Figure 4.

Signal properties. A, Modulation of the MUA illustrated in Figure 1A (recorded from PMd) during prehension. The monkey was required to reach in six directions and grasp an object using a power (left) or a precision (right) grip. Data are shown from 1600 ms before movement onset (vertical red lines) until 400 ms after. Horizontal lines, 6 μV. Each panel shows the MUA obtained by smoothing single trials (Gaussian kernel, SD, 30 ms) and averaging over 15 trials (±1 SEM). Activity is strongest for reaches in the top right direction regardless of grip type and for a power grip regardless of reach direction. Bottom, The MUA was used to predict reach and grasp. B, Single-channel prediction accuracies. Averages are shown for 615 SUs, 471 MSPs, LFPs, and MUA recordings, and 69 spikeless MUA recordings. The accuracy of single-channel MUA is higher than the accuracy of any other signal. C, Single-channel SNRs. Vertical red line, Movement onset; bands around each line, SEM. Before movement, the SNR of MUA is highest. D, Single-channel stability. Error bars indicate SEM. The MUA is the most stable signal. E, Channel-pair noise-correlations. A total of 2866 simultaneously recorded MSP, LFP, and MUA pairs (and 5700 SU pairs) were divided into five distance bins, each containing 573–574 sample points (1140 for SUs), and correlations (mean ± SEM) were computed separately for each bin. MUA correlations are of the same order of magnitude as MSP correlations and an order of magnitude lower than LFP correlations.