| dc.description.abstract | Cross-frequency coupling (CFC) serves a critical role to define the interaction and synchronization between different systems. When systems begin to communicate, the phase, frequency, or amplitude of these systems may indicate similar pattern.
In electroencephalogram (EEG), the low frequency oscillators’ phase could modulate the high frequency oscillators’ amplitude, which is known as phase-amplitude coupling (PAC). PAC occurs in EEG especially when the subject losses consciousness. Therefore, PAC is an important factor to monitor both the depth of unconsciousness due to anesthesia in surgery and sleepiness in sleep medicine. Moreover, phase frequency coupling (PFC) , another kind of CFC, reflects the interaction between respiratory system and the cardiovascular system. The respiratory sinus arrhythmia (RSA) is defined as the increase and decrease of the rate of heartbeat during inhalation and expiration, respectively. Subject with terrible autonomic nervous function has poor RSA. That is, PFC is a practical tool to evaluate autonomic nervous system.
Given that different modulations are able to explain mechanisms between systems, it is essential to develop the signal processing tool that precisely quantitate coupling activities. CFCs are phenomena comprised of amplitude modulation (AM) and the frequency modulation (FM) in communication domain. AM and FM are non-linear frequency interactions that pose obstacle for Fourier-based method to access correct frequency. The traditional method is to acquire modulation index with constant bandwidth band-pass filter, through this method is not able to discover non-stationary coupling. In this paper, we aim to propose a method based on time frequency representation (TFR) that distinguishes different CFC precisely. TFR also provides an opportunity to deal with non-stationary coupling. We are looking forward to applying our method to other CFCs, including amplitude-amplitude coupling (AAC) and phase-phase coupling (PPC). Eventually, with proposed toolbox, we expect to establish a standard to observe the CFC correctly. | en_US |