SfN 2014 Poster: Layer-specific differences in the mouse auditory corticocollicular pathway: an anatomical study

The auditory corticocollicular (CC) projection has recently garnered much attention due to its ability to alter response properties of cells in the inferior colliculus (IC). However, the basic anatomical organization of this pathway still remains poorly understood. CC cells emanate from two distinct bands of the auditory cortex – layer 5 and deep layer 6 – and differ in their firing properties and cellular morphology. In the present study, we sought to characterize potential anatomical differences between layer 5 and layer 6 CC cells using retrograde and anterograde tract-tracing techniques. We injected fluorogold, a retrograde tracer, into the IC of the mouse and used Neurolucida to create 3-D reconstructions of the cellular distribution of CC cells in layer 5 and 6 of the auditory cortex (AC). Reconstructions were aligned with acoustically-driven response maps obtained with transcranial flavoprotein autofluorescence imaging. We found heterogeneity in the distributions of the two layers, such that there exists a rostro-ventral area of the AC in which layer 6 corticocollicular cells were more dominant than layer 5 corticocollicular cells. To investigate potential differences in terminal size and projection patterns between layer 5 and layer 6 CC neurons, we injected dextran amine anterograde tracers into either layer 5 or layer 6 of the AC of mice. We found projections from both layer 5 and layer 6 in all subdivisions of the IC. On average, layer 5 axons were thicker than layer 6 axons and their terminals were larger and had a wider distribution of lengths than layer 6 terminals. These data further suggest that the layer 5 and layer 6 CC projections differ in their basic organization and, therefore, could serve distinct functions in auditory processing.Ope

Layer 5 and 6 neurons projecting to the inferior colliculus comprise two distinct and heterogeneous populations in the cortex

Top-down modulation is a powerful mechanism by which the brain can disambiguate signals arriving at the sensory periphery, and descending projections are believed to be an important anatomical substrate by which this modulation may occur. One of such projections - the corticocollicular projection - has recently garnered much attention due to its potential to alter response properties of cells in the inferior colliculus (IC). However, the anatomical organization of this pathway remains poorly understood. The corticocollicular neurons emanate from two distinct bands of the auditory cortex - layer 5 and deep layer 6 - and differ in their morphology and biophysical properties. The current mouse study from our laboratory demonstrates significant heterogeneity in the global distributions of layer 5 and 6 corticocollicular neurons, with layer 6 generally covering a broader area of the cortex than layer 5. As confirmed by more detailed analysis of serial reconstructions obtained in Neurolucida, we found that layer 6 cellular distribution is centered more ventrally and anteriorly than layer 5, also forming a rostro-ventral area in the cortex consisting only of layer 6 cells. Combining in vivo imaging in GCaMP mice, followed by a retrograde tracer injection and post-hoc anatomical reconstructions, we found the rostro-ventral area of layer 6 cells to be acoustically irresponsive to pure tones, noise or species specific mouse calls. Further small injections of an anterograde tracer (BDA) or retrograde tracer (CTb) into this area revealed its connections with the amygdala and a number of subcortical structures, including paralaminar thalamic nuclei. These data extend previous findings that suggest that layer 5 and layer 6 corticocollicular projections have different organizations and, presumably, different roles in modifying inferior colliculus function.NIDCD R01 DC013073 02Ope

Layer 5 and 6 auditory corticocollicular neurons are differentially distributed with respect to their subcortical targets in the mouse

The auditory corticocollicular projection has recently garnered much attention due to its ability to alter response properties of cells in the inferior colliculus. However, the basic anatomical organization of this pathway remains poorly understood. Corticocollicular neurons emanate from two distinct bands of the auditory cortex – layer 5 and deep layer 6 – and differ in their firing properties and cellular morphology. In addition, preliminary results from our laboratory in mouse demonstrate significant heterogeneity in the global distributions of layer 5 and 6 corticocollicular projections, with layer 6 cells spanning a broader region of the auditory cortex, extending more anteriorly and ventrally than layer 5, while layer 5 neurons are more concentrated in the primary auditory cortex, as confirmed by parvalbumin and SMI32 immunoreactivity. To further characterize the differences within the corticocollicular system, we ipsilaterally injected two retrograde tracers Cholera toxin B and Fluorogold into the inferior colliculus and the medial geniculate body, respectively. A subset of layer 5 corticothalamic neurons were also found to project to the inferior colliculus, while layer 6 corticocollicular neurons were found in a band that was distinct from layer 6 corticothalamic neurons. These data extend previous findings that suggest that layer 5 and layer 6 corticocollicular projections have different organizations and, presumably, different roles in modifying inferior colliculus function.NIDCD R01 DC013073 02Ope

