The Müller-Lyer illusion seen by the brain: an event-related brain potentials study.

In two experiments, event-related brain potentials (ERPs) were used to examine the neural correlates of a visual illusion effect in Müller-Lyer illusion tasks (illusion stimuli) and baseline tasks (no-illusion stimuli). The behavioral data showed that the illusion stimuli indeed yielded an illusion effect. Scalp ERP analysis revealed its neurophysiological substrate: the Müller-Lyer illusion tasks (Illusion tasks 1-3) elicited a more negative ERP deflection than did the baseline tasks about 400 ms after onset of the stimuli. Dipole source analysis of the difference wave (Illusion task 2-Baseline task 1) and the original waveforms of the different conditions (Illusion tasks 2 and 3 and Baseline task 2) indicated that the anterior cingulate cortex (ACC)/superior frontal cortex may contribute to the illusion effect, possibly in relation to high-level cognitive control. The results indicated that apparent distortions of the Müller-Lyer illusion might be influenced by top-down control.