Barton Jason J S, Cherkasova Mariya V, Lindgren Kristen, Goff Donald C, Intriligator James M, Manoach Dara S
Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.
Ann N Y Acad Sci. 2002 Apr;956:250-63. doi: 10.1111/j.1749-6632.2002.tb02824.x.
Executive functions allow us to respond flexibly rather than stereotypically to the environment. We examined two such functions, task switching and inhibition in the antisaccade paradigm, in two studies. One study involved 18 normal subjects; the other, 21 schizophrenic patients and 16 age-matched controls. Subjects performed blocks of randomly mixed prosaccades and antisaccades. Repeated trials were preceded by the same type of trial (i.e., an antisaccade following an antisaccade), and switched trials were preceded by a trial of the opposite type. We measured accuracy rate and latency as indices of processing costs. Whereas schizophrenic patients had a threefold increase in error rate for antisaccades compared to normals, the effect of task switching on their accuracy did not differ from that in normal subjects. Moreover, the accuracy rate of trials combining antisaccade and task switching was equivalent to a multiplication of the accuracy rates from trials in which each was done alone. Schizophrenic latencies were disproportionately increased for antisaccades, but again they were no different from normal subjects in the effect of task switching. In both groups the effect of task switching on antisaccades was a paradoxical latency reduction. We conclude that the executive dysfunction in schizophrenia is not generalized but selective, sparing task switching from exogenous cues, in which the switch is limited to a stimulus-response remapping. The accuracy data in both groups support independence of antisaccade and task-switching functions. The paradoxical task-switching benefit in antisaccadic latency effects challenges current models of task switching. It suggests either carryover inhibition by antisaccadic performance in the prior trial or facilitation of antisaccades by simultaneous performance of other cognitive operations.
执行功能使我们能够灵活而非刻板地应对环境。在两项研究中，我们考察了反扫视范式中的两种此类功能，即任务切换和抑制。一项研究涉及18名正常受试者；另一项研究涉及21名精神分裂症患者和16名年龄匹配的对照组。受试者执行随机混合的顺向扫视和反扫视组块。重复试验之前是相同类型的试验（即反扫视之后接反扫视），而切换试验之前是相反类型的试验。我们测量准确率和反应时作为加工成本的指标。与正常人相比，精神分裂症患者反扫视的错误率增加了两倍，但任务切换对其准确率的影响与正常受试者并无差异。此外，将反扫视和任务切换相结合的试验的准确率相当于单独进行每项试验时准确率的乘积。精神分裂症患者反扫视的反应时不成比例地增加，但同样，任务切换对他们的影响与正常受试者没有差异。在两组中，任务切换对反扫视的影响都是反应时的反常缩短。我们得出结论，精神分裂症中的执行功能障碍并非普遍存在而是具有选择性的，从外部线索进行任务切换未受影响，其中切换仅限于刺激 - 反应重映射。两组的准确率数据支持反扫视和任务切换功能的独立性。反扫视反应时效应中反常的任务切换益处挑战了当前的任务切换模型。这表明要么是前一次试验中反扫视表现的遗留抑制，要么是同时进行其他认知操作对反扫视的促进作用。
