Effects of alphabeticality, practice and type of instruction on reading an artificial script: an fMRI study

In neuroimaging studies of word reading in natural scripts, the effect of alphabeticality is often confounded with the effect of practice. We used an artificial script to separately manipulate the effects of practice and alphabeticality following training with and without explicit letter instructions. Participants received multi-session training in reading nonsense words, written in an artificial script, wherein each phoneme was represented by 2 discrete symbols . Three training conditions were compared: alphabetical whole words with letter decoding instruction (explicit); alphabetical whole-words (implicit) and non-alphabetical whole-words (arbitrary). Each participant was trained on the arbitrary condition and on one of the alphabetical conditions (explicit or implicit). fMRI scans were acquired after training during reading of trained words and relatively novel words in the alphabetical and arbitrary conditions. Our results showed greater activation in the explicit compared to the arbitrary conditions, but only for relatively-novel words, in the left posterior inferior frontal gyrus (IFG). In the implicit condition, the left posterior IFG was active in both trained and relatively novel words. These results indicate the involvement of the left posterior IFG in letter decoding, and suggest that reading of explicitly well-trained words did not rely on letter decoding, while in implicitly trained words letter decoding persisted into later stages. The superior parietal lobules showed reduced activation for items that received more practice, across all training conditions. Altogether, our results suggest that the alphabeticality of the word, the amount of practice and type of instructions have independent and interacting effects on brain activation during reading.