Neurophysiological signs of rapidly emerging visual expertise for symbol strings

The current study examined whether the repeated visual presentation of novel, meaningless symbol strings triggers rapid changes in event related potentials (ERP). Adult participants performed three versions of a word and symbol string repetition detection task in the same experimental session. Analyses focussed on the occipito-temporal NI (similar to 150 ms) known to reflect early word-specific processing and stimulus categorisation. While the NI to words did not change, the occipito-temporal negativity to symbol strings increased over runs and converged with the word NI. Later (similar to 220 ms) more positive occipito-temporal amplitudes to repeated words in the third compared to the first run implied a repetition priming effect. This suggests that symbol String processing changed over time due to visual learning and increased perceptual expertise. (C) 2005 Lippincott Williams Wilkins.