| Notes: | Advisor: Nicholas G. Hatsopoulos.
Thesis (Ph.D.)--The University of Chicago, Division of the Biological Sciences, and The Pritzker School of Medicine, Committee on Computational Neuroscience, 2011.
Dissertation Abstracts International, Volume: 72-12, Section: B, page: 7209.
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| Summary: | There are many examples of sensory neurons that are more responsive to natural, ethologically relevant stimuli, rather than artificial stimuli: in zebra finches, neurons in the auditory circuit of the vocal control system are more responsive to the bird's own song, compared to noise, tones, a conspecific's song, and even the bird's own song played in reverse. In macaque primary visual cortex, spatiotemporal receptive fields (STRF) that are estimated with natural vision movies predict natural visual responses significantly better than STRFs estimated with synthetic sinusoidal gratings. In the motor system, encoding studies tie movement parameters, instead of stimuli, to a neuron's response. In order to reduce the strong correlations between the joint angle kinematics and kinetics in a given naturalistic movement, investigators typically train their animal to perform a constrained, or artificial, movement. If neurons in motor cortex encode an ethologically relevant movement instead of a single joint angle or muscle activation, they would exhibit less activation during a constrained version of the movement.
The goal of this thesis was to study how neurons in the arm and hand area of the macaque's primary motor cortex (MI) encode a reach-to-grasp movement. As an ethologically relevant behavior in the macaque's repertoire, reaching and grasping, or prehension, is ideally suited to study how their motor cortex encodes upper limb movement. We used a combination of extracellular multi-electrode array recordings and infrared camera-based three dimensional motion tracking of the arm, hand and finger kinematics to study how MI neurons in monkeys encode isolated grasping movements and later, reach-to-grasp movements. The results provide evidence that single MI neurons encode isolated grasping and reach-to-grasp movements in terms of their joint kinematic trajectories, of about 350ms in duration. These trajectories represent multiple time-varying features of the hand and arm, rather than individual joints, at one point in time.
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