Direct Current Stimulation Alters Neuronal Input/Output Function

Abstract

Background Direct current stimulation (DCS) affects both neuronal firing rate and synaptic efficacy. The neuronal input/output (I/O) function determines the likelihood that a neuron elicits an action potential in response to synaptic input of a given strength. Changes of the neuronal I/O function by DCS may underlie previous observations in animal models and human testing, yet have not been directly assessed. Objective Test if the neuronal input/output function is affected by DCS Methods Using rat hippocampal brain slices and computational modeling, we provide evidence for how DCS modulates the neuronal I/O function. Results We show for the first time that DCS modulates the likelihood of neuronal firing for a given and fixed synaptic input. Opposing polarization of soma and dendrite may have a synergistic effect for anodal stimulation, increasing the driving force of synaptic activity while simultaneously increasing spiking probability at the soma. For cathodal stimulation, however, the opposing effects tend to cancel. This results in an asymmetry in the strength of the effects of stimulation for opposite polarities. Conclusions Our results may explain the asymmetries observed in acute and long term effects of transcranial direct current stimulation.

Current intensity‐ and polarity‐specific online and aftereffects of transcranial direct current stimulation: An fMRI study

“…Collectively, these findings would be supportive of a monotonic input-output function between induced electric field strength and cerebral blood flow (Zheng et al, 2011). It should also be noted that with respect to the target M1 electrode, the anode electrode induced greater changes in perfusion against baseline, as compared to the cathode across all active intensities, suggesting a slightly superior effect of the anode electrode, as predicted by animal and computational models (Lafon, Rahman, Bikson, & Parra, 2017).…”

“…Collectively, these findings would be supportive of a monotonic input–output function between induced electric field strength and cerebral blood flow (Zheng et al, ). It should also be noted that with respect to the target M1 electrode, the anode electrode induced greater changes in perfusion against baseline, as compared to the cathode across all active intensities, suggesting a slightly superior effect of the anode electrode, as predicted by animal and computational models (Lafon, Rahman, Bikson, & Parra, ). Moreover, when the anodal electrode served as the return electrode over the right prefrontal region (i.e., cathodal M1 tDCS), intensities of 0.5 and 1.0 mA did not effectively alter perfusion, whereas higher intensities of 1.5 and 2.0 mA induced early increases in CBF.…”

Temporal interference stimulation targets deep brain regions by modulating neural oscillations

“…Model of Electric field in the network: The effect of stimulation was implemented as a small current ( ) injected into excitatory neurons 6,18,67 . This approach captures the induced membrane polarization of the single compartment due to external electric field application.…”

Direct current stimulation boosts associative Hebbian synaptic plasticity and maintains its pathway specificity

“…Perhaps the most well characterized cellular effect of electrical stimulation is the modulation of somatic membrane potential and firing probability (18,20,61,(65)(66)(67)(68)(69)(70). In human tDCS studies, it is the modulation of motor-evoked potentials, which have been linked to long-term plasticity (48,71,72).…”