Additive and interaction effects of working memory and motor sequence training on brain functional connectivity

Abstract

Although shared behavioral and neural mechanisms between working memory (WM) and motor sequence learning (MSL) have been suggested, the additive and interactive effects of training have not been studied. This study aimed at investigating changes in brain functional connectivity (FC) induced by sequential (WM + MSL and MSL + WM) and combined (WM × MSL) training programs. 54 healthy subjects (27 women; mean age: 30.2 ± 8.6 years) allocated to three training groups underwent twenty-four 40-min training sessions over 6 weeks and four cognitive assessments including functional MRI. A double-baseline approach was applied to account for practice effects. Test performances were compared using linear mixed-effects models and t-tests. Resting state fMRI data were analysed using FSL. Processing speed, verbal WM and manual dexterity increased following training in all groups. MSL + WM training led to additive effects in processing speed and verbal WM. Increased FC was found after training in a network including the right angular gyrus, left superior temporal sulcus, right superior parietal gyrus, bilateral middle temporal gyri and left precentral gyrus. No difference in FC was found between double baselines. Results indicate distinct patterns of resting state FC modulation related to sequential and combined WM and MSL training suggesting a relevance of the order of training performance. These observations could provide new insight for the planning of effective training/rehabilitation.

Figure 1

Study procedures. Each assessment (BL 1, BL2, T3 and T4) included an MRI and cognitive testing.

Figure 2

Comparison between session 1 and 4 across the whole sample. The NBS results showed increased connectivity between fronto-parietal regions in the right hemisphere and between left temporal and right parietal regions (Table 4).

Figure 3

Different patterns of increased connectivity across subgroups assessed computing Cohen’s d for all significant connections in the whole sample analysis. The numbers represent the connections displayed in Table 4. Red represents group WM + MSL, black represents group MSL + WM and green represents the group WM × MSL. (A) session 1 versus session 3; (B) session 1 versus session 4.