Paradoxical, causal effects of sensory gain modulation on motor inhibitory control \u2013 a tDCS, EEG-source localization study

Julia Friedrich,Christian Beste

doi:10.1038/s41598-018-35879-2

Abstract

Response inhibition is a key component of executive functioning, but the role of perceptual processes has only recently been focused. Although the interrelation of incoming information and resulting behavioural (motor) effects is well-known to depend on gain control mechanisms, the causal role of sensory gain modulation for response inhibition is elusive. We investigate it using a somatosensory response inhibition (Go/Nogo) task and examine the effects of parietal (somatosensory) cathodal and sham tDCS stimulation on a behavioural and neurophysiological level. For the latter, we combine event-related potential (ERP) and source localization analyses. Behavioural results reveal that cathodal stimulation leads to superior inhibition performance as compared to sham stimulation depending on the intensity of tDCS stimulation. The neurophysiological data show that an early (perceptual) subprocess of the Nogo-N2 ERP-component is differentially modulated by the type of stimulation but not a later (response-related) Nogo-N2 subcomponent. Under cathodal stimulation, the early N2 amplitude is reduced and the right inferior frontal gyrus (BA45) is less active. Cathodal tDCS likely enhances inhibition performance via decreasing the efficiency of gain control and the impact of sensory stimuli to trigger prepotent responses. Thereby, response inhibition processes, associated with structures of the response inhibition network, become less demanded.

Highlights

In everyday life, sensory information is constantly used to guide behaviour
We investigate this in a tactile GO/NOGO task[6] and examine associated neurophysiological mechanisms using EEG recordings, i.e. event-related potential (ERP) and source localization analyses
To examine the underlying system neurophysiological mechanisms modulated by transcranial direct current stimulation (tDCS)-induced gain control mechanisms, ERP and source localization analyses were combined

Summary

Introduction

Sensory information is constantly used to guide behaviour. Short-term changes of the environment sometimes require “deliberate overriding of dominant or prepotent responses”[1] which describes one of the core executive functions, namely response inhibition. We propose that reduced gain control may not always compromise behavioural output and we hypothesize that it may rather enhance inhibitory control This is because the neuronal representation of the GO stimulus strongly affects the strength of the evoked prepotent response tendency[19,20,21]. Since gain control processes relate to the modulation of sensory information processing, it is likely that the (Nogo)-N2 component reflects modulations on the perceptual rather than on the cognitive control level This is because cathodal stimulation is assumed to reduce neuronal excitability by a decrease in membrane potential. When the signal-to-noise ratio is attenuated, the strength of neuronal representation of the GO stimulus is expected to decline This is assumed to reduce the prepotent response tendency associated with the GO stimulus so that inhibition becomes more effective; i.e. the “braking function” of inhibitory control is more efficient. Later occurring components (i.e. P3) are analyzed

Methods

Results

Conclusion