Physiology and Biophysics

Steve Perlmutter Ph.D.

Research Associate Professor

Ph.D. Neuroscience and Physiology
Northwestern University, 1991

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Neural Control of Limb Movements

Primates generate an incredibly varied repertoire of motor behaviors. How does the nervous system accomplish this flexibility? We are interested in neural processes in the spinal cord and cerebral cortex that generate skillful voluntary movements of the arm and hand.

Information about the intended goal of a movement must be transformed into a spatial and temporal pattern of muscle activity, a "motor pattern", to implement an appropriate behavior. Cortical and spinal pathways execute this transformation by integrating signals specifying behavioral intent, the state of the musculoskeletal system, and external constraints and loads. This transformation is dynamic and eminently plastic - the motor system has a rich capacity to adapt motor patterns to changing task requirements, environmental conditions, and even internal damage. We are studying how the brain and spinal cord achieve these transformations.

My interest in this field is motivated by its relevance to clinical issues of motor impairment and recovery of function following central nervous system damage. Abnormal patterns of muscle activation following brain and spinal cord injury contribute to weakness and loss of coordination. We still do not understand the neural mechanisms of motor deficit and of natural or therapy-induced restoration of function following lesions of the central nervous system. Our research will advance our understanding of the capacity of lesioned motor systems for neural plasticity and adaptation, and suggest ways to exploit this potential for improved function.

The laboratory's approach is multidisciplinary. Neurophysiological, anatomical, behavioral and computational techniques are employed. We record the activity of individual neurons, pairs of neurons, and localized groups of neurons (local field potentials) in behaving macaque monkeys during performance of different motor behaviors. Neuron recordings are done in conjunction with stimulation and correlational techniques to identify inputs and outputs, and with local iontophoresis to characterize specific neurotransmitter and neuromodulatory systems. Neuroanatomical experiments trace neural projections, and neural network models explore the computational properties of neural circuits. Together, these techniques allow us to elucidate the organization and function of the cortical and spinal circuitry that controls movement.