Today, Thursday, December 16, 2021
Ph. D Candidate:
Ms. Violeta Pellicer Morata
Molecular and Translational Physiology
The Department of Anatomy and Neurobiology
The University of Tennessee Health Science Center
“Mechanisms Underlying Hand-to-Face Reorganization in Animal Model”
The goal of this study is to examine mechanisms underlying cortical reorganization in rat primary somatosensory (SI) cortex that follows forelimb deafferentation. The majority of human patients suffering from limb loss or brachial plexus avulsion, as well as patients that receive brachial plexus anesthesia, report phantom limb sensations/pain which is often associated with cortical reorganization. Patients with upper-limb deafferentation report sensations of the missing hand during tactile stimulation of the face, and this phenomenon has been termed hand-to-face remapping. Our model system is the layer IV barrel field in rat SI cortex where cell clusters, called barrels, represent localized regions of the skin surface. The forepaw barrel subfield (FBS), consisting of approximately 26 barrels, receives somatotopically organized input from the contralateral glabrous and hairy skin surfaces of the forepaw. When input from the forelimb is no longer available following limb amputation, brachial plexus nerve cut or brachial plexus anesthesia, neurons in the deafferented FBS begin responding to previously unexpressed input from the lower jaw; here, we define this phenomenon as hand-to-face cortical reorganization. In this research, electrophysiological mapping of SI was used to examine hand-to-face cortical reorganization in the FBS. Immediately following each type of deafferentation, lower jaw input became expressed in the rostral part of the FBS; conversely, 9-to-27 weeks after limb amputation, lower jaw input became expressed throughout the entire FBS. Anatomical tracers were used to explore the source(s) of the newly expressed lower jaw input in the deafferented rostral and caudal FBS. We identified a corticocortical projection from the neighboring lower jaw barrel subfield (LJBSF) to the rostral part of the FBS and speculate that the caudal FBS is served by a subcortical source. The present study, along with ongoing work in our lab, documents cortical reorganization in a rodent animal model, explores the source(s) of the newly expressed input, and speculates on cortical and subcortical mechanisms underlying reorganization.
Please send an email to Dedra Jeffries (firstname.lastname@example.org) if you are interested in the seminar.