N-Back Related ERPs Depend on Stimulus Type, Task Structure, Pre-processing, and Lab Factors

Abstract

The N-Back, a common working memory (WM) updating task, is increasingly used in basic and applied psychological research. As such, an increasing number of electroencephalogram (EEG) studies have sought to identify the electrophysiological signatures of N-Back task performance. However, stimulus type, task structure, pre-processing methods, and differences in the laboratory environment, including the EEG recording setup employed, greatly vary across studies, which in turn may introduce inconsistencies in the obtained results. Here we address this issue by conducting nine different variations of an N-Back task manipulating stimulus type and task structure. Furthermore, we explored the effect of the pre-processing method used and differences in the laboratory environment. Results reveal significant differences in behavioral and electrophysiological signatures in response to N-Back stimulus type, task structure, pre-processing method, and laboratory environment. In conclusion, we suggest that experimental factors, analysis pipeline, and laboratory differences, which are often ignored in the literature, need to be accounted for when interpreting findings and making comparisons across studies.

Letter identification and spatial localization during visual working memory are enabled by unique sequences of stimulus-dependent neural operations

“…We hypothesized that ERP amplitude for match and non-match trial types would be more pronounced for verbal compared to spatial stimuli, particularly within approximately 200 to 350 msec post-stimulus (P2, N2, and early P3 range). This was anticipated because of the potential increased processing demand required for semantic and phonological aspects of verbal information compared to spatial location (e.g., Mecklinger and Pfeifer, 1996;Shalchy et al, 2020). We also hypothesized that ERP activity in the P3 range would show similar amplitude across stimulus modalities for the lure trial type, in line with prior studies that have indicated that the P3 re ects domain-general executive control processes.…”

“…One widely used paradigm for studying WM performance is the n-back task. In general, n-back tasks require stimulus encoding and the ongoing short-term maintenance of information, selective attention, discrimination of target and non-target stimuli, ltering of distracting information, and continuous updating of the contents of WM (Postle et al, 2000;Sandrini, Rossini, and Miniussi, 2008;Gevins and Cutillo, 1993;Shalchy et al, 2020). During an n-back task, participants are required to determine if a stimulus presented in a sequence of stimuli is the same or different than a stimulus presented n trials back.…”

“…Obtaining electroencephalographic (EEG) measures during n-back performance has the advantage of providing high temporal resolution of neural functioning, which can enable characterization of dynamically shifting neural processes that are engaged during WM. Event-related potentials (ERPs), which are derived by averaging stimulus-locked EEG data over repeated presentations of task stimuli, provide an index of the onset of stimulus-speci c neural processing in real time at different stages of information processing (Mecklinger and Pfeifer, 1996;Shucard et al, 2009;Shalchy et al, 2020). Earlier occurring, primarily exogenously driven components of the ERP such as P1, N1, and P2 (positive, negative, and positive-going peaks, respectively, occurring approximately 100-200 msec after stimulus onset) are generally thought to re ect the processing of physical parameters of the stimulus, and, therefore, can offer insight into attentional demands during initial sensory input.…”

A comparative experimental study of visual brain event-related potentials to a working memory task: virtual reality head-mounted display versus a desktop computer screen

“…For example, early responses at ~ 40–150 ms post-stimulus, termed P1 and N1 components, have been reported (Pratt et al 2011 ; Liu et al 2017 ; Zhao et al 2020 ). The N1 and P1 components are thought to reflect early attentional processing and low level features (Hillyard and Anllo-Vento 1998 ; Woodman 2010 ; Pratt et al 2011 ; Hinojosa et al 2015 ; Shalchy et al 2020 ).…”

EEG Analysis of Working Memory Between Sober State and Intoxicated State

“…The differences in WM-load are a significant part of the WM studies. The N-back paradigm is one of the tasks frequently mentioned in WM, which is used to manipulate the high and low cognitive WM-loads [13]. By utilizing the subjective assessment based on different task difficulties under the N-back experiments, it has been found that the tasks with the high-load levels are more suitable for assessing WM capacity [14].…”