Optimization of the Touchscreen-Based Visuomotor Conditional Learning Task in Mice

The translational gap between animal models and clinical trials is a longstanding, yet largely unresolved, limitation in the study of cognition. This discrepancy is largely due to the differences in how cognition is assessed in animal models compared to those in clinical populations. In the stimulus-response (S-R) learning literature, for example, the techniques used to assess the acquisition of habitual behaviour differ greatly across species, leading to poor cross-species translation and often conflicting results. As a result, we set out to optimize a S-R learning task in mice using the touchscreen-based operant technologies. Similar to human studies, this touchscreen technique encourages animals to respond to visual stimuli displayed on a touchscreen according to a specific rule. Allowing for very similar, if not identical, cognitive assays in mice and men, this technique promotes high translational potential and a high degree of standardisation. Originally developed for rats, the Visuomotor Conditional Learning (VMCL) task encourages animals to learn arbitrary associations between visual stimuli and motor responses. In naïve C57BL/6 mice, we sought to optimize VMCL task parameters to promote better and more efficient responding, identifying the length of inter-trial intervals and the limited hold period as two potential candidates. The validation of this task will provide a novel means through which to study the neural correlates of S-R learning, and its use in conjunction with fiber photometry recordings may be provided

Functional dissociation of behavioral effects from acetylcholine and glutamate released from cholinergic striatal interneurons

In the striatum, cholinergic interneurons (CINs) have the ability to release both acetylcholine and glutamate, due to the expression of the vesicular acetylcholine transporter (VAChT) and the vesicular glutamate transporter 3 (VGLUT3). However, the relationship these neurotransmitters have in the regulation of behavior is not fully understood. Here we used reward-based touchscreen tests in mice to assess the individual and combined contributions of acetylcholine/glutamate co-transmission in behavior. We found that reduced levels of the VAChT from CINs negatively impacted dopamine signalling in response to reward, and disrupted complex responses in a sequential chain of events. In contrast, diminished VGLUT3 levels had somewhat opposite effects. When mutant mice were treated with haloperidol in a cue-based task, the drug did not affect the performance of VAChT mutant mice, whereas VGLUT3 mutant mice were highly sensitive to haloperidol. In mice where both vesicular transporters were deleted from CINs, we observed altered reward-evoked dopaminergic signalling and behavioral deficits that resemble, but were worse, than those in mice with specific loss of VAChT alone. These results demonstrate that the ability to secrete two different neurotransmitters allows CINs to exert complex modulation of a wide range of behaviors

New frontiers in translational research: Touchscreens, open science, and the mouse translational research accelerator platform

© 2020 International Behavioural and Neural Genetics Society and John Wiley & Sons Ltd Many neurodegenerative and neuropsychiatric diseases and other brain disorders are accompanied by impairments in high-level cognitive functions including memory, attention, motivation, and decision-making. Despite several decades of extensive research, neuroscience is little closer to discovering new treatments. Key impediments include the absence of validated and robust cognitive assessment tools for facilitating translation from animal models to humans. In this review, we describe a state-of-the-art platform poised to overcome these impediments and improve the success of translational research, the Mouse Translational Research Accelerator Platform (MouseTRAP), which is centered on the touchscreen cognitive testing system for rodents. It integrates touchscreen-based tests of high-level cognitive assessment with state-of-the art neurotechnology to record and manipulate molecular and circuit level activity in vivo in animal models during human-relevant cognitive performance. The platform also is integrated with two Open Science platforms designed to facilitate knowledge and data-sharing practices within the rodent touchscreen community, touchscreencognition.org and mousebytes.ca. Touchscreencognition.org includes the Wall, showcasing touchscreen news and publications, the Forum, for community discussion, and Training, which includes courses, videos, SOPs, and symposia. To get started, interested researchers simply create user accounts. We describe the origins of the touchscreen testing system, the novel lines of research it has facilitated, and its increasingly widespread use in translational research, which is attributable in part to knowledge-sharing efforts over the past decade. We then identify the unique features of MouseTRAP that stand to potentially revolutionize translational research, and describe new initiatives to partner with similar platforms such as McGill\u27s M3 platform (m3platform.org)

Multisensory integration: is medial prefornetal cortex signaling relevant for the treatment of higher-order visual dysfunctions?

