Hybrid dedicated and distributed coding in PMd/M1 provides separation and interaction of bilateral arm signals
Fig 8
Behaviorally specific information exists within a subspace that captures bilateral activity.
(A) Illustration of the population partitioning approach. Each unit is represented as a pie-chart displaying the relative modulation during left and right arm trials. Most units in the left hemisphere are more strongly modulated during right arm movements (mostly purple pie-charts), yet some prefer left arm movements (mostly yellow pie-charts). Regardless as to which hemisphere each unit is in, the population may be subdivided into left and right arm preferring sub-populations. On the extreme that all information about each arm is contained within dedicated sub-populations, this simple division will fully segregate the signals such that movements of the non-preferred arm cannot be classified. (B) Modulation as a function of time, taken as the mean over all units during trials of their preferred or non-preferred arm, +/- standard error. Horizontal bars at the top indicate the phase windows used in analysis. (C) Target classification accuracy using LDA for movements of the preferred arm. Models are trained on each time point and tested on each time point to provide high temporal resolution and inform cross-phase generalization of the classifier. Plots are averaged over all sessions (13 Monkey O, large plots, 7 Monkey W, small plots) and both sub-populations (left-preferring, right-preferring). (D) Same as (C), but for non-preferred arm movements. (E) Summary data of (C,D) for monkey O, top panel, and monkey W, bottom panel. Mean +/- standard deviation across datasets. (F) Ratio of the variance captured in the distributed subspace for the two limbs.