Development of deactivation of the default-mode network during episodic memory formation

Abstract

Task-induced deactivation of the default-mode network (DMN) has been associated in adults with successful episodic memory formation, possibly as a mechanism to focus allocation of mental resources for successful encoding of external stimuli. We investigated developmental changes of deactivation of the DMN (posterior cingulate, medial prefrontal, and bilateral lateral parietal cortices) during episodic memory formation in children, adolescents, and young adults (ages 8-24), who studied scenes during functional magnetic resonance imaging (fMRI). Recognition memory improved with age. We defined DMN regions of interest from a different sample of participants with the same age range, using resting-state fMRI. In adults, there was greater deactivation of the DMN for scenes that were later remembered than scenes that were later forgotten. In children, deactivation of the default-network did not differ reliably between scenes that were later remembered or forgotten. Adolescents exhibited a pattern of activation intermediate to that of children and adults. The hippocampal region, often considered part of the DMN, showed a functional dissociation with the rest of the DMN by exhibiting increased activation for later remembered than later forgotten scene that was similar across age groups. These findings suggest that development of memory ability from childhood through adulthood may involve increased deactivation of the neocortical DMN during learning.

Keywords: Children; Memory encoding; Resting-state fMRI; Task suppression; fMRI.

Figure 1

DMN in 82 participants of 8–24 years of age, defined from resting-state connectivity data in an independent sample of participants. A = PCC; B = MPFC; C = LLP; D = RLP; E = left hippocampal region; F = right hippocampal region

Figure 2

Recognition memory accuracy. Accuracy for “Remembered” (R) and “Know” (K) trial types were calculated by subtracting the corresponding false alarm rate from the hit rate for R or K trial types (R accuracy: R − FA_R; K accuracy: K/(1−R) − FA_K, adjusted for being mathematically constrained by R responses).

Figure 3

Subsequent memory deactivations in the DMN in each age group. A = PCC; B = MPFC; C = LLP; D = RLP. Dark grey bars represent trials in which a scene was later remembered (R). Light grey bars represent trials in which a scene was later forgotten (F). Error bars are standard errors of the mean. ** p < .01 for R < F. * p < .05 for R < F.

Figure 4

Regions within DMN ROIs that showed deactivations for remembered trials compared to forgotten trials for each age group.

Figure 5

Subsequent memory activations in hippocampal regions. A = left hippocampus; B = right hippocampus. Dark grey bars represent trials in which a scene was later remembered (R). Light grey bars represent trials in which a scene was later forgotten (F). Error bars are standard errors of the mean. ** p < .01 for R > F.