Prefrontal transcranial direct current stimulation (tDCS) enhances behavioral and EEG markers of proactive control

ABSTRACT

This study examined the effects of stimulation targeting dorsolateral prefrontal cortex (DLPFC) on behavioral and neural oscillatory markers of proactive cognitive control in healthy adults. We hypothesized that active stimulation targeting the DLPFC would enhance proactive control compared to sham, leading to changes in the pattern of error rates and gamma-band power on the Dot Pattern Expectancy (DPX) task. We recorded EEG while participants completed the DPX, after receiving either 20 minutes of active DLPFC stimulation at 2 mA or sham stimulation in a counterbalanced within-participants design. The results showed significant tDCS-induced changes in the pattern of error rates on the DPX task indicative of enhanced proactive control, as well as predicted increases in gamma power associated with the engagement of proactive control. These results provide support for the role of DLPFC-mediated gamma activity in proactive cognitive control, and further, indicate that proactive control can be enhanced with non-invasive neurostimulation.

KEYWORDS:

• tDCS
• gamma
• proactive control
• EEG

Acknowledgements

This work was supported by: National Institute of Mental Health (5R01MH059883) to C.S.C.; California Center for Behavioral Health Excellence to C.R.; Vannevar Bush Fellowship (Office of Naval Research Grant N00014-15-1-0033) to C.R. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Office of Naval Research or the U.S. Department of Defense.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

¹ While this electrode montage is commonly used to enhance activity in DLPFC, it is important to keep in mind that the bipolar nature of tDCS means that changes in electric fields will not be restricted to those induced by the anode. For this reason, it is not recommended to place anodal and cathodal electrodes in the same location on either side of the brain, as this can make it difficult to interpret whether stimulation effects in the targeted region are anodal, cathodal or a combination of the two (Reinhart, Cosman, Fukuda, & Woodman, 2017). While we have avoided this configuration in the current study, the placement of the cathode on FP2 does still impact electric fields in some cortical regions, although current flow modeling of this configuration shows consistent electric fields in the superior frontal and middle frontal gyri (BA9 and BA46) (see Laakso et al., 2016).

Additional information

Funding

This work was supported by the National Institute of Mental Health [5R01MH059883 to C.S.C];Office of Naval Research [Vannevar Bush Fellowship Grant N00014-15-1-0033].