Using the anti-correlation between oxy and deoxy hemoglobin for NIRS data quality

46 sec read

Back in 2009 we published a paper titled “Functional near infrared spectroscopy (NIRS) signal improvement based on negative correlation between oxygenated and deoxygenated hemoglobin dynamics“. In a nutshell, we found the oxy- and deoxy-Hb are negatively correlated when noise level is low. When noise level increases, their correlation becomes more and more positive.

Correlation between oxy and deoxy-Hb
Correlation between oxy and deoxy-Hb

Based on this phenomenon we can check the noise level of a channel using the correlation. Below is the script. You simply input the hbo and hbr data (both matrix), and the output is the bad channels.

function badChannels = checkDataQuality(hbo,hbr)

% function badChannels = checkDataQuality(hbo,hbr)
% Check data quality using correlation between hbo and hbr as indicator
% if the correlation is strictly -1, then bad channel
% if the correlation is > 0.5, then bad channel
% Input: hbo and hbr are NxM matrix, N is number of scan, and M number of
% channels
% output: array of bad channels
%
% Xu Cui
% 2009/11/25

n = size(hbo,2);
for ii=1:n
    tmp = corrcoef(hbo(:,ii), hbr(:,ii));
    c(ii) = tmp(2);
end

pos = find(c==-1);
if ~isempty(pos)
    disp(['Channels with -1 correlation: ' num2str(pos)])
end

pos2 = find(c>0.5);
if ~isempty(pos2)
    disp(['Channels with >0.5 correlation: ' num2str(pos2)])
end

badChannels = [pos pos2];



写作助手,把中式英语变成专业英文


Want to receive new post notification? 有新文章通知我

第四十七期fNIRS Journal Club通知2023/12/02, 10am 卢宏亮

协作是合作最基本、最底层的行为方式。从自然界中的狼群配合提高狩猎几率,再到人类社会中作战单元协作完成军事任务,协作都发挥着关键作用。然而,目前大部分协作研究依然停留在行为或脑活动观察水平,并未对两者因
Xu Cui
10 sec read

第四十六期fNIRS Journal Club视频 张腾飞

Youtube: https://www.youtube.com/watch?v=L4qc5gCttpc&feature=youtu.be Youku: https://v.youku.com
Xu Cui
14 sec read

第四十六期fNIRS Journal Club通知2023/10/28, 10am 张腾飞

在语言交流的过程中,预测起到了极为关键的作用。以往研究多在单脑情景下对语言预测加工进行检验,但在自然交流过程中,人际之间的预测如何发生呢?北京师范大学认知神经科学与学习国家重点实验室卢春明教授课题组的
Xu Cui
7 sec read

10 Replies to “Using the anti-correlation between oxy and deoxy hemoglobin for…”

  1. @Gu Yue
    Good question! I however do not know the answer. You can try it and see if it increase your data quality. I’d love to know the result.

  2. Dear Cui,

    I’m wondering how to deal with these bad channels. Can I use the interpolation method which has been frequently employed in processing EEG data? I mean used the average value of whole channels to replace the bad channels Or just delete data on the bad channels?

    I’m looking forward to hearing from you!

    Yafeng Pan

  3. Dear Pan,
    Have you used the average value of whole channels to replace the bad channels of fNIRS? could you tell me your article name? thank you

    wenfeng Wu

  4. Dear Xu Cui,

    How/why did you choose the threshold of 0.5 (if if the correlation is > 0.5, then bad channel)? I read your paper but I could not figure out why 0.5 should be the right value, but I am very curious to know! Thank you.

    Kind regards,
    Carly

    1. Carly,

      The threshold 0.5 is arbitrarily chosen based on our observation. There is no theoretical basis. Please feel free to use your own threshold.

      Xu

  5. I was wondering if the code you gave is used then should we use the original signal or the filtered and de-headed signal?

      1. Hi Xu Cui,

        I believe the questions is whether any preprocessing should be performed before calculation of the correlation. For example, should the data be band-pass filtered and then we calculate the correlation?

        As a second question, I was wondering if having a longer block would affect the negative correlation bet oxy and deoxy hemoglobin, considering that during the plateau blocks, the anticorrelation decreases. Up to what block length would you expect that the negative correlation assumption holds true?

        Kind regards,
        Paulo

Leave a Reply to Xu Cui Cancel reply

Your email address will not be published. Required fields are marked *