Department of Biology, Emory University, Atlanta, GA 30322, USA.
Department of Psychology, Emory University, Atlanta, GA 30322, USA.
Behav Brain Res. 2022 Feb 10;418:113622. doi: 10.1016/j.bbr.2021.113622. Epub 2021 Oct 12.
Headbobs are up-down movements of the cranium associated with the use of motion parallax for depth perception. Mongolian gerbils (aka jirds; Meriones unguiculatus) often execute a series of headbobs prior to jumping between surfaces. Gerbils were tested in a jumping stand task and headbobs videotaped under three light levels approximating low daylight, dawn/dusk, and moonlight across a range of distances to target. Headbobs per trial increased linearly with increasing distance to the target platform, whereas headbob frequency (rate of headbobbing pre-jump on the start platform) increased with gap distance up to an intermediate level and then decreased. Overall, gerbils made the most headbobs per trial under the darkest conditions, whereas their headbobbing rate was highest for medium illumination, especially for medium-long gap distances. There was a positive correlation between headbob frequency and volume of the superior colliculus (SC), but no relationship between headbobs and relative size of the temporo-posterior (TP) visual cortex. The results suggest that gerbils employ a specific visuomotor strategy for depth perception differentially under different conditions. We suggest that the deployment of headbobs under specific conditions may be part of an SC-driven vigilant state, of which more rapid sampling of the visual environment using headbobs for depth estimation is one component. Moreover, the findings highlight the importance of considering ecological factors in designing studies of visual behavior and its underpinnings in rodents.
头部摆动是颅骨的上下运动，与使用运动视差进行深度感知有关。蒙古沙鼠（又名跳鼠；Meriones unguiculatus）在跳跃之前经常会进行一系列的头部摆动。沙鼠在跳跃站立任务中进行测试，并在三种接近低日光、黎明/黄昏和月光的光照水平下，在一系列距离到目标的范围内进行头部摆动的视频记录。每个试验的头部摆动次数与到目标平台的距离呈线性增加，而头部摆动频率（跳跃前在起始平台上的头部摆动率）在间隔距离增加到中间水平后增加，然后减小。总的来说，沙鼠在最暗的条件下进行的头部摆动次数最多，而在中等光照下，它们的头部摆动率最高，尤其是在中等长的间隔距离下。头部摆动频率与上丘（SC）的体积呈正相关，但头部摆动与颞后（TP）视皮层的相对大小之间没有关系。结果表明，沙鼠在不同条件下采用特定的视觉运动策略来进行深度感知。我们认为，在特定条件下进行头部摆动可能是 SC 驱动警惕状态的一部分，其中更快速地使用头部摆动对深度进行估计以采样视觉环境是一个组成部分。此外，这些发现强调了在设计啮齿动物视觉行为及其基础的研究时考虑生态因素的重要性。
