Miniscope GRIN Lens System for Calcium Imaging of Neuronal Activity from Deep Brain Structures in Behaving Animals

Abstract

Visualizing neural activity from deep brain regions in freely behaving animals through miniature fluorescent microscope (miniscope) systems is becoming more important for understanding neural encoding mechanisms underlying cognitive functions. Here we present our custom-designed miniscope GRadient INdex (GRIN) lens system that enables simultaneously recording from hundreds of neurons for months. This protocol includes miniscope design, the surgical procedure for GRIN lens implantation, miniscope mounting on the head of a mouse, and data acquisition and analysis. First, a target brain region is labeled with virus expressing GCaMP6; Second, a GRIN lens is implanted above the target brain region; Third, following mouse surgical recovery, a miniscope is mounted on the head of the mouse above the GRIN lens; Finally, neural activity is recorded from the freely behaving mouse. This system can be applied to recording the same population of neurons longitudinally, enabling the elucidation of neural mechanisms underlying behavioral control.

Diving into the brain: deep-brain imaging techniques in conscious animals

“…The glass tube can then be held with an electrode holder on the stereotaxic arm. Once the GRIN lens has been positioned in the brain and cemented in place, acetone can be carefully introduced into the glass tube in order to dissolve the Super Glue, thus freeing the GRIN lens (Zhang et al 2019).…”

“…GRIN lenses exist in different lengths and diameters. For brain regions such as the dorsal striatum ( Zhang et al 2019 ), prelimbic cortex ( Pinto & Dan 2015 ) or hippocampus ( Ziv et al 2013 ), a 1 mm diameter GRIN lens can be used to increase the field of view. For deep-brain areas such as the amygdala ( Li et al 2017 ) or hypothalamus ( Jennings et al 2015 ), a lens of approximatively 0.5 mm diameter can be used in order to minimize tissue damage during lens implantation.…”

An open source motorized swivel for in vivo neural and behavioral recordings

“…1 Overview of the system. (A) Diagram showing a practical application of the proposed system paired with in vivo calcium imaging with miniScope [8 , 2] . (B) A picture of the assembled commutator.…”

EZcalcium: Open-Source Toolbox for Analysis of Calcium Imaging Data

“…To understand brain function, neuroscientists are increasingly turning to synthetic and genetically encoded fluorescence indicators (calcium and voltage sensors) for monitoring dynamic fluorescence signals produced by neurons and glia (Lin and Schnitzer, 2016;Yang and Yuste, 2017). In particular, calcium imaging with two-photon microscopy (Svoboda and Yasuda, 2006;Mostany et al, 2015) and microendoscopy with miniscopes or fiber photometry (Ghosh et al, 2011;Liberti et al, 2017;Jacob et al, 2018;Aharoni et al, 2019;Zhang et al, 2019) have provided key insights, such as how developing cortical networks undergo drastic transitions (Golshani et al, 2009;Rochefort et al, 2009) or how large neuronal ensembles encode spatial navigation (Dombeck et al, 2010). Calcium imaging offers several distinct advantages over traditional electrode recording techniques (Grewe and Helmchen, 2009;Grienberger and Konnerth, 2012): (1) it can be combined with genetic approaches (e.g., Cre-Lox) to probe neuronal activity in specific sub-populations of neurons (Goel et al, 2018;Yaeger et al, 2019) and glia (Srinivasan et al, 2016), either in specific subcellular compartments (e.g., axon boutons, dendritic spines, glial microdomains; Cichon and Gan, 2015;Broussard et al, 2018) or in specific brain regions or cortical layers (Lacefield et al, 2019); (2) recordings can be carried out over periods of days or even weeks (Chen et al, 2013;He et al, 2018); (3) recordings can be made simultaneously in a large population of hundreds or thousands of neurons in multiple brain regions (e.g., an entire sub-network; Sofroniew et al, 2016); (4) calcium imaging can also be combined with optogenetic manipulations, which makes it possible to perform all-optical probing of circuit function (Packer et al, 2015); (5) recordings can be performed in freely moving animals, providing a key link between circuit activity and behavior (Lin and Schnitzer, 2016); and (6) calcium imaging is less invasive than traditional electrode recordings (e.g., tetrodes, silicon probes).…”