The Role of the Posterior Parietal Cortex In Working Memory

Abstract

The neural underpinnings of WM rely on the frontoparietal networks including structures in prefrontal and posterior parietal cortices (PPC). Often referred to as ‘association cortex’, the role of the PPC in Working Memory (WM) remains an open question. Among a number of proposals, two classes of accounts provide different roles: that the PPC is for attending to items in WM or that the PPC is for maintaining WM representations. This dissertation tests these accounts in a series of experiments. Each study uses transcranial direct current stimulation (tDCS) to modulate PPC function. In Experiment 1 we investigated the maintenance hypothesis by manipulating the WM retrieval demands. Experiments 2a and 2b tested material general and material specific predictions of the attention hypothesis by manipulating the attentional demands of the WM task. In Experiment 3 we investigated WM maintenance demands. We also examined the important question of whether tDCS benefits for individuals with low WM capacity (WMC) could be enhanced by high definition (HD)-tDCS. WM performance under HD-tDCS and conventional tDCS conditions revealed that stimulation type interacted with high and low WMC. In summary, across these four experiments, the results provide support predominantly for an attentional role of PPC in WM. Furthermore they hold implications for translational usage of tDCS among the general population.