Latency of P3 in semantic categorization of Chinese characters: preliminary report

ERPs to target stimulation with tone and semantic categorization of Chinese characters were studied in 100 healthy subjects. Age ranged from 40-50 years old (80 subjects) and 50-68 years old (20 subjects). Two hundred Chinese characters were divided into four groups in accordance with the meaning of characters. The probability of each group was 25%. Each group could be used as target stimulus. The latencies of the exogenous components on these two different tasks were the same. The endogenous components on the semantic categorization of Chinese characters were longer than with tone stimulation. In the 40-50 years age group the mean latencies of positive waves at Fz, Cz, C3, and Pz were 546.1034 msec, 547.8621 msec, 548.0345 msec and 547.3103 msec, respectively; latencies in the 50-68 years group were 542.9412 msec, 545.2941 msec, 543.8824 msec and 553.0588 msec respectively. A positive wave, which we called P550 and divided into P550a and P550b, could be recognized in 27.5% of them.