Spontaneous Pupillary Oscillation Signal Analysis Applying Hilbert Huang Transform
Fabiola M. Villalobos-Castaldi, José Ruiz-Pinales, Nicolás C. Kemper-Valverde, Mercedes Flores-Flores, Laura G. Ramírez-Sánchez, Metztli G. Ortiz-Hernández · 2016
This paper proposes a new application of the Hilbert-Huang transform (HHT). Pupillogram recordings were analyzed through the non-traditional HHT to investigate patterns in the time-frequency parameters of Spontaneous Pupillary Oscillation (SPO) signals. The traditional Fourier transform is only useful for linear stationary signals analysis, but the HHT was designed for the analysis of non-linear and non-stationary signals. However, the HHT is a more suitable tool to study SPO signals which are fundamentally non-stationary. The intrinsic properties of the Spontaneous Pupillary Oscillation signals were highlighted by the HHT scheme and the results showed that SPO waves present local and intermittent variations through the time span. The numerical parameters demonstrated that it is a wide inter-subject variation in the intrinsic time-frequency parameters contribution from each yielding mode to the total signal content.