Behavioral oscillation in global/local processing: Global alpha oscillations mediate global precedence effect.

Abstract

A visual scene always contains hierarchically organized structures, and determining how the brain coordinates the processing of global and local features is thus central for understanding visual perception. Recent neuroimaging studies have shown that global/local analyses are separately mediated through neuronal oscillations at different frequencies. However, it remains unclear how these rhythmic profiles are associated with and contribute to the global precedence effect (GPE) , the classical finding that global properties are perceived faster than local ones. Here, by using a time-resolved psychophysical method, we demonstrate that the global/local behavioral traces consist of two temporal components: one that resembles the classic GPE and one that manifests oscillatory pattern. Specifically, these behavioral oscillations occur in the alpha-band (∼10 Hz) and beta-band (∼20 Hz) for global and local tasks respectively ("Global-alpha" and "Local-beta"). Importantly, subjects with stronger Global-alpha not only show larger GPE but also are less vulnerable to local interference. Together, these findings constitute novel behavioral evidence supporting the idea that neuronal oscillations at different frequencies mediate and coordinate the global/local analysis of visual inputs and further reveal the possible neural basis underlying global precedence.