Fig. 2: SVM decoding results.
From: Cortical depth profiles in primary visual cortex for illusory and imaginary experiences
Results for experiment 1 (n = 16) are shown in (A, B); experiment 2 (n = 10) results are shown in (C). The white dashed lines in the images on the right depict the visual field areas that were used to define the ROIs in V1 from which we decoded. The black dashed lines in the plots represent chance level; asterisks denote significant above-chance decoding (Padj < 0.05, one-sided bootstrapping of the mean, multiple-comparison corrected); error bars represent ± SEM. The left column denotes our main conditions of interest: perception (black), illusory perception (blue) and imagery (pink). The right column denotes our illusory control conditions: amodal (cyan) and mock (grey), benchmarked against illusory perception (blue). See Supplementary Figs. 10–12 for individual subject plots. When participants imagined a central disc, colour was decodable only at deep depths in both experiments. Importantly, these findings were restricted to the ROIs that represented the visual area where participants imagined the stimuli (A, C, left); no significant decoding was found in the peripheral ROI of experiment 1 (B, left), which lay at the fringes of the imagery field. Conversely, illusory colour was only decodable in the second superficial layers of the peripheral ROI of experiment 1 (B), which represented areas along the illusory boundaries of the neon colour-spreading stimulus. However, when the illusory contour was shifted to a central location in experiment 2, the illusory colour was also decodable in the second superficial layer of the foveal ROI (C). Hence, experiment 2 shows that the deep-layer effect for imagery and the superficial-layer effect for illusory perception were detectable within the same ROI. In the perceptual condition, we could significantly decode colour at all depths and in all ROIs of the two experiments. The two control conditions of the illusory stimulus showed no significant decoding in either of the two ROIs in experiment 1. In experiment 2, the ‘amodal’, i.e., occluded version of the illusory stimulus showed significant decoding in the most superficial layer (\(\hat{\mu }\) = 0.56, Padj = 0.03, 90% CI [0.52, 0.60]). Source data are provided as a Source Data file.
