Significance Memory consolidation following emotionally significant events is enhanced by glucocorticoid hormones. Our report identifies the anteroventral bed nuclei of the stria terminalis (avBST) as capable of bidirectionally modulating memory consolidation in rats following inhibitory avoidance learning. Follow-up experiments revealed that divergent pathways from avBST are responsible for the mnemonic effects of avBST inhibition and stimulation and that they occur via glucocorticoid-dependent and -independent mechanisms, respectively.
Purpose: To provide rapid 3D QA and treatment verification for Varian's Rapid Arc. Method and Materials: Our 3D QA system is composed of a fast laser CT scanner (OCTOPUS-IQ, MGS Research, Inc., Madison, CT), re-usable acrylic cylindrical inserts for self-developing polymer gels (BANG gel, MGS Research, Inc.), and a Virtual Water solid pelvic phantom (Med-Cal, Inc., Verona, WI). A single focused laser beam is moved at 10 Hz frequency across a rotating gel cylinder immersed in a refractive-index matching liquid in an aquarium. The field of view is adjustable up to 250 mm, the maximum length of scan is 250 mm, and the spatial resolution is adjustable down to 0.25 mm. The 3D distribution of optical attenuation coefficients in the polymer gel is reconstructed by a filtered back-projection open-source program written in Matlab (MathWorks, Inc., Natick, MA). Image registration and data analysis are performed using Matlab's Image Processing Toolbox. The gel phantom was scanned with a GE lightspeed 16 slice CT scanner. The gel's CT DICOM images were transferred to Eclipse treatment planning system. A QA plan was then generated by projecting a patient's RapidArc plan onto the gel's phantom CT data set. The calculated dose was exported via DICOM for analysis. The gel phantom was then set up on the Linac and irradiated with Varian 2300iX equipped with RapidArc. Results: With isotropic voxel size 2.5 mm (equivalent to TPS grid resolution), it takes less than half hour to scan the entire irradiated gel volume. Gamma maps indicate agreement within 3% dose difference, 3mm distance to agreement level. Conclusions: Our study demonstrates excellent performance of our fast 3D QA system for Rapid Arc. The system is very robust, easy to use, and saves time for 3D QA and treatment verification for Rapid Arc and other complex 3D treatment techniques.
The question of how the brain links behavioral and biological features of defensive responses has remained elusive. The importance of this problem is underscored by the observation that behavioral passivity in stress coping is associated with elevations in glucocorticoid hormones, and each may carry risks for susceptibility to a host of stress-related diseases. Past work implicates the medial prefrontal cortex (mPFC) in the top-down regulation of stress-related behaviors; however, it is unknown whether such changes have the capacity to buffer against the longer-lasting biological consequences associated with aversive experiences. Using the shock probe defensive burying test in rats to naturalistically measure behavioral and endocrine features of coping, we observed that the active behavioral component of stress coping is associated with increases in activity along a circuit involving the caudal mPFC and midbrain dorsolateral periaqueductal gray (PAG). Optogenetic manipulations of the caudal mPFC-to-dorsolateral PAG pathway bidirectionally modulated active (escape and defensive burying) behaviors, distinct from a rostral mPFC–ventrolateral PAG circuit that instead limited passive (immobility) behavior. Strikingly, under conditions that biased rats toward a passive coping response set, including exaggerated stress hormonal output and increased immobility, excitation of the caudal mPFC–dorsolateral PAG projection significantly attenuated each of these features. These results lend insight into how the brain coordinates response features to overcome passive coping and may be of importance for understanding how activated neural systems promote stress resilience.
Deafness is the most common sensory impairment, affecting approximately 5% or 430 million people worldwide as per the World Health Organization1. Aging or presbycusis is a primary cause of sensorineural hearing loss and is characterized by damage to hair cells, spiral ganglion neurons (SGNs), and the stria vascularis. These structures reside within the cochlea, which has a complex, spiral-shaped anatomy of membranous tissues suspended in fluid and surrounded by bone. These properties make it technically difficult to investigate and quantify histopathological changes. To address this need, we developed a light-sheet microscope (TSLIM) that can image and digitize the whole cochlea to facilitate the study of structure-function relationships in the inner ear. Well-aligned serial sections of the whole cochlea result in a stack of images for three-dimensional (3D) volume rendering and segmentation of individual structures for 3D visualization and quantitative analysis (i.e., length, width, surface, volume, and number). Cochleae require minimal processing steps (fixation, decalcification, dehydration, staining, and optical clearing), all of which are compatible with subsequent high-resolution imaging by scanning and transmission electron microscopy. Since all the tissues are present in the stacks, each structure can be assessed individually or relative to other structures. In addition, since imaging uses fluorescent probes, immunohistochemistry and ligand binding can be used to identify specific structures and their 3D volume or distribution within the cochlea. Here we used TSLIM to examine cochleae from aged mice to quantify the loss of hair cells and spiral ganglion neurons. In addition, advanced analyses (e.g., cluster analysis) were used to visualize local reductions of spiral ganglion neurons in Rosenthal's canal along its 3D volume. These approaches demonstrate TSLIM microscopy's ability to quantify structure-function relationships within and between cochleae.
