Cathodal transcranial direct current stimulation over posterior parietal cortex enhances distinct aspects of visual working memory

Abstract

In this study, we investigated the effects of tDCS over the posterior parietal cortex (PPC) during a visual working memory (WM) task, which probes different sources of response error underlying the precision of WM recall. In two separate experiments, we demonstrated that tDCS enhanced WM precision when applied bilaterally over the PPC, independent of electrode configuration. In a third experiment, we demonstrated with unilateral electrode configuration over the right PPC, that only cathodal tDCS enhanced WM precision and only when baseline performance was low. Looking at the effects on underlying sources of error, we found that cathodal stimulation enhanced the probability of correct target response across all participants by reducing feature-misbinding. Only for low-baseline performers, cathodal stimulation also reduced variability of recall. We conclude that cathodal- but not anodal tDCS can improve WM precision by preventing feature-misbinding and hereby enhancing attentional selection. For low-baseline performers, cathodal tDCS also protects the memory trace. Furthermore, stimulation over bilateral PPC is more potent than unilateral cathodal tDCS in enhancing general WM precision.

Individual Differences and Long-term Consequences of tDCS-augmented Cognitive Training

“…For example, a number of studies also suggest a selective tDCS benefit among low-baseline populations, both within the WM domain (Gozenman & Berryhill, 2016;Heinen et al, 2016;Minichino et al, 2015;Tseng et al, 2012) as well as in other cognitive domains, such as attention and dual tasking (Reinhart et al, 2016;London & Slagter, 2015;Zhou et al, 2015). However, one critical difference between these studies and ours is that ours is a training study involving multiple sessions of stimulation in conjunction with task performance, rather than only a single session (but see also Looi et al, 2016).…”

“…Several studies have demonstrated selective tDCS benefits among individuals with low, but not high, baseline WM abilities (Gozenman & Berryhill, 2016;Heinen et al, 2016;Tseng et al, 2012), and meta-analyses tend to report stronger effect sizes in clinical or older adult populations compared with the higher-performing young adult population (Dedoncker, Brunoni, Baeken, & Vanderhasselt, 2016;Hill, Fitzgerald, & Hoy, 2016;Hsu, Ku, Zanto, & Gazzaley, 2015;Summers, Kang, & Cauraugh, 2015). Moreover, the evidence extends beyond the WM domain.…”

Individual Differences and State-Dependent Responses in Transcranial Direct Current Stimulation

“…More importantly, they also found that the tDCS effect varied with participants’ baseline digit span performance: only the high WM capacity group enjoyed an improvement after stimulation but not the low WM capacity group. Recently, Heinen et al (2016) also provided another evidence of tDCS effect varying with participants’ baseline performance. They showed that only cathodal stimulation enhanced WM precision, especially for those participants whose baseline performance was low.…”

“…Given the growing number of studies reporting varied effects of tDCS with different baseline performances (Gözenman and Berryhill, 2016; Heinen et al, 2016; Looi et al, 2016), it is important for studies to choose an appropriate baseline on which to evaluate the effect of tDCS. The studies mentioned above have mostly adopted participants’ behavioral performances from the sham condition to serve as a baseline to split the participants into different groups (Tseng et al, 2012, 2016; Hsu et al, 2014).…”

Source memory performance is modulated by transcranial direct current stimulation over the left posterior parietal cortex

“…Further studies are needed to examine whether indeed the dorsal and ventral parts of the LPPC have different roles in episodic memory retrieval and the cognitive operations subserved by these regions. In addition, it has been shown that the tDCS exerts its effects to brain regions that are functionally connected to the stimulated area (e.g., Heinen, Sagliano, Candini, Husain, Cappelletti, & Zokaei, 2016;Liang et al 2014;Yu, Tseng, Hung, Wu, & Juan, 2015). The LPPC, together with the hippocampus, the parahippocampal cortex, the medial prefrontal cortex, and the retrosplenial/posterior cingulate cortex have been thought to form the "core recollection network" (King, de Chastelaine, Elward, Wang, & Rugg, 2015).…”