Figures and data
Demographic information of each group and clinical scores of the USN and non-USN patients matched by Mahalanobis distance
Experimental paradigm.
The strobe light flickered for 10 seconds in 3-Hz steps, from 3 Hz to 30 Hz, with 10-second inter-train intervals. Participants were lying down with their eyes closed during the EEG recording.
SSVEP power for different responses and flicker frequencies.
Normalized power spectrum of the response frequency (y-axis) at the O2 electrode (affected hemisphere for patients) as a function of flicker frequency (x-axis). The fundamental frequency and the first harmonics (gray dashed lines) can be seen in all groups.
Hemispheric differences in SSVEP power at different flicker frequencies.
Power in the intact hemisphere was stronger than that in the affected hemisphere with 9-Hz stimulation (***p < 0.001) in the USN group only (middle panel). Error bars represent 2 standard errors.
Hemispheric differences in SSVEP power at different flicker frequencies.
(A) No hemispheric difference between C3 and C4 electrodes. (B) No hemispheric difference between F3 and F4 electrodes. Error bars represent 2 standard errors.
SSVEP power during stimulation at 9 Hz and rest.
(A) Box plots indicate the power of SSVEP responses in the intact (O1 electrode) and affected (O2 electrode) hemispheres. A significantly higher response power was observed in the intact hemisphere of the USN group than in the left hemisphere of the healthy control group. The non-USN patients also displayed higher alpha power in both hemispheres than healthy controls without hemispheric bias (***p < 0.001). (B) During the resting state interval, no significant differences in alpha power were observed between groups. Box plots depict medians and 25th/75th percentiles, with whiskers showing the 10th/90th percentiles overlaid onto individual data points (circles). The + represents outliers. Outliers exceeding a power value of 50 were truncated and plotted at the 50 mark.
Hemispheric differences in PAC in response to 9-Hz flickering stimuli.
The MI measuring the coupling between the alpha phase (7–12 Hz) and gamma power (35–45 Hz) represents the hemispheric asymmetry in the USN group (indicated by the black outline). No such pattern was present in the non-USN or healthy control group.
Hemispheric differences in information flow between the visual and frontal areas in response to 9-Hz flickering stimuli.
(A) Box plots show left-right hemispheric asymmetry in transfer entropy (TE) from visual to frontal areas (feedforward direction). In the USN group, information flow from the right visual cortex (O2) to the left frontal area (left panel) was significantly stronger than from the left visual cortex (O1) to the left frontal area (*p < 0.05), and this asymmetry was significantly greater than in healthy controls (**p < 0.01). No significant hemispheric differences were observed in information flow to the right frontal area (right panel). (B) Box plots show left-right hemispheric asymmetry in TE from frontal to visual areas (feedback direction), with no significant asymmetry detected in any group for either left or right frontal areas. Arrows on topographical plots indicate the direction of information flow. Box plots show medians and 25th/75th percentiles, with whiskers at 10th/90th percentiles. The + represents outliers.
Correlation between SSVEP power and BIT score in USN patients.
(A) Scatter plots represent the relationship between SSVEP power at 9 Hz and BIT score for the left hemisphere (O1 electrode, left panel) and right hemisphere (O2 electrode, right panel). A significant positive correlation was found in the right hemisphere (r = 0.70, p < 0.007) but not in the left hemisphere (r = 0.38, p = 0.18). (B) Correlation coefficients between SSVEP power and BIT score across frequencies (3–30 Hz) for each hemisphere. Significant correlations were observed in the right hemisphere only at 9 and 12 Hz after FDR correction (**p < 0.01).
Hemispheric imbalance in model simulations.
Upper panels (A-C) show schematic illustrations of three different model configurations. Lower panels show corresponding order parameter differences between hemispheres across stimulus frequencies. (A) Model with asymmetric interhemispheric coupling (KR→L = 0.8, KL→R = 0.2) reproduced the experimental findings, showing significant hemispheric bias at 9 Hz. The red bar indicates the values without external stimulation (F(t) = 0). (B) Model with enhanced left intrahemispheric coupling (KL = 0.8, KR = 0.2) produced a persistent bias across frequencies. (C) Model with different natural frequencies between hemispheres (ωL = 7, ωR = 9) led to frequency-specific biases at both hemispheres’ natural frequencies. Asterisks indicate significant differences (*p < 0.05, FDR corrected). Error bars represent 2 standard errors
Lesion patterns in USN patients.
Examples of T2-weighted axial MRI images showing right hemisphere lesions in three patients with unilateral spatial neglect (USN). All images are labeled with ‘R’ to indicate the right hemisphere.
