Two signatures of visual responses measured with ECoG.

(a) Mapping stimuli. Three examples of the bar stimuli and one image of the blank stimulus during the mapping experiment (brown and black outlines, respectively). The contrast within the bar is increased here for visibility. (b) A close-up view of the right occipital cortex of Patient 2. The surface colors show several visual field maps derived from an atlas, with V1 in red, V2 in orange, and V3 in yellow. Black circles indicate ECoG electrode locations. (See Supplementary Figure 1 for all patients) (c) The power spectral density (PSD) is shown for electrode Oc17, averaged across stimulus trials (brown) and blanks trials (black). The stimulus causes a broadband power increase, spanning frequencies from 1 Hz to 150 Hz. The dotted black rectangle indicates the frequency range shown in zoom in panel d. (d) During the blank, but not during visual stimulation, there is a peak in the spectrum at around 13 Hz (alpha oscillation, dashed vertical line). See makeFigure1.m.

Interaction between the alpha rhythm and broadband power.

(Left column) PSDs from 3 electrodes in Patient 2 without baseline correction show that the stimulus-related alpha power can slightly increase (Oc18), slightly decrease (Oc17) or substantially decrease (Oc25) relative to a blank stimulus. (Right column) After correcting for the broadband shift, it is clear that for all three electrodes, the alpha oscillation is suppressed by visual stimulation. The dashed vertical lines indicate the alpha peak frequency. See Methods and makeFigure2.m.

Example time series and pRF fits.

Representative data from a V3 electrode (‘GB103’) from Patient 8. The left column shows the time series averaged across six 190-s mapping runs, during which bar stimuli swept the visual field 8 times (with 4 blank periods indicated by the gray bars). Each data point (black circle) is a summary value–either broadband or alpha–for one stimulus position (Equations 1-3). Predicted responses from a pRF model are shown as solid lines. The insets on the right show how the broadband and alpha summary metrics were computed for an example stimulus location. Model predictions below baseline in broadband and above baseline in alpha were possible because of the Difference of Gaussians (DoG) pRF model (see Supplementary Figure 2). The rightmost panel shows the location of the pRFs fitted to the broadband and alpha times series. The circles show the 1-sigma pRF bootstrapped 100 times across the 6 repeated runs. See makeFigure3.m.

Alpha and broadband pRFs.

For visualization purposes, each electrode was plotted only once, with the V1–V3 or dorsolateral group, even though the probabilistic assignment could have non-zero weights for both groups of maps. (We plot the electrodes with the cluster that has higher probability). (a) pRF locations in V1–V3 displayed for each electrode, as in Figure 3. (b) pRFs in V1–V3 were normalized by rotation (subtracting the broadband pRF polar angle from both the broadband and alpha pRF) and then scaling (dividing the eccentricity and size of both pRFs by the broadband pRF eccentricity). This puts the broadband pRF center at (0,1) for all electrodes, indicated by an ‘x’. Within this normalized space, the average pRF across electrodes was computed 5,000 times (bootstrapping across electrodes). 100 of these averages are indicated as dotted lines, and the average across all 5,000 bootstraps is indicated as a solid line. (c,d) Same as A and B but for dorsolateral electrodes. See makeFigure4.m.

Correlations of alpha and broadband pRF parameters.

(a) Each panel shows the relation between broadband and alpha pRF parameters in 2-D histograms. 53 electrodes were randomly sampled with replacement 5,000 times (bootstrapping), and each time they were selected they were probabilistically assigned to a visual area. The colormap indicates the frequency of pRFs in that bin (see Comparison of alpha and broadband pRFs in Methods 4.7). The two top panels show the relation of polar angle for V1–V3 (left) and dorsolateral retinotopic maps (right). Note that the phases in the horizontal and vertical axes are wrapped to show their circular relations. The middle and bottom panels show the relation of eccentricity and pRF sizes, respectively. Yellow ellipses indicate the 1-sd covariance ellipses. (b) Plots show pRF size vs eccentricity, both for broadband (blue) and alpha (red). As in panel A, the 53 electrodes were bootstrapped 5,000 times. The regression lines are the average across bootstraps, and the shaded regions are the 16th to 84th percentile evaluated at each eccentricity. Each electrode is plotted once, either for V1–V3 or dorsolateral maps, even though in the bootstrapping plus probabilistic assignment procedure, they could be assigned to either group. See makeFigure5.m.

A comparison of model-based and frequency-band alpha pRFs.

