Occipital and parietal non-invasive brain stimulation enhances perceptual learning and transfer: evidence from...

Perceptual training yields specific, long-lasting improvements, yet its transfer to untrained conditions is often limited. This tension has been proposed to involve interactions between early sensory plasticity and higher-order parietal processes, with the early visual cortex contributing to stimulus-specific learning and parietal regions potentially supporting more flexible generalization. However, causal evidence comparing how occipital and parietal stimulation modulates learning and transfer remains limited. To address this gap, we combined high-frequency transcranial random noise stimulation (tRNS) with a classical perceptual training paradigm. We examined whether occipital and parietal tRNS differentially enhance learning and whether they modulate transfer. Forty-one participants were randomly assigned to one of three groups: active tRNS over occipital cortex, active tRNS over parietal cortex, or sham stimulation, during multi-session training on a contour detection task. Results revealed that the learning dynamics exhibited distinct stage-specific modulations, with parietal tRNS accelerating early-stage acquisition and occipital tRNS sustaining learning rates during the later asymptotic phase. Furthermore, both active stimulations significantly increased the overall magnitude of learning gains compared to sham. Importantly, however, only parietal tRNS reliably enhanced transfer, particularly across curvature. These results provide causal evidence that occipital and parietal stimulation differentially modulate the behavioral dynamics of perceptual learning and transfer. This pattern is consistent with hierarchical accounts in which sensory and higher-order systems may contribute differently to learning stability and flexibility, while also highlighting the potential of targeted neuromodulation to enhance distinct phases and outcomes of perceptual learning.