The temporal features of self-referential processing evoked by Chinese handwriting.

To explore the temporal features and underlying brain structures of self-referential processing, participants were shown examples of Chinese handwriting, half of which were their own and the other half belonged to others, and asked to judge whether the handwriting was their own. In Experiment 1, the task was to categorize the handwriting by pressing the correct key as quickly as possible. In Experiment 2, after the participants recognized the stimuli, they were required to gaze at the handwriting for 3000 msec before making a response rather than responding immediately after stimulus onset. The results showed prominent differences in event-related potentials elicited by own and other handwriting conditions in the 200-500 msec and 1000-2000 msec time windows. Dipole analyses of the difference waves, own minus other, were conducted in both of these time windows. There were two dipoles in the 200-500 msec time window localized to the medial-temporal lobe and the anterior cingulate cortex (ACC), and MTL activation preceded ACC activation. Only one dipole at the posterior cingulate cortex was fitted to the 1000-2000 msec time window. These structures were activated sequentially in a temporal course, which provides evidence that the cortex middle structures potentially form a specific self-related processing unit, which is involved in processing various aspects of the self.