200629/2005-0) at the Physiology, Anatomy & Genetics and Clinical Neurology (FMRIB Centre), Departments of the University of Oxford, Oxford, England, United Kingdom. The authors are grateful to Daoud Hibrahim Elias Filho for expert technical assistance. D. H. Elias Filho was the recipient of a technician scholarship from FAPESP (TT-2, proc. 02/01497-1) and is the recipient of a technician scholarship Inhibitors,research,lifescience,medical from CNPq (Edital CNPq 057/2005;
Bolsas de Apoio Técnico; Ciências da Vida; proc. 501858/2005-9). Conflict of Interest None declared.
Functional neuroimaging studies typically manipulate cognitive demand of tasks by changing executive load (e.g., n-back tasks; Owen et al. 2005 for meta-analysis) or number of items on the display over
a temporal delay (e.g., Sternberg tasks; Manoach et al. 1997; Rypma et al. 1999, 2002; Inhibitors,research,lifescience,medical Jha and McCarthy 2000). Researchers have also identified a set of areas that are active when a cognitive task is not required, during rest (e.g., Spreng et al. 2009 for meta-analysis). Knowledge of the brain areas Inhibitors,research,lifescience,medical that underlie cognitive load versus rest activity is expanding, but their interrelation is not well understood. We used functional magnetic resonance imaging (fMRI) and a working memory task with graded increases in cognitive load (Arsalidou et al. 2010), to examine, using linear regression, whole-brain changes in activity as a function of task difficulty. A classic working memory protocol used to manipulate cognitive load is the n-back task. In a typical n-back paradigm, participants view
a series of stimuli and indicate whether the current stimulus matches the stimulus n items earlier in the series. As n increases, the number of Inhibitors,research,lifescience,medical interpolated stimuli between criterion and target increases, and thus cognitive load increases. Cognitive demand increases Inhibitors,research,lifescience,medical qualitatively (e.g., 0-back, recognition, 1-back, maintenance, 2-back, maintenance and monitoring), and because cognitive load increases nonlinearly from one level to the next, these changes are not easily Bcl-2 apoptosis quantifiable. In a coordinate-based Thymidine kinase meta-analysis of 24 n-back studies, Owen et al. (2005) identified six cortical regions that were reliably activated by n-back tasks. In prefrontal regions, activity was typically elicited in inferior frontal (BA 45/47), middle frontal (BA 9/46), and anterior medial frontal gyri (BA 10; Owen et al. 2005). Other areas included the dorsal cingulate gyrus (BA 32), the premotor cortex (BA 6), and parietal regions (BA 7/40; Owen et al. 2005). In this study, by manipulating cognitive load, we expected to replicate this set of areas typically found with adults, and also show how brain activity elicited by graded increases in cognitive load might also affect activity found in the control conditions (i.e., no task). Shulman et al.