Modelling neural correlates of working memory: a coordinate-based meta-analysis

Abstract

Working memory subsumes the capability to memorize, retrieve and utilize information for a limited period of time which is essential to many human behaviours. Moreover, impairments of working memory functions may be found in nearly all neurological and psychiatric diseases. To examine what brain regions are commonly and differently active during various working memory tasks, we performed a coordinate-based meta-analysis over 189 fMRI experiments on healthy subjects. The main effect yielded a widespread bilateral fronto-parietal network. Further meta-analyses revealed that several regions were sensitive to specific task components, e.g. Broca's region was selectively active during verbal tasks or ventral and dorsal premotor cortex were preferentially involved in memory for object identity and location, respectively. Moreover, the lateral prefrontal cortex showed a division in a rostral and a caudal part based on differential involvement in task set and load effects. Nevertheless, a consistent but more restricted "core" network emerged from conjunctions across analyses of specific task designs and contrasts. This "core" network appears to comprise the quintessence of regions, which are necessary during working memory tasks. It may be argued that the core regions form a distributed executive network with potentially generalized functions for focussing on competing representations in the brain. The present study demonstrates that meta-analyses are a powerful tool to integrate the data of functional imaging studies on a (broader) psychological construct, probing the consistency across various paradigms as well as the differential effects of different experimental implementations.

Figure 1

Main effect across all 189 working memory experiments revealing consistent bilateral activation of a fronto-parietal network.

Figure 2

Figure 2A. Task set versus task load effects: Red denotes regions, which show higher convergence in task set effects, while regions showing stronger convergence in experiments analysing load effects are displayed in green Figure 2B. A conjunction analysis of task set and load effects displays a bilateral fronto-parietal network similar to the main effect.

Figure 3

Figure 3A. Verbal versus non-verbal tasks. Significant activation for verbal tasks (red) was found in area 44/45 in the left hemisphere; regions, which show stronger convergence for non-verbal tasks are coloured in green. Figure 3B. A conjunction analysis over verbal and non-verbal tasks show activation of a fronto-parietal network similar to the main effect.

Figure 4

Figure 4A. Object identity versus object location. Regions where experiments on memory for object location showed a significantly higher convergence of reported activations than those probing memory for object identity are shown in green. Regions showing stronger convergence of activation in experiments on object identity are displayed in red. Figure 4B. Conjunction analysis of object identity and object location.

Figure 5. The working memory core network

Left dominant bilateral activation of regions showing converging activations in each of the following analyses: task effects for n-back and Sternberg tasks, verbal and non-verbal tasks, load effects and all three phases (encoding, maintenance, recall).