[A comparative study of N400 in generalized anxiety disorder versus obsessive compulsive disorder patients]

To explore the features of events-related potentials (ERP) component N400 in generalized anxiety disorder (GAD) versus obsessive compulsive disorder (OCD) patients and understand the cognitive pattern and processing characteristic for Chinese characters.ERP component N400 was recorded by Guangzhou Runjie WJ-1 ERP apparatus. And 41 GAD patients, 69 OCD patients and 58 normal controls (NC) were tested by the Chinese idioms ending with matching (congruent) or mismatching (incongruent) words.(1) Latencies: Significant differences were found of N400 latencies in ending words with the same pronunciation but different forms and meanings (NC: (377 ± 40) ms, OCD: (395 ± 43) ms, GAD: (396 ± 43) ms, congruent; NC: (415 ± 32) ms, OCD: (429 ± 35) ms, GAD: (430 ± 36) ms, incongruent), ending words with the same meaning but different pronunciations and forms (NC: (411 ± 32) ms, OCD: (424 ± 40) ms, GAD: (433 ± 39) ms, incongruent), ending words with different pronunciations, forms and meanings (NC: (399 ± 47) ms, OCD: (427 ± 53) ms, GAD: (434 ± 42) ms, congruent; NC: (442 ± 36) ms, OCD: (465 ± 35) ms, GAD: (474 ± 35) ms, incongruent) (P0.05 - 0.01). Compared with NC, the N400 latencies were prolonged in GAD and OCD patients. Compared with OCD patients, the GAD patients also showed prolonged N400 latencies in ending words with different pronunciations, forms and meanings (incongruent situation). (2) Significant differences were found of N400 amplitudes in ending words with the same pronunciation but different forms and meanings (NC: (9 ± 5) µV, OCD: (6 ± 5) µV, GAD: (6 ± 5) µV, congruent; NC: (11 ± 6) µV, OCD: (5 ± 4) µV, GAD: (6 ± 4) µV, incongruent), ending words with similar forms but different pronunciations and meanings (NC: (9 ± 5) µV, OCD: (5 ± 4) µV, GAD: (7 ± 5) µV, congruent; NC: (14 ± 6) µV, OCD: (6 ± 5) µV, GAD: (9 ± 7) µV, incongruent), ending words with different pronunciations, forms and meanings (NC: (9 ± 5) µV, OCD: (5 ± 4) µV, GAD: (5 ± 3) µV, congruent; NC: (14 ± 6) µV, OCD: (9 ± 7) µV, GAD: (9 ± 7) µV, incongruent) (P0.05 - 0.01). Compared with NC, N400 amplitudes decreased in GAD and OCD patients respectively. Compared with OCD patients, the GAD patients also showed elevated N400 amplitudes in ending words with similar forms but different pronunciations and meanings (congruent).The cognitive and emotional problems in GAD and OCD may be measured by N400 elicited by Chinese idioms. Notable N400 priming effects can be found in Chinese idioms.