A METHOD FOR DETECTING THE TIME-COURSE OF CORRELATION BETWEEN SINGLE-UNIT ACTIVITY AND EMG DURING A BEHAVIORAL TASK

The chance that a change in excitability of one neuron leads to a chan ge in excitability of another is likely to vary within a single voliti onal act. This temporal variability in functional connectivity is impo ssible to assess with standard analytical procedures to accurately tha t measure the correlation between such elements. This reports describe s a technique designed to overcome this limitation by expressing a cor relation measure calculated repeatedly in short epochs throughout a be havioral trial. The activity of two elements, a motor cortical neuron and a shoulder muscle, that might take place during a drawing task was first simulated so that the correlation could be manipulated. Various correlation algorithms (standard cross-correlation, spike-triggered a verage, impulse-response function, impulse-response surface) were test ed with these data. Spike trains from a monkey's motor cortex and rect ified EMG from its posterior deltoid muscle were compared using the sa me techniques and shown to have a correlation that changed in a charac teristic manner throughout a task that required the monkey to draw a s inusoid.