Academic journal article Cognitive, Affective and Behavioral Neuroscience

Behavioral and Neural Correlates of Memory Selection and Interference Resolution during a Digit Working Memory Task

Academic journal article Cognitive, Affective and Behavioral Neuroscience

Behavioral and Neural Correlates of Memory Selection and Interference Resolution during a Digit Working Memory Task

Article excerpt

Neuroimaging studies have shown the involvement of prefrontal and posterior parietal cortexes in regulating information processing. We conducted behavioral and fMRI experiments to investigate the relationship between memory selection and proactive interference (PI), using a delayed recognition task with a selection cue presented during the delay indicating which two of the four studied digits were relevant to the present test. PI was indexed by the response time differences between rejecting probes matching and not matching the no longer relevant digits. By varying the delay intervals, we found that the effect of PI did not diminish, even for cases in which the postcue interval was extended to 9 sec, but was stronger when the precue interval was lengthened to 5 sec. By examining the correlation between PI index and neural correlates of memory selection, we found that stronger PI is predicted by lower selection-related activity in the left inferior parietal lobe, the precuneus, and the dorsal middle frontal gyrus. Our results suggest that activity in the prefrontal-parietal network may contribute to one's ability to focus on the task-relevant information and may proactively reduce PI in working memory.

The term working memory refers to the temporary maintenance and processing of information to fulfill ongoing task demands required by complex cognitive tasks such as mental arithmetic and reasoning (Baddeley, 1986; Baddeley & Hitch, 1974). It is known that the capacity of working memory is rather limited (Cowan, 2001) and that a main source of such limitation is caused by proactive interference (PI), interference from information that has become no longer relevant (Brown, 1954; Underwood, 1957). A dominant view of interference resolution is that attentional processes are involved in selecting taskrelevant information and ignoring irrelevant or no longer relevant information (see reviews by Jonides et al., 2008; Postle, 2006). Such selection processes presumably are mediated by the lateral prefrontal cortex (PFC) and the posterior parietal cortex (PPC) (see Deco & Rolls, 2005; Desimone & Duncan, 1995; Miller & Cohen, 2001).

Behavioral studies have provided evidence to support the involvement of attentional processes in controlling information accessibility in working memory. Cowan (1988, 1995, 1999) has proposed a component called the focus of attention as a mechanism to keep a small amount of information more accessible. Oberauer (2001, 2002, 2005) refined the model by conducting a set of elegant experiments to test whether information can be removed from the focus of attention in achieving the task goal. In his 2001 study, Oberauer used a modified delayed recognition task; two lists of words were presented as memory sets followed by a cue informing the subjects which list would remain relevant for the later recognition test. Besides finding the typical PI effect or intrusion cost (i.e., longer response times [RTs] to no longer relevant words relative to words not in the original memory sets), he found increases in RT only with an increasing number of relevant words. The number of no longer relevant words did not affect RT when the delay between cue and probe was at least 1 sec (Oberauer, 2001). These findings suggested that, although the relevant words are maintained in the focus of attention for matching with the probe, the no longer relevant words are removed from the focus of attention 1 sec after the cue presentation and no longer occupy the central capacity of working memory. Further, Nobre and colleagues (Lepsien, Griffin, Devlin, & Nobre, 2005; Lepsien & Nobre, 2007) investigated the effect of memory selection on later probe recognition, using informative cues in comparison with neutral or uninformative cues during visual work- ing memory tasks; they observed relatively shorter RTs to cued probes, suggesting that informative cues presented during the delay period can facilitate target recognition (Griffin & Nobre, 2003; Lepsien et al. …

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