Kalogeraki Evgenia, Pielecka-Fortuna Justyna, Löwel Siegrid
Department of Systems Neuroscience, J.F.B. Institut für Zoologie und Anthropologie, Universität Göttingen, Göttingen, Germany.
Göttingen Graduate School of Neurosciences, Biophysics and Molecular Biosciences (GGNB), Göttingen, Germany.
PLoS One. 2017 Oct 26;12(10):e0186999. doi: 10.1371/journal.pone.0186999. eCollection 2017.
In standard cage (SC) raised mice, experience-dependent ocular dominance (OD) plasticity in the primary visual cortex (V1) rapidly declines with age: in postnatal day 25-35 (critical period) mice, 4 days of monocular deprivation (MD) are sufficient to induce OD-shifts towards the open eye; thereafter, 7 days of MD are needed. Beyond postnatal day 110, even 14 days of MD failed to induce OD-plasticity in mouse V1. In contrast, mice raised in a so-called "enriched environment" (EE), exhibit lifelong OD-plasticity. EE-mice have more voluntary physical exercise (running wheels), and experience more social interactions (bigger housing groups) and more cognitive stimulation (regularly changed labyrinths or toys). Whether experience-dependent shifts of V1-activation happen faster in EE-mice and how long the plasticity promoting effect would persist after transferring EE-mice back to SCs has not yet been investigated. To this end, we used intrinsic signal optical imaging to visualize V1-activation i) before and after MD in EE-mice of different age groups (from 1-9 months), and ii) after transferring mice back to SCs after postnatal day 130. Already after 2 days of MD, and thus much faster than in SC-mice, EE-mice of all tested age groups displayed a significant OD-shift towards the open eye. Transfer of EE-mice to SCs immediately abolished OD-plasticity: already after 1 week of SC-housing and MD, OD-shifts could no longer be visualized. In an attempt to rescue abolished OD-plasticity of these mice, we either administered the anti-depressant fluoxetine (in drinking water) or supplied a running wheel in the SCs. OD-plasticity was only rescued for the running wheel- mice. Altogether our results show that raising mice in less deprived environments like large EE-cages strongly accelerates experience-dependent changes in V1-activation compared to the impoverished SC-raising. Furthermore, preventing voluntary physical exercise of EE-mice in adulthood immediately precludes OD-shifts in V1.
在标准笼（SC）饲养的小鼠中，初级视觉皮层（V1）中依赖经验的眼优势（OD）可塑性会随着年龄快速下降：在出生后第25 - 35天（关键期）的小鼠中，4天的单眼剥夺（MD）足以诱导OD向睁开的眼睛偏移；此后，则需要7天的MD。在出生后第110天之后，即使14天的MD也无法在小鼠V1中诱导OD可塑性。相比之下，在所谓“丰富环境”（EE）中饲养的小鼠表现出终身的OD可塑性。EE小鼠有更多的自主体育锻炼（跑步轮），经历更多的社交互动（更大的饲养群体）和更多的认知刺激（定期更换迷宫或玩具）。V1激活的依赖经验的偏移在EE小鼠中是否发生得更快，以及将EE小鼠转回SC环境后可塑性促进作用会持续多久，尚未得到研究。为此，我们使用内在信号光学成像来可视化V1激活：i）在不同年龄组（1 - 9个月）的EE小鼠进行MD前后，以及ii）在出生后第130天将小鼠转回SC环境后。仅在MD 2天后，所有测试年龄组的EE小鼠就比SC小鼠更快地表现出明显的向睁开眼睛的OD偏移。将EE小鼠转移到SC环境中会立即消除OD可塑性：在SC环境饲养和MD 1周后，OD偏移就不再可见。为了挽救这些小鼠被消除的OD可塑性，我们要么给予抗抑郁药氟西汀（加入饮用水中），要么在SC环境中提供一个跑步轮。只有跑步轮小鼠的OD可塑性得到了挽救。我们的结果总体表明，与贫困的SC饲养环境相比，在像大型EE笼这样剥夺较少的环境中饲养小鼠，会强烈加速V1激活中依赖经验的变化。此外，在成年期阻止EE小鼠的自主体育锻炼会立即阻止V1中的OD偏移。
