STATSLAB: An open-source EEG toolbox for computing single-subject effects using robust statistics.

Research on robust statistics during the past half century provides concrete evidence that classical hypothesis tests that rely on the sample mean and variance are problematic. Even seemingly minor departures from normality are now known to create major problems in terms of increased error rates and decreased power. Fortunately, numerous robust estimation techniques have been developed that circumvent the need for strict assumptions of normality and equal variances, leading to increased power and accuracy when testing hypotheses. Two robust methods that have been shown to have practical value across a wide range of applied situations are the trimmed mean and percentile bootstrap test. To facilitate the uptake of robust methods into the behavioural sciences, especially when dealing with trial-based data such as EEG, we introduce STATSLAB: An open-source EEG toolbox for computing single-subject effects using robust statistics. With the STATSLAB toolbox users can apply the percentile bootstrap test, with trimmed means, to a variety of neural signals including voltages, global field amplitude, and spectral features for both scalp channels and independent components. The toolbox offers a range of analytical strategies and is packaged with a fully functional graphical user interface that includes documentation.

A functional classification of medial frontal negativity ERPs: Theta oscillations and single subject effects.

Theta oscillations in the EEG have been linked to several ERPs that are elicited during performance-monitoring tasks, including the error-related negativity (ERN), no-go N2, and the feedback-related negativity (FRN). We used a novel paradigm to isolate independent components (ICs) in single subjects' (n = 27) EEG accounting for a medial frontal negativity (MFN) to response cue stimuli that signal a potential change in future response demands. Medial frontal projecting ICs that were sensitive to these response cues also described the ERNs, no-go N2s, and, to a lesser extent, the FRNs, that were elicited in letter flanker, go/no-go, and time-estimation tasks, respectively. In addition, percentile bootstrap tests using trimmed means indicated that the medial frontal ICs show an increase in theta activity during the ERN, no-go N2, and FRN across tasks and within individuals. Our results provide an important validation of previous studies by showing that increases in medial frontal theta to cognitively challenging events in multiple paradigms is a reliable effect within individuals and can be elicited by basic stimulus cues that signal the potential need to adjust response control. Thus, medial frontal theta reflects a neural response common to all MFN paradigms and characterizes the general process of controlling attention without the need to induce error commission, inhibited responses, or to present negative feedback.