We report development of a continuous scanning procedure and the use of a time delay integration (TDI) line scan camera for a light-sheet based microscope called a thin-sheet laser imaging microscope (TSLIM). TSLIM is an optimized version of a light-sheet fluorescent microscope that previously used a start/stop scanning procedure to move the specimen through the thinnest portion of a light-sheet and stitched the image columns together to produce a well-focused composite image. In this paper, hardware and software enhancements to TSLIM are described that allow for dual sided, dual illumination lasers, and continuous scanning of the specimen using either a full-frame CCD camera and a TDI line scan camera. These enhancements provided a ~70% reduction in the time required for composite image generation and a ~63% reduction in photobleaching of the specimen compared to the start/stop procedure.
The bed nuclei of the stria terminalis (BST) are critically important for integrating stress-related signals between the limbic forebrain and hypothalamo-pituitary-adrenal (HPA) effector neurons in the paraventricular hypothalamus (PVH). Nevertheless, the circuitry underlying BST control over the stress axis and its role in depression-related behaviors has remained obscure. Utilizing optogenetic approaches in rats, we have identified a novel role for the anteroventral subdivision of BST in the coordinated inhibition of both HPA output and passive coping behaviors during acute inescapable (tail suspension, TS) stress. Follow-up experiments probed axonal pathways emanating from the anteroventral BST which accounted for separable endocrine and behavioral functions subserved by this cell group. The PVH and ventrolateral periaqueductal gray were recipients of GABAergic outputs from the anteroventral BST that were necessary to restrain stress-induced HPA activation and passive coping behavior, respectively, during TS and forced swim tests. In contrast to other BST subdivisions implicated in anxiety-like responses, these results direct attention to the anteroventral BST as a nodal point in a stress-modulatory network for coordinating neuroendocrine and behavioral coping responses, wherein impairment could account for core features of stress-related mood disorders.Dysregulation of the neural pathways modulating stress-adaptive behaviors is implicated in stress-related psychiatric illness. While aversive situations activate a network of limbic forebrain regions thought to mediate such changes, little is known about how this information is integrated to orchestrate complex stress responses. Here we identify novel roles for the anteroventral bed nuclei of the stria terminalis in inhibiting both stress hormone output and passive coping behavior via divergent projections to regions of the hypothalamus and midbrain. Inhibition of these projections produced features observed with rodent models of depression, namely stress hormone hypersecretion and increased passive coping behavior, suggesting that dysfunction in these networks may contribute to expression of pathological changes in stress-related disorders.
We report replacement of one side of a static illumination, dual sided, thin-sheet laser imaging microscope (TSLIM) with an intensity modulated laser scanner in order to implement structured illumination (SI) and HiLo image demodulation techniques for background rejection. The new system is equipped with one static and one scanned light-sheet and is called a scanning thin-sheet laser imaging microscope (sTSLIM). It is an optimized version of a light-sheet fluorescent microscope that is designed to image large specimens (<15 mm in diameter). In this paper we describe the hardware and software modifications to TSLIM that allow for static and uniform light-sheet illumination with SI and HiLo image demodulation. The static light-sheet has a thickness of 3.2 µm; whereas, the scanned side has a light-sheet thickness of 4.2 µm. The scanned side images specimens with subcellular resolution (<1 µm lateral and <4 µm axial resolution) with a size up to 15 mm. SI and HiLo produce superior contrast compared to both the uniform static and scanned light-sheets. HiLo contrast was greater than SI and is faster and more robust than SI because as it produces images in two-thirds of the time and exhibits fewer intensity streaking artifacts.
