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. 2023 Aug 10;12:e81701. doi: 10.7554/eLife.81701

Figure 2. Scatterplots of object orientation tuning function correlations across tilts.

(a) Scatterplot of correlations for full scene stimuli. Correlations of tuning in the gravitational reference frame (y axis) are plotted against correlations in the retinal reference frame (x axis). Marginal distributions are shown as histograms. Neurons with significant correlations with respect to gravity are colored pink and neurons with significant correlations with respect to the retinae are colored cyan. Neurons with significant correlations in both dimensions are colored dark gray, and neurons with no significant correlation are colored light gray. (b) Scatterplot for isolated object stimuli. Conventions the same as in (a). (c) Same scatterplot as in (a), but balanced for number of comparison orientations between gravitational and retinal analysis. (d) Same as (b), but balanced for number of comparison orientations between gravitational and retinal analysis. Comparable plots based on individual monkeys are shown in . Anatomical locations of neurons in individual monkeys are shown in Figure 2—figure supplements 4 and 5 .

Figure 2.

Figure 2—figure supplement 1. Scatterplot of object orientation tuning function correlations for isolated objects surrounded by a circular aperture.

Figure 2—figure supplement 1.

The circular aperture, with gray inside and black screen outside, provided a nearby, high-contrast frame for the object, intended to overwhelm the framing effects of the screen edges and thus diminish visual cues for the orientation of gravity. The circular surround conveys no visual information about the direction of gravity and would maintain a constant relationship to the object regardless of object-tilt. Details as in Figure 2. The results in this condition were comparable to the main results, with significant tendencies toward object orientation functions correlated with gravity (pink, p = 1.5259 X 10-10, two-tailed randomization t-test for center-of-mass relative to 0) and with the retinae (cyan, p = 8.8879 X 10-6). This supports the proposition that vestibular/somatosensory cues alone suffice for gravitationally aligned tuning in AIT.
Figure 2—figure supplement 2. Results in Figure 2 plotted only for monkey 2.

Figure 2—figure supplement 2.

Figure 2—figure supplement 3. Results in Figure 2 plotted only for monkey 1.

Figure 2—figure supplement 3.

Figure 2—figure supplement 4. Anatomical locations of neurons in individual monkeys plotted in saggital projections.

Figure 2—figure supplement 4.

Anatomical locations of neurons in the three recording hemispheres (columns) (horizontal axis represents mm rostral to ear bars, vertical axis represents mm dorsal to ear bars). Color conventions as in Figure 2. Top row (a, b, c) shows results for the full scene experiments, bottom row (d, e, f) shows results for the isolated object experiments.
Figure 2—figure supplement 5. Anatomical locations of neurons in individual monkeys plotted in horizontal projections.

Figure 2—figure supplement 5.

Anatomical locations of neurons in the three recording hemispheres (columns) (horizontal axis represents mm lateral to midline, vertical axis represents mm rostral to ear bars). Color conventions as in Figure 2. Top row (a, b, c) shows results for the full scene experiments, bottom row (d, e, f) shows results for the isolated object experiments. Based on locations in Figure 2—figure supplements 4 and 5, slightly over 80% of neurons were recorded from STS (lower bank of superior temporal sulcus, where neurons have been found to be primarily object-sensitive Vaziri et al., 2014), 10% from Ted (lateral convexity of inferior temporal lobe, where a majority of neurons have been found to be scene-sensitive), and a small number from TEv (the basal surface of the inferior temporal lobe) and the bottom lip of the superior temporal sulcus.
Figure 2—figure supplement 6. Scatterplot of object orientation tuning function correlations in gravitational space as measured in the scene conditions (0° horizon experiment) and the isolated object condition (floating).

Figure 2—figure supplement 6.

Significant correlations (pink) included 8 exclusive to the isolated object condition (triangles), 11 exclusive to the scene condition (squares), and 23 apparent in both conditions (circles). Thus, gravitational alignment was observable in both conditions for a majority of cases. The 11 cells exclusive to the scene condition might suggest a necessary contribution of visual cues in some cases. However, the converse result with eight cells suggests a more complex dependency on cues and/or conflicting interactions produced by scene backgrounds. Across all 79 cells tested this way, there was no significant difference in the correlations under the two conditions (two-tailed paired t-test of correlation differences; p = 0. 1045, mean difference = 0.1077). This suggests that visual cues had little influence in our main experiments beyond the effects of clear, static vestibular and somatosensory cues.