New Approaches to Cognitive Neurobiology: Methods for Two-Photon in Vivo Imaging of Cognitively Active Neurons

Abstract

This review addresses the potential of current methods of in vivo two-photon imaging of the activity of neurons involved in episodes of cognitive activity in animals. The principles of fluorescent two-photon microscopy are described and methods for in vivo imaging of neuron activity using calcium indicators of two types – calcium stains and genetically encoded calcium indictors (GECI) – are discussed. A new approach is also considered, using in vivo imaging of genomic activation of cerebral neurons in transgenic animals with fluorescent probes for the expression of the immediate early genes c-fos, Arc, and Egr-1. The main advantages and disadvantages of these approaches are compared and the potentials for the development of in vivo two-photon imaging of neuron activity for studies of the cellular basis of higher brain functions are addressed.