Pellizzer Giuseppe, Stephane Massoud
Brain Sciences Center (11B), Veterans Affairs Medical Center, 1 Veterans Drive, Minneapolis, MN 55417, USA.
Exp Brain Res. 2007 Jul;180(4):705-14. doi: 10.1007/s00221-007-0892-5. Epub 2007 Feb 20.
Schizophrenia patients tend to have longer and more variable latencies of response than healthy control subjects. However, the distributions of data from the two groups overlap to a large extent. Therefore, we investigated (1) whether the process of response selection in schizophrenia patients is like that of slow control subjects or has different properties, and (2) whether the intra-individual variability of schizophrenia patients is intrinsically greater than that of control subjects or reflects their longer mean latency. To answer these questions we tested schizophrenia patients and healthy control subjects in a choice reaction time (RT) task with 2-choice and 4-choice conditions. We analyzed how mean RT in the 2-choice condition predicted mean RT in the 4-choice condition and found that the relation was significantly different between the two groups. In contrast, the intra-individual variability of RT was related to mean RT in the same way for schizophrenia patients and control subjects. These results indicate that the response selection process of schizophrenia patients was not simply a slower version of the same process engaged by control subjects, but it was a selection process with different dynamic properties. In contrast, schizophrenia patients did not have a greater intrinsic variability than control subjects. Furthermore, we found that the difference Deltat between RT measured in the 4-choice condition and RT predicted for the control group in the same condition could be used to discriminate effectively patients and control subjects. However, there was no significant association between Deltat and clinical variables. These results suggest that Deltat could reflect a trait impairment of schizophrenia independent from symptom profile. Finally, we suggest that the impairment of the process of selection of the motor response in schizophrenia reflects the alteration of the time-dependent patterns of neural activity that result from anomalies in the connectivity of the brain areas engaged for the selection of the motor response.
精神分裂症患者的反应潜伏期往往比健康对照受试者更长且更具变异性。然而，两组数据的分布在很大程度上重叠。因此，我们研究了：（1）精神分裂症患者的反应选择过程是像反应较慢的对照受试者那样，还是具有不同的特性；（2）精神分裂症患者个体内部的变异性是否本质上大于对照受试者，或者是否反映了他们较长的平均潜伏期。为了回答这些问题，我们在二选一和四选一条件的选择反应时（RT）任务中对精神分裂症患者和健康对照受试者进行了测试。我们分析了二选一条件下的平均反应时如何预测四选一条件下的平均反应时，发现两组之间的关系存在显著差异。相比之下，精神分裂症患者和对照受试者的反应时个体内部变异性与平均反应时的关系相同。这些结果表明，精神分裂症患者的反应选择过程并非简单地是对照受试者所进行的相同过程的较慢版本，而是一个具有不同动态特性的选择过程。相比之下，精神分裂症患者并没有比对照受试者具有更大的内在变异性。此外，我们发现四选一条件下测量的反应时与同一条件下对照组预测的反应时之间的差异Δt可有效区分患者和对照受试者。然而，Δt与临床变量之间没有显著关联。这些结果表明，Δt可能反映了独立于症状特征的精神分裂症特质损害。最后，我们认为精神分裂症中运动反应选择过程的损害反映了参与运动反应选择的脑区连接异常导致的神经活动时间依赖性模式的改变。
