TY - JOUR T1 - Filter Based Phase Shifts Distort Neuronal Timing Information JF - eneuro JO - eNeuro DO - 10.1523/ENEURO.0261-17.2018 SP - ENEURO.0261-17.2018 AU - Dorin Yael AU - Jacob J. Vecht AU - Izhar Bar-Gad Y1 - 2018/04/11 UR - http://www.eneuro.org/content/early/2018/04/11/ENEURO.0261-17.2018.abstract N2 - Filters are widely used for the modulation, typically attenuation, of amplitudes of different frequencies within neurophysiological signals. Filters, however, also induce changes in the phases of different frequencies whose amplitude is unmodulated. These phase shifts cause time lags in the filtered signals, leading to a disruption of the timing information between different frequencies within the same signal and between different signals. The emerging time lags can be either constant in the case of linear phase (LP) filters, or vary as a function of the frequency in the more common case of non-linear phase (NLP) filters. Since filters are used ubiquitously online in the early stages of data acquisition, the vast majority of neurophysiological signals thus suffer from distortion of the timing information even prior to their sampling. This distortion is often exacerbated by further multiple offline filtering stages of the sampled signal. The distortion of timing information may cause misinterpretation of the results and lead to erroneous conclusions. Here we present a variety of typical examples of filter-induced phase distortions and discuss the evaluation and restoration of the timing information underlying the original signal.Significance Statement Filters are a common tool used in the processing of neuronal signals. In addition to their effect on the amplitude of different frequencies, filters also have a significant impact on their phases, which results in the distortion of the underlying timing information. This distortion, which arises by the online filters used in most neurophysiological systems and is exacerbated by further offline filtering, may cause severe misinterpretation of the results and lead to false conclusions. This manuscript presents different cases in which the timing information is disrupted and discusses the evaluation and correction of the underlying phase shifts. ER -