Kehagia Angie A, Barker Roger A, Robbins Trevor W
Institute of Psychiatry, King's College London, UK; Behavioural and Clinical Neuroscience Institute, University of Cambridge, UK.
J Neuropsychol. 2014 Mar;8(1):53-74. doi: 10.1111/jnp.12004. Epub 2012 Dec 20.
This study investigated the hypothesis that rule reconfiguration in task switching can isolate aspects of intact and impaired control at different stages of Parkinson's disease (PD) by comparing switches between concrete naming rules pertaining to stimulus selection, to switches between abstract rules which allocate categorization responses to these stimuli. Based on previous findings, it was hypothesized that attentional switches, where task set competition emerges at the stimulus but not response set level, highlights striatal dopaminergic function. Conversely, increasing the degree of task set competition to encompass reconfiguration of response set when switching between abstract rules, represents a condition which engages the prefrontal cortex (PFC) and renders this manipulation sensitive to frontal damage. To this end, we investigated task switching with concrete and abstract rules in unilaterally (Hoehn & Yahr stage I) and bilaterally (Hoehn & Yahr stage II) affected PD patients, as well as striatally intact frontal lesion patients. As predicted, frontal lesion patients demonstrated switching deficits only with abstract categorization rules, where switching engendered complete task set reconfiguration and a new response, as did stage II PD patients with presumed frontal cortical pathology. Replicating previous findings, stage I PD patients with relatively circumscribed striatal pathology demonstrated no such impairment. Disease severity also impacted on attentional switching indexed by naming rules, since medicated stage II but not stage I patients demonstrated switching deficits emerging from stimulus set reconfiguration, suggesting that the ameliorative efficacy of dopaminergic medication is inversely related to the severity of the striatal deficit. These findings illustrate that the nature of the rules that are switched, and its implication in terms of reconfiguring different task set elements, highlights different neural characters of cognitive flexibility. These manipulations may help decipher the differential effects of progressive neurodegeneration on parkinsonian cognition, and provide a framework in which to conceptualize the contributions of cortical and subcortical regions to cognitive control.
在任务切换中，规则重新配置可以通过比较与刺激选择相关的具体命名规则之间的切换，与将分类反应分配给这些刺激的抽象规则之间的切换，来分离帕金森病（PD）不同阶段完整和受损控制的各个方面。基于先前的研究结果，我们假设，在注意切换中，任务集竞争出现在刺激而非反应集水平，这突出了纹状体多巴胺能功能。相反，当在抽象规则之间切换时，增加任务集竞争的程度以包括反应集的重新配置，代表了一种涉及前额叶皮层（PFC）的情况，并使这种操作对额叶损伤敏感。为此我们研究了单侧（Hoehn & Yahr I期）和双侧（Hoehn & Yahr II期）受影响的PD患者以及纹状体完整的额叶病变患者在具体和抽象规则下的任务切换情况。正如预测的那样，额叶病变患者仅在抽象分类规则下表现出切换缺陷，在这种情况下，切换会导致完整的任务集重新配置和新的反应，假定存在额叶皮质病变的II期PD患者也是如此。重复先前的研究结果，具有相对局限纹状体病变的I期PD患者没有这种损伤。疾病严重程度也影响了由命名规则索引的注意切换，因为药物治疗的II期而非I期患者表现出刺激集重新配置导致的切换缺陷，这表明多巴胺能药物的改善效果与纹状体缺陷的严重程度呈负相关。这些发现表明，所切换规则的性质及其在重新配置不同任务集元素方面的含义，突出了认知灵活性的不同神经特征。这些操作可能有助于解读进行性神经退行性变对帕金森病认知的不同影响，并提供一个框架来概念化皮质和皮质下区域对认知控制的贡献。
