Article Figures & Data
Figures
- Fig. 1.
Stimuli. A, Two-dimensional shapes used to derive the 3-D stimuli of the search test. B,Vertical 3-D shape. The monocular images are shown for the correlated (first row), the decorrelated (second row), the solid 3-D shape (third row), and the 3-D rim (fourth row). The icons on theright schematically illustrate the perceived 3-D structure when the images are crossed fused. In all four vertical 3-D shapes, the outer contours were identical and curved in depth along the vertical axis. The surface of the correlated vertical 3-D shape was also curved in depth, as indicated by the luminance gradient in the icon of the correlated vertical 3-D shape. The surface of the 3-D boundary stimuli was uninformative about depth, indicated by the homogeneously dark (decorrelation), gray (solid), or blank (rim) surface in the icons on the right.C, Surface stimuli. The monocular images are shown for the restricted surface (top row) and the large surface (bottom row) stimuli, together with schematic illustrations of the perceived 3-D structure (right). The disparity varied along the surface of the shape in the vertical and in the horizontal direction. Both scale bars on the left of the monocular images indicate 2°. The scale bar for the restricted surface also applies to B and D. Note that the icons on the right only represent the 3-D percept, whereas the actual 2-D shape of the stimulus can be seen in the monocular images. Thus, only the large surface was square-shaped.D, Horizontal 3-D shape. The disparity varied only along the horizontal axis on both surface and boundary.
- Fig. 2.
Position-in-depth test. A, Example neuron. The icons above the peristimulus time histograms depict the position-in-depth of the stimulus for an observer viewing from the left (left column, near; right column, far). The horizontal scale bar (top right) indicates 0.25° disparity. Below the PSTHs, the mean position of left (red) and right eye (blue) are shown. The vertical bar on theleft of the eye position traces indicates 1°, and eachhorizontal bar indicates the duration of stimulus presentation (600 msec). The green lines are plotted as a reference at 200 msec after stimulus onset. The large scale bar on the right indicates 72 spikes/sec. The neuron fired strongly and selectively to the convex 3-D shape at every position in depth, and the selectivity was present in the initial part of the response. B, Population PSTH of all neurons that preferred the convex 3-D shape (N = 52). Same conventions as in A. The 3-D shape-preference is preserved at every position in depth. C, Population PSTH for all neurons that preferred the convex 3-D shape and for which binocular eye movements were recorded (N = 12). The mean positions of left (red) and right eye (blue) are plotted below the histograms. Same conventions as in A. Again, the response difference between convex and concave can be observed in the initial part of the response at every position in depth and is not influenced by the small (0.1°) vergence eye movement. D, Population PSTH of all neurons that preferred the concave 3-D shape (N= 52). Same conventions as in A.
- Fig. 3.
Selectivity for 3-D boundaries. A,Neuron showing selectivity for the correlated vertical, the decorrelated, and the solid shape pair but no selectivity for the 3-D surfaces. B, Neuron showing selectivity for the correlated vertical 3-D shape and for the restricted surface but no significant response differences for the decorrelated, the solid 3-D shape, or the large surface stimulus. The responses to the preferred 3-D shape (either concave or convex) are plotted in the top row (below the icons), the responses to the nonpreferred 3-D shape in the bottom row. The scale bars inA and B indicate 65 spikes/sec.
- Fig. 4.
Time course of 3-D boundary selectivity.A, Normalized population PSTH for all boundary neurons (N = 37), showing the average normalized response to the preferred (red) and nonpreferred (blue) correlated vertical (full line), the decorrelated (dashed line), and the solid shape pair (dotted line). B,Normalized population PSTH for all boundary neurons for which binocular eye movements were recorded (N = 12). Same conventions as in A.C, Mean difference in horizontal position between the left and the right eye, for the correlated vertical (first row), the decorrelated (second row), and the solid shape pair (bottom row), for convex (green) and concave (black) 3-D shapes. The vertical calibration bar on theleft indicates 1°. The pink vertical lineis a reference positioned at 200 msec after stimulus onset.
- Fig. 5.
Rim test. A, Example neuron showing selectivity for all 3-D boundaries tested. The calibration bar on theright indicates 67 spikes/sec. B, Normalized population PSTH for all neurons selective for the 3-D rim (N = 11). Same conventions as in Figure 3.
