Article Figures & Data
Figures
- Fig. 1.
Histological demonstration of the BS representation in V1. A, Schematic diagram showing the lateral surface of the macaque cerebral cortex. The dotted line indicates where the section illustrated inB was cut. B, Parasagittal section through a posterior region of the cerebral cortex. The hatched region in the posterior wall of the calcarine sulcus (CS) represents an approximate location of the BS representation in V1. C, TMB-stained tangential section through the posterior wall of the CS. WGA-HRP was injected into the contralateral eye before killing the animal; the HRP-labeled region appears light, whereas the unlabeled region is dark. A, Anterior;D, dorsal; L, lateral; LS, lunate sulcus; M, medial; P, posterior;V, ventral.
- Fig. 2.
Responses of two representative V1 neurons activated by visual stimuli presented at the blind spot.A, Responses of a neuron (30494_1) to a large homogeneous white rectangular stimulus (surface stimulus) covering the entire blind spot. Left, The spatial relationship between the stimulus, which extended 6.7° horizontally and 10° vertically (thin line forming arectangle), and the blind spot (thick line). Middle, Responses recorded while only the BE was open (BE-viewing). Right, Responses recorded while the NE was open (NE-viewing). PSTHs and rasters are aligned with the onset of the stimuli, which were presented for 400 msec and are indicated by the thick horizontal line below each PSTH. Short vertical lines on the raster display indicate cell discharges; successive lines represent successive trials. In these PSTHs and those in other figures, the tick marks on thex-axis are every 500 msec, the bin width is 20 msec, and the calibration bar at the left of each histogram is 50 spikes/sec. B, Visual field representation of the recording site of the neuron in A as indicated by the receptive fields of other neurons recorded from the same penetration. The boundary of the blind spot is indicated by a broken line. Receptive fields of three single and multiple units (solid lines) recorded in the binocular condition are superimposed. They were located clearly inside of the visual field corresponding to the blind spot. C, Responses of another neuron (22594_1) to the surface stimulus. Conventions for rasters and PSTHs are as described in A.D, Visual field representation of the recording site of the neuron in C as indicated by the receptive fields of three other neurons recorded from the same penetration. For the sake of simplicity, all receptive fields are plotted as if they were located in the right hemifield in this and the following figures.deg, Degree; s, sec; spks, spikes.
- Fig. 3.
Comparison of responses to surface stimuli obtained under BE- and NE-viewing conditions. y-axis, Responses obtained while BE-viewing; x-axis, those obtained while NE-viewing. Each symbol represents a cell; solid symbols represent cells that responded to the surface stimulus during BE-viewing, whereas open symbols represent those that did not. Squaresrepresent cells whose responses were tested monocularly during NE-viewing; circles represent those tested binocularly during NE-viewing. Broken lines indicate where the response magnitudes are zero. The diagonal lineindicates the points at which responses obtained under the different conditions are the same.
- Fig. 4.
Responses of the same neurons shown in Figure 2,A and B, to a small square stimulus (0.67 × 0.67°) presented inside and outside of the blind spot while BE-viewing. The locations and size of the stimulus relative to the blind spot are shown as solid squares. Responses to each stimulus are shown below the squaresas PSTHs.
- Fig. 5.
Responses of a neuron to a small stimulus (0.67 × 0.67°) presented at various locations inside and outside of the blind spot (B; solid line) or its corresponding region (A; dashed line). Insets, Responses of this neuron to the surface stimulus. A, Responses obtained during NE-viewing. Each PSTH is plotted at the position where the stimulus was presented. Significance of the responses is indicated byasterisks: **p < 0.01, and *0.01 ≤ p < 0.05 in ttests. The boundary of the receptive field was determined as shown by the solid circle. B, Responses obtained during monocular BE-viewing. Note that there was no response when the stimulus was presented within the blind spot, but responses to stimuli outside of the blind spot were similar to those shown in A.
- Fig. 6.
