Lexical and Sublexical Cortical Tuning for Print in Early Childhood, Oddball Fast Periodic Visual Stimulation Study

The specificity of visual, sublexical and lexical stages of word processing in early childhood was investigated using an oddball fast periodic visual stimulation approach. Children (N=56, age range 3.6-9.33 years) were presented with a sequence of visual stimuli at a frequency of 6 Hz (6 stimuli per second). Every fifth stimulus was a deviant category stimulus, so the frequency of deviant stimulation was 6/5=1.2Hz. This approach allows to detect a discriminative response at the frequency of deviant stimulation if the stimuli of the basic and deviant categories are subjectively perceived as different. Three stimulus sequences (conditions): nonwords versus pseudofonts strings, pseudowords versus nonwords, and pseudowords versus real words -were used to separate coarse print tuning, sublexical processing and lexical processing, respectively. The electroencephalogram was recorded (32 channels). Discrimination response was observed in nonword versus pseudofonts condition, but not in conditions corresponding with more advanced levels of word processing. The absence of the observed discriminatory response as well as age dynamics for these processes suggests much later periods of their development.