Rosa M G, Schmid L M
Department of Physiology and Pharmacology, University of Queensland, Australia.
Vis Neurosci. 1994 Nov-Dec;11(6):1037-57. doi: 10.1017/s0952523800006878.
It has been proposed that flying foxes (genus Pteropus) have a primate-like pattern of representation in the superficial layers of the superior colliculus (SC), whereby the visual representation in this structure is limited by the same decussation line that limits the retino-geniculo-cortical projection (Pettigrew, 1986). To test this hypothesis, visual receptive fields were plotted based on single- and multi-unit recordings in the SC of ten flying foxes. A complete representation of the contralateral hemifield was observed in the SC. Although the binocular hemifield of vision in Pteropus is 54 deg wide, receptive-field centers invaded the ipsilateral hemifield by only 8 deg, and the receptive-field borders by 13 deg. This invasion is similar to that observed at the border between visual areas V1 and V2 in the occipital cortex. The extent of the ipsilateral invasion was not affected by a lesion that completely ablated the occipital visual areas, thus suggesting that this invasion may be consequence of a zone of nasotemporal overlap in the retinal projections to the two colliculi. Neurones located in the superficial layers typically responded briskly to stimulation of both eyes, with a bias towards the contralateral eye. After cortical lesions the neuronal responses to the ipsilateral eye were depressed, and the ocular-dominance histograms shifted towards an even stronger dominance by the contralateral eye. However, cells located in the rostral pole of the SC remained responsive to the ipsilateral eye after cortical lesions. Responses in the stratum opticum and stratum griseum intermediale were more severely affected by cortical lesions than those in the stratum griseum superficiale. Our results demonstrate that the SC in flying foxes retain some generalized mammalian characteristics, such as the stronger direct projections of the contralateral eye and the location of the upper, lower, central, and peripheral representations in the SC. Nonetheless, the extent of visual representation in the SC demonstrates a specialized, primate-like pattern. These observations are consistent with the hypothesis that megachiropterans are members of a group that branched off early during the differentiation of primates from basal mammals.
有人提出，狐蝠（狐蝠属）在上丘（SC）浅层具有类似灵长类动物的表征模式，即该结构中的视觉表征受限于与限制视网膜 - 膝状体 - 皮质投射相同的交叉线（佩蒂格鲁，1986年）。为了验证这一假设，基于对十只狐蝠上丘的单单位和多单位记录绘制了视觉感受野。在上丘中观察到对侧半视野的完整表征。虽然狐蝠的双眼半视野宽54度，但感受野中心仅侵入同侧半视野8度，感受野边界侵入13度。这种侵入类似于在枕叶皮质视觉区域V1和V2之间的边界处观察到的情况。同侧侵入的程度不受完全切除枕叶视觉区域的损伤的影响，因此表明这种侵入可能是视网膜投射到两个上丘的鼻颞重叠区域的结果。位于浅层的神经元通常对双眼刺激反应迅速，对侧眼有偏向。皮质损伤后，对同侧眼的神经元反应受到抑制，眼优势直方图向对侧眼更强的优势方向移动。然而，位于上丘嘴端的细胞在皮质损伤后仍对同侧眼有反应。视层和中间灰质层的反应比浅灰质层受皮质损伤的影响更严重。我们的结果表明，狐蝠的上丘保留了一些一般哺乳动物的特征，如对侧眼更强的直接投射以及上丘中上部、下部、中央和周边表征的位置。尽管如此，上丘中视觉表征的程度显示出一种特殊的、类似灵长类动物的模式。这些观察结果与大蝙蝠是在灵长类动物从基础哺乳动物分化早期分支出来的群体成员这一假设一致。
