Eleonore Schiltz

During odor-guided navigation, animals combine sensory cues with spatial information to make behavioral choices. The integration of olfactory and spatial information involves a highly interconnected olfactory-hippocampal circuit, yet it remains unclear whether task-relevant odor representations are distributed across this network or emerge within specialized nodes. Moreover, decisions in natural environments often do not just depend on physical stimulus properties, but on higher-order, categorical stimulus features. Here, we trained freely moving mice to learn such an abstract decision rule, whereby odor novelty, rather than odor identity, determined reward location. Simultaneous recordings from posterior piriform cortex, lateral entorhinal cortex (LEC), CA1, and dentate gyrus revealed that neural population activity across the network was dominated by spatial task variables. During odor sampling, the piriform cortex and LEC encoded odor identity and novelty. Remarkably, only the piriform cortex maintained stable novelty representations across behavioral epochs, from odor sampling to reward approach. These findings identify the posterior piriform as a key hub for maintaining abstract, task-relevant representations that link sensory cues to spatial decisions.

Two‐photon polymerization (TPP) is an additive manufacturing technique with micron‐scale resolution that is rapidly gaining ground for a range of biomedical applications. TPP is particularly attractive for the creation of microscopic three‐dimensional structures in biocompatible and noncytotoxic resins. Here, TPP is used to develop microfluidic interfaces which provide chronic fluidic access to the brain of preclinical research models. These microcatheters can be used for either convection‐enhanced delivery (CED) or for the repeated collection of liquid biopsies. In a brain phantom, infusions with the micronozzle result in more localized distribution clouds and lower backflow compared to a control catheter. In mice, the delivery interface enables faster, more precise, and physiologically less disruptive fluid injections. A second microcatheter design enables repeated, longitudinal sampling of cerebrospinal fluid (CSF) over time periods as long as 250 days. Moreover, further in vivo studies demonstrate that the blood‐CSF barrier is intact after chronic implantation of the sampling interface and that samples are suitable for downstream molecular analysis for the identification of nucleic acid‐ or peptide‐based biomarkers. Ultimately, the versatility of this fabrication technique implies a great translational potential for simultaneous drug delivery and biomarker tracking in a range of human neurological diseases.