Veterans Administration San Diego Healthcare System San Diego, CA, USA ; Department of Psychiatry, University of California San Diego, CA, USA.
Department of Psychology, University of Texas Austin, TX, USA ; Institute for Neuroscience, University of Texas Austin, TX, USA.
Front Syst Neurosci. 2014 Feb 19;8:14. doi: 10.3389/fnsys.2014.00014. eCollection 2014.
Previously we found that Parkinson's disease (PD) patients are impaired in procedural-based category learning when category membership is defined by a nonlinear relationship between stimulus dimensions, but these same patients are normal when the rule is defined by a linear relationship (Maddox and Filoteo, 2001; Filoteo et al., 2005a,b). We suggested that PD patients' impairment was due to a deficit in recruiting "striatal units" to represent complex nonlinear rules. In the present study, we further examined the nature of PD patients' procedural-based deficit in two experiments designed to examine the impact of (1) the number of categories, and (2) category discontinuity on learning. Results indicated that PD patients were impaired only under discontinuous category conditions but were normal when the number of categories was increased from two to four. The lack of impairment in the four-category condition suggests normal integrity of striatal medium spiny cells involved in procedural-based category learning. In contrast, and consistent with our previous observation of a nonlinear deficit, the finding that PD patients were impaired in the discontinuous condition suggests that these patients are impaired when they have to associate perceptually distinct exemplars with the same category. Theoretically, this deficit might be related to dysfunctional communication among medium spiny neurons within the striatum, particularly given that these are cholinergic neurons and a cholinergic deficiency could underlie some of PD patients' cognitive impairment.
先前我们发现，当类别成员由刺激维度之间的非线性关系定义时，帕金森病（PD）患者在基于程序的类别学习中受损，但当规则由线性关系定义时，这些患者是正常的（Maddox 和 Filoteo，2001；Filoteo 等人，2005a，b）。我们认为 PD 患者的损伤是由于在代表复杂非线性规则时缺乏“纹状体单位”的招募。在本研究中，我们通过两个实验进一步研究了 PD 患者基于程序的缺陷的性质，旨在检查（1）类别数量和（2）类别不连续性对学习的影响。结果表明，PD 患者仅在不连续类别条件下受损，但当类别数量从两个增加到四个时，他们是正常的。在四类别条件下没有损伤表明与基于程序的类别学习相关的纹状体中间棘神经元的正常完整性。相比之下，与我们之前观察到的非线性缺陷一致，PD 患者在不连续条件下受损的发现表明，当这些患者必须将感知上不同的范例与相同类别联系起来时，他们就会受损。从理论上讲，这种缺陷可能与纹状体中间神经元之间的功能障碍性通信有关，特别是考虑到这些神经元是胆碱能神经元，而胆碱能缺乏可能是 PD 患者认知障碍的部分原因。
