BRAin-wide Neuron quantification Tool reveals strong sexual dimorphism in the evolution of fear memory

The neuronal and molecular mechanisms underlying behavioral responses triggered by fear have received wide interest now, especially with the surge of fear-related disorders associated with the recent Covid-19 pandemic. Fear responses are functionally adaptive behaviors that are strengthened as memories. Indeed, knowing fear circuitry could be the turning point for the comprehension of this emotion and its pathological states, even addressing potential treatments. Understanding memory dynamics presents fundamental technological challenges and calls for the development of new tools and methods able to analyze the entire brain with single-neuron resolution. In this context, we developed the BRAin-wide Neuron quantification Tool (BRANT) for mapping neuronal activation at micron resolution, combining tissue clearing protocol, high-resolution light-sheet microscopy, and automated 3D image analysis. This method allowed us to quantify the evolution of neuronal activation patterns across multiple phases of memory. This approach highlighted a strong sexual dimorphism in the circuits recruited during memory recall, which had no counterpart in the behaviour. The methodology presented here paves the way for a comprehensive functional characterization of the evolution of fear memory.