2006). The FIT predates the CMT and was chosen to evaluate its performance. In a developmental study, CMT and FIT were significantly correlated and yielded very similar quantitative working memory capacity scores (Arsalidou et al. 2010). In the current adult data, we also found that correlations between CMT-clown and FIT were very high (0.93) suggesting that these tasks are measures of the same latent variable. Response accuracy decreased with the cognitive demand (difficulty), even though the cortical activity in working memory regions increased with the
items’ cognitive load. Negative Inhibitors,research,lifescience,medical correlations (from −0.65 to −0.89) were obtained with percent signal change and the FIT, which was not studied with fMRI. Inhibitors,research,lifescience,medical This high negative relation using an alternative
measure confirms that the pattern of cortical activity reflects a graded relation of covariation between activity in brain regions and the participants’ use of working memory, which FIT has measured independently. An extended correlation table including all ROIs can be found in Supporting Information (Table S1). Linear trend analyses Carboplatin nmr showed that several regions congruent with working memory processes become progressively active as cognitive load increases. The linear patterns, however, did not show the same signature. Inhibitors,research,lifescience,medical Areas in the prefrontal cortex gradually increase until about D7 and leveled off or decreased at D8, whereas posterior regions, such as the precuneus and fusiform gyri, produced a distinct increase between D4 and D5 with Inhibitors,research,lifescience,medical a more steady increase to D7. The cingulate gyrus, on the other hand, appeared to produce its own pattern with activity progressing gradually up to the highest level of difficulty. We compare these patterns to those produced by areas that showed a decrement in activity as cognitive load increased, related to the default mode. Implications of this finding with reference to working memory capacity measurement are discussed in the Inhibitors,research,lifescience,medical section on capacity limits of working memory. Default mode The coordinated deactivation in regions linked to the control task was also linear, supporting the hypothesis of an inverse
regulation between default-mode and working memory processes (Raichle and Gusnard 2002), and this relation was maintained across increasing difficulty levels (McKiernan et al. 2003). Although our control tasks/baselines do not represent a pure isothipendyl resting state, they carried very limited cognitive demand, and responses induced by sensory processing disrupt only minimal activity in default-mode areas (Greicius et al. 2003). Our obtained linear patterns (Fig. 4) agree with these results. Areas that decreased in activity as a function of difficulty were medial prefrontal cortex, posterior cingulate, and superior temporal gyri, which have been linked with self-relevant thoughts, integrating information, and memory associations, respectively (Buckner et al. 2008).