We compared pRF solutions for alpha using our spectral model (“model-based”) vs by computing power within the alpha band (‘frequency band”). Left: Variance explained. The white dots are the median and the gray bars are the interquartile range. Each colored dot is one electrode and the shaded regions are smoothed histograms. Middle: Response gain, plotted in the same manner as variance explained. Gain is quantified as the maximum or minimum value in the pRF fitted time series (maximal for electrodes with positive gain, minimal for electrodes with negative gain). A value above 1 means that the response increased relative to baseline (positive gain). A value below 1 means the response decreased (negative gain). Right: pRF size vs eccentricity. Electrodes are colored by the sign of the gain (filled for negative, open for positive). See makeFigure6.m.

Inter-electrode coherence across distances in high-density grids. Coherence between electrode pairs was computed within each 1-s epoch and then averaged epochs. Seed electrodes were those which had a reliable pRF fit, and these seed electrodes were compared to all other electrodes on the grid. The curved lines indicate the average fit of an exponential decay function across 5,000 bootstraps; shading indicates 16th 84th percentile of bootstraps; dashed lines indicate the baselines the coherence converges to. See Supplementary Figure 8 for coherence as a function of frequency. See makeFigure7.m.

Asymmetric profile of alpha pRF and asymmetric effect of exogenous attention.

The left panel shows an asymmetric profile of alpha pRF across normalized eccentricity in V1–V3. The right panel shows asymmetric effects of exogenous attention on normalized cue–target locations. Black line represents response time changes induced by exogenous attention from Downing and Pinker 30, relative to the response time without any attentional cue. Golden line represents response time changes induced by exogenous attention from Shulman et al. 29, relative to the response time when targets appeared at the attended locations. Results from the Shulman et al. paper with foveal cue locations at 0.5 degree eccentricity were excluded from the plot because after normalizing, the data from this condition has no overlap with the other conditions perhaps because at such a small eccentricity, a minor error in attended location makes a large difference on a normalized scale. The experimental results for each cue location are shown in Supplementary Figure 10. See makeFigure8.m.

Overview of patient data included in this dataset.

The patient number and subject code for BIDS do not always match because the 9 subjects with pRF data are a subset of 11 subjects from a larger BIDS dataset (https://openneuro.org/datasets/ds004194). Two of the 11 patients did not take part in pRF experiments.

Schematics of model-based alpha computation.

The left panel shows the average power spectra elicited by the pRF mapping stimuli (brown) and blanks (black) from a representative electrode. The middle panel shows the ratio between the two power spectra (green). This ratio, evaluated on log-log axes, is modeled (dashed red) as the sum of a broadband elevation (right panel, top) and an alpha suppression (right panel, bottom). The magnitude of alpha suppression is the coefficient of the Gaussian bump (βalpha, black arrow). See Equation 1 and makeFigure9.m.

Overview of electrodes and patients per visual area and figure

. The totals are lower than the sum of V1–V3 and Dorsolateral because some electrodes are counted toward both (see Electrode Localization, section 4.6). The electrodes in visual areas indicate electrodes which have at least 5% probability to be assigned to a visual area.

Electrode locations and visual areas.

The electrode locations and visual areas on brain surfaces for each patient. The retinotopic atlas is modified from Wang et al. 68. Only the cortices with electrodes are shown: left cortex for Patient 1, 4, 5, and 9; right cortex for Patient 2, 3, 6, and 8; both cortices for Patient 7. See makeFigureS1.m

PRF model comparisons between two Gaussian models.

Cross-validated variance explained in pRF models are almost the same between two Gaussian models (Difference of Gaussians VS One Gaussian) both in V1–V3 (blue circle) and dorsolateral (purple triangle), but the Difference of Gaussians shows advantage in some electrodes. Each dot indicates electrode which is randomly selected according to the visual area probabilities in 5,000 bootstraps. See makeFigureS2.m

Distributions of Variance Explained in alpha and broadband pRFs.

The distributions of variance explained in alpha and broadband pRFs from all visual areas show rightward tendency compared to shuffled distributions. (A negative variance explained is common for cross-validation when making predictions with an inappropriate model.) The medians shown as black arrows have larger values in the raw distributions than the shuffled distributions (24% vs -21% in broadband and 5% vs -18% in alpha), suggesting the prediction accuracy of the pRF model fit is meaningful both in broadband and alpha. The false positive criterions were set at 95% of the values in this null distribution (dashed line: 31% for broadband and 22% for alpha). The electrodes shown in the right side of the false positive criterion (dark gray bars) were included for the comparison between broadband and alpha pRFs. in broadband pRFs are the visually selected electrodes. The electrodes shown in the right side of the false positive criterion in alpha pRFs are considered as the alpha sensitive electrodes. See makeFigureS3_S4.m.

