1. Volume 27, Issue 2, Pages 155-165 (January 2017)
Invariant Temporal Dynamics Underlie Perceptual Stability in Human Visual Cortex 
Ella Podvalny, Erin Yeagle, Pierre Mégevand, Nimrod Sarid, Michal Harel, Gal Chechik, Ashesh D. Mehta, Rafael Malach 
Current Biology 
Volume 27, Issue 2, Pages (January 2017)
DOI: /j.cub
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2. Figure 1 NV and FS Experimental Settings
(A) Patients wore eye-tracking glasses with a frontal video camera for external scene recording. No experimental stimuli or instructions were presented to the subjects, and they observed and interacted with their immediate environment.
(B) Example of eye position (horizontal, x; and vertical, y) that was recorded with the eye-tracking glasses. For each fixation, one video frame corresponding to the fixation halftime was extracted and cropped around the fixation position at the ∼18° region of interest (ROI). Fixation contrast was computed as the absolute difference between corresponding pixel intensities, averaged across pixels.
(C) For each fixation frame ROI, face presence and position were detected (green rectangle).
(D) Flash Stimulation paradigm. The patients viewed images from seven categories: face, body, object, building, pattern, word, and animal. Images were superimposed with a small fixation dot and flashed for 250 ms at a rate of 1 Hz.
See also Supplemental Experimental Procedures.
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3. Figure 2
Anatomic Location and Recordings Examples of Visual Electrodes
(A) Early visual electrodes were defined by anatomic location and latency of HFA response to flash stimulation (FS). Late responsive visual electrodes were tested for category selectivity, i.e., difference in responses to face and non-face categories; area under the curve (AUC) in a 100- to 500-ms time window since event onset was tested for each electrode (t test, p < 0.05, Bonferroni corrected). All visual electrodes are shown on the unfolded cortex map, and most of the electrodes are visible also on the inflated brain inferior view. A, anterior; L, left; R, right; P, posterior. STS, superior temporal sulcus; TOS, transverse occipital sulcus; IOS, inferior occipital sulcus; CaS, calcarine sulcus; CoS, collateral sulcus.
(B) HFA time-course example (2 min) for face-selective and early electrodes (white arrows on the map in A) in NV and FS paradigms. Each fixation time was indicated with the same color as used in Figure 1C (orange, face; yellow, nearby face; and gray, no face).
See also Figures S1 and S2 and Tables S1 and S2.
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4. Figure 3
Neural Responses in Early Visual Cortex during NV Are Sensitive to Input Parameters and Deviate from Responses to Laboratory FS Stimuli
(A) Fixation contrast distribution for all patients and contrast groups (divided into roughly similar number of fixations in each group). Fixation contrast was computed as the difference between two consecutive ROI frames, a measure of external visual input change between fixations.
(B) Fixation-related HFA in different contrast groups averaged over all early visual electrodes (n = 44) with average pre-fixation baseline (−70 to −150 ms) subtracted; fixation groups and color coding are as defined in (A). The gray area indicates significant difference between groups, which was tested for each time sample (one-way ANOVA, p < 0.05, Bonferroni corrected). The solid lines indicate the mean, while the shaded area of the same color represents ±SEM.
(C) Fixation-related HFA in different contrast groups normalized (Norm.) by peak amplitude compared to stimulus-locked HFA in flash stimulation. The gray area indicates significant difference between the FS and NV conditions; note no significant difference between fixation duration groups in HFA rising phase 78–156 ms (one-way ANOVA, p < 0.05, Bonferroni corrected).
(D) Distribution of responses during different fixation durations in all patients.
(E) Fixation-related HFA in different fixation duration groups averaged as in (B).
(F) Fixation-related HFA in different duration groups normalized by peak amplitude and compared to FS. No significant difference between groups was in HFA rising phase 90–132 ms (one-way ANOVA, p < 0.05, Bonferroni corrected).
See also Figure S3 and Table S3.
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5. Figure 4
Baseline and Peak Activation Comparison between the FS and NV Paradigms
(A) Mean baseline (150 ms prior to fixation/stimulus onset) in HFA locked to a general fixation onset in NV or stimulus onset in FS. Inset histogram presents distribution of differences (diff) between NV and FS baselines. NV baseline was significantly higher than FS, as assessed by paired t test (p < 0.05).
(B) Absolute (not normalized) peak amplitude during NV versus absolute peak amplitude during FS. Inset histogram presents distribution of differences between NV and FS peak amplitude; no significant difference was found, as assessed by paired t test (p > 0.05).
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6. Figure 5
Comparison of Selectivity Profile Comparison during the NV and the FS Paradigms
(A) Averaged stimulus-locked HFA responses to faces (orange) and non-faces (black) in the flash stimulation (FS) paradigm in face-selective electrodes. The gray area denotes significant difference (one-way ANOVA, p < 0.05, Bonferroni corrected). The shaded area represents ±SEM. Inset bar plot presents mean HFA in the 70- to 400-ms range; asterisks denote significant difference from zero (p < 0.05, paired t test). The p value given in the inset denotes the difference between the groups (two-sample t test).
(B) Same as in (A) but for the NV paradigm; non-face fixation frames were randomly chosen to match the face-fixations contrast. The distributions are given below.
(C) Same as in (A) but for non-face-selective electrodes.
(D) Same as (B) but for non-face-selective electrodes.
(E) Fixation contrast distribution for face and non-face fixations.
See also Figure S4 and Tables S3 and S4.
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7. Figure 6 Face Response Dynamics in High-Order Visual Cortex
(A) Distribution of fixation durations divided into short and long groups.
(B) Single electrodes examples of HFA responses to faces during long and short fixations, locked to fixation onset. The shaded area represents ±SEM. Norm., normalized.
(C) Same as in (B), averaged over all face-selective electrodes (n = 11). Between-groups difference was assessed with a two-sample t test for each time sample; no significant difference was found (p > 0.05 for all time samples).
(D) Comparison of response dynamics to faces in NV and FS paradigms. HFA was normalized by peak amplitude; no significant differences were found between the groups (one-way ANOVA, p > 0.05).
See also Figure S5.
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8. Figure 7 Baseline and Peak Activation in High-Order Visual Electrodes
(A) Comparison of baseline HFA (150 ms prior to fixation/stimulus onset) in NV and FS paradigms for face-selective electrodes. Inset bar plot depicts baseline difference, difference mean ± SEM, and p value for paired t test.
(B) Same as in (A), but for non-face-selective electrodes.
(C) Same as in (A), but for HFA peak amplitude.
(D) Same as in (C), but for non-face-selective electrodes.
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