NIRS hyperscanning data analysis (4) coherence analysis

1 min read

NIRS hyperscanning data analysis (1)
NIRS hyperscanning data analysis (2)
NIRS hyperscanning data analysis (3)
NIRS hyperscanning data analysis (4)

How do we analyze hyperscanning data to find out the relationship between two brains? Obviously correlation is the first thought. However, raw correlation analysis might be susceptible to noise in the data (e.g. physiological noise such as heart beating, or motion noise). Wavelet coherence is a great way to find correlation between two signals – at the same time not affected by physiological noises. To understand wavelet coherence, you might want to read:

  1. Wavelet coherence
  2. What does a wavelet coherence plot tell you?

Let’s look at the data of a pair of subjects (please click the image to zoom):

Wavelet coherence of a pair of subjects
Wavelet coherence of a pair of subjects

There are 22 channels in total in each participant. Each small plot in the figure above is for one channel. The plots are arranged following the real position of the channel on the participant’s head. How did I arrange them? I cut and paste and arrange in PowerPoint 🙂 You can imagine it took me some time. I wish there is a handy tool.

By looking at this figure, a pattern pops out – there is a band in the period 6.4s in multiple channels. Maybe this band (increase of coherence) is a signature of collaboration. To quantify this, we average the coherence value around the band (between periods 3.2 and 12.8s in the task block, and the rest period in between):

[Rsq,period,scale,coi,sig95] = wtc(signal1,signal2,'mcc',0, 'ms',128);
period32 = find(period>32);
period32 = period32(1);
b1 = mean(mean(Rsq(period32:end, marktime(1):marktime(2))));
bi = mean(mean(Rsq(period32:end, marktime(2):marktime(3))));
b2 = mean(mean(Rsq(period32:end, marktime(3):marktime(4))));

Now we get a 3 values for each channel. I normally define “coherence increase” as the average of the coherence during task minus the coherence in rest. So CI = (b1+b2)/2 – bi

For each channel in each subject pair, we got a single value (CI). Then for each channel, we can do a group analysis using T-test. After we get all the T-values for all channels, then we can plot the map using plotTopoMap

Group coherence T map
Group coherence T map

This is basic analysis. You can go much deeper from here. Below are some examples:

  1. Is there a learning effect? i.e. is the performance during the 2nd block better than the 1st block? Is the coherence increase higher than the 1st block?
  2. Does coherence increase in the collaboration block differ from other blocks (such as competition, independent blocks)?
  3. Does the phase of the coherence carry any information?



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

4 Replies to “NIRS hyperscanning data analysis (4) coherence analysis”

  1. Dear Dr.Cui:
    I am little confused about the formual” b1 = mean(mean(Rsq(period32:end, marktime(1):marktime(2))))”,especiall the period32:end.

    In the context, you said the period between 3.2-12.8(32-128) was your instrested, so if you want to extra the correlation value of that band, the formal is Rsq(period32:period128, marktime(1):marktime(2)), right?

  2. Hi Prof. Cui,
    I’m trying to add support for 3×10 to plotTopoMap.
    In plotTopoMap.m, during testing of my new version, I’ve found m(10,2:3) and m(4,12) miscomputed (divided by a wrong number). Maybe your team (if not done yet) would like to program it in an more efficient way:) It really took me several hours to read and understand and generate a new one>_< Haha!
    best,
    Sam

Leave a Reply

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