Beyond common resources: the cortical basis for resolving task interference

Abstract

Recent studies have suggested that declining inhibitory control observed during simultaneous increases in working memory (WM) demands may be due to sharing common neural resources, although it is relatively unclear how these processes are successfully combined at a neural level. Event-related functional MRI was used to examine task performance that required inhibition of varying numbers of items held in WM. Common activation regions for WM and inhibition were observed and this functional overlap may constitute the cortical basis for task interference. However, maintaining successful inhibitory control under increasing WM demands tended not to increase activation in these overlapping regions as might be expected if these common areas reflect common resources essential for task performance. Instead, increased activation was observed predominantly in unique, inhibition-specific regions including dorsolateral prefrontal cortex. The finding that successfully maintaining weaker stimulus -response relationships in the face of competition from stronger, prepotent responses requires greater activity in these regions reveals the means by which the brain resolves task interference and supports theories of how top-down attentional control is implemented. D

Flexible cognitive control: Effects of individual differences and brief practice on a complex cognitive task

“…It is also a novel examination of the effects of brief practice of the WMI task on general cognitive task processes and the effects of itemspecific practice occurring as a result of repeated exposure to the same stimuli over a single block of trials. We observed that withholding a prepotent response to items held in WM activated a predominantly right-hemisphere network of regions, including middle and inferior frontal cortex, insula, midline frontal areas (SMA, pre-SMA, and ACC), inferior parietal cortex, striatum and thalamus, consistent with Hester et al (2004b) and previous neuroimaging studies of response inhibition (e.g., Garavan et al, 1999;Kelly et al, 2004;Liddle et al, 2001;Rubia et al, 2003;Watanabe et al, 2002). Errors of commission activated lateral frontal, midline, and insular areas also consistent with previous studies (Hester et al, 2004b;Holroyd et al, 2004;Ullsperger and Von Cramon, 2003;Ridderinkhof et al, 2004;Kiehl et al, 2000).…”

“…Participants performed the FWorking Memory Inhibitory Task_ (WMI task, Hester et al, 2004b), which comprises a Sternberg verbal WM task embedded in a GO/NOGO task. The task was programmed and displayed using E-prime 1.1 (Psychology Software Tools).…”

“…In the present study, participants performed the WMI task at the highest level of load used in the Hester et al (2004b) study, at what is thought to be the capacity limit of human WM storage (Cowan, 2001). Participants were first shown a target memory list of 5 uppercase letters, presented in white font on a black background.…”

“…Participants were instructed to indicate as quickly as possible whether each letter was or was not part of the memory list. Participants were trained to use their index finger to press a button for each trial featuring a letter that was not part of the memory list (GO trials) and withhold their response for items that were part of the memory list (NOGO trials) (see Hester et al, 2004b, Fig. 1, for a graphical depiction of the WMI task).…”

“…In a recent study, Hester et al (2004b) further investigated the neural bases of the relationship between WM and inhibitory control. Taking into consideration that the decline in inhibitory control resulting from increases in WM load may be due to these processes sharing a common attentional network, they assessed how the brain succeeds in exerting inhibitory control as the number of items being rehearsed in WM increases.…”