Visualization of cortical, subcortical and deep brain neural circuit dynamics during naturalistic mammalian behavior with head-mounted microscopes and chronically implanted lenses

Abstract

Genetically encoded calcium indicators for visualizing dynamic cellular activity have greatly expanded our understanding of the brain. However, due to light scattering properties of the brain as well as the size and rigidity of traditional imaging technology, in vivo calcium imaging has been limited to superficial brain structures during head fixed behavioral tasks. This limitation can now be circumvented by utilizing miniature, integrated microscopes in conjunction with an implantable microendoscopic lens to guide light into and out of the brain, thus permitting optical access to deep brain (or superficial) neural ensembles during naturalistic behaviors. Here, we describe procedural steps to conduct such imaging studies using mice. However, we anticipate the protocol can be easily adapted for use in other small vertebrates. Successful completion of this protocol will permit cellular imaging of neuronal activity and the generation of data sets with sufficient statistical power to correlate neural activity with stimulus presentation, physiological state, and other aspects of complex behavioral tasks. This protocol takes 6–11 weeks to complete.

Molecular basis of dendritic atrophy and activity in stress susceptibility

“…To test this, AAV-DIO- Egr3 -miR-LacZ or AAV-DIO-SS-miR-LacZ was co-injected with AAV-DIO-GCaMP6f in the NAc of D1-Cre mice to reduce NAc Egr3 expression or as a control, respectively (Supplementary Figures 3a, b). A chronically implantable gradient-index (GRIN) lens 39–41 was inserted in the NAc (Figure 5a) to observe calcium transients in vivo (Figure 5b Supplementary Movies 1 and 2). No differences were observed in frequency of calcium transients when mice were outside of the interaction zone (Supplementary Figure 3c) or when frequency was examined across the entire session (Supplementary Figure 3d).…”

Encoding of danger by parabrachial CGRP neurons

“…Mice were prepared for calcium imaging as described 41 . Briefly, three weeks after AAV1-CBA-DIO-GCaMP6m virus injection, Calca Cre/+ mice were anesthetized (as described above) and implanted with a microendoscope lens (6.1 mm length, 0.5 mm diameter; Inscopix, catalogue #100-000588) with assistance of a ProView implant kit (Inscopix, catalogue #100-000754) that allowed for visualizing the fluorescent activity during the lens implant.…”

An Objective and Reproducible Test of Olfactory Learning and Discrimination in Mice

“…As implantable activity monitors, such as Graded-lndex (GRIN) lenses and multi-unit electrodes, continue to improve, we may soon be able to combine those technologies with this protocol 17,18 . By recording form relevant brain areas during olfactory learning, it is possible to probe how neuronal activities change during associative learning.…”