Data from: Left cortical specialization for visual letter strings predicts rudimentary knowledge of letter-sound association in preschoolers

Reading, one of the most important cultural inventions of human society,
critically depends on posterior brain areas of the left hemisphere in
proficient adult readers. In children, this left hemispheric cortical
specialization for letter strings is typically detected only after
approximately 1 y of formal schooling and reading acquisition. Here, we
recorded scalp electrophysiological (EEG) brain responses in 5-y-old (n =
40) prereaders presented with letter strings appearing every five items in
rapid streams of pseudofonts (6 items per second). Within 2 min of
recording only, letter strings evoked a robust specific response over the
left occipito-temporal cortex at the predefined frequency of 1.2 Hz (i.e.,
6 Hz/5). Interindividual differences in the amplitude of this
electrophysiological response are significantly related to letter
knowledge, a preschool predictor of later reading ability. These results
point to the high potential of this rapidly collected behavior-free
measure to assess reading ability in developmental populations. These
findings were replicated in a second experiment (n = 26 preschool
children), where familiar symbols and line drawings of objects evoked
right-lateralized and bilaterally specific responses, respectively,
showing the specificity of the early left hemispheric dominance for letter
strings. Collectively, these findings indicate that limited knowledge of
print in young children, before formal education, is sufficient to develop
specialized left lateralized neuronal circuits, thereby pointing to an
early onset and rapid impact of left hemispheric reentrant sound mapping
on posterior cortical development.