Timing/phase distortions produced by filters

Yael, D., Vecht, J. J., & Bar-Gad, I. (2018). Filter Based Phase Shifts Distort Neuronal Timing Information. eNeuro 11 April 2018, ENEURO.0261-17.2018; DOI: 10.1523/ENEURO.0261-17.2018

This new paper describes how filters can distort the timing/phase of neurophysiological signals, including LFPs, ECoG, MEG, and EEG/ERPs.

See also the following papers (written with boot camp alumns Darren Tanner and Kara Morgan-Short), which show how improper filtering can create artificial effects (e.g., making a P600 look like an N400).

Tanner, D., Morgan-Short, K., & Luck, S. J. (2015). How inappropriate high-pass filters can produce artifactual effects and incorrect conclusions in ERP studies of language and cognition. Psychophysiology, 52, 997-1009.

Tanner, D., Norton, J. J., Morgan-Short, K., & Luck, S. J. (2016). On high-pass filter artifacts (they’re real) and baseline correction (it's a good idea) in ERP/ERMF analysis. Journal of Neuroscience Methods, 266, 166–170.

Bottom line: Filters are a form of controlled distortion that must be used carefully.  The more heavily you filter, the more you are distorting the temporal information in your signal.