Superimposed plots of the receptive fields of V1 neurons recorded from the BS representation. These receptive fields (thin solid lines) were recorded by the use of small stationary stimuli (0.33 × 0.33 to 1.3 × 1.3° squares) while NE-viewing. Thick broken lines indicate the boundary of the BS-corresponding region. A, Receptive fields of neurons responsive to the surface stimulus. Note that many neurons had large receptive fields that covered most of the blind spot and even extended outside of it. B, Receptive fields of neurons that did not respond to the surface stimulus. A few neurons had large receptive fields extending outside of the blind spot.
- Fig. 7.
Stimulus size–response relationships of neurons activated by the surface stimulus while BE-viewing. A, Various-sized square stimuli were used to assess spatial summation properties. For each neuron, all stimuli were centered on the same position within the BS-corresponding region (broken line). The actual position differed from cell to cell, however, and a representative example is shown. B, The relationship between stimulus size and response magnitude in 10 neurons is shown. The responses were recorded while NE-viewing and are normalized to the maximum response of each neuron.C, Ranges of the stimulus size that caused a response magnitude greater than half of that of the optimum size for each of the 10 neurons in B are indicated as solid horizontal bars. Lowercase letters to theleft of each bar correspond to those inB. The optimum size is indicated by an open circle, and the range of sizes that yielded responses that were statistically not different from the maximum response (ttest, p > 0.05) are indicated by horizontal lines above each bar. The receptive field sizes (√ horizontal extent × vertical extent) of nine of these neurons are indicated by arrowheads. At thebottom, the range of the stimulus size causing responses in one of the neurons unresponsive to the surface stimulus is indicated as a shaded horizontal bar. A short gapnear the left or right ends of thebars indicates that the response was greater than half of the maximum for the smallest or the largest stimuli used.
- Fig. 8.
Comparison of response latencies obtained under BE- and NE-viewing conditions. The x- andy-axes plot the latencies of responses obtained while NE- or BE-viewing, respectively. For each cell under each condition, PSTHs were convolved with Gaussian (ς = 10 msec), and the time required for the resultant spike density profile to reach threshold (2 SD above the background discharge rate) was taken as the latency. Each circle represents a cell; solid circles depict cells in which the magnitudes of evoked responses during a 100 msec period after the latency did not differ significantly (t test, p > 0.05) under the two viewing conditions; open circles depict cells in which response magnitudes did differ significantly under the two viewing conditions. The line indicates where the latency is the same under the two viewing conditions. Note that for most cells, the latency was larger in BE-viewing.
- Fig. 9.
Time courses of the responses to the surface stimulus. Responses are shown as spike density plots in which PSTHs were subjected to Gaussian (ς = 10 msec) smoothing. In eachpanel, the dotted line represents BE-viewing; the solid line represents NE-viewing.A, Responses of a representative cell in which the magnitudes of evoked responses during a 100 msec period after the latency did not differ significantly (t test,p > 0.05) under the two viewing conditions.B, The mean responses of eight such neurons. The period of stimulus presentation is indicated by the thick horizontal line. The calibrations bars on the left are 50 spikes/sec, and background discharge rates were subtracted from each plot.
- Fig. 10.
Relationship between recording depth and the receptive field sizes (√ horizontal extent × vertical extent) of 65 V1 neurons in the BS representation. Solid squaresrepresent neurons that responded to the surface stimulus while BE-viewing; open circles represent neurons that did not. The x-axis shows the distance between the entrance to the posterior bank of the CS and the recording site for each neuron; a value of zero corresponds to layer 6, whereas a negative value arises when the electrode was retracted slightly to maintain isolation of a single unit. Inset, Schematic diagram showing the electrode track. The electrode first passed through the surface cortex of V1, then passed through the white matter, and finally entered the posterior bank of the CS from layer 6.
Tables
Orientation selective Color selective Cells responsive to the surface stimulus in BE-viewing 3/6 (50%) 5/5 (100%) Cells unresponsive to the surface stimulus in BE-viewing 16/23 (69.6%) 10/16 (62.5%) Frequencies of the cells exhibiting selectivity (selectivity index > 0.5; p < 0.05, ANOVA) for orientation and color are shown. Frequencies of the cells responsive and those unresponsive to the surface stimulus in BE-viewing are indicated separately.
In this issue
