Working memory updating training modulates a cascade of event-related potentials depending on task load

Abstract

The brain mechanisms of working memory (WM) training in humans remain unclear. Here we examined how WM updating training modulates a cascade of event-related potentials (ERPs) elicited at different processing stages. We hypothesized that WM updating training results to decreases in the early responses reflecting stimulus selection and response preparation, and increases the late slow responses reflecting maintenance of to-be-remembered materials. Healthy adults were randomized to a WM updating group that trained an adaptive dual n-back task (n=20), and an active control group that played a computer game (n=20). Both groups performed three 25-min training sessions per week for five weeks. Pretest-posttest comparisons showed that the training group significantly improved their performance as compared to the active controls, but this was limited to the trained task. In line with our hypothesis, P2-N2-P3 complex showed changes from pre-to posttest. In the training group this was observed as decreased loadeffect while in the control group there was an opposite pattern at some latencies. Slow waves elicited during the maintenance were decreased in the easy task and increased in the difficult task. Taken together, our findings suggest that the early and late ERPs are differentially affected by training. When task demands are high, training may lead to an improved ability to actively maintain several stimuli in memory, and when they are low, training results in more efficient processing and automatization.

Total Sleep Deprivation Triggers Greater Activation in the Parietal Brain in the Visual Working Memory Updating Processes: An Event-Related Potentials Study

“…The N-back task requires participants to decide whether the current stimulus is as same as (match) or different from (mismatch) the one that presented n-steps previously in the stimulus sequence. Since the n-back task is frequently used in WMU-related studies ( McElree, 2001 ; Ecker et al, 2010 ; Vilà-Balló et al, 2018 ; Salmi et al, 2019 ), we used visual two-back tasks in the current study.…”

“…Among the approved event-related potential (ERP) components triggered by each event—P1, N1, P2, N2, P3, and LPP—the P2 and P3 components were considered suitable for the current study. Modulation of the P2 component has been reported in many WMU tasks ( McEvoy et al, 1998 ; Rämä et al, 2000 ; Lenartowicz et al, 2010 ; Luu et al, 2014 ; Vilà-Balló et al, 2018 ; Salmi et al, 2019 ); it is commonly associated with primary top-down attentional control processing ( Freunberger et al, 2007 ) and useful selection of information at the sensory cortices ( Crowley and Colrain, 2004 ). Modulation of the P3 component is one of the most repeated findings in ERP studies in the field of WMU; in particular, the P3b subcomponent is related to downstream cognitive control processing and allocation of attentional resources ( Donchin et al, 1986 ; Lenartowicz et al, 2010 ; Daffner et al, 2011 ; Vilà-Balló et al, 2018 ; Salmi et al, 2019 ).…”

“…Modulation of the P2 component has been reported in many WMU tasks ( McEvoy et al, 1998 ; Rämä et al, 2000 ; Lenartowicz et al, 2010 ; Luu et al, 2014 ; Vilà-Balló et al, 2018 ; Salmi et al, 2019 ); it is commonly associated with primary top-down attentional control processing ( Freunberger et al, 2007 ) and useful selection of information at the sensory cortices ( Crowley and Colrain, 2004 ). Modulation of the P3 component is one of the most repeated findings in ERP studies in the field of WMU; in particular, the P3b subcomponent is related to downstream cognitive control processing and allocation of attentional resources ( Donchin et al, 1986 ; Lenartowicz et al, 2010 ; Daffner et al, 2011 ; Vilà-Balló et al, 2018 ; Salmi et al, 2019 ). Since TSD is more detrimental to cognitive functions, which depends more on mental effort, rather than more automatic control processes ( Kusztor et al, 2019 ), we hypothesized that TSD would affect the allocation of attentional resources, instead of the primary selection of information, during WMU processes.…”

Impact of strategy use during N-Back training in older adults

“…Additionally, these results should be interpreted with caution due to the lack of follow-ups for testing whether transfers to other cognitive domains are preserved in older individuals. Moreover, although we were aware that other ERP components might be affected by WM training, such as early visual and late positive components (LPC) (Luria et al, 2016;Salmi et al, 2019) reflecting load effect and maintenance of to-be-remembered materials (Vilà-Balló et al, 2018), it was impossible to investigate these positive and negative slow waves as they occur in a time window that overlaps our feedback stimuli and collected our button press responses. Consequently, it would have been very difficult to extract this component from the feedback stimulus and button press responses.…”

“…However, although to a lesser extent, other ERP components might be affected as well such as the early visual ERP components-P1, N1, N2, P2 -and late positive components (LPC) or slow wave (Luria et al, 2016;Ruchkin et al, 1995). Salmi et al (2019) suggested that early and late ERPs are differentially affected by N-Back training. In particular, pre-and post-tests showed ERP changes indicative of a decreased load-effect for the training group, and slow wave amplitude that decreased in the easy task and increased in the difficult task, reflecting maintenance of to-be-remembered items (Luria et al, 2016;Vilà-Balló et al, 2018).…”