Network-level mechanisms underlying effects of transcranial direct current stimulation (tDCS) on visuomotor learning

Abstract

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation approach in which low level currents are administered over the scalp to influence underlying brain function. Prevailing theories of tDCS focus on modulation of excitation-inhibition balance at the local stimulation location. However, network level effects are reported as well, and appear to depend upon differential underlying mechanisms. Here, we evaluated potential network-level effects of tDCS during the Serial Reaction Time Task (SRTT) using convergent EEG- and fMRI-based connectivity approaches. Motor learning manifested as a significant ( p <.0001) shift from slow to fast responses and corresponded to a significant increase in beta-coherence ( p <.0001) and fMRI connectivity ( p <.01) particularly within the visual-motor pathway. Differential patterns of tDCS effect were observed within different parametric task versions, consistent with network models. Overall, these findings demonstrate objective physiological effects of tDCS at the network level that result in effective behavioral modulation when tDCS parameters are matched to network-level requirements of the underlying task.

Grey-box modeling and hypothesis testing of functional near-infrared spectroscopy-based cerebrovascular reactivity to anodal high-definition tDCS in healthy humans

“…The current applied by surface electrodes in tDCS is shunted through the scalp and cerebrospinal fluid (CSF) and only a fraction of the current reaches the cortex, producing a weak electric field (~0.3 V/m per 1mA of applied current) [ 21 , 22 ] that can subthreshold polarize the neurons. However, persistent (>9 min) weak electric field can lead to neuroplastic changes and excitability after-effects, postulated to be driven by persistent calcium flux, which in turn can affect cortical excitability [ 23 ], alter the firing rate of neurons [ 24 , 25 ], and modify spatiotemporal brain networks related to information transfer in the brain [ 26 ]. So, a majority of research on tDCS has focused on cortical neuronal after-effects following long duration (>9 min) weak electric field stimulation [ 17 ]; however, investigation of the immediate effects of the electric field on all neurovascular targets in the cortical tissue may accord to better understanding of the vascular neural network [ 12 ] mechanisms to hemodynamic response.…”

Applications of open-source software ROAST in clinical studies: A review

“…In addition, many studies run the models on the example head included with ROAST or an individual sample from the investigators. These work cover various clinical applications including: attention-deficit hyperactivity disorder [ 61 , 62 ], aging [ 63 ], associative memory [ 64 , 65 ], attention [ 66 – 68 ], body awareness [ 69 ], cognitive control and function [ 70 ]; Fusco et al [ 125 ]; [ 71 , 72 ], connectivity [ 73 ], decision making [ 74 – 77 ]; Schulreich and Schwabe [ 126 ], declarative learning [ 78 ], depressive disorder [ 79 ], electroencephalography (EEG) research [ 80 – 83 ], imitation [ 84 ], memory retrieval [ 85 – 87 ], mind wandering [ 88 , 89 ], motor learning [ 90 – 95 ], motor skills [ 96 – 98 ], neurorehabilitation [ 60 ], neurovascular coupling [ 99 ], obsessive-compulsive disorder [ 100 ], phantom limb pain [ 101 ], post-anoxic leukoencephalopathy [ 102 ], reading speed [ 103 ], schizophrenia [ 104 ], social anxiety disorder [ 105 ], stroke [ 106 ], visual perception [ 107 , 108 ], and working memory [ 109 – 115 ].…”

Transcranial Direct Current Stimulation to Modulate fMRI Drug Cue Reactivity in Methamphetamine Users: A Randomized Clinical Trial

“…In addition to task-based functional activity, recently, the use of task-based fMRI has become critical in probing tDCS induced changes in connectivity modulation, which may be especially advantageous in a context-dependent analysis (Sehatpour et al 2020, Li et al 2019, Ganho-Ávila et al 2019, Wu et al 2015). Task-modulated connectivity suggests that functional connectivity may largely depend on the task that is performed during the application of tDCS.…”