Boosting vision through combined perceptual learning and non-invasive transcranial random noise stimulation

Abstract

Introduction Perceptual learning has been shown to produce an improvement of visual functions such as an increase of visual acuity and contrast sensitivity both in participants with cortical visual defects such as amblyopia as well as refractive defects such as myopia or presbyopia. Additionally, transcranial random noise stimulation (tRNS), a type of alternating current stimulation, has proven to be efficacious in accelerating neural plasticity and boosting visual perceptual learning in healthy participants. This work investigates whether a short visual behavioural training regime using a contrast detection task, combined with online hf-tRNS, is more effective than the training plus sham stimulation, or stimulation alone, in improving visual functions (VA and CS) in participants with visual defects, specifically: mild myopia and amblyopia. Method A battery of tests measuring visual functions was administered prior to (pre-test) and following the training (post-test). Eight consecutive training sessions on a contrast detection task (combined or not with tRNS) were undertaken by the participants. A third group of participants in the myopia group underwent solely brain stimulation, in the absence of any visual training. Results The experimental groups (tRNS + PL) reached a larger improvement, with respect to the control groups, in both VA (mean improvement of 0.18 LogMAR) and CS at intermediate spatial frequencies. Conclusions These results suggest that neuromodulatory techniques can boost perceptual learning and its generalization to non-trained visual functions, strongly reducing the duration of behavioural trainings needed to improve sight in people both with non-corrected refractive defects as well as with cortical visual defects such as amblyopia.