Hoffmann Susanne, Vega-Zuniga Tomas, Greiter Wolfgang, Krabichler Quirin, Bley Alexandra, Matthes Mariana, Zimmer Christiane, Firzlaff Uwe, Luksch Harald
Technische Universität München, Liesel-Beckmann-Str. 4, 85354, Freising-Weihenstephan, Germany.
Eur J Neurosci. 2016 Nov;44(9):2685-2697. doi: 10.1111/ejn.13394. Epub 2016 Sep 23.
The midbrain superior colliculus (SC) commonly features a retinotopic representation of visual space in its superficial layers, which is congruent with maps formed by multisensory neurons and motor neurons in its deep layers. Information flow between layers is suggested to enable the SC to mediate goal-directed orienting movements. While most mammals strongly rely on vision for orienting, some species such as echolocating bats have developed alternative strategies, which raises the question how sensory maps are organized in these animals. We probed the visual system of the echolocating bat Phyllostomus discolor and found that binocular high acuity vision is frontally oriented and thus aligned with the biosonar system, whereas monocular visual fields cover a large area of peripheral space. For the first time in echolocating bats, we could show that in contrast with other mammals, visual processing is restricted to the superficial layers of the SC. The topographic representation of visual space, however, followed the general mammalian pattern. In addition, we found a clear topographic representation of sound azimuth in the deeper collicular layers, which was congruent with the superficial visual space map and with a previously documented map of orienting movements. Especially for bats navigating at high speed in densely structured environments, it is vitally important to transfer and coordinate spatial information between sensors and motor systems. Here, we demonstrate first evidence for the existence of congruent maps of sensory space in the bat SC that might serve to generate a unified representation of the environment to guide motor actions.
中脑上丘（SC）在其浅层通常具有视觉空间的视网膜拓扑表征，这与在其深层由多感觉神经元和运动神经元形成的图谱一致。层间的信息流被认为使上丘能够介导目标导向的定向运动。虽然大多数哺乳动物在定向时强烈依赖视觉，但一些物种，如回声定位蝙蝠，已经发展出了替代策略，这就提出了一个问题，即这些动物的感觉图谱是如何组织的。我们探究了回声定位蝙蝠褐果蝠的视觉系统，发现双眼高敏锐度视觉朝前定向，因此与生物声纳系统对齐，而单眼视野覆盖了大面积的周边空间。在回声定位蝙蝠中，我们首次能够证明，与其他哺乳动物不同，视觉处理仅限于上丘的浅层。然而，视觉空间的拓扑表征遵循一般的哺乳动物模式。此外，我们在丘深层发现了声音方位的清晰拓扑表征，这与浅层视觉空间图谱以及先前记录的定向运动图谱一致。特别是对于在密集结构环境中高速飞行的蝙蝠来说，在传感器和运动系统之间传递和协调空间信息至关重要。在这里，我们首次证明了蝙蝠上丘中存在感觉空间的一致图谱，这些图谱可能有助于生成环境的统一表征以指导运动行为。
