimotor loop.
abstract: The trigeminal loop in the brainstem comprises the innermost level of sensorimotor feedback in the rat vibrissa system. Anatomy suggests that this loop relays tactile information from the vibrissae to the motoneurons that control vibrissa movement. We demonstrate, using in vitro and in vivo recordings, that the trigeminal loop consists of excitatory pathways from vibrissa sensory inputs to vibrissa motoneurons in the facial nucleus. We further show that the trigeminal loop implements a rapidly depressing reflex that provides positive sensory feedback to the vibrissa musculature during simulated whisking and contact. On the basis of these findings, we propose that the trigeminal loop provides an enhancement of vibrissa muscle tone upon contact during active touch.
authors.affiliation: Department of Physics, University of California at San Diego, La Jolla, California 92093, USA.
authors.forename: Quoc-Thang
authors.initials: QT
authors.lastname: Nguyen
authors.forename: David
authors.initials: D
authors.lastname: Kleinfeld
mesh_terms: D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D001933:Brain Stem / Q000033:anatomy & histology / Q000502:physiology*; D004525:Efferent Pathways / Q000502:physiology; D004576:Electromyography; D005154:Facial Nerve / Q000502:physiology; D005246:Feedback / Q000502:physiology; D008465:Mechanoreceptors / Q000502:physiology; D009046:Motor Neurons / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D009434:Neural Pathways / Q000033:anatomy & histology / Q000502:physiology*; D009924:Organ Culture Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D009435:Synaptic Transmission / Q000502:physiology; D014110:Touch / Q000502:physiology*; D014276:Trigeminal Nerve / Q000502:physiology; D014738:Vibrissae / Q000294:innervation / Q000502:physiology*