Neural effects of short-term training on working memory

Abstract

Working memory training has been the focus of intense research interest. Despite accumulating behavioral work, knowledge about the neural mechanisms underlying training effects is scarce. Here, we show that 7 days of training on an n-back task led to substantial performance improvements in the trained task; furthermore, the experimental group showed cross-modal transfer, as compared with an active control group. In addition, there were two neural effects that emerged as a function of training: first, increased perfusion during task performance in selected regions, reflecting a neural response to cope with high task demand; second, increased blood flow at rest in regions where training effects were apparent. We also found that perfusion at rest was correlated with task proficiency, probably reflecting an improved neural readiness to perform. Our findings are discussed within the context of the available neuroimaging literature on n-back training.

Figures

Figure 1

Design matrix used in the second level analysis. The main effects of interest are represented to the right of the figure: (1) a constant mean effect across all scans, (2) the effect of coming in for a second scanning session (regardless of training), (3) the effect of group (having received WM or control training), (4) the effect of time, and (5) the TMS effect.

Figure 2

Performance in the visuospatial n back task as a function of test session, n back level, and group. As expected, all participants performed near ceiling level at 1 back in both sessions, but there was a significant improvement in the experimental group in the 4 back condition from pre to post test which was not reliably present in the control group.

Figure 3

Performance in the untrained auditory n back task as a function of test session, n back load, and group. The benefit of visuospatial n back training was especially pronounced in the 3 back condition.

Figure 4

Task related perfusion in the 4 back minus 1 back contrast. The numbers next to each slice represent the z coordinates in MNI space. This figure corresponds to the data reported in Table 1.

Figure 5

Perfusion at rest. The numbers next to each slice represent the z coordinates in MNI space. This figure corresponds to the data reported in Table 2.

Figure 6

Brain region that showed an increased perfusion during task performance after training and an increased perfusion during rest.