Northwestern University

Apr
16
Mon 12:00 PM

Dr. Andrew Miri: Connecting motor cortical firing dynamics to descending circuit operation

When: Monday, April 16, 2018
12:00 PM - 1:00 PM  

Where: Shirley Ryan AbilityLab, 355 E. Erie, Chicago, IL 60611 map it

Audience: Faculty/Staff - Student - Public - Post Docs/Docs - Graduate Students

Cost: None

Contact: Tommi Raij, MD, PhD   312.238.4401

Group: Shirley Ryan AbilityLab Research Seminar Series

Category: Lectures & Meetings

Description:

Abstract

The patterns of muscle activation that drive movement reflect an interplay between spinal circuits and brain regions such as the motor cortex that engage these circuits through descending projections. My work combines genetically-mediated approaches for measuring and perturbing activity in neuronal subpopulations with quantitative and model-based analyses to understand how descending projections steer movement. In this talk, I will first discuss recently published work that aims to resolve divergent views of motor cortical function. Blocking motor cortical output with lesions or pharmacological inactivation has identified a limited set of movements that require motor cortex. However, results from electrical recording and stimulation suggest that motor cortex could play a broader role. We addressed this ambiguity using measurement and perturbation of motor cortical activity together with forelimb EMG in mice during two forelimb movements that differ in their requirement for cortical involvement. Rapid optogenetic silencing and electrical stimulation indicated that short-latency pathways linking motor cortex with spinal motor neurons are selectively activated during one behavior. Analysis of motor cortical activity revealed a dramatic change between behaviors in the coordination of firing patterns across neurons that could account for this differential influence. Our results suggest that changes in motor cortical output patterns enable a behaviorally-selective engagement of short-latency effector pathways. I will also discuss two on-going projects. One examines how motor cortex engages spinal circuits to enable the simultaneous co-activation of antagonist muscles. We have developed a behavioral paradigm in which mice switch between phases of antagonist muscle alternation and co-activation. Using EMG, multi-electrode array recording and optogenetic perturbation, we are testing existing ideas from primate studies. Another on-going project uses viral methods for accessing corticospinal neurons targeting different spinal interneuron subtypes to probe the functional roles of corticospinal projection types. Finally, I will briefly touch on plans for my new lab here at Northwestern.

 

Speaker

Andrew Miri, PhD, received undergraduate degrees in neuroscience and mathematics from Brown University (2002). After a stint as a high school mathematics teacher in Boston, he pursued a Ph.D. under the supervision of David Tank at Princeton University where he was awarded a predoctoral fellowship from the National Science Foundation. His graduate work used calcium indicator imaging and cell-attached recordings in behaving larval zebrafish to address the circuit architecture of the oculomotor neural integrator. Since completing his dissertation (2011), he has worked in the laboratory of Tom Jessell at Columbia University where he was awarded a postdoctoral fellowship from the Helen Hay Whitney Foundation. His postdoctoral work built mechanistic understanding of motor circuit function by combining contemporary approaches for measuring and perturbing neural activity together with genetically-mediated approaches for targeting neuronal subtypes and computational analyses of neural activity dynamics.

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