We understand surprisingly little about how complex motor sequences are orchestrated in the brain. The role of higher brain centers, such as neocortex, in driving these behaviors in the rodent brain remains unclear, in part because of the difficulties inherent in observing well-characterized complex behaviors. To address this issue, I employed the Scotinomys teguina, a tropical rodent that robustly produces audible, stereotyped vocalizations consisting of a rapid sequence of frequency-modulated notes of increasing duration. First, plethysmography was used to demonstrate that each note consists of brief exhalations surrounded by inspiratory mini-breaths. Next, using electromyography, laryngeal muscle activity was shown to be highly correlated with ongoing song. Using intracortical microstimulation, a compact subregion of the motor cortex was identified that formed a functional projection to the larynx through a downstream pathway. Delivering electrical stimulation to the laryngeal motor cortex (LMC) during song often resulted in stimulation-locked sequence pauses and premature song arrest, strongly suggesting the motor sequence underlying vocalization is cortically driven. Importantly, sequence progression was suspended during the duration of the pause, suggesting the necessity of motor cortical involvement to advance the sequence. Local temperature modulation within the LMC slowed the progression of the sequence, further supporting the notion that motor cortical circuits are playing an active role in driving behavioral sequences in the rodent. These findings are the first demonstration that motor cortex helps to generate motor sequences in rodents, opening the door to a circuit understanding of cortically mediated skilled behaviors.
|Advisor:||Long, Michael A.|
|Commitee:||Buzsaki, Gyorgy, Froemke, Robert C., Jarvis, Erich D., Rinberg, Dmitry|
|School:||New York University|
|Department:||Basic Medical Science|
|School Location:||United States -- New York|
|Source:||DAI-B 77/07(E), Dissertation Abstracts International|
|Subjects:||Biology, Neurosciences, Behavioral Sciences|
|Keywords:||Motor control, Neocortex, Rodent, Scotinomys, USV, Vocalization|
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