Can we exploit event-related potentials for retraining language after stroke?

To ascertain the utility of event-related potentials in studying language processing in patients suffering from aphasia.

Recent methods to evaluate event related potentials in response to spoken words were applied in two young patients suffering from a recent aphasia in whom expressive deficits were particularly marked. Recordings were made on three occasions for each patient at the same time of the day. The second recording session took place after six months and the final one after one year. Eighteen right-handed subjects in normal health (10 women, 8 men) were enrolled as controls.

Three kinds of potential were obtained over time, P300, P340 and N400. P300 was useful to monitor attention and discrimination. It improved over time. Both of our patients lacked a defined P340 potential, but longitudinal recordings could show a very slow reappearance over time although with a frequently inverted polarity. Apparently, the expressive aphasia did not improve over a one year interval. In contrast to P340, N400 was relatively preserved. This potential is linked to semantic judgement. The patients with relatively preserved comprehension were able to exhibit a N400 soon after stroke. The bilateral representation indicated that the right hemisphere was involved in some kind of language processing.

The results indicate that digitized spoken words appear to be an appropriate tool because they permit the study of EEG changes on a millisecond-to-millisecond basis. Apparently, ERPs enable us to study receptive processes in patients with expressive aphasia. Moreover, they appear to be particularly suitable for monitoring the recovery of neural mechanisms responsible for language.