An Introduction to In Vitro Slice Approaches for the Study of Neuronal Circuitry

Abstract The acute slice preparation can be a powerful tool to study brain networks that would otherwise be difficult to manipulate at the synaptic and cellular levels. In the first part of this chapter, we discuss the specific challenges of preparing brain slices to study neural networks, and we review solutions to overcome problems that can be faced during slice preparation and maintenance. In addition, we describe slice preparations that preserve the connectivity between multiple brain areas, such as hippocampal and thalamocortical slices. In the second part, we introduce several techniques that can be used to stimulate specific cells or networks in acute slices. We begin by reviewing methods for electrical stimulation, glutamate-based stimulation, and optogenetic stimulation. An additional procedure that combines the use of laser photostimulation with flavoprotein autofluorescence is also presented. We discuss advantages and disadvantages of these methods for neural network investigation in the acute slice preparation

Expert system model for educational personnel selection

Se presenta, en este artículo, un modelo de sistema experto para la selección de personal docente universitario. Esta labor no es una tarea trivial, debido a la subjetividad que puede presentarse en su evaluación. Este proceso se puede complementar usando un sistema de apoyo a la toma de decisiones. El sistema desarrollado se dividió en cuatro fases: toma de requisitos, diseño, implementación y puesta en marcha. Con el prototipo software, se logró modelar el conocimiento específico del experto en recursos humanos, lo que permitió obtener una recomendación sobre el tipo de contrato al que puede aspirar un docente universitario, dependiendo de su perfil profesional.The staff selection is a difficult task due to the subjectivity that the evaluation means. This process can be complemented using a system to support decision. This paper presents the implementation of an expert system to systematize the selection process of professors. The management of software development is divided into 4 parts: requirements, design, implementation and commissioning. The proposed system models a specific knowledge through relationships between variables evidence and objective

High-level synthesis design of scalable ultrafast ultrasound beamformer with single FPGA

Ultrafast ultrasound imaging is essential for advanced ultrasound imaging techniques such as ultrasound localization microscopy (ULM) and functional ultrasound (fUS). Current ultrafast ultrasound imaging is challenged by the ultrahigh data bandwidth associated with the radio frequency (RF) signal, and by the latency of the computationally expensive beamforming process. As such, continuous ultrafast data acquisition and beamforming remain elusive with existing software beamformers based on CPUs or GPUs. To address these challenges, the proposed work introduces a novel method of implementing an ultrafast ultrasound beamformer specifically for ultrafast plane wave imaging (PWI) on a field programmable gate array (FPGA) by using high-level synthesis. A parallelized implementation of the beamformer on a single FPGA was proposed by 1) utilizing a delay compression technique to reduce the delay profile size, which enables both run-time pre-calculated delay profile loading from external memory and delay reuse 2) vectorizing channel data fetching which is enabled by delay reuse, and 3) using fixed summing networks to reduce consumption of logic resources. Our proposed method presents two unique advantages over current FPGA beamformers: 1) high scalability that allows fast adaptation to different FPGA resources and beamforming speed demands by using Xilinx High-Level Synthesis as the development tool, and 2) allow a compact form factor design by using a single FPGA to complete the beamforming instead of multiple FPGAs. With the proposed method, a sustainable average beamforming rate of 4.83 G samples/second in terms of input raw RF sample was achieved. The resulting image quality of the proposed beamformer was compared with the software beamformer on the Verasonics Vantage system for both phantom imaging and in vivo imaging of a mouse brain

Accelerated in vivo proliferation of memory phenotype CD4+ T-cells in human HIV-1 infection irrespective of viral chemokine co-receptor tropism.

