Fig. 3: Activity modes coding stimulus, choice and action are supported by distinct neuronal populations.
From: Thalamus-driven functional populations in frontal cortex support decision-making
a, Activity modes correspond to weighted sums of individual neuron activities. The weights show contribution of individual neurons. b, Neuron weights in the t-SNE. Dots, individual neurons. Dot size shows weight magnitude and colors indicate positive (red) or negative (blue) weights. Only neurons with more than five error trials of each trial type are included (n = 3,966). c, Top: a seven-dimensional vector represents each neuron’s contributions to the activity modes. For neuronal populations with random mixtures of selectivity, coding vectors are uniformly distributed around the origin, which can be quantified by angles between nearest neighbors (ePAIRS test). Bottom: the distribution of angles deviates significantly from random distribution of coding vectors and from a synthetic population coding random mixtures of activity modes, indicating that distinct task selectivity is not randomly mixed within ALM populations. P < 1 × 10−4, one-sided test (Methods). d, A two-dimensional vector represents each neuron’s contributions to a pair of activity modes. If neurons encode random mixtures of each activity mode, rather than encoding one mode or another, these vectors are uniformly distributed. Neuronal populations coding single activity modes are located around 0° and 90°. Neural coding of stimulus, choice and action exhibits significant peaks at 0° and 90°. In contrast, coding of choice and ramping shares the same neuronal population. Dashed line, synthetic population coding mixtures of activity modes. Stimulus and choice, P = 0.0018; choice and action, P = 4.40 × 10−6; stimulus and action, P = 2.27 × 10−9; ramping and choice, P = 0.19, Kolmogorov–Smirnov test, observed distribution versus synthetic population, one-sided test. e, Left: k-means clustering on activity mode weights delineates neurons into six clusters (Methods). Right: clusters shown in the t-SNE. Clusters carrying the most variance for the stimulus, choice and action modes are termed stimulus, choice and action coding (Extended Data Fig. 5a). f, Classification of stimulus, choice and action coding neurons using a nearest-neighbor classifier in the t-SNE (Methods). Mean ± s.e.m. (bootstrap across neurons). Only neurons with more than five error trials of each trial type are included (n = 3,966). g, Distribution of stimulus, choice and action coding neurons across depth. Fraction is relative to all neurons from each functional population (stimulus coding, n = 583 neurons/73 mice; choice coding, n = 694 neurons/73 mice; action coding, n = 491 neurons/73 mice). Mean ± s.e.m. across mice (dots). K-S, Kolmogorov–Smirnov test; W, weight.
