Empirical Mode Decomposition Processing To Improve Multifocal-Visual-Evoked-Potential Signal Analysis In Multiple Sclerosis (Vol 13, E0194964, 2018)

ObjectiveTo study the performance of multifocal-visual-evoked-potential (mfVEP) signals filtered using empirical mode decomposition (EMD) in discriminating, based on amplitude, between control and multiple sclerosis (MS) patient groups, and to reduce variability in interocular latency in control subjects.MethodsMfVEP signals were obtained from controls, clinically definitive MS and MS-risk progression patients (radiologically isolated syndrome (RIS) and clinically isolated syndrome (CIS)). The conventional method of processing mfVEPs consists of using a 1-35 Hz bandpass frequency filter (X-DFT).The EMD algorithm was used to decompose the X-DFT signals into several intrinsic mode functions (IMFs). This signal processing was assessed by computing the amplitudes and latencies of the X-DFT and IMF signals (X-EMD). The amplitudes from the full visual field and from ring 5 (9.8-15 degrees eccentricity) were studied. The discrimination index was calculated between controls and patients. Interocular latency values were computed from the X-DFT and X-EMD signals in a control database to study variability.ResultsUsing the amplitude of the mfVEP signals filtered with EMD (X-EMD) obtains higher discrimination index values than the conventional method when control, MS-risk progression (RIS and CIS) and MS subjects are studied. The lowest variability in interocular latency computations from the control patient database was obtained by comparing the X-EMD signals with the X-DFT signals. Even better results (amplitude discrimination and latency variability) were obtained in ring 5 (9.8-15 degrees eccentricity of the visual field).ConclusionsFiltering mfVEP signals using the EMD algorithm will result in better identification of subjects at risk of developing MS and better accuracy in latency studies. This could be applied to assess visual cortex activity in MS diagnosis and evolution studies.