Prediction accuracy of alpha pRF model.

The average two-fold cross-validated variance explained of alpha pRF models was higher in the visually selective (blue) than in the non-selective electrodes (red) in V1–V3 and dorsolateral visual areas. Visually selective electrodes were defined as those whose broadband pRF model accurately predicted the broadband time course (see Supplementary Figure 3). Dorsolateral includes the V3A/B, LO-1/2, TO-1/2, and IPS maps. Electrodes were assigned to visual field maps probabilistically across 5,000 samples. Data points and error bars are means +/- 1 standard deviation of the mean across the 5000 samples. See makeFigureS3_S4.m.

Power in the broadband response and alpha oscillation.

Each panel shows the spectral power changes averaged across all electrodes between BLANK and in-pRF stimulation (STIMULUS) conditions in V1–V3 and dorsolateral. (a) PSD for in-pRF (brown line) is higher than for BLANK (black line) and across all frequencies including not only high frequencies (blue region) but also low frequencies (green region) in V1–V3. In dorsolateral, on the other hand, PSD for in-pRF is higher than for BLANK only in high frequencies. Gaussian bumps at peak alpha frequencies (red dashed lines) are observed only in BLANK condition. (b) The ratio of PSDs between in-pRF and BLANK is positive in high-frequency broadband and negative at alpha frequency consistently in V1–V3 and dorsolateral. The ratio in low-frequency broadband is also positive in V1–V3 but is almost zero in dorsolateral. See makeFigureS5.m.

Low broadband model comparisons.

PRF parameters are highly correlated between the high-frequency broadband estimates (x-axis) and the low-frequency broadband estimates (y-axis) in V1–V3. Yellow ellipses indicate the 1-sd covariance ellipses. See makeFigureS6.m.

PRF parameters from high-density grid. (a)

Patient 8. (Upper left) The electrode locations and visual areas on the brain surface from Patient 8. (Upper right) The visual area assignments of electrodes from the high-density grid. White spaces indicate absence of electrodes. (Second row) Two-fold cross-validated variance explained in pRF fitting for broadband and alpha across electrodes in the high-density grid. Electrode locations which were excluded in the preprocessing are shown as white. (Third and Fourth rows) Polar angles and eccentricities of estimated pRFs. Electrodes which had low variance explained (under 31% and 22% for broadband and alpha, respectively) are shown as white. See makeFigureS7.m.

PRF parameters from high-density grid. (b)

Patient 9. (Upper left) The electrode locations and visual areas on the brain surface from Patient 9. (Upper right) The visual area assignments of electrodes from the high-density grid. White spaces indicate absence of electrodes. Gray spaces indicate electrodes which were not assigned to any visual areas. (Second row) Two-fold cross-validated variance explained in pRF fitting for broadband and alpha across electrodes in the high-density grid. Electrode locations which were excluded in the preprocessing are shown as white. (Third and Fourth rows) Polar angles and eccentricities of estimated pRFs. Electrodes which had low variance explained (under 31% and 22% for broadband and alpha, respectively) are shown as white. See makeFigureS7.m.

Inter-electrode coherence in the high-density grids across 1–200 Hz.

Each curve indicates the coherence averaged across electrode-pairs, binned by inter-electrode distance. The coherence for electrode pairs more than 2 cm apart was used as a baseline, and subtracted from each curve. For both patients, the coherence is highest around 10 Hz, the frequency of the alpha oscillation. See makeFigureS8.m.

Schematics of neural excitation and excitability changes induced by visual stimulation.

The upper panels show stimulus position relative to the broadband and alpha pRFs for a given electrode. The lower panel shows predicted alpha and neural responses from that electrode, with stimulus onset indicated by the black horizontal bar. In the left and right panels, stimulus onset causes the alpha oscillations to be suppressed and cortex to become more excitable (red shading). In the right panel, the alpha oscillation increases slightly and cortex becomes less excitable (gray shading).

Response time costs in previous exogenous attention experiments.

Left panels represent response time changes induced by exogenous attention from Downing and Pinker 30, relative to the response time without any attentional cue. Right panels represent response time changes induced by exogenous attention from Shulman et al. 29, relative to the response time when targets appeared at the attended locations. Lower panels are the same results as top panels after normalizing target eccentricities by dividing by the cue eccentricities. Results from the Shulman et al. paper with foveal cue locations at 0.5 degree eccentricity were excluded from the plot because after normalizing, the data from this condition has no overlap with the other conditions. See makeFigureS10.m.