In the mammalian brain, information processing in sensory modalities and global mechanisms of multisensory integration facilitate perception. Emerging experimental evidence suggests that the contribution of multisensory integration to sensory perception is far more complex than previously expected. Here we revise how associative areas such as the prefrontal cortex, which receive and integrate inputs from diverse sensory modalities, can affect information processing in unisensory systems via processes of down-stream signaling. We focus our attention on the influence of the medial prefrontal cortex on the processing of information in the visual system and whether this phenomenon can be clinically used to treat higher-order visual dysfunctions. We propose that non-invasive and multisensory stimulation strategies such as environmental enrichment and/or attention-related tasks could be of clinical relevance to fight cerebral visual impairment

Functional dissociation of behavioral effects from acetylcholine and glutamate released from cholinergic striatal interneurons

International audienceIn the striatum, cholinergic interneurons (CINs) have the ability to release both acetylcholine and glutamate, due to the expression of the vesicular acetylcholine transporter (VAChT) and the vesicular glutamate transporter 3 (VGLUT3). However, the relationship these neurotransmitters have in the regulation of behavior is not fully understood. Here we used reward-based touchscreen tests in mice to assess the individual and combined contributions of acetylcholine/glutamate co-transmission in behavior. We found that reduced levels of the VAChT from CINs negatively impacted dopamine signalling in response to reward, and disrupted complex responses in a sequential chain of events. In contrast, diminished VGLUT3 levels had somewhat opposite effects. When mutant mice were treated with haloperidol in a cue-based task, the drug did not affect the performance of VAChT mutant mice, whereas VGLUT3 mutant mice were highly sensitive to haloperidol. In mice where both vesicular transporters were deleted from CINs, we observed altered reward-evoked dopaminergic signalling and behavioral deficits that resemble, but were worse, than those in mice with specific loss of VAChT alone. These results demonstrate that the ability to secrete two different neurotransmitters allows CINs to exert complex modulation of a wide range of behaviors

Informe final del proyecto: Gravedad cuántica y física de los agujeros negros

Los agujeros negros son uno de los objetos más fascinantes del Universo. Aunque a primera vista muy simples: bastan tres magnitudes para describirlos: masa, carga y momentum angular se producen un conjunto de fenómenos excepcionales para cuyo estudio se requiere del uso simultáneo de la Relatividad General, Teoría de campos y Termodinámica. Aun no se dispone de una teoría completa que permita estudiar sus regiones centrales. Hemos desarrollado en este proyecto avances hacia tal teoría que permitieron un tratamiento de dichas regiones centrales donde los agujeros negros tienen propiedades cuánticas [1,2]. Los mismos valen para agujeros negros esféricamente simétricos y, en algunos casos, con simetría axial [3,4]. También se estudió su formación [5,6] y evaporación [7,8]. En paralelo se estudiaron efectos de gravedad cuántica en el régimen opuesto de largas distancias, el cual es dominado por gravitones de baja energía. Se lograron avances en la descripción de las simetrías asintóticas que caracterizan a estos gravitones [9,10,11]. Se realizaron una quincena de publicaciones que ya han recibido más de 200 citas [1-17]. Cuatro tesis de doctorado resultaron de este Proyecto. Un review de los resultados aparecerá próximamente en el Handbook of Quantum Gravity publicado por Springer [18].Agencia Nacional de Investigación e Innovació

Basal Ganglia Dysfunction Contributes to Physical Inactivity in Obesity

Obesity is associated with physical inactivity, which exacerbates the health consequences of weight gain. However, the mechanisms that mediate this association are unknown. We hypothesized that deficits in dopamine signaling contribute to physical inactivity in obesity. To investigate this, we quantified multiple aspects of dopamine signaling in lean and obese mice. We found that D2-type receptor (D2R) binding in the striatum, but not D1-type receptor binding or dopamine levels, was reduced in obese mice. Genetically removing D2Rs from striatal medium spiny neurons was sufficient to reduce motor activity in lean mice, whereas restoring Gi signaling in these neurons increased activity in obese mice. Surprisingly, although mice with low D2Rs were less active, they were not more vulnerable to diet-induced weight gain than control mice. We conclude that deficits in striatal D2R signaling contribute to physical inactivity in obesity, but inactivity is more a consequence than a cause of obesity.Fil: Friend, Danielle M.. National Institutes of Health; Estados UnidosFil: Devarakonda, Kavya. National Institutes of Health; Estados UnidosFil: O'Neal, Timothy J.. National Institutes of Health; Estados UnidosFil: Skirzewski, Miguel. National Institutes of Health; Estados UnidosFil: Papageorgiou, Ioannis. National Institutes of Health; Estados UnidosFil: Kaplan, Alanna R.. National Institutes of Health; Estados UnidosFil: Liow, Jeih San. National Institutes of Health; Estados UnidosFil: Guo, Juen. National Institutes of Health; Estados UnidosFil: Rane, Sushil G.. National Institutes of Health; Estados UnidosFil: Rubinstein, Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Fisiología, Biología Molecular y Celular; Argentina. University of Michigan; Estados UnidosFil: Alvarez, Verónica A.. National Institutes of Health; Estados UnidosFil: Hall, Kevin D.. National Institutes of Health; Estados UnidosFil: Kravitz, Alexxai V.. National Institutes of Health; Estados Unido

