Table 3:

Example source code (compatible with both Matlab and Octave) to extract processed variables and scaled EEG data from a dataset stored on a USB device by a BIS Vista monitor, and also to apply the correct microvolt scaling to the EEG data.

Example Retrieval of EEG Data and Variables from the Vista USB

Commentary

function [t,BIS,EMG,SEF,POW,EEG,EEGuV] = readStudyFromUSB(studyID) fid = fopen(fullfile(studyID,sprintf('%s.spa',studyID)),'rt'); c = textscan(fid,repmat('%s',1,54),'Delimiter','∣','Headerlines',2); fclose(fid); t = c{1}; SEF = cellfun(@(x)str2double(x),c{37}); SEF(SEF<0) = NaN; BIS = [cellfun(@(x)str2double(x),c{12}) … cellfun(@(x)str2double(x),c{26}) … cellfun(@(x)str2double(x),c{40})]; BIS(BIS<0) = NaN; POW = cellfun(@(x)str2double(x),c{43}); POW(POW<0) = NaN; EMG = cellfun(@(x)str2double(x),c{44}); EMG(EMG<0) = NaN; fid = fopen(fullfile(studyID,sprintf('%s.r2a',studyID)),'rb'); EEG = fread(fid,[2 inf],'int16'); fclose(fid); EEGuV = EEG * 1675.42688 / 32767;

Unlike the BIS A-2000, whose only output is a low bandwidth RS232 serial port, the BIS Vista has a rear-facing USB port that can be used to store study data on common USB flash drives. The stored studies have a standard file structure format. The SPA file contains a large plaintext tabulation of the processed variables produced by the monitor. This is similar to, but more complete, than the similar tabulation presented over the A-2000 serial port. These values can be read and extracted by simple, appropriate text parsing of the SPA file. Additionally, EEG data is stored in a scaled format as signed 16-bit integers (−32768 to +32767) in the R2A file. The data is channel-interleaved. The scaled EEG data can be converted into microvolts by multiplying by a 0.0511 uV/step scale factor.