Awareness in the crowd: Beta power and alpha phase of prestimulus oscillations predict object discrimination in visual crowding.

Abstract

Visual crowding is among the factors that most hamper conscious object perception. However, we currently ignore the neural states that predispose to an accurate perception within different crowding regimes. Here, we performed single-trial analyses of the electroencephalographical (EEG) oscillations, evaluating the prestimulus power and phase differences between correct and incorrect discrimination during a letter-crowding task, where irrelevant letters were placed nearby (strong crowding) or far (mid crowding) relative to the target. Results show that prestimulus alpha (8-12Hz) power was related to target discrimination in the mid, but not in the strong, crowding condition. Importantly, accurate discrimination in the strong crowding condition was predicted by the phase of alpha and by the power of beta (13-20Hz) oscillations. These evidence suggest that both periodic visual sampling mechanisms, reflected in the alpha phase, and network predisposition to extract local information, reflected in the beta power, predispose to object discrimination in a crowded scene.