Nan Jin^1,2, Yongchun Cai¹; ¹Zhejiang University, ²Ludwig-Maximilians-Universität München

Recent computational and electrophysiological studies suggest that short-term co-activation of mutually inhibitory neural populations can strengthen their inhibitory interaction, consistent with anti-Hebbian plasticity, whereas temporally uncorrelated activation should theoretically weaken it. However, evidence for such inhibitory plasticity in the human visual system remains limited. Here, we tested whether the strength of visual surround suppression (a phenomenon in which responses to a central stimulus are reduced by peripheral stimulation) can be modulated by short-term decorrelated activity between central and peripheral populations. We recorded steady-state visual evoked potentials (SSVEPs) while participants (N = 30) viewed two 20-s flicker conditions: (1) central gratings flickering at 20 Hz, and (2) the same central gratings surrounded by a peripheral grating flickering independently at 24 Hz. The decorrelated 20/24 Hz condition induced sustained uncorrelated activity between center and surround populations. Surround suppression was quantified as the differences of the 20 Hz SSVEP signal-to-noise ratio (SNR) across the two conditions during the 20-second stimulation. To dissociate adaptation from inhibitory modulation, we implemented a divisive normalization model that accounted for independent adaptation within center and surround channels. As predicted, surround suppression progressively weakened during decorrelated (20/24 Hz) stimulation, indicating a rapid reduction of inhibitory influence between center and surround populations. Our results demonstrate that inhibitory interactions underlying visual contextual modulation are not static but dynamically adjust to the recent input statistics, providing neural evidence for short-term anti-Hebbian plasticity in the human visual cortex. This dynamic modulation may represent a fundamental mechanism by which the visual system maintains flexible sensitivity to contextual changes in the environment.