Optimization toolbox

The EEG was amplified by 50,000 over an amplifier pass-band of 1 to 100 Hz (−6 dB) using Grass P511 amplifiers. The sampling rate was 600 Hz (16 bits). The electrode montage consisted of Oz, O1, and O2 each referenced to Cz. Spectrum analysis was used to extract the amplitude and phase of the evoked response at the first (1F) and second (2F) harmonics of the stimulus frequency as these were the largest and most reliable response components. The absolute values of these complex spectral components at each displacement amplitude were averaged across subjects within the two groups being compared. Error bars were estimated by boot-strapping, taking the standard deviation of 5000 random resamplings of subjects with replacement within each group. The statistical significance of differences between the two groups at each displacement was evaluated by a t-test for two samples with unequal variance. For the response functions, a four-parameter descriptive function was fit to the mean of each resampling of subjects during the bootstrap procedure above. The four-parameter descriptive function for the VEP response amplitude (y) as a function of displacement (x) was:
where parameters were estimated using the Optimization Toolbox in MATLAB (Mathworks, Natick, MA, USA).

Functional imaging data were preprocessed as previously described (Cramer et al., 2019b (link)). In particular, the seed-to-seed FCs between eight previously defined seeds were calculated as Pearson’s correlation between the time course of each of these seeds and Fisher’s z transformation. For left intrahemispheric connectivity, the mean of the Fisher’s z-transformed Pearson’s correlation coefficient of each connection between the seeds located in the left hemisphere was calculated. The overall homotopic connectivity was calculated as the mean of all Fisher’s z-transformed Pearson’s correlation coefficients of each homotopic connection between the seeds in both hemispheres. The time course of left intrahemispheric and overall homotopic connectivity was displayed from baseline and days 42 to 84 after stroke, ensuring the visibility of all seeds after disappearance of the autofluorescent lesion. Fisher’s z-transformed Pearson’s correlation was calculated using MATLAB (MathWorks R2016b with Optimization Toolbox, Statistics and Machine Learning Toolbox, Signal Processing Toolbox and Image Processing Toolbox; MathWorks).