Precise 3D Localization of Intracerebral Implants with a simple Brain Clearing Method.

Accurately determining the localization of intracerebral implants stands as a critical final step in numerous in-vivo studies, especially when targeting deep, small nuclei. Conventional histological approaches, reliant on manual estimation through sectioning and slice examination, often introduce errors and damage, potentially complicating data interpretation. Leveraging recent advancements in tissue-clearing techniques and light-sheet fluorescence microscopy, we introduce a method enabling virtual brain slicing in any orientation, offering precise implant localization without the limitations of traditional sectioning. To illustrate this method's efficacy, we present findings from the acute implantation of linear silicon probes in the midbrain interpeduncular nucleus (IPN) of anesthetized transgenic mice expressing chanelrhodopsin-2 EYFP under the choline acetyltransferase ChAT promoter/enhancer regions (ChAT-Chr2-EYFP mice). Utilizing a fluorescent dye applied to the electrode's surface, we visualize both the targeted area and electrode position. Brain scans, presented effortlessly in video format across various orientations, showcase the technique's versatility. Additionally, automated registration accurately pinpoints implant localization, enabling enhanced inter-subject comparisons.