Figure 4:

Effects of feature competition on population encoding of orientation

(a) Naïve-Bayes decoding of orientation from population activity during influence blocks. Error bars, mean ± sem, logistic regression mixed-effects model, non-overlapping bins. Line, logistic regression on non-binned data with a continuous similarity predictor; p = 0.00056, n = 54,187 trials, F-test.

(b) Population activity (deconvolved ΔF/F) along dimension for 0-degree oriented stimuli on control trials, example experiment. Activity along this dimension was high only during 0-degree stimuli, showing that population dimensions allow orientation discrimination. Shading, mean ± sem (bootstrap)

(c) Following (b), population activity along the 0-degree dimension during a 0-degree stimulus was decreased by photostimulation of example neurons preferring a similar stimulus (10-degrees) but not neurons preferring alternate stimuli (45-degrees).

(d) Following (b-c), photostimulation triggered little change along dimensions not aligned (0-degree dimension) with the presented stimulus (45-degrees).

(e) Changes in population encoding as a function of similarity between the orientation of visual stimulus and a photostimulated neuron’s preference. Dots, mean ± sem for 5 non-overlapping bins; line, linear regression on non-binned data using a single continuous predictor. The population response along the dimension of presented stimulus (‘gain’ dimension) was suppressed when orientations were similar, c = 0.0115, p = 0.0076, Spearman rank correlation. n = 54,187 trials.

(f) Responses along other directions were not affected, orthogonal orientation projection, c = 0.0045, p = 0.2974, n = 54,187 trials.

(g) Responses along the uniform dimension were not affected, c = −0.0046, p = 0.2880, n = 54,187 trials.

(h) Rate-network model. Neuron i receives feedforward input u_i and has functional connection w_i,j with neuron j.

(i) Model neuron responses for a 90 degree stimulus (dashed line). Feedforward inputs were identical for all networks.

(j) Model neuron responses for a linear sum of 60 and 120 degree stimuli. Gray lines, summed network response to the stimuli presented individually. Feedforward inputs have maxima ~70 and 110 degrees.