Monitoring the morphological and biochemical information of neurons and glial cells at high temporal resolution in three-dimensional (3D) volumes of in vivo is pivotal for understanding their structure and function, and quantifying the brain microenvironment. Conventional two-photon fluorescence lifetime volumetric imaging speed faces the acquisition speed challenges of slow serial focal tomographic scanning, complex post-processing procedures for lifetime images, and inherent trade-offs among contrast, signal-to-noise ratio, and speed. This study presents a two-photon fluorescence lifetime volumetric projection microscopy using an axially elongated Bessel focus and instant frequency-domain fluorescence lifetime technique, and integrating with a convolutional network to enhance the imaging speed for in vivo neurodynamics mapping. The proposed method is validated by monitoring intracellular Ca