急性週邊本體感覺操弄策略之測試與小鼠虛擬實境空間行為模式之整合

Abstract

以闡明機制為目的的研究，將周邊神經訊息的處理過程與目標導向的認知功能進行因果上的連結，是神經科學中的新興領域。動物通過整合外部與內部的感覺輸入，在腦中形成自身與環境關係的神經表徵，從而指導行為。在涉及空間導航的多感官模態情境中（如現實世界場景），自我運動資訊相較於外部感官線索的因果重要性仍未明確。一些理論指出，身體本身可能是空間感知的關鍵基準。然而，現有的實驗方法通常無法精確控制外部與自我運動驅動的感官回饋。在本研究中，我們開發了一種動物模型系統，用於操控記憶依賴性、類空間導航行為環境中的聽覺、視覺及本體感覺輸入。這個系統使用自製設計的虛擬實境與通過生物冷光光遺傳學技術對本體感覺回饋進行急性調控。小鼠背根神經節中的parvalbumin陽性神經元，作為本體感覺機械傳導的媒介，被基因轉殖所表達的 Luminopsin 3（LMO3）通道所選擇性調控。利用LMO3的配體，coelenterazine（CTZ），我們嘗試建立一個系統，能夠在不影響一般運動能力的情況下損害本體感覺信號的傳遞，這與傳統會損害一般運動能力的 Piezo2 基因剔除方法不同。接受肌肉內注射 CTZ 的小鼠在一般運動技能、肢體協調性以及尋求獎勵的動機方面均表現正常。令人意外的是，這些小鼠在被認為需要本體感覺回饋維持身體平衡的任務中，其表現與對照組無顯著差異。然而，在需要整合過去運動信息以導航至虛擬目標位置的記憶依賴性任務中，這些小鼠在跑步機上的精確目標導向行為中表現出輕微的行為變化。 這些結果表明，PV-LMO3 系統可能會影響小鼠在相對複雜的空間決策中整合本體感覺信號的方式，但不會影響其感知和調節身體動作的能力。我們的發現提供了支持本體感覺在不同層面影響行為決策的初步證據，並展示了在空間導航中使用生物冷光光遺傳學技術調控本體感覺神經的潛力。 儘管目前的方法效果有限，但未來仍有許多可探索的改進選項，包括改良的 LMO3 版本、更高劑量的 CTZ，以及通過在周邊神經系統植入光纖進行光遺傳神經干擾，以進一步闡明本體感覺在複雜行為中的角色。綜合來說，我們設計、實現並測試了一套可編程、進行急性操控的策略，用於研究小鼠在虛擬實境中的記憶導向空間導航，實現了對聽覺、視覺和自我運動感官輸入的動態精確控制。

Mechanistic studies that causally link peripheral neural processes with goal-directed cognitive functions is a new frontier in neuroscience. Animals integrate external and internal sensory inputs to form neural representations of their relationship with the environment, which guide behavior. In multimodal settings of spatial navigation, including real-world scenarios, the causal importance of self-motion information relative to external sensory cues remains largely unclear. Some theories suggest that the body itself serves as a key metric for spatial perception. However, existing experimental methods often fail to precisely control external and self-motion-driven sensory feedback. In this study, we developed an animal model system to manipulate auditory, visual, and proprioceptive inputs during memory-dependent, spatial-navigation-like behavior settings. This was achieved with a multiplexed approach combining custom-designed virtual reality for mice with acute modulation of proprioceptive feedback via bioluminescent optogenetics. Proprioceptive mechanical transduction, mediated by parvalbumin-positive neurons in the dorsal root ganglia, was selectively manipulated by transgenic expression of Luminopsin 3 (LMO3) channels in mice. Using the extracellular ligand coelenterazine (CTZ), we aimed to establish a system to impair proprioceptive signaling without compromising locomotion, unlike conventional Piezo2 knockouts. Mice receiving intramuscular CTZ injections exhibited normal motor skills and coordination in general assessments as well as normal motivation for seeking rewards. Surprisingly, these mice performed comparably well to their controls (or control conditions) in tasks thought to require proprioceptive feedback, such as balance-beam tasks. However, they displayed mild behavioral changes in memory-dependent tasks requiring integration of past movements to navigate to a virtual location, engaged in precise goal-dependent behavior on a treadmill. These results suggest that the PV-LMO3 system might influence how mice integrate proprioceptive signals for relatively complex spatial decision-making, while leaving their ability to grossly sense and tune body movements intact. Our finding supports the idea regarding task-specific nature of proprioceptive functions, and demonstrate the potential utility of chemo- or optogenetic control of proprioceptive nerves for modulating peripheral proprioceptive signaling during spatial navigation. Although the current approach showed limited effects in certain tasks, future studies can be carried out to investigate improved options including new LMO3 variants, higher CTZ doses, and optogenetic perturbation of nerves with peripheral optical-fiber implants, to further elucidate the roles of proprioception in complex behaviors. Together, we designed, implemented and tested a suite of programmable and acute manipulation strategies for memory-guided spatial navigation research for mice in virtual reality, which realizes dynamic and precise control of audio-visual and self-motion-based sensory inputs.