Laboratory of Biological Psychology, University of Leuven (KU Leuven) , Leuven , Belgium.
J Neurophysiol. 2018 Sep 1;120(3):926-941. doi: 10.1152/jn.00673.2017. Epub 2018 May 9.
Similar to primates, visual cortex in rodents appears to be organized in two distinct hierarchical streams. However, there is still little known about how visual information is processed along those streams in rodents. In this study, we examined how repetition suppression and position and clutter tolerance of the neuronal representations evolve along the putative ventral visual stream in rats. To address this question, we recorded multiunit spiking activity in primary visual cortex (V1) and the more downstream visual laterointermediate (LI) area of head-restrained Long-Evans rats. We employed a paradigm reminiscent of the continuous carry-over design used in human neuroimaging. In both areas, stimulus repetition attenuated the early phase of the neuronal response to the repeated stimulus, with this response suppression being greater in area LI. Furthermore, stimulus preferences were more similar across positions (position tolerance) in area LI than in V1, even though the absolute responses in both areas were very sensitive to changes in position. In contrast, the neuronal representations in both areas were equally good at tolerating the presence of limited visual clutter, as modeled by the presentation of a single flank stimulus. When probing tolerance of the neuronal representations with stimulus-specific adaptation, we detected no position tolerance in either examined brain area, whereas, on the contrary, we revealed clutter tolerance in both areas. Overall, our data demonstrate similarities and discrepancies in processing of visual information along the ventral visual stream of rodents and primates. Moreover, our results stress caution in using neuronal adaptation to probe tolerance of the neuronal representations. NEW & NOTEWORTHY Rodents are emerging as a popular animal model that complement primates for studying higher level visual functions. Similar to findings in primates, we demonstrate a greater repetition suppression and position tolerance of the neuronal representations in the downstream laterointermediate area of Long-Evans rats compared with primary visual cortex. However, we report no difference in the degree of clutter tolerance between the areas. These findings provide additional evidence for hierarchical processing of visual stimuli in rodents.
类似于灵长类动物，啮齿动物的视觉皮层似乎组织在两个不同的层次流中。然而，关于视觉信息如何在这些流中沿这些流在啮齿动物中处理，仍然知之甚少。在这项研究中，我们检查了在大鼠假设的腹侧视觉流中，神经元表示的重复抑制以及位置和混乱容忍度如何演变。为了解决这个问题，我们记录了头固定的长耳大鼠初级视觉皮层（V1）和下游视觉中隔（LI）区域的多单位尖峰活动。我们采用了一种类似于人类神经影像学中连续传递设计的范式。在两个区域中，刺激重复减弱了对重复刺激的神经元反应的早期阶段，LI 区域的反应抑制更大。此外，尽管两个区域的绝对响应对位置变化非常敏感，但在 LI 区域中位置之间的刺激偏好更相似。相比之下，两个区域中的神经元表示在耐受有限的视觉混乱方面都同样出色，就像呈现单个侧翼刺激一样建模。当用特定于刺激的适应来探测神经元表示的耐受性时，我们在两个检查的脑区中均未检测到位置耐受性，而相反，我们在两个区域中均检测到了混乱耐受性。总体而言，我们的数据表明，啮齿动物和灵长类动物腹侧视觉流中的视觉信息处理存在相似之处和差异。此外，我们的结果强调在使用神经元适应来探测神经元表示的耐受性时要谨慎。新的和值得注意的啮齿动物正在成为一种流行的动物模型，可与灵长类动物一起用于研究更高水平的视觉功能。与灵长类动物的发现相似，我们在 Long-Evans 大鼠的下游中隔区域中显示了更大的神经元表示的重复抑制和位置容忍度，与初级视觉皮层相比。然而，我们报告说，两个区域之间的混乱容忍度没有差异。这些发现为啮齿动物中视觉刺激的分层处理提供了更多证据。
