1.1 Multiple Approaches Are Used to Obtain Single Trial ERP Measures
Research efforts to derive measures of brain activity from single trial (ST) ERPs have employed a wide variety of techniques such as peak-picking the amplitudes of raw EEG or bandpass filtered data (e.g., Spencer, 2005), template matching methods including use of Woody filter (e.g., Fein & Turetsky, 1989; Gavin et al. 2019; Patterson, Michalewski, & Starr, 1988; Pfefferbaum, Ford, Roth, & Kopell, 1980), maximum likelihood estimation methods (e.g., Jaśkowski & Verleger, 1999; Möcks et al., 1988), regression-based estimation (e.g., Mayhew et al., 2006), wavelet filtering or smoothing (Hu, Mouraux, Hu, & Iannetti, 2010; Hu et al., 2011; Quian Quiroga, Atienza, Cantero, & Jongsma, 2007; Rey, Ahmadi, & Quian Quiroga, 2015; Roth, Roesch-Ely, Bender, Weisbrod, & Kaiser, 2007), decomposition methods such as residue iteration decomposition (RIDE; Ouyang, Sommer, & Zhou, 2015), principal components analysis (PCA) or independent component analysis (ICA) (e.g., De Vos et al., 2012; Saville et al., 2015), and graph theory (Dimitriadis, Brindley, Evans, Linden, & Singh, 2018). For partial reviews on these techniques, see De Vos et al. (2012) who compared four of these techniques and Ouyang, Hildebrandt, Sommer, and Zhou (2017) who compared eight of these techniques. Interestingly, De Vos et al. (2012) stated “At present, little information exists as to which ST estimation method is the more powerful” (p. 1197). Most of these techniques were developed to assess a single measure, usually a mid to late component of the ERP such as the N2 or P3, with some focusing on measuring amplitude while other techniques focus on determining latency variability (Spencer, 2005). Though informative, none of these articles report the psychometric properties of both amplitude and latency measures of multiple components obtained in single trials commonly found in the averaged ERP. That is, these articles do not provide quantified descriptions of ERP components from the viewpoint of classical measurement and statistical theories for either the averaged wave forms or averages of ST measures (e.g., measures of central tendency, variability, and distribution) nor are reliability coefficients of split-half or test-retest provided. Consequently, to date none of the methods cited above have been adopted by the research community at large.