Carter C S, Perlstein W, Ganguli R, Brar J, Mintun M, Cohen J D
Department of Psychiatry, University of Pittsburgh, Western Psychiatric Institute and Clinic, PA 15213, USA. cscarter+@pitt.edu
Am J Psychiatry. 1998 Sep;155(9):1285-7. doi: 10.1176/ajp.155.9.1285.
Hypofrontality is a common but not invariable finding in schizophrenia. Inconsistencies in the literature may reflect, in part, the fact that abnormal physiological responses in the prefrontal cortex are best identified under conditions that place well-specified functional demands on this region.
The authors studied eight patients with schizophrenia and eight matched comparison subjects using [(15)O]H2O positron emission tomography and the "N-back" task, which activates the prefrontal cortex as a function of working memory load in normal subjects.
Under low-working-memory-load conditions, the accuracy of both groups in the N-back task was equal, but when the memory load increased, the patients' performance deteriorated more than did that of the comparison subjects. The regional cerebral blood flow response to increased working memory load was significantly reduced in the patients' right dorsolateral prefrontal cortex.
These results confirm the importance of using tasks that tap specific cognitive functions, linked to specific neural systems, in studies of brain-behavior relationships in schizophrenia. Hypofrontality is reliably demonstrated in schizophrenia during tasks that engage working memory functions of the prefrontal cortex.
前额叶功能低下是精神分裂症常见但并非一成不变的表现。文献中的不一致可能部分反映了这样一个事实，即前额叶皮质的异常生理反应在对该区域提出明确功能需求的条件下最易被识别。
作者使用[（15）O]H2O正电子发射断层扫描和“N-回溯”任务对8例精神分裂症患者和8例匹配的对照受试者进行了研究，在正常受试者中，“N-回溯”任务会随着工作记忆负荷激活前额叶皮质。
在低工作记忆负荷条件下，两组在N-回溯任务中的准确率相同，但当记忆负荷增加时，患者的表现比对照受试者恶化得更明显。患者右侧背外侧前额叶皮质对增加的工作记忆负荷的局部脑血流反应显著降低。
这些结果证实了在精神分裂症脑-行为关系研究中使用与特定神经系统相关的、挖掘特定认知功能的任务的重要性。在涉及前额叶皮质工作记忆功能的任务中，精神分裂症患者前额叶功能低下得到了可靠的证实。
