Inferior parietal activation correlates with verbal learning success in a standardized training paradigm

Abstract

Word learning is a first fundamental step in language acquisition. Understanding underlying neural correlates during the progress of verbal learning is of interest for improving language therapies for naming disorders. In order to study neural correlates of verbal learning, 14 healthy participants learnt 40 pseudowords each with three belonging semantics in a standardized training program. In three fMRI scans the neural correlates of verbal learning were studied. During the first fMRI scan, accomplished before the pseudoword training started, participants were asked to name 40 black-white drawings plus three associated semantics. The second fMRI scan took place on the first day of the pseudoword training, the last fMRI scan after the end of training. In scan 2 and 3 pseudoword naming and naming of the learnt semantics were requested. Participants learnt pseudowords successfully during the training. Familiar word naming activated typical neural correlates of speech production as frontal and temporal regions. Interestingly, for pseudoword learning occipital areas and the inferior parietal lobule showed elevated responses next to typical speech production areas. Regarding the change of neural correlates during the learning progress, bilateralized caudate and right cerebellum were more strongly activated during the first acquisition phase. Cerebellar involvement in verbal working memory activity was recently found, while caudate activation could reflect suppression of unwanted responses. When the pseudowords became better consolidated the inferior parietal lobule showed increased activation maybe reflecting phonological storage. Activation of inferior and inferior parietal areas, as well as orbitofrontal areas correlated also with learning success. It will be interesting for future research to compare our findings of neural correlates of verbal learning in healthy subjects with those of aphasic or schizophrenic patients, in order to refine treatment possibilities.