Research

Large-Scale Cortical Dynamics Leading to Spontaneous and Task-related Movements

We are examining the neural substrate for spontaneous and task-related movements with a global view of the brain activity, i.e. using wide field imaging data. We are (a) developing a novel method termed `Localized Non-negative Matrix Factorization' (LocaNMF) to decompose neural data into a labeled low-dimensional set of neural signals in order to jointly model the dynamics of global cortical activity, and (b) using machine learning tools to efficiently represent high-dimensional behavior. This work is in collaboration with Elizabeth Hillman and Anne Churchland.

Computational Principles underlying Speed Control in the Primary Motor Cortex

How do we make the same movement but faster? We are examining computational principles governing M1 neurons' activity during very similar movements performed at different speeds. The dynamics of M1 neurons may be thought of as semi-autonomous, as uncovered by a metric known as 'tangling' in high-dimensional spaces. We examine differences in the dynamics displayed by neural and muscle signals during movement at different speeds, using both computational and theoretical models. This work is in collaboration with Mark Churchland.

Fundamental Limitations of the Sensorimotor Control System

We examined the fundamental limitations in making fast movements due to the neural processing of signals. The ability to move fast and accurately track moving objects is constrained by the biophysics of neurons and dynamics of the muscles involved. Yet, the corresponding tradeoffs between these factors and tracking motor commands have not been rigorously quantified. We use feedback control principles to identify performance limitations of the sensorimotor control system to track fast periodic movements.

Designing a Neural Decoder that Ensures Stability in Closed Loop

We explored real-time decoding schemes for spiking neurons and analyzed the stability of these schemes in closed loop. The research can be applied towards a Brain-Machine Interface to drive a prosthetic or a compensatory device in a closed loop system involving visual and sensory feedback.

The Role of Basal Ganglia Neurons in Movement Generation

We performed an in-depth analysis of the firing patterns of Globus Pallidus internus neurons within the basal ganglia that relay information between the somatosensory cortex and the motor cortex. We analyzed the behavior of basal ganglia neurons in healthy subjects and in subjects with Parkinson’s Disease in order to quantify the effect of this disease. We also studied the effect of Deep Brain Stimulation as well as movement-related behavioral tasks on the activity of individual neurons.

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