ERPs, semantic processing and age.
ERPs (N400, LPC and CNV) were elicited in two sets of subjects grouped according to age (young vs. elderly) using a word-pair category matching paradigm. Each prime consisted of a Japanese noun (constructed from two to four characters of the Hiragana) followed by one Chinese character (Kanji) as the target, this latter representing one of five semantic categories. There were two equally probable target conditions: match or mismatch. Each target was preceded by a prime, either belonging to, or not belonging to, the same semantic category. The subjects were required to respond with a specified button press to the given target according to the condition. We found RTs to be longer in the elderly subjects and under the mismatch condition. N400 amplitude was reduced in the elderly subjects under the mismatch condition and there was no difference between match and mismatch response, which were similar in amplitude to that under match condition for the young subjects. In addition, the CNV amplitudes were larger in the elderly subjects. These results suggested that functional changes in semantic processing through aging (larger semantic networks and diffuse semantic activation) were the cause of this N400 reduction, attributing a subsidiary role to attentional disturbance. We also discuss the importance of taking age-related changes into consideration in clinical studies.
Miyamoto
T
T
Department of Psychiatry and Neurology, School of Medicine, Hokkaido University, Sapporo, Japan. tmiyamot@med.hokudai.ac.jp
Katayama
J
J
Koyama
T
T
D000328:Adult; D000368:Aged; D000375:Aging / Q000523:psychology*; D003265:Contingent Negative Variation / Q000502:physiology; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D006801:Humans; D007802:Language; D008297:Male; D008875:Middle Aged; D010465:Perception / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology