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. 2015 Mar 4;85(5):1070–1085. doi: 10.1016/j.neuron.2015.01.027

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© 2015 The Authors

This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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The Optic Tectum Shows Non-Linear Cooperative and Competitive Dynamics

(A) Activation probability of spontaneous assembly neurons as a function of the correlation between the assembly pattern and the spontaneous tectal network activity. Average activation probability “facilitation” profiles for the upper-third most-steep curves (red, non-linear step-like group) and for the rest of the curves (blue, linear group). As a control, the curves for null models are presented in black. Curves, regression fits across assemblies; confidence interval, SEs.

(B) Top: topography examples of spontaneous assemblies with step-like non-linear dynamics (assembly neurons in yellow). Bottom: corresponding raw data (dots) and regression fits (black curves) of the activation probabilities of the assembly’s neurons. Note the all-or-none-like nature of these curves, suggesting highly recurrent facilitatory cooperative dynamics.

(C) Percentage of responsive neurons (top) and the population average of the mean ΔF/F responses across trials (bottom; only responsive neurons) of individual-light-spot and simultaneous-light-spot stimulation, schematically indicated by a single and a pair of black dots, respectively. Gray lines, single experiments; red lines, average. In top panel, percentages are relative to the combined total of neurons responsive to the two light spots presented individually.

(D) Two examples of single-trial (rasters) and average (bar plots) tectal response patterns to individual light spots (top and middle panels; 10 trials; red and green for most rostral and most caudal light spots, respectively) and simultaneous stimulation with both light spots (bottom panel, 20 trials, yellow). Grayscale: ΔF/F amplitude in rasters. Only responsive neurons are shown. Respective color-coded topographies of neurons that preferentially responded to either the most rostral or most caudal light spot in individual light-spot stimulation (top) and of the average ΔF/F tectal response pattern to simultaneous-light-spot stimulation (bottom). Note how responses to simultaneous stimulation are dominated by the most rostral or the most caudal light-spot representation in examples 1 and 2, respectively.

(E) Visualization of the linear decomposition analysis of the two examples shown in (D). Decomposition weights of single-trial responses to individual (red dots, rostral; green dots, caudal) and simultaneous (yellow dots) light spots with respect to the two average single-spot templates (bar plots in D). Dashed line: equal (balanced) weights. Note how yellow dots overlap with red (top) and green (bottom) dots.

(F) Left to right, visualization of the decomposition analysis of pooled experiments according to four categories: bias competition for rostral neuronal group, bias competition for the caudal group, alternated bias across trials, and balanced responses (no bias of a given group). Top: decomposition weights, color code as in (E). Bottom: distributions of the corresponding imbalance indexes. As a control, we show the expected distribution for a balanced linear response summation scenario estimated from all the possible pair-wise sums of the corresponding individual-light-spot trial responses (black line).