Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong SAR, China.
Neuroimage. 2011 Oct 1;58(3):878-84. doi: 10.1016/j.neuroimage.2011.06.055. Epub 2011 Jun 29.
In rats, the superior colliculus (SC) is a main destination for retinal ganglion cells and is an important subcortical structure for vision. Electrophysiology studies have observed that many SC neurons are highly sensitive to moving objects, but complementary non-invasive functional imaging studies with larger fields of view have been rarely conducted. In this study, BOLD fMRI is used to measure the SC and nearby lateral geniculate nucleus' (LGN) hemodynamic responses, in normal adult Sprague Dawley (SD) rats, during a dynamic visual stimulus similar to those used in long-range apparent motion studies. The stimulation paradigm consists of four light spots arranged in a linear array and turned on and off sequentially at different rates to create five effective speeds of motion (7, 14, 41, 82, and 164°/s across the visual field). Stationary periods (same light spot always on) are interleaved between the moving periods. The speed response function (SRF), the hemodynamic response amplitude at each speed tested, is measured. Significant responses are observed in the SC and LGN at all speeds. In the SC, the SRF increases monotonically from 7 to 82°/s. The minimum response amplitude occurs at 164°/s. The results suggest that the SC is sensitive to slow moving visual stimuli but the hemodynamic response is reduced at higher speeds. In the LGN, the SRF exhibits a similar trend to that of the SC, but response amplitude during 7°/s stimulation is comparable to that during 164°/s stimulation. These findings are in good agreement with previous electrophysiology studies conducted on albino rats like the SD strain. This work represents the first fMRI study of stimulus speed dependence in the SC and is also the first fMRI study of motion responsiveness in the rat.
在大鼠中，上丘（SC）是视网膜神经节细胞的主要靶区，也是视觉的重要皮质下结构。电生理学研究观察到，许多 SC 神经元对运动物体高度敏感，但具有更大视场的互补非侵入性功能成像研究却很少进行。在这项研究中，使用 BOLD fMRI 测量正常成年 SD 大鼠在类似于远距离似动研究中使用的动态视觉刺激期间，SC 和附近外侧膝状体核（LGN）的血流动力学反应。刺激范式由四个以线性阵列排列的光点组成，并以不同的速率依次打开和关闭，以创建五个有效的运动速度（7、14、41、82 和 164°/s 跨越视野）。在运动期间，会插入静止期（同一光点始终打开）。测量每个测试速度的速度响应函数（SRF），即血流动力学响应幅度。在 SC 和 LGN 中均观察到显着反应。在 SC 中，SRF 从 7 到 82°/s 单调增加。最小响应幅度发生在 164°/s。结果表明，SC 对缓慢移动的视觉刺激敏感，但在更高速度下血流动力学响应会降低。在 LGN 中，SRF 表现出与 SC 相似的趋势，但在 7°/s 刺激期间的响应幅度与在 164°/s 刺激期间的响应幅度相当。这些发现与以前在白化大鼠（如 SD 品系）上进行的电生理学研究结果一致。这项工作代表了 SC 中刺激速度依赖性的第一个 fMRI 研究，也是大鼠中运动反应性的第一个 fMRI 研究。
