Gradient Index Microlens Implanted in Prefrontal Cortex of Mouse Does Not Affect Behavioral Test Performance over Time

Abstract

Implanted gradient index lenses have extended the reach of standard multiphoton microscopy from the upper layers of the mouse cortex to the lower cortical layers and even subcortical regions. These lenses have the clarity to visualize dynamic activities, such as calcium transients, with subcellular and millisecond resolution and the stability to facilitate repeated imaging over weeks and months. In addition, behavioral tests can be used to correlate performance with observed changes in network function and structure that occur over time. Yet, this raises the questions, does an implanted microlens have an effect on behavioral tests, and if so, what is the extent of the effect? To answer these questions, we compared the performance of three groups of mice in three common behavioral tests. A gradient index lens was implanted in the prefrontal cortex of experimental mice. We compared their performance with mice that had either a cranial window or a sham surgery. Three presurgical and five postsurgical sets of behavioral tests were performed over seven weeks. Behavioral tests included rotarod, foot fault, and Morris water maze. No significant differences were found between the three groups, suggesting that microlens implantation did not affect performance. The results for the current study clear the way for combining behavioral studies with gradient index lens imaging in the prefrontal cortex, and potentially other regions of the mouse brain, to study structural, functional, and behavioral relationships in the brain.

Cellular Analysis and Chemotherapeutic Potential of a Bi-Functionalized Halloysite Nanotube

“…Images were scanned in three dimensions with x- and y-dimensions of 248 μm (1024 × 1024-pixel resolution), with z-steps of 2 μm (z stack) to produce z stacks of 36 and 46 μm to ensure that all cells were captured within the volume. Pixel dwell time was set to 2 μL with pixel averaging of 5/scan to acquire z stack images [ 17 , 18 ].…”

Head-mounted microendoscopic calcium imaging in dorsal premotor cortex of behaving rhesus macaque

“…It is important to note that, except for the tissue damage created by the cortical incision made just prior to lens insertion, the actual lens itself may simply displace the remaining tissue without necessarily causing additional damage. More studies are needed to characterize the injury to the brain during implantation and the foreign body response to the chronically implanted lens (Barretto et al, 2011;Kozai et al, 2015;Lee et al, 2016). Another limitation associated with the use of a microendoscopic GRIN lens, particularly when combined with a one-photon miniscope, is the lower spatial resolution as compared to that of a two-photon microscope.…”

TRIO Platform: A Novel Low Profile In vivo Imaging Support and Restraint System for Mice

“…We used a polymer head plate instead of a metal plate or bar to minimize the mass of the plate and permit easy modification of the number of ports and their placement. Minimizing the mass of the head plate, which was ~0.2 g, was important for our work because many of our mice are used for behavioral experiments in between imaging sessions (Lee et al, 2016 ).…”

“…Aseptic surgery was performed to install either a cranial window or a GRIN lens mounted on a cranial window, as previously described (Murray and Levene, 2012 ; Lee et al, 2016 ). Briefly, after confirming the mouse was in a surgical plane of anesthesia using noxious toe pinches, an incision was made in the scalp and connective tissue was cleared.…”

“…Furthermore, by counterstaining the vasculature, blood flow rates have been determined (Pinard et al, 2000 ; Levene et al, 2004 ), and vessel permeability and leukocyte trafficking have been observed (Pai et al, 2012 ). The ability to monitor these activities over time in a mouse model has tremendous importance to both basic research and preclinical studies (Ricard and Debarbieux, 2014 ; Lee et al, 2016 ). Yet, the means by which mice are positioned and maintained for imaging has relied primarily on old technology and non-standardized custom made components.…”