| Popis: |
For better understanding of brain functions, more than one type brain signals has to be studied so that information transfer between the brain lobes can be analyzed in detail. A very small amplitude (in micro-volts) electrical signal acquired from brain surface is called electroencephalogram (EEG). Cranial photoplethysmogram (CPPG) is a hemodynamic brain signal in millivolts. The relationship between neuronal activity and the hemodynamic response (neurovascular coupling) is the subject of most of the ongoing cutting age research in the field of neurology as is not well understood till date. However, it is very clearly observed and studied a powerful correlation in neural activity and blood flow. The setup which can observes both electrical and hemodynamic signals concurrently is of great benefit in understanding of functional cortical activity and of neurovascular coupling. The work was carried out by the authors to study the coherence related changes in EEG and CPPG during music evoked emotions. PSD, CPSD, MS coherence, and phase coherence were estimated for concurrent EEG and CPPG signals. The methodology was applied to real subjects of both the genders, and all of them were right-handed subjects between the age group of 22–63 years. It was observed that MS coherence was greater (in the mid-range, i.e., around 0.5) when it was calculated between EEG-EEG or CPPG (LPF)-CPPG (RPF), whereas as much variations was not observed in Phase Coherence with change in the combination of signals. |
