BME MS Defense: Evan Kirsch
Primary Motor Cortex Neuron Activity and Kinematic Synergies during Individuated Finger and Wrist Movements
Supervised by Prof. Marc H. Schieber, M.D., Ph.D.
Dimensionality reduction techniques such as principal component analysis might be used to simplify the complex control required to manipulate the many rotational degrees of freedom (DoFs) in the hand. Previous studies have shown that a small number of kinematic synergiesâidentified by principal component analysis of the wrist and digit DoFsâcan explain most of their covariation during hand movements. To test whether neurons in the primary motor cortex intrinsically use kinematic synergies to simplify the complexity of hand movement control, we examined single neurons recorded from two male rhesus macaques performing an individuated finger and wrist movement task. The task apparatus provided six analog signals representing the simultaneous positions of each the five digits and the wrist. Principal component analysis was performed on these six position signals. We then cross-correlated each neuronâs instantaneous frequency with each of the six original position waveforms, and with each of the principal component temporal weighting vectors. Comparing the values of the maximum absolute correlation with the individual digit kinematics and with the temporal weighting vectors, we found that motor cortex neurons correlated significantly better with the individual digit kinematics than with kinematic synergies.