Behavioral quantification and multi-photon microscopy during gap crossing in freely moving rodents

Measuring behavior in the freely moving animal allows for the quantification of temporal patterns of neural activity during specific behaviors such as decision making tasks all while maintaining the complete mosaic and integrity of sensory input within an ethologically relevant context. Here, we present a gap crossing task, performed by rodents in either light and dark conditions, in which an animal must evaluate a gap of varying distances and choose to cross or not using its vision, whiskers, or both. To quantify whisker strikes on the target platform, we developed a detection system based on expanded and collimated IR laser light. Here we show that both whisker and vision based gap crossing behaviors can be distinguished and quantified using this approach. Cross attempt times (i.e. time taken to reach the decision to cross or to refuse) tracked in parity with animals crossing psychometrics. Attempt times rose significantly at the limit of whisking range, most notably in the absence of visual cues (dark), and remained elevated for vision only gap distances.  We additionally show differences in the whisking behavior of mice and rats, e.g. whisking frequency. Further, utilizing head-mounted three-photon excitation-based microscopy, we correlated neuronal activity from discrete cortical layers with single-cell resolution to crossing behaviors.

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