Cyto- and myeloarchitectural brain atlas of the pale spear-nosed bat (Phyllostomus discolor) in CT Aided Stereotaxic Coordinates

Abstract

The pale spear-nosed bat Phyllostomus discolor, a microchiropteran bat, is well established as an animal model for research on the auditory system, echolocation and social communication of species-specific vocalizations. We have created a brain atlas of Phyllostomus discolor that provides high-quality histological material for identification of brain structures in reliable stereotaxic coordinates to strengthen neurobiological studies of this key species. The new atlas combines high-resolution images of frontal sections alternately stained for cell bodies (Nissl) and myelinated fibers (Gallyas) at 49 rostrocaudal levels, at intervals of 350 µm. To facilitate comparisons with other species, brain structures were named according to the widely accepted Paxinos nomenclature and previous neuroanatomical studies of other bat species. Outlines of auditory cortical fields, as defined in earlier studies, were mapped onto atlas sections and onto the brain surface, together with the architectonic subdivisions of the neocortex. X-ray computerized tomography (CT) of the bat’s head was used to establish the relationship between coordinates of brain structures and the skull. We used profile lines and the occipital crest as skull landmarks to line up skull and brain in standard atlas coordinates. An easily reproducible protocol allows sectioning of experimental brains in the standard frontal plane of the atlas. An electronic version of the atlas plates and supplementary material is available from 10.12751/g-node.8bbcxy

Structural arrangement of auditory brainstem nuclei in the bats Phyllostomus discolor and Carollia perspicillata

“…Brains were removed and postfixed in PFA for 4–24 h at 4°C. Thereafter, brains were washed three times each 10 min in phosphate‐buffered saline (PBS) consisting of (in mM): 138 NaCl, 2.7 KCl, 10.2 Na 2 HPO 4 , and 1.76 KH 2 PO 4 , adjusted to pH 7.4 and then embedded in 4% agarose in a custom‐made positioning device enabling a standardized brain orientation (Radtke‐Schuller et al., 2020). After trimming the brainstem, 50‐μm‐thick transvers slices were prepared with a VT1200S vibratome (Leica) or a Ci 7000 smz2 vibratome (Campden Instruments) and stored in PBS.…”

“…In both bats, echolocation is based on frequency‐modulated (FM) calls (Esser & Kiefer, 1996; Rother & Schmidt, 1985; Thies, 1998). For both species, at least a partial brain atlas is available (Radtke‐Schuller et al., 2020; Scalia et al., 2013). However, only for P. discolor this atlas includes the auditory brainstem.…”

The pale spear‐nosed bat: A neuromolecular and transgenic model for vocal learning

“…Given the important role that structure plays in the functional capabilities of a brain, it is essential to have a thorough understanding of the structural organization of an organism's brain. In P. discolor , meticulous histological approaches have given a broad view of brain structure as well as detailed maps of primarily subcortical components of the brain 59 . In the cortex, electrophysiological studies have given a deep understanding of the location and computational properties of auditory cortical regions 28,32,55 .…”

“…We report both T1-and T2-weighted MRI images (see Table S4 for scanning conditions) and fractional anisotropy (FA) color direction mapping based on DTI, as well as dispersion and fiber orientation maps based on PLI. By comparing the coronal sections of the MRI, DTI, and PLI images with precise histological maps from the published atlas, 59 we observed strong concordance and were able to identify the same gray matter structures (e.g., the caudate nucleus and putamen; Evidence from several bat species has implicated another specialized frontal cortex region in the auditory processing pathway known as the frontal auditory field (FAF), which has been suggested to be a homolog of the mammalian PFC/M2. This brain region receives auditory input directly from the AC 62,63 and also from the SG via the extralemniscal pathway.…”

Communication breakdown: Limits of spectro-temporal resolution for the perception of bat communication calls

“…After completion of the experiments, a neuronal marker (BDA 3000, Sigma-Aldrich, St-Louis, USA; 5% in phosphate buffer) was pressure-injected (Nanoliter 2010 injector, World Precision Instruments, Sarasota, FL, USA) into the brains in order to reconstruct the position of the recording sites in standardized stereotactic coordinates 73 of a brain atlas of P. discolor 75 , 76 . Subsequently, the bats were euthanized with an intraperitoneally applied lethal dose of pentobarbital (Narcoren, Boehringer-Ingelheim, 0.16 mg/g bodyweight) and transcardially perfused with 4% paraformaldehyde.…”