Fig. 2: Clustering of neurons with ON/OFF-dominant receptive fields.

a–c Presentation of flashed sine-wave gratings (a), L-cone-isolating stimuli (for example) were presented 4 frames per second (4 f/s) to the anesthetized macaque monkey (b) during simultaneous two-photon calcium imaging (c) in primary visual cortex (V1). Scale bar in c is 200 µm. Repetition of experiments is shown in Supplementary Table 1. d–h Higher magnification view of the imaging region (d, scale bar: 20 µm) with four neurons selected as examples to show their fluorescence signals, inferred spike rates, and their receptive fields computed from spike-triggered average (STA) shown in e–h. The color of traces in e–h are matched with the color of circles (for indicating neurons only, not the actual ROIs for exacting signals) in d to indicate the origin of the signals. Responses of the four different neurons to four different stimuli, L-cone-isolating (e), M-cone isolating (f), S-cone isolating (g), or achromatic (h) flashed sine-wave gratings, are shown as four panels. The fluorescence signal (upper trace in each panel) is normalized to the response to blank condition (∆F/F). The spike rate (lower trace in each panel) is inferred from raw fluorescence signal. Red colors in the STA images indicate ON subregions of spatial receptive fields, and blue indicates OFF subregions. Each grid in the STA images is 0.2°, and total size is 1.6°. i, j Functional maps of the locations of neurons with ON-dominant (red dots) and OFF-dominant (blue dots) receptive fields in response to each stimulus type (L-, M-, and S-cone isolating and achromatic (Achro.)). Neurons are organized in ON and OFF clusters. i, j are two imaging regions from animal A1 (more examples are shown in Supplementary Fig. 1 and also summarized in Supplementary Table 1); both panels illustrate results from two merged imaging planes. Scale bar in j: 200 µm; applies to all panels in i and j.