CD4(+) T-cell loss is the hallmark of HIV-1 infection. CD4 counts fall more rapidly in advanced disease when CCR5-tropic viral strains tend to be replaced by X4-tropic viruses. We hypothesized: (i) that the early dominance of CCR5-tropic viruses results from faster turnover rates of CCR5(+) cells, and (ii) that X4-tropic strains exert greater pathogenicity by preferentially increasing turnover rates within the CXCR4(+) compartment. To test these hypotheses we measured in vivo turnover rates of CD4(+) T-cell subpopulations sorted by chemokine receptor expression, using in vivo deuterium-glucose labeling. Deuterium enrichment was modeled to derive in vivo proliferation (p) and disappearance (d*) rates which were related to viral tropism data. 13 healthy controls and 13 treatment-naive HIV-1-infected subjects (CD4 143-569 cells/ul) participated. CCR5-expression defined a CD4(+) subpopulation of predominantly CD45R0(+) memory cells with accelerated in vivo proliferation (p = 2.50 vs 1.60%/d, CCR5(+) vs CCR5(-); healthy controls; P<0.01). Conversely, CXCR4 expression defined CD4(+) T-cells (predominantly CD45RA(+) naive cells) with low turnover rates. The dominant effect of HIV infection was accelerated turnover of CCR5(+)CD45R0(+)CD4(+) memory T-cells (p = 5.16 vs 2.50%/d, HIV vs controls; P<0.05), naïve cells being relatively unaffected. Similar patterns were observed whether the dominant circulating HIV-1 strain was R5-tropic (n = 9) or X4-tropic (n = 4). Although numbers were small, X4-tropic viruses did not appear to specifically drive turnover of CXCR4-expressing cells (p = 0.54 vs 0.72 vs 0.44%/d in control, R5-tropic, and X4-tropic groups respectively). Our data are most consistent with models in which CD4(+) T-cell loss is primarily driven by non-specific immune activation

Deciphering the Code for Retroviral Integration Target Site Selection

Upon cell invasion, retroviruses generate a DNA copy of their RNA genome and integrate retroviral cDNA within host chromosomal DNA. Integration occurs throughout the host cell genome, but target site selection is not random. Each subgroup of retrovirus is distinguished from the others by attraction to particular features on chromosomes. Despite extensive efforts to identify host factors that interact with retrovirion components or chromosome features predictive of integration, little is known about how integration sites are selected. We attempted to identify markers predictive of retroviral integration by exploiting Precision-Recall methods for extracting information from highly skewed datasets to derive robust and discriminating measures of association. ChIPSeq datasets for more than 60 factors were compared with 14 retroviral integration datasets. When compared with MLV, PERV or XMRV integration sites, strong association was observed with STAT1, acetylation of H3 and H4 at several positions, and methylation of H2AZ, H3K4, and K9. By combining peaks from ChIPSeq datasets, a supermarker was identified that localized within 2 kB of 75% of MLV proviruses and detected differences in integration preferences among different cell types. The supermarker predicted the likelihood of integration within specific chromosomal regions in a cell-type specific manner, yielding probabilities for integration into proto-oncogene LMO2 identical to experimentally determined values. The supermarker thus identifies chromosomal features highly favored for retroviral integration, provides clues to the mechanism by which retrovirus integration sites are selected, and offers a tool for predicting cell-type specific proto-oncogene activation by retroviruses

Identifying associations between diabetes and acute respiratory distress syndrome in patients with acute hypoxemic respiratory failure: an analysis of the LUNG SAFE database

Background: Diabetes mellitus is a common co-existing disease in the critically ill. Diabetes mellitus may reduce the risk of acute respiratory distress syndrome (ARDS), but data from previous studies are conflicting. The objective of this study was to evaluate associations between pre-existing diabetes mellitus and ARDS in critically ill patients with acute hypoxemic respiratory failure (AHRF). Methods: An ancillary analysis of a global, multi-centre prospective observational study (LUNG SAFE) was undertaken. LUNG SAFE evaluated all patients admitted to an intensive care unit (ICU) over a 4-week period, that required mechanical ventilation and met AHRF criteria. Patients who had their AHRF fully explained by cardiac failure were excluded. Important clinical characteristics were included in a stepwise selection approach (forward and backward selection combined with a significance level of 0.05) to identify a set of independent variables associated with having ARDS at any time, developing ARDS (defined as ARDS occurring after day 2 from meeting AHRF criteria) and with hospital mortality. Furthermore, propensity score analysis was undertaken to account for the differences in baseline characteristics between patients with and without diabetes mellitus, and the association between diabetes mellitus and outcomes of interest was assessed on matched samples. Results: Of the 4107 patients with AHRF included in this study, 3022 (73.6%) patients fulfilled ARDS criteria at admission or developed ARDS during their ICU stay. Diabetes mellitus was a pre-existing co-morbidity in 913 patients (22.2% of patients with AHRF). In multivariable analysis, there was no association between diabetes mellitus and having ARDS (OR 0.93 (0.78-1.11); p = 0.39), developing ARDS late (OR 0.79 (0.54-1.15); p = 0.22), or hospital mortality in patients with ARDS (1.15 (0.93-1.42); p = 0.19). In a matched sample of patients, there was no association between diabetes mellitus and outcomes of interest. Conclusions: In a large, global observational study of patients with AHRF, no association was found between diabetes mellitus and having ARDS, developing ARDS, or outcomes from ARDS. Trial registration: NCT02010073. Registered on 12 December 2013