Stimulating the parietal cortex by transcranial direct current stimulation (tDCS): no effects on attention and memory.

Mirela Dubravac,Beat Meier

doi:10.3934/neuroscience.2021002

Abstract

Selective attention is relevant for goal directed behavior as it allows people to attend to task-relevant target stimuli and to ignore task-irrelevant distractors. Attentional focus at encoding affects subsequent memory for target and distractor stimuli. Remembering selectively more targets than distractors represents memory selectivity. Brain imaging studies suggest that the superior parietal cortex is associated with the dorsal attentional network supporting top-down control of selective attention while the inferior parietal cortex is associated with the ventral attentional network supporting bottom-up attentional orienting. To investigate the roles of the dorsal and ventral networks in the effect of selective attention during encoding on long-term memory, we stimulated the left superior and the right inferior parietal cortex. Building on previous work, we applied transcranial direct current stimulation (tDCS) during a study phase where pictures and words were presented simultaneously and participants had to switch between a picture and a word decision. A subsequent recognition test assessed memory for target and distractor pictures and words. We hypothesized that a relative increase in activity in the dorsal network would boost selective attention while increased activity in the ventral network would impair selective attention. We also expected to find corresponding effects on memory. Enhanced selective attention should lead to higher memory selectivity, while impaired selective attention should lead to lower memory selectivity. Our results replicated that task switching reduced memory selectivity. However, we found no significant effects of tDCS. Thus, the present study questions the effectiveness of the present tDCS protocol for modulating attention during task switching and subsequent memory.

Highlights

In order to navigate successfully through our environment, we rely on two attentional systems; top-down focusing and bottom-up orienting
Brain imaging studies suggest that the superior parietal cortex is associated with the dorsal attentional network supporting top-down control of selective attention while the inferior parietal cortex is associated with the ventral attentional network supporting bottom-up attentional orienting
Enhanced selective attention should lead to higher memory selectivity, while impaired selective attention should lead to lower memory selectivity

Summary

Introduction

In order to navigate successfully through our environment (e.g., driving a car), we rely on two attentional systems; top-down focusing (e.g., on the road) and bottom-up orienting (e.g., to incoming cyclists). On switch trials, when the appropriate task-set is reconfigured, attention is broadened so that more distractors are encoded at the expense of targets. This explanation is in line with fMRI studies suggesting a correspondence between attention control and episodic retrieval in the posterior parietal cortex [9]. As episodic memory can be modulated by stimulating parietal substrates of attention during encoding [10], in the present study, we applied transcranial direct current stimulation (tDCS) over the parietal cortex to establish a causal link between the activity of two neural networks involved in top-down and bottom-up control during task switching. Based on previous behavioral as well as brain imaging and stimulation findings, we assumed a corresponding effect on subsequent memory selectivity

Methods

Results

Discussion

Conclusion