Tracking the time course of sign recognition using ERP repetition priming.

Repetition priming and event-related potentials (ERPs) were used to investigate the time course of sign recognition in deaf users of American Sign Language. Signers performed a go/no-go semantic categorization task to rare probe signs referring to people; critical target items were repeated and unrelated signs. In Experiment 1, ERPs were time-locked either to the onset of the video or to sign onset within the video; in Experiment 2, the same full videos were clipped so that video and sign onset were aligned (removing transitional movements), and ERPs were time-locked to video/sign onset. All analyses revealed an N400 repetition priming effect (less negativity for repeated than unrelated signs) but differed in the timing and/or duration of the N400 effect. Results from Experiment 1 revealed that repetition priming effects began before sign onset within a video, suggesting that signers are sensitive to linguistic information within the transitional movement to sign onset. The timing and duration of the N400 for clipped videos were more parallel to that observed previously for auditorily presented words and was 200 ms shorter than either time-locking analysis from Experiment 1. We conclude that time-locking to full video onset is optimal when early ERP components or sensitivity to transitional movements are of interest and that time-locking to the onset of clipped videos is optimal for priming studies with fluent signers.