State-dependent effectiveness of cathodal transcranial direct current stimulation on cortical excitability

Abstract

The extensive use of transcranial direct current stimulation (tDCS) in experimental and clinical settings does not correspond to an in-depth understanding of its underlying neurophysiological mechanisms. In previous studies, we employed an integrated system of Transcranial Magnetic Stimulation and Electroencephalography (TMS-EEG) to track the effect of tDCS on cortical excitability. At rest, anodal tDCS (a-tDCS) over the right Posterior Parietal Cortex (rPPC) elicits a widespread increase in cortical excitability. In contrast, cathodal tDCS (c-tDCS) fails to modulate cortical excitability, being indistinguishable from sham stimulation. Here we investigated whether an endogenous task-induced activation during stimulation might change this pattern, improving c-tDCS effectiveness in modulating cortical excitability. In Study 1, we tested whether performance in a Visuospatial Working Memory Task (VWMT) and a modified Posner Cueing Task (mPCT), involving rPPC, could be modulated by c-tDCS. Thirty-eight participants were involved in a two-session experiment receiving either c-tDCS or sham during tasks execution. In Study 2, we recruited sixteen novel participants who performed the same paradigm but underwent TMS-EEG recordings pre- and 10 minutes post-sham and c-tDCS. Behavioral results showed that c-tDCS significantly modulated mPCT performance compared to sham. At a neurophysiological level, c-tDCS significantly reduced cortical excitability in a frontoparietal network involved in task execution. Taken together, our results provide evidence of the state dependence of c-tDCS in modulating cortical excitability effectively. The conceptual and applicative implications are discussed.

Combining transcranial magnetic stimulation with training to improve social cognition impairment in schizophrenia: a pilot randomized controlled trial

“…The few previous studies using NiBS to improve social cognition in schizophrenia, indeed, applied tDCS or rTMS as stand-alone interventions ( Wölwer et al, 2014 ; Jin et al, 2023 ). However, it is well-established that NiBS effects are state-dependent and interact with the state of the network targeted by the stimulation, thus influencing brain activity and behavioral outcomes and possibly reducing interindividual differences ( Luber and Lisanby, 2014 ; Romei et al, 2016 ; Sathappan et al, 2019 ; Vergallito et al, 2022 ; Sack et al, 2023 ; Vergallito et al, 2023b ).…”

“…First, previous works applied the stimulation at resting state without time-locking stimulation with behavioral or cognitive tasks engaging the same neural network. Over the past years, however, experimental neuroscience provided compelling evidence on the state-dependency of NiBS effects ( Silvanto et al, 2008 ; Pisoni et al, 2018 ; Borgomaneri et al, 2020 ; Sack et al, 2023 ; Vergallito et al, 2023b ); therefore, the possibility of combining psychological, cognitive, or behavioral interventions with time-locked brain stimulation seems to be a promising approach to boost through NiBS the spontaneous neuroplastic changes induced by the training per se and rebalancing pathological brain activity and connectivity patterns ( Sathappan et al, 2019 ; Gainsford et al, 2020 ; Dedoncker et al, 2021 ; Vergallito et al, 2021 ; Tatti et al, 2022 ). A second limitation concerns the lack of follow-up evaluations.…”

Betting on Non-Invasive Brain Stimulation to Treat Gambling Disorder: A Systematic Review and Meta-Analysis

“…For example, when tDCS is applied at rest, current typically impacts the default-mode network’s activity, which comprises brain regions activated when individuals are not engaged in attention-demanding or goal-directed tasks [ 162 , 163 , 164 ]. Conversely, when stimulation is applied during task execution, its effects are typically traceable in the network involved in the task [ 156 , 162 , 165 ]. Moreover, the endogenous activity induced by a task has been suggested to be crucial for detecting the cathodal tDCS effect [ 165 ] compared with a resting state condition [ 166 ].…”

“…Conversely, when stimulation is applied during task execution, its effects are typically traceable in the network involved in the task [ 156 , 162 , 165 ]. Moreover, the endogenous activity induced by a task has been suggested to be crucial for detecting the cathodal tDCS effect [ 165 ] compared with a resting state condition [ 166 ]. Crucially, rTMS protocols can be preferentially used as a priming (before the task) or as a consolidator (after the task) [ 122 ] due to the noise and somatosensory discomfort elicited during stimulation.…”