For the 2nd and bottom row, shaded areas represent SEMs across neurons. We show mean relative pseudo-R 2 over time, of the upcoming movement (green) and hand position (purple) covariates. Here, we show the importance of parameters in the GLM, across time, for PMd neurons. d We utilized a generalized linear model (GLM) to control for confounds in the PSTHs, including different distributions of starting positions, upcoming movements, and previous movements. c PSTHs of reaches opposite the PD, with a starting hand position near the PD (blue) vs. a position opposite the PD (higher probability of moving near the PD red). b PSTHs of reaches near the PD, with a starting hand position near the PD (lower probability of moving near the PD blue) vs. a PSTHs of reaches near the preferred direction (PD black) vs. a-c Peristimulus time histograms (PSTHs) for PMd neurons, aligned to target onset. Bottom row: Normalized averages of PR neurons. Third row: A potentialresponse (PR) neuron. Second row: Normalized averages of SR neurons. First row: A selected-response (SR) neuron. We used these divisions for plotting, rather than standard quartiles, to ensure In panels b and d, distances from the center are divided as follows: "closest" is 0-20% of distances from the center, "mid-close" is 20-40%, "mid-far" is 40-60%, and "farthest" is 60-100%.
In panels c and d, error bars represent SEMs. "Unexpected" reaches had an angular difference of more than 120°. "Expected" reaches are those that had an angular difference between the actual and expected target directions of less than 60°. d The difference in mean latency between expected and unexpected reaches (expected minus unexpected), depending on the hand's distance from the center. c The mean latency of reaches as a function of the angular difference between the actual and expected target directions. Error bars are standard errors of the median. Different traces are shown for hand positions at varying distances from the center of the workspace. Negative biases signify movement away from the expected direction. A bias of 1 signifies that the direction of the trajectory is toward the expected target direction, while a bias of 0 signifies that the direction of the trajectory is toward the actual target direction. b The median bias of the trajectory over time. The inset shows an enlarged view of the beginning of the reach. It later moves in the actual direction of the target. The initial direction of the reach (green) starts toward the expected direction of the target, given the current hand position. Across the population, PMd activity represents probability distributions of individual upcoming reaches, which depend on rapidly changing information about the body’s state in the environment.īehavior. PMd, but not M1, neurons have increased activity when the monkey’s hand position makes it likely the upcoming movement will be in the neurons’ preferred directions. The hand’s position within the workspace creates probability distributions of possible upcoming targets, which affect movement trajectories and latencies.
![twomon cant extend twomon cant extend](https://y31uv4ra1.vo.llnwd.net/content/wp/tweaklibrary_com/uploads/2020/11/extend-volume-of-the-drive.png)
Here, we record from dorsal premotor cortex (PMd) and primary motor cortex (M1) while monkeys reach to randomly placed targets. However, little is known about how the brain represents such distributions, and uses them in movement planning. More generally, the distribution of possible movements is conditioned on the state of our bodies in the environment, which is constantly changing. For example, when our arm is fully outstretched, we cannot extend it further. Our bodies and the environment constrain our movements.