Dysfunction in different phases of working memory in schizophrenia: evidence from ERP recordings.
The present study combined a time-locked paradigm and high-time-resolution event-related potential (ERP) recordings to examine different phases of working memory, including early visual processing and late memory-related processes of encoding, maintenance, and retrieval, in 67 adults with schizophrenia and 46 healthy controls. Alterations in ERP components were correlated with task performance. Patients performed significantly worse in the working memory task than healthy subjects, although all subjects' accuracy exceeded 80%. During encoding, the N1 and P2 component amplitudes were lower while the P300 amplitude was higher in schizophrenic patients compared to healthy controls. There were no differences between groups with respect to the mean amplitudes of the negative slow waves in the early stage (the first 400 ms) of the maintenance phase. However, in the next 500-ms time window, the patients exhibited a more negative deflection in the middle fronto-central region than the control group. Likewise, a similar pattern was observed in the second 500-ms period in the middle fronto-central region, although the effect was marginally significant. There were no differences between groups in the remaining 1000 ms. During retrieval, the P1, N1 and P2 amplitudes were lower while the P300 amplitude and latency were higher in schizophrenic patients. The present results indicate early visual deficits in the working memory task in adults with schizophrenia. Impairments in the maintenance phase were confined to the late rehearsal stage. The increased P300 amplitude at the fronto-central electrode sites along with the poorer behavioral performance suggests that schizophrenic patients have an inefficient working memory system.
Center for Psychiatric Research, Beijing Huilongguan Hospital, Beijing 100096, China.
Yan Li
YL
Zhao
Shu Ping
SP
Tan
Fu De
FD
Yang
Li Li
LL
Wang
Wen Feng
WF
Feng
Raymond C K
RC
Chan
Xiao
X
Gao
Dong Feng
DF
Zhou
Bin Bin
BB
Li
Chong Sheng
CS
Song
Feng Mei
FM
Fan
Yun Long
YL
Tan
Jin Guo
JG
Zhang
Yun Hui
YH
Wang
Yi Zhuang
YZ
Zou
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D003265:Contingent Negative Variation; D004569:Electroencephalography; D004585:Electrooculography; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000175:diagnosis* / Q000209:etiology*; D008570:Memory, Short-Term / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology; D008875:Middle Aged; D009483:Neuropsychological Tests; D010775:Photic Stimulation; D011569:Psychiatric Status Rating Scales; D011930:Reaction Time; D012559:Schizophrenia / Q000150:complications*; D013997:Time Factors; D055815:Young Adult