tRNS boosts perceptual learning in peripheral vision.

Visual crowding, the difficulty of recognizing elements when surrounded by similar items, is a widely studied perceptual phenomenon and a trademark characteristic of peripheral vision. Perceptual Learning (PL) has been shown to reduce crowding, although a large number of sessions is required to observe significant improvements. Recently, transcranial random noise stimulation (tRNS) has been successfully used to boost PL in low-level foveal tasks (e.g., contrast detection, orientation) in both healthy and clinical populations. However, no studies so far combined tRNS with PL in peripheral vision during higher-level tasks. Thus, we investigated the effect of tRNS on PL and transfer in peripheral high-level visual tasks. We trained two groups (tRNS and sham) of normal-sighted participants in a peripheral (8° of eccentricity) crowding task over a short number of sessions (4). We tested both learning and transfer to untrained spatial locations, orientations, and tasks (visual acuity). After training, the tRNS group showed greater learning rate with respect to the sham group. For both groups, learning generalized to the same extent to the untrained retinal location and task. Overall, this paradigm has potential applications for patients suffering from central vision loss but further research is needed to elucidate its effect (i.e., increasing transfer and learning retention).