Altered distribution of ATG9A and accumulation of axonal aggregates in neurons from a mouse model of AP-4 deficiency syndrome

<div><p>The hereditary spastic paraplegias (HSP) are a clinically and genetically heterogeneous group of disorders characterized by progressive lower limb spasticity. Mutations in subunits of the heterotetrameric (ε-β4-μ4-σ4) adaptor protein 4 (AP-4) complex cause an autosomal recessive form of complicated HSP referred to as “AP-4 deficiency syndrome”. In addition to lower limb spasticity, this syndrome features intellectual disability, microcephaly, seizures, thin corpus callosum and upper limb spasticity. The pathogenetic mechanism, however, remains poorly understood. Here we report the characterization of a knockout (KO) mouse for the <i>AP4E1</i> gene encoding the ε subunit of AP-4. We find that AP-4 ε KO mice exhibit a range of neurological phenotypes, including hindlimb clasping, decreased motor coordination and weak grip strength. In addition, AP-4 ε KO mice display a thin corpus callosum and axonal swellings in various areas of the brain and spinal cord. Immunohistochemical analyses show that the transmembrane autophagy-related protein 9A (ATG9A) is more concentrated in the <i>trans</i>-Golgi network (TGN) and depleted from the peripheral cytoplasm both in skin fibroblasts from patients with mutations in the μ4 subunit of AP-4 and in various neuronal types in AP-4 ε KO mice. ATG9A mislocalization is associated with increased tendency to accumulate mutant huntingtin (HTT) aggregates in the axons of AP-4 ε KO neurons. These findings indicate that the AP-4 ε KO mouse is a suitable animal model for AP-4 deficiency syndrome, and that defective mobilization of ATG9A from the TGN and impaired autophagic degradation of protein aggregates might contribute to neuroaxonal dystrophy in this disorder.</p></div

An optimized acetylcholine sensor for monitoring in vivo cholinergic activity

© 2020, The Author(s), under exclusive licence to Springer Nature America, Inc. The ability to directly measure acetylcholine (ACh) release is an essential step toward understanding its physiological function. Here we optimized the GRABACh (GPCR-activation-based ACh) sensor to achieve substantially improved sensitivity in ACh detection, as well as reduced downstream coupling to intracellular pathways. The improved version of the ACh sensor retains the subsecond response kinetics, physiologically relevant affinity and precise molecular specificity for ACh of its predecessor. Using this sensor, we revealed compartmental ACh signals in the olfactory center of transgenic flies in response to external stimuli including odor and body shock. Using fiber photometry recording and two-photon imaging, our ACh sensor also enabled sensitive detection of single-trial ACh dynamics in multiple brain regions in mice performing a variety of behaviors

Increased accumulation of mutant huntingtin aggregates and decreased mobility of autophagosomes in the axon of AP-4 ε KO hippocampal neurons.

<p>(A) Imaging of cultured hippocampal neurons from WT and AP-4 ε KO mice co-transfected with plasmids encoding aggregation-prone HTT103Q-GFP (green) and cyan fluorescent protein (CFP) together with either LC3B-mCherry (mCh) (red) (top two rows), or ATG9A-mCherry (red) (bottom row). Single-channel images are shown in inverted grayscale. Arrowheads indicate axonal aggregates containing both GFP-and mCherry-labeled proteins. Bars: 20 μm. (B) Magnified and straightened axon terminals and dendrites from WT and AP-4 ε KO neurons shown in A. (C) Quantification of the number of HTT103Q-GFP foci with LC3B-mCherry or ATG9A-mCherry per 100 μm of axon. Values are the mean ± SD from 10 neurons. **P<0.005, ***P<0.0005. Notice the increased number of axonal HTT103Q-GFP and LC3B-mCherry aggregates in KO relative to WT neurons, and the suppression of this increase by overexpression of ATG9A-mCherry. (D) Straightened 50 μm segments of axon terminals from DIV8 WT and AP-4 ε KO hippocampal neurons expressing LC3B-GFP (top) and corresponding kymographs (bottom). Vesicles moving to the right or the left of the top panel represent anterograde or retrograde movement, respectively. Lines with negative or positive slopes in the kymographs (bottom) correspond to anterograde or retrograde movement, respectively. Note the retrogradely moving LC3B-GFP vesicles in the WT axon, and the absence of moving vesicles in the AP-4 ε KO axon. (E) Quantification of the number of anterograde, retrograde and static LC3B-GFP particles in the distal axon of WT and AP-4 ε KO neurons. The number of moving and static particles is expressed as a percentage of the total number of events in each kymograph. Values are the mean ± SEM from nine WT and five AP-4 ε KO neurons. *P<0.05, **P<0.005, ***P<0.0005.</p