Year of Graduation
2024
Level of Access
Restricted Access Thesis
Embargo Period
5-16-2027
Department or Program
Neuroscience
First Advisor
Manuel Diaz Rios
Abstract
Vertebrate motor control employs central and peripheral neural circuitry to activate muscles within the forelimb, hindlimb, and axial regions. Within the cervical and lumbar regions of the mammalian spinal cord, central pattern generator (CPG) networks produce rhythmic activity that governs forelimb and hindlimb locomotion, respectively. Between these limb-controlling segments, thoracic spinal nerves innervate trunk muscles and organs critical for everyday function. However, investigation of the rhythmic capabilities of the thoracic network is limited. Current literature generally consigns the thoracic network to serving as a connective synaptic highway between limb CPGs, leaving questions regarding its intrinsic rhythmogenic abilities unanswered. To characterize the rhythmic capabilities and investigate the structural organization of thoracic neural circuitry, spinal cords from postnatal mice (P1-P6) were extracted. Spinal preparations were maintained as full thoracolumbar cords or isolated thoracic preparations (T2-T12). Motor activity recordings were obtained extracellularly from thoracic or lumbar ventral roots. To assess the effects of neuromodulation on thoracic motor rhythms, pharmacological experiments using serotonin, NMDA, or dopamine were conducted. The organization of thoracic neural circuitry was investigated though the introduction of glutamatergic receptor antagonists. The present study determined that the thoracic spinal network can produce and sustain its own distinct rhythmic motor activity patterns once released from lumbar entrainment that seem to correspond to motor and autonomic trunk behaviors. Preliminary findings suggest that contralateral synchronization, typical of thoracic rhythms, is mediated by excitatory glutamatergic synapses. Further, elimination of glutamatergic activity revealed an underlying left-right alternating circuitry, posing intriguing evolutionary and functional questions.
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Available only to users on the Bowdoin campus.