Related to Materials and methods. (A) Time course of grasp task. Start of Movement, Maximum Aperture, and Grasp epochs were inferred based on hand kinematics. Arrows indicate motion of the robot presenting the object or motion of the hand. (B) Multi-electrode arrays were used to record neuronal activity. (C) Probability density of the range of motion, where each instance is the difference between the maximum and minimum angle of a joint DOF during a single trial. Instances are pooled across joint DOFs, sessions, and animals. (D) Probability density of mean joint angular speed, where each instance is the mean speed of a single joint degree of freedom (DOF) during a single trial. (E) Performance of a linear discriminant analysis to decode object identity on the basis of hand posture (DOFs). Objects are most discriminable just before object contact (Grasp) but are also discriminable well above chance long before contact is established (for example, at maximum aperture). Trace indicates the mean, error bars the S.E.M. across monkeys. (F) Scree plots, for both reach- and grasp-related M1 responses used in the jPCA analysis, indicating the cumulative variance explained by the first n principal components of neural activity. Principal components analysis was applied to rate-normalized, trial-averaged, Gaussian-smoothed firing rates. (G) Relationship between the mean speed and mean range of motion for each DOF. Neither the mean joint angular speed (two-sample equal-variance t-test [t(202780) = 0.65, p=0.51) nor the joint angular range of motion (t(202780) = 1.8462, p=0.0649]) differs between reach and grasp. Moreover, the two DOFs tracked during reach follow the same trend as joint DOFs during grasp (R2 = 0.9820). In other words, grasping and reaching movements are associated with overlapping distributions of joint angular speeds and ranges of motion.
© 2019, Elsevier. Panels A-E and G are reproduced from Goodman et al., 2019, with permission from Elsevier. It is not covered by the CC-BY 4.0 licence and further reproduction of this panel would need permission from the copyright holder.