Topographic changes in event-related potentials because of learning of meaningful Kanji characters.

Japanese Kanji constitutes meaningful logograms, and its processing shows interhemispheric features. In the present study, human semantic learning of Kanji characters in 18 healthy native German adults was examined. Twenty Kanji characters were presented before and after a learning phase of about 20 min, and the electroencephalographic activity was recorded from 30 electrodes and averaged for each condition. Twenty different Kanji characters served as control stimuli. Successful learning was observed in all participants. The evoked potential maps showed the largest component occurring over occipital areas at latencies between 100 and 130 ms. Significant differences in the field strength (global field power) were observed for this component before and after learning. After learning, the distribution between the left and the right hemispheres significantly changed the negative centroid location from the left to the right hemisphere and from the posterior to the anterior area in each hemisphere. These effects were observed only after successful learning, and our findings suggest that the acquisition of meaning of Kanji characters following intensive short-term learning is related to neurophysiological changes at an early stage of processing. The topographical changes in electrical brain activity reflect plasticity presumably in primary sensory areas during learning of meaningful materials that is related to top-down information processing.