Common deactivation patterns during working memory and visual attention tasks: an intra-subject fMRI study at 4 Tesla

Abstract

This parametric functional magnetic resonance imaging (fMRI) study investigates the balance of negative and positive fMRI signals in the brain. A set of visual attention (VA) and working memory (WM) tasks with graded levels of difficulty was used to deactivate separate but overlapping networks that include the frontal, temporal, occipital, and limbic lobes; regions commonly associated with auditory and emotional processing. Brain activation (% signal change and volume) was larger for VA tasks than for WM tasks, but deactivation was larger for WM tasks. Load-related increases of blood oxygenation level-dependent (BOLD) responses for different levels of task difficulty cross-correlated strongly in the deactivated network during VA but less so during WM. The variability of the deactivated network across different cognitive tasks supports the hypothesis that global cerebral blood flow vary across different tasks, but not between different levels of task difficulty of the same task. The task-dependent balance of activation and deactivation might allow maximization of resources for the activated network.

Figure 1

Performance accuracy and reaction times for working memory and visual attention tasks.

Figure 2

Statistical maps of positive (top; red) and negative (top; blue) BOLD signals during working memory (WM) and visual attention (VA) tasks, differential BOLD signals between tasks (middle), and positive and negative correlation of BOLD signals with task difficulty (Bottom). The color bars are t‐score windows; for the bottom panel they indicate the significance of the voxel‐wise fit of the linear regression with parametric variation of the task difficulty, i.e., reaction time/performance accuracy. Sample size: Twenty‐two healthy subjects, random‐effects analyses (repeated ANOVA). IFG, inferior frontal gyrus; medFG, medial frontal gyrus; FusG, fusiform gyrus; SPL, superior parietal lobe; PostCG, postcentral gyrus; PCL, paracentral lobule; Prec, precuneus; ACG, anterior cingulate gyrus; CG, cingulate gyrus; PCG, posterior cingulate gyrus; LG, lingual gyrus;

Figure 3

Average BOLD signals at specific regions of interest in the activated network (see Table I).

Figure 4

Average BOLD signals at specific regions of interest in the deactivated network (see Table II).

Figure 5

Correlation of load effects in regions of interest (ROIs) that deactivated for visual attention (VA; A) and working memory (WM; B) tasks, and BOLD signal distribution in the paracentral lobule (PCL; C) and the precuneus (D) for WM and VA tasks. Average signal amplitudes in bilateral cubic ROIs (27 3 × 3 × 3 mm³ voxels) for all subjects and conditions (22 subjects × 2 repetitions × 2 sides [left and right] × 3 tasks [zero‐, one‐, and two‐back] = 264 measurements [full and open circles]).