Novel visual word learning tracked with FPVS-EEG

Throughout life, we constantly learn novel written words that are integrated in neural circuits of our brain. Here, we investigate the impact of two learning methods on the emergence of novel neural representations for words in 32 monolingual adults. Half of the 32 rare French words were provided with orthographic and phonological information only (OP hereafter), the other half were also provided with explicit semantic information (OPS hereafter, with an associated image).
We used EEG recordings and fast periodic visual stimulation (FPVS) displaying base stimuli (pseudowords) at 10 Hz with deviant stimuli (words) every fifth item (at 2Hz) before/ after a learning task. This approach allows to measure the discrimination of words among pseudowords (thus, lexical access) implicitly. We contrasted 4 word-conditions: novel words OP, novel words OPS, unknown words, and known words. Every condition was repeated 4 times for a total of 16 sequences of 1 min.
EEG results show a significant learning effect (p<0.001), with larger word-selective responses over the left occipital-temporal cortex at post-test with both methods, while no pre/post difference was seen for control conditions (known and unknown words). However, contrary to our hypothesis, larger amplitudes (suggesting stronger orthographic representations) were found with the OP rather than the OPS method (p=0.036). Moreover, behavioral lexical decision results reveal that new lexical traces of the novel words induced significant increases in reaction times for novel words’ orthographic neighbors and for 1-letter-close pseudowords, suggesting competition effects arising with new lexicalizations. Those effects were stronger for OP words, as in EEG responses. This unexpected greater benefit of learning without semantic will be discussed with regards to education methods, as it suggests that the simultaneous presentation of image and word (e.g., Duolingo, Babel) drags the participant’s attention away from the orthographic form which is not an efficient strategy for the brain.