Signal Processing Techniques

Bridging brain signals across scales requires mathematical and signal processing tools (such as power spectral density and coherence), which are often studied only at one level and their limitations are not well understood at other levels. To build links across scales, we need to thoroughly investigate the properties of such tools. For example, we have shown that a popular metric of phase consistency called coherence is also modulated by amplitude correlations between the signals (Srinath and Ray, 2014, Journal of Neurophysiology), and using reference schemes such as average referencing can change the phase differences between two signals by 90 degrees (Shirhatti, Borthakur and Ray, 2016, Neural Computation). We have developed a publically available toolbox to study brain signals using a technique called Matching Pursuit (Subhash Chandran, Mishra, Shirhatti and Ray, 2016, Journal of Neuroscience; * indicates joint authorship), which can better resolve transients as well as rhythms present in a signal, and used Matching Pursuit to determine the duration of gamma rhythm accurately (Subhash Chandran, Seelamantula and Ray, 2017, Journal of Neurophysiology).