Functional Effects of Bilateral Dorsolateral Prefrontal Cortex Modulation During Sequential Decision-Making: A Functional Near-Infrared Spectroscopy Study With Offline Transcranial Direct Current Stimulation

Abstract

The ability to learn sequential contingencies of actions for predicting future outcomes is indispensable for flexible behavior in many daily decision-making contexts. It remains open whether such ability may be enhanced by transcranial direct current stimulation (tDCS). The present study combined tDCS with functional near-infrared spectroscopy (fNIRS) to investigate potential tDCS-induced effects on sequential decision-making and the neural mechanisms underlying such modulations. Offline tDCS and sham stimulation were applied over the left and right dorsolateral prefrontal cortex (dlPFC) in young male adults (N = 29, mean age = 23.4 years, SD = 3.2) in a double-blind between-subject design using a three-state Markov decision task. The results showed (i) an enhanced dlPFC hemodynamic response during the acquisition of sequential state transitions that is consistent with the findings from a previous functional magnetic resonance imaging (fMRI) study; (ii) a tDCS-induced increase of the hemodynamic response in the dlPFC, but without accompanying performance-enhancing effects at the behavioral level; and (iii) a greater tDCS-induced upregulation of hemodynamic responses in the delayed reward condition that seems to be associated with faster decision speed. Taken together, these findings provide empirical evidence for fNIRS as a suitable method for investigating hemodynamic correlates of sequential decision-making as well as functional brain correlates underlying tDCS-induced modulation. Future research with larger sample sizes for carrying out subgroup analysis is necessary in order to decipher interindividual differences in tDCS-induced effects on sequential decision-making process at the behavioral and brain levels.

TDCS Modulates Working Memory Maintenance Processes in Healthy Individuals

“…Indeed, similar views have been expressed using event-related potentials obtained during the n -back task (Hill, Rogasch, Fitzgerald, & Hoy, 2019; Keeser et al, 2011), including previously reported analyses of the present dataset (Nikolin et al, 2018). These findings suggest a greater role for EEG, and more broadly neuroimaging techniques, including functional magnetic resonance imaging (Fischell, Ross, Deng, Salmeron, & Stein, 2020; Lin et al, 2019; Vaqué-Alcázar et al, 2020) and functional near infra-red spectroscopy (Schommartz, Dix, Passow, & Li, 2021), for investigations of the neuromodulatory effects of tDCS on cognitive processes. In the absence of behavioural changes following tDCS, these techniques may be used instead to gain insights into the mechanisms of action of tDCS, and thereby optimise stimulation parameters to achieve larger and more consistent cognitive effects.…”

Cortical processes of multisensory plausibility modulation of vibrotactile perception in virtual environments in middled-aged and older adults

“…At pre-processing, bad channels were identified and excluded using the hmrR_PruneChannels function with a SNR threshold criterion of 6.67 (equivalent to coefficient of variation (CV) = 15%; SNR = 1/CV*100). Datasets which consisted of more than 25% of bad channels (i.e., CV less than 15% 88 , 89 ) were excluded from further analysis ( N = 2). Raw signals of light intensity were then converted into changes in optical density using the hmrR_Intensity2OD function.…”

A brief real-time fNIRS-informed neurofeedback training of the prefrontal cortex changes brain activity and connectivity during subsequent working memory challenge

“…The montage design used an optode set with 8 sources and 8 detectors, resulting in 18 source-detector pairs (channels). The optodes were placed according to the International 10-20 system for EEG electrode placement with the distance between the sources and detectors being 30 mm (Jasper 1958; Schommartz et al 2020) (see Figure 2, note: channel 6 served as the target channel).…”