Research ArticleNEUROPHYSIOLOGY

Subdomains within orientation columns of primary visual cortex

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Science Advances  05 Jun 2019:
Vol. 5, no. 6, eaaw0807
DOI: 10.1126/sciadv.aaw0807
  • Fig. 1 Highly accurate and quantitative determination of PC locations.

    (A) Vascular pattern of the cortical surface. (B) The color-coded orientation map of the cortex in (A). (C) Two neighboring PCs (locations 1 and 2) and three evenly spaced intervening points (DP, location 3; DM, locations 4 and 5) in the orientation domain. The eight stimulus orientations are color coded at 22.5° intervals. Scale bars, 500 μm (A and B) and 100 μm (C). (D) Examples of the sine-like LFP orientation-tuning curve at false PC sites. The three LFP curves were recorded at a false PC site [maximal orientation scatter (MOS) = 18°] in depths of 47, 125, and 214 μm from the pial surface, respectively. Their non–sine-like index (NSI) values are all 0 (highly sine-like). (E) Examples of the non–sine-like LFP orientation-tuning curve at true PC sites. The three LFP curves were obtained at depths of 82, 146, and 272 μm, respectively, at a true PC site (MOS = 65°). Their NSI values are 0.34, 0.46, and 0.32, respectively. (F) Determining the NSI threshold for PCs. (G) Application of the NSI threshold to recorded sites and the population of cells recorded at sites of PC, DM, and DP, which are targeted using LFP methods.

  • Fig. 2 Orientation tuning width, SF, and TF characteristics.

    (A) Orientation tuning curves of three cells located at PC (blue), DM (green), and DP (red) (color-coding same for all graphs). The tuning curves are fit with a Gaussian function (dashed lines). Horizontal arrows show WHH. (B) SF curves of three cells. The peak values show the optimal SF. (C) TF curves of three cells. The peak values show the optimal TF. Shadings in (A) to (C) represent the SDs. (D to F) Boxplots of WHH values and preferred SF and TF for PC, DM, and DP neurons. *, **, and *** represent the P values in individual comparison and are smaller than 0.05, 0.01, and 0.001 respectively. n.s., not significant.

  • Fig. 3 CRF size, surround suppression strength, and surround orientation tuning.

    (A and B) The response in spikes per second (y axis) is plotted against the diameter of the circular grating patch (x axis). Dashed lines indicate the best-fitting Gaussian function integrals. Shadings represent the SDs. Arrows indicate stimulus diameter at which responses were maximal and asymptotic. (A) A cell (at location “3” in Fig. 1C) exhibiting no suppressive surround (SI = 0). (B) A cell (at location “1” in Fig. 1C) showing suppressive surround (SI = 0.38). (C) The average normalized tuning curves of surround for PC, DM, and DP neurons. The shadings represent ±SEM. (D) Boxplot of CRF size for PC, DM, and DP neurons. (E) Boxplot of SI for PC, DM, and DP neurons. (F) Boxplot of ISD for PC, DM, and DP neurons. *, **, and *** represent the P values in individual comparison are smaller than 0.05, 0.01, and 0.001 respectively. n.s., not significant.

  • Fig. 4 Response latencies of DM and PC neurons.

    (A) The mean normalized LFP response curves of DM (solid lines) and PC (dashed lines) sites. Shadings represent the SEs. (B) Histogram distribution of response latencies (time to peak) at DM and PC. The time to peak of LFP at DM sites (mean ± SEM, 74.5 ± 1.48 ms; n = 35) is significantly shorter than that at PC sites (mean ± SEM, 88.2 ± 3.03 ms; n = 26; P < 0.01, U test). (C) The mean normalized single-unit PSTHs of DM (solid lines) and PC (dashed lines) neurons. Shadings represent the SEs. (D) The distribution of response latencies (time to 15% of the response peak) of complex neurons at DM and PC. The mean latency of DM neurons (mean ± SEM, 39.8 ± 2.39 ms; n = 38) is significantly shorter than that of PC neurons (mean ± SEM, 56.0 ± 4.56 ms; n = 29) (P < 0.01, U test).

  • Fig. 5 Orientation column summary template of PC, DM, and DP neuron properties.

    (A) Orientation column template: The three concentric rings represent the subdomains of a pinwheel-like architecture centered on PC. Inner circle, PC; intermediate circle, DM; and outer circle, DP. Each dot represents one neuron. The circular position of each dot represents its orientation preference (angular coordinate). Radial position represents HI value (white arrows: 0 to 1 HI index for each zone). Dot size represents CRF size. Dot color represents value of SI (0 = no surround suppression, 1 = maximal surround suppression; color scale bar below). (B) Enlarged column template of the PC subdomain in (A). The size and color scale of the dots are identical to those in (A).

  • Fig. 6 Model depicting proposed three components of contour processing.

    (A to C) Top row: Oriented neurons (black ovals with oriented line segments) within orientation subdomains [green ovals: (A) DP subdomain, (B) DM subdomain, and (C) PC subdomain]. Middle row: Schematic orientation tuning curves for DP, DM, and PC neurons. Bottom row: Functional characteristics of DP, DM, and PC neurons and their proposed roles in contour processing (straight, curved, and corner symbols at the bottom). (A) DP subdomains are linked to other DP subdomains of similar orientation selectivity. This represents an iso-orientation network. (B) DM subdomains receive inhibitory input from similarly oriented neurons in the same orientation column. (C) PC subdomains receive inhibitory input from differently oriented columns. (D) Model of the orientation organization circuit as it relates to contour processing. DP, DM, and PC locations receive inputs (red arrows). DP, locus of linear contour segment representation; DM, orientation-dependent suppression from DP inputs (blue); PC, orientation-independent suppression from DM inputs (green). Bottom: Red circles indicate different parts of a heart shape image that would be processed by DP (line), DM (curve), and PC (corner). Arrows, excitatory inputs; line with dot, inhibitory input.

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    • Fig. S1. Ensuring the electrode is perfectly perpendicular to cortical surface.

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