Online Transcranial Random Noise stimulation improves perception at high levels of visual white noise

Abstract

Keywords: tRNS1, perception2, stimulation3, noise4, psychophysics5, vision6. (Min.5-Max. 8) 26 27 tRNS improves vision-in-noise 2 Abstract (250 words) 28 29Transcranial random noise stimulation (tRNS), a relatively recent addition to the field of non-30 invasive, electrical brain stimulation, has been shown to improve perceptual and cognitive functions 31 across a wide variety of tasks. However, the underlying mechanisms of visual improvements caused 32 by tRNS remain unclear. To study this question, we employed a well-established, equivalent-noise 33 approach, which measures perceptual performance at various levels of external noise and is 34 formalized by the Perceptual Template Model (PTM). This approach has been used extensively to 35 infer the underlying mechanisms behind changes in visual processing, including those from 36 perceptual training, adaptation and attention. Here, we used tRNS during an orientation 37 discrimination task in the presence of increasing quantities of external visual white noise and fit the 38 PTM to gain insights into the effects of tRNS on visual processing. Our results show that tRNS 39 improves visual processing when stimulation is applied during task performance, but only at high 40 levels of external visual white noise-a signature of improved external noise filtering. There were no 41 significant effects of tRNS on task performance after the stimulation period. Of interest, the reported 42 effects of tRNS on visual processing mimic those previously reported for endogenous spatial 43 attention, offering a potential area of investigation for future work. 44 45 46 47 tRNS improves vision-in-noise 3

Characterising modulatory effects of transcranial random noise stimulation using the perceptual template model

“…This explanation is consistent with findings from van der Groen and Wenderoth [15], who found no effects of performance at 1.5mA. Interestingly, however, Melnick et al [16] did find that 2mA hf-tRNS improved performance under high external noise levels compared to sham. This finding is consistent with an increased ability to filter external noise.…”

“…Specifically, Melnick [16] presented a persistent current over a 20-minute period during task completion. However, we presented 20 minutes stimulation intermittently, using 2-minute stimulation periods with 1-minute breaks where stimulation ceased.…”

“…Using the PTM, Melnick et al [16] did not observe significant effects of 2mA hf-tRNS on internal additive noise, with no difference in performance noted across low levels of external noise between stimulation conditions (Figure 1). One possible explanation for this lack of an effect is that the used current intensity was not large enough to increase internal noise to a level that detrimentally affects perceptual performance.…”

“…In this regard, the perceptual template model (PTM) has been used to quantitatively estimate the intrinsic properties of observers under sham (0mA) and active (2mA) hf-tRNS applied to V1 during completion of a visual orientation discrimination task [16]. The PTM assumes that visual processing systems contain a constant amount of internal noise, and that perceptual performance is determined by the type of noise (i.e., internal or external) that dominates the system [17].…”

Transcranial Random Noise Stimulation Modulates Neural Processing of Sensory and Motor Circuits, from Potential Cellular Mechanisms to Behavior: A Scoping Review

“…For visual tasks ( N = 10), hf-tRNS acutely increases sensitivity for low contrast visual stimuli as demonstrated for contrast detection task ( van der Groen and Wenderoth, 2016 ), orientation discrimination task ( Melnick et al, 2020 ), lateral visual masking protocols ( Battaglini et al, 2019 ), and exploring stimulation effects using visual stimuli with various properties ( Battaglini et al, 2020 ). It was further shown that delivering central noise via hf-tRNS influences state-switching dynamics of binocular rivalry ( van der Groen et al, 2019 ) and accelerates perceptual decision-making in a motion discrimination task ( Campana et al, 2016 ; Ghin et al, 2018 ; van der Groen et al, 2018 ; Pavan et al, 2019 ; O’Hare et al, 2021 ).…”