Digit Working Memory Span Effects Of Brain Mechanisms Of Response Inhibition

Ignoring irrelevant information becomes more difficult with disrupting working memory functions. The present cross-sectional study addressed this issue by investigating working memory capacity differences in the ability to withhold a response to non-target stimuli.12 high span (20-24 years) and 14 low span (20-24years) participants performed two go/nogo tasks (simple vs. complex). In the simple task the subjects responded to blue X and red O (target go stimuli) while withholding responses to the blue O and red X (conflict nogo stimuli) and to numbers of either color (irrelevant nogo stimuli). In the complex version,4 vowels and 4 consonants were used instead of 0 and X. Accuracy, response times (RTs) and event-related potentials (ERPs)were recorded.Both high span and low span groups made more commission errors to conflict nogo stimuli (mean 6% and 9% in the simple and complex tasks, respectively, capacity differences not significant) than to irrelevant nogo stimuli (mean< 1%), indicating difficulty in withholding a response when a pertinent stimulus feature (letter identity) was shared with the go stimuli. In addition to later RTs to go stimuli and later P3 waves for the conflicting stimuli than the high span group, low span participants showed a very prominent left posterior P2 and a large pre-central P3 to the irrelevant nogo stimuli. These findings suggest that low span groups have difficulty in ignoring irrelevant nogo stimuli even when they are easily distinguishable from the go stimuli.