Impact of tDCS on performance and learning of target detection: Interaction with stimulus characteristics and experimental design

Abstract

We have previously found that transcranial direct current stimulation (tDCS) over right inferior frontal cortex (RIFC) enhances performance during learning of a difficult visual target detection task (Clark et al., 2012). In order to examine the cognitive mechanisms of tDCS that lead to enhanced performance, here we analyzed its differential effects on responses to stimuli that varied by repetition and target presence, differences related to expectancy by comparing performance in single-and double-blind task designs, and individual differences in skin stimulation and mood. Participants were trained for 1 h to detect target objects hidden in a complex virtual environment, while anodal tDCS was applied over RIFC at 0.1 mA or 2.0 mA for the first 30 min. Participants were tested immediately before and after training and again 1 h later. Higher tDCS current was associated with increased performance for all test stimuli, but was greatest for repeated test stimuli with the presence of hidden-targets. This finding was replicated in a second set of subjects using a double-blind task design. Accuracy for target detection discrimination sensitivity (d ' ; Z(hits) − Z(false alarms)) was greater for 2.0 mA current (1.77) compared with 0.1 mA (0.95), with no differences in response bias (β). Taken together, these findings indicate that the enhancement of performance with tDCS is sensitive to stimulus repetition and target presence, but not to changes in expectancy, mood, or type of blinded task design. The implications of these findings for understanding the cognitive mechanisms of tDCS are discussed.

Augmenting Visual Search Performance with Transcranial Direct Current Stimulation (tDCS)

“…In previous research studies ( Eun-Kyoung & Nam-Jong, 2011;Hauser, Rotzer, Grabner, Merillat, & Jancke, 2013;Coffman et al, 2012), wet sponge electrodes were used to administer the electrical current for tDCS. Here, we used a custom design of silver/silver chloride electroencephalographic (EEG) electrode.…”

Transcranial direct current stimulation (tDCS) and language

“…Intriguingly, no report described negative results in aphasic patients. Although tDCS-induced benefits in language might partly depend on improved learning64 or working-memory65 tDCS could improve activation in lesioned and vicarious cortical speech areas and reduce activation in competing homologous contralateral cortical areas,49 54–56 60 ultimately improving language.…”

The Effects of Electrical Brain Stimulation Upon Visual Attention and Neglect

“…Signal detection theory was also applied by Clark, Coffmann, and colleagues Coffman, Trumbo, Flores et al, 2012). In a different visual search task, placed in a more naturalistic (although still artificial) scenery, they trained participants for 1 hour to detect target objects concealed in a complex virtual environment, while applying anodal tDCS over right inferior frontal cortex (IFC, F10) or right parietal cortex (P4).…”