- Fig. 6.
Comparison of selectivity for correlated vertical and boundary stimuli. The NRDs for the decorrelated 3-D shape (triangles), the solid shape (asterisks), and the 3-D rim (squares) are plotted as a function of the NRD for the correlated vertical 3-D shape, for all boundary neurons (N = 37). The arrows on thevertical axis indicate the median NRDs for each boundary stimulus, and the arrow on the horizontal axis indicates the median NRD for the correlated vertical 3-D shape.
- Fig. 7.
Selectivity for 3-D surfaces. A,Example neuron showing strong selectivity for the restricted surface and a weaker selectivity for the large surface stimulus.B, Example neuron showing equally strong selectivity for the restricted and the large surface stimulus, together with a weak selectivity for the vertical correlated 3-D shape. Same conventions as in Figure 3. The scale bars on the right indicate 65 spikes/sec in A and 75 spikes/sec inB.
- Fig. 8.
Surface selectivity of the population.A, Normalized population PSTH for all surface-selective neurons (N = 79). The average response is plotted to the preferred (black) and nonpreferred (gray) restricted surface (full line) and large surface (dotted line).B, Scatterplot of the NRD for the large surface stimulus as a function of the NRD for the restricted surface stimulus, plotted separately for neurons selective (circles) or not selective (squares) for the large surface. Thearrows indicate the median NRDs for large and restricted surface.
- Fig. 9.
Mixed selectivity for 3-D boundaries and surfaces. Example neuron showing robust selectivity for the correlated vertical, decorrelated and solid 3-D shape, as well as for the restricted surface. Same conventions as in Figure 3. The vertical calibration bar on the right indicates 150 spikes/sec.
- Fig. 10.
Selectivity for vertical and horizontal 3-D shapes of the population. A, Four example neurons showing selectivity for the vertical but not for the horizontal 3-D shape (a), for both vertical and horizontal 3-D shape (b), for horizontal but not for vertical 3-D shape (c), and for vertical but the inverted selectivity for horizontal (d). Same conventions as in Figure 3. B, Scatterplot of the NRD for the horizontal 3-D shape plotted as a function of the NRD for the vertical correlated 3-D shape, separately for the neurons selective (circles) or not selective (squares) for the horizontal 3-D shape. The letters indicate the subsets illustrated in A.
- Fig. 11.
Vertical and horizontal selectivity.A,B, Normalized population PSTHs for preferred (black) and nonpreferred (gray) horizontal 3-D shape, for all neurons selective for the horizontal 3-D shape (N = 29;A), and for those horizontal neurons for which binocular eye movements were recorded (N = 7;B). C, The mean difference in horizontal eye position for concave (black) and convex (gray) horizontal 3-D shape. The vertical gray line is a reference at 200 msec after stimulus onset. Thevertical scale bar indicates 1°.
Tables
- Table 1.
Comparison between the results of the boundary–surface and the outline control test
Boundary/ surface test Outline control test Dot size 0.032 0.064 Number of neurons 61 76 % significant effect of decorrelation 64 54 % selective in decorrelation condition 48 62 Median SI correlation 0.84 0.82 Median SI decorrelation 0.61 0.55 No significant differences were observed in the number of neurons showing a significant effect of decorrelation, in the number of neurons selective for the decorrelated 3-D shape pair, in the median SI for the correlated vertical, or in the median SI for the decorrelated 3-D shape pair.
- Table 2.
Relative numbers of neurons selective for the correlated vertical 3-D shape compared with the number of surface-selective neurons
Surface selectivity Absent Present Total Boundary− Boundary+ Present 12 24 43 36 79 Absent 12 13 0 25 25 24 37 43 61 104 The numbers in italics indicate the numbers of neurons selective (Boundary+) or not selective (Boundary−) for the 3-D boundaries.
- Table 3.
Relative numbers of neurons selective for the correlated vertical 3-D shape compared with the number of neurons selective for the horizontal 3-D shape
Selectivity for vertical 3-D shape Absent Present Total Present 45 16 61 Absent 30 13 43 75 29 104
