Friday, April 8, 2011
Just to recap from the last article, the N170 is an ERP component that differentiates between words and symbol strings in normal reading adults. This the specialization developed after learning to read, or does it have something to do with the visual properties of symbols?
Maurer and colleagues tested pre-reading kindergartners to see whether the specialization is there before they learn to read. They had kids perform the same task as adults (looking at a series of words, pseudowords, symbol strings, and pictures).
They found several things:
1. Adults again had the same N170 (called N1 in this paper), which was stronger for words than symbols.
2. Kids also had an N1, but it was later, had a larger amplitude, and most importantly, did not distinguish between words and symbols, suggesting that this N1 specialization stems from experience with words.
3. Some of the kids, the ones with high letter knowledge, did have an N1 that differentiated between letters and symbols. However, the pattern was different from adults. While adults had the strongest effect on the left side of the brain, these children showed an effect on the right side.
So in conclusion, the N1 specialization seems to be related to reading. However, there seem to be some intermediate steps in the development of the specialization. At least in an early stage, the right hemisphere is involved, and then the processing becomes more left lateralized.
Maurer U, Brem S, Bucher K, & Brandeis D (2005). Emerging neurophysiological specialization for letter strings. Journal of cognitive neuroscience, 17 (10), 1532-52 PMID: 16269095