Himmelbach Marc, Erb Michael, Karnath Hans-Otto
Section Neuropsychology, Center for Neurology, Hertie-Institute for Clinical Brain Research, Eberhard Karls University, Hoppe-Seyler-Str, 3, 72076 Tübingen, Germany.
BMC Neurosci. 2007 Aug 14;8:66. doi: 10.1186/1471-2202-8-66.
Visual, oculomotor, and - recently - cognitive functions of the superior colliculi (SC) have been documented in detail in non-human primates in the past. Evidence for corresponding functions of the SC in humans is still rare. We examined activity changes in the human tectum and the lateral geniculate nuclei (LGN) in a visual search task using functional magnetic resonance imaging (fMRI) and anatomically defined regions of interest (ROI). Healthy subjects conducted a free visual search task and two voluntary eye movement tasks with and without irrelevant visual distracters. Blood oxygen level dependent (BOLD) signals in the SC were compared to activity in the inferior colliculi (IC) and LGN.
Neural activity increased during free exploration only in the SC in comparison to both control tasks. Saccade frequency did not exert a significant effect on BOLD signal changes. No corresponding differences between experimental tasks were found in the IC or the LGN. However, while the IC revealed no signal increase from the baseline, BOLD signal changes at the LGN were consistently positive in all experimental conditions.
Our data demonstrate the involvement of the SC in a visual search task. In contrast to the results of previous studies, signal changes could not be seen to be driven by either visual stimulation or oculomotor control on their own. Further, we can exclude the influence of any nearby neural structures (e.g. pulvinar, tegmentum) or of typical artefacts at the brainstem on the observed signal changes at the SC. Corresponding to findings in non-human primates, our data support a dependency of SC activity on functions beyond oculomotor control and visual processing.
过去已在非人灵长类动物中详细记录了上丘（SC）的视觉、眼球运动以及最近发现的认知功能。关于人类SC相应功能的证据仍然很少。我们使用功能磁共振成像（fMRI）和解剖学定义的感兴趣区域（ROI），在一项视觉搜索任务中检查了人类顶盖和外侧膝状体核（LGN）的活动变化。健康受试者进行了一项自由视觉搜索任务以及两项有或没有无关视觉干扰物的自主眼球运动任务。将SC中的血氧水平依赖（BOLD）信号与下丘（IC）和LGN中的活动进行了比较。
与两个对照任务相比，仅在自由探索期间SC中的神经活动增加。扫视频率对BOLD信号变化没有显著影响。在IC或LGN中未发现实验任务之间的相应差异。然而，虽然IC未显示出相对于基线的信号增加，但在所有实验条件下LGN处的BOLD信号变化始终为正。
我们的数据证明了SC参与视觉搜索任务。与先前研究的结果相反，信号变化并非单独由视觉刺激或眼球运动控制驱动。此外，我们可以排除任何附近神经结构（例如丘脑枕、被盖）或脑干处典型伪影对SC处观察到的信号变化的影响。与非人灵长类动物的研究结果一致，我们的数据支持SC活动依赖于眼球运动控制和视觉处理之外的功能。
