No effects of transcranial direct current stimulation on visual evoked potential and peak gamma frequency

Abstract

Evidence suggests that the visual evoked potential (VEP) and gamma oscillations elicited by visual stimuli reflect the balance of excitatory and inhibitory (E-I) cortical processes. As tDCS has been shownto modulate E-I balance, the current study investigated whether amplitudes of VEP components (N1 and P2) and peak gamma frequency are modulated by transcranial direct current stimulation (tDCS). Healthy adults underwent two electroencephalography (EEG) recordings while viewing stimuli designed to elicit a robust visual response. Between the two recordings, participants were randomly assigned to three tDCS conditions (anodal-, cathodal-, and sham-tDCS) or received no-tDCS. tDCS electrodes were placed over the occipital cortex (Oz) and the left cheek with an intensity of 2 mA for 10 min. Data of 39 participants were analysed for VEP amplitudes and peak gamma frequency using mixed-model ANOVAs.The results showed no main effects of tDCS in any metric. Possible explanations for the absence of tDCS effects are discussed.

Short-term ocular dominance plasticity is not modulated by visual cortex tDCS but increases with length of monocular deprivation

“…Although many studies have reported a-tDCS effects on visual cortex function and plasticity 10 – 16 , our study is not the first to observe no effect. For instance, while Ding et al 16 and Frase et al 10 demonstrated a modulation of VEP amplitude using a-tDCS, other studies 29 , 30 did not observe such an effect. Abuleil et al 31 observed that tDCS did not modulate binocular rivalry dynamics, while a type of repetitive transcranial magnetic stimulation, namely continuous theta burst stimulation (cTBS), had an effect.…”

Individual/Peak Gamma Frequency: What Do We Know?

“…Finally, as neuromodulational techniques are increasingly used to change the state of the brain, the effect of neuromodulation on peak gamma frequencies was tested. However, the knowledge is still limited: Transcranial alternating current stimulation (tACS) was reported to increase IGF [4,83,84], whereas transcranial direct current stimulation (tDCS) did not modulate IGF [85][86][87]. In addition, non-invasive vagal nerve stimulation was shown to decrease IGF [88].…”