Golla Heidrun, Thier Peter, Haarmeier Thomas
Department of Cognitive Neurology, Hertie-Institute for Clinical Brain Research, University of Tübingen, Klinikum Schnarrenberg, Tübingen, Germany.
Brain. 2005 Jul;128(Pt 7):1525-35. doi: 10.1093/brain/awh523. Epub 2005 May 4.
In an attempt to provide a common denominator for cognitive deficits observed in cerebellar patients, it has been suggested that they might be secondary to impaired control of attention, a 'dysmetria of attention', conceptually analogous to motor dysmetria. Albeit appealing and quite influential, the concept of attentional dysmetria as a consequence of cerebellar disease remains controversial. In an attempt to test this concept in a direct way, we compared the performance of patients with cerebellar disorders to that of normal controls on tasks requiring either overt or covert shifts of spatial attention. In the first experiment, visually guided saccades, i.e. overt shifts of spatial attention, were elicited. In the second experiment, covert shifts of attention were evoked by the need to discriminate the orientation of a Landolt C observed during controlled fixation and presented in the same locations as the saccade targets in the previous experiment. The allocation of attention was assessed by comparing acuity thresholds determined with and without spatial cueing. The patients exhibited dysmetric saccades as reflected by larger absolute position errors or a higher number of corrective saccades compared to controls. In contrast, the ability to shift attention covertly was unimpaired in the patients, as indicated by a robust improvement in visual acuity induced by spatial cueing which did not differ from the one observed in the controls and which was independent of the range of SOAs (stimulus onset asynchronies) tested. Finally, the individual amount of saccadic dysmetria did not correlate with the individual performance in the covert attentional paradigm. In summary, we conclude that the contributions of the cerebellum to attention are confined to overt manifestations based on goal-directed eye movements.
为了找到小脑疾病患者认知缺陷的共同特征，有人提出这些缺陷可能继发于注意力控制受损，即“注意力辨距不良”，这一概念在概念上类似于运动辨距不良。尽管注意力辨距不良这一概念颇具吸引力且颇具影响力，但小脑疾病导致注意力辨距不良的观点仍存在争议。为了直接验证这一概念，我们将小脑疾病患者与正常对照组在需要明显或隐蔽的空间注意力转移的任务中的表现进行了比较。在第一个实验中，诱发了视觉引导的眼跳，即明显的空间注意力转移。在第二个实验中，通过辨别在控制注视期间观察到的Landolt C的方向来诱发隐蔽的注意力转移，该Landolt C出现在与前一个实验中眼跳目标相同的位置。通过比较有无空间线索时测定的视力阈值来评估注意力的分配。与对照组相比，患者表现出眼跳辨距不良，表现为绝对位置误差更大或校正眼跳次数更多。相反，患者隐蔽转移注意力的能力未受损，空间线索引起的视力显著改善表明了这一点，这种改善与对照组观察到的情况没有差异，并且与测试的刺激起始异步范围无关。最后，眼跳辨距不良的个体程度与隐蔽注意力范式中的个体表现无关。总之，我们得出结论，小脑对注意力的作用仅限于基于目标导向的眼球运动的明显表现。
