122 research outputs found

    MULTIMODAL ASSESSMENT OF CETACEAN CENTRAL NERVOUS AUDITORY PATHWAYS WITH EMPHASIS ON FORENSIC DIAGNOSTICS OF ACOUSTIC TRAUMA

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    Cetaceans encompass some of the world’s most enigmatic species, with one of their greatest adaptations to the marine environment being the ability to “see” by hearing. Their anatomy and behavior are fine-tuned to emit and respond to underwater sounds, which is why anthropogenic noise pollution is likely to affect them negatively. There are many effects of noise on living organisms, and while knowledge on their entire palette and interplay remain incomplete, evidence for insults ranging from acoustic trauma over behavioral changes, to masking and stress, is accumulating. Humans are subject to peak interest in terms of medical research on noise-induced hearing loss. As major health concerns can be expected across species, addressing this problem in free-ranging cetacean populations will lead to a more sustainable management of marine ecosystems, more effective and balanced policies, and successes in conservation. While progress has been made in behavioral monitoring, electrophysiological hearing assessments and post-mortem examination of the inner ear of cetaceans, but very little is known about the neurochemical baseline and neuropathology of their central auditory pathways. In the present work, we reviewed the known effects of sound on cetaceans in both wild and managed settings and explored the value of animal models of neurodegenerative disease. We began by evaluating a row of antibodies associated with neurodegeneration in a more readily available species, the dog, where acute neurological insult could be derived from clinical history. We then set out to systematically validate a key panel of protein biomarkers for the assessment of similar neurodegenerative processes of the cetacean central nervous system. For this, we developed protocols to adequately sample cetacean auditory nuclei, optimized the immunohistochemical workflow, and used Western blot and alignment of protein sequences between the antigen targeted by our antibodies and the dolphin proteome. A Histoscore was used to semi-quantitively categorize immunoreactivity patterns and dolphins by age and presence of pathology. First results indicated significant differences both between sick and healthy, and young and old animals. We then expanded our list of validated antibodies for use in the bottlenose dolphin and the techniques used to assess them in a multimodal, quantitative way. 7T-MRI and stereology were implemented to assess the neuronal, axonal, glial and fiber tract counts in the inferior colliculus and ventral cochlear nucleus of a healthy bottlenose dolphin, which created a baseline understanding of protein expression in these structures, and the influence of tissue processing. This will make a valuable comparison for when positive controls of acoustic trauma would become available. Furthermore, we explored the connectome and neuronal morphology of auditory nuclei and experimented with probe designs and machine learning algorithms to quantify structures of interest. Comparisons with pathological human brains revealed similarities in the configuration of extracellular matrix components to those of a healthy dolphin, in line with existing knowledge on the tolerance to hypoxia in these diving animals. This could have interesting implications in future investigation of the evolutionary development of marine mammal brains, as well as help diversify out-of-the-box approaches to researching human neurodegenerative disease, as is being done with hibernating species. The data and methodologies described herein contribute to the knowledge on neurochemical signature of the cetacean central nervous system. They are intended to facilitate understanding of auditory and non-auditory pathology and build an evidence-based backbone to future policies regarding noise and other form of anthropogenic threats to the marine environment.Cetaceans encompass some of the world’s most enigmatic species, with one of their greatest adaptations to the marine environment being the ability to “see” by hearing. Their anatomy and behavior are fine-tuned to emit and respond to underwater sounds, which is why anthropogenic noise pollution is likely to affect them negatively. There are many effects of noise on living organisms, and while knowledge on their entire palette and interplay remain incomplete, evidence for insults ranging from acoustic trauma over behavioral changes, to masking and stress, is accumulating. Humans are subject to peak interest in terms of medical research on noise-induced hearing loss. As major health concerns can be expected across species, addressing this problem in free-ranging cetacean populations will lead to a more sustainable management of marine ecosystems, more effective and balanced policies, and successes in conservation. While progress has been made in behavioral monitoring, electrophysiological hearing assessments and post-mortem examination of the inner ear of cetaceans, but very little is known about the neurochemical baseline and neuropathology of their central auditory pathways. In the present work, we reviewed the known effects of sound on cetaceans in both wild and managed settings and explored the value of animal models of neurodegenerative disease. We began by evaluating a row of antibodies associated with neurodegeneration in a more readily available species, the dog, where acute neurological insult could be derived from clinical history. We then set out to systematically validate a key panel of protein biomarkers for the assessment of similar neurodegenerative processes of the cetacean central nervous system. For this, we developed protocols to adequately sample cetacean auditory nuclei, optimized the immunohistochemical workflow, and used Western blot and alignment of protein sequences between the antigen targeted by our antibodies and the dolphin proteome. A Histoscore was used to semi-quantitively categorize immunoreactivity patterns and dolphins by age and presence of pathology. First results indicated significant differences both between sick and healthy, and young and old animals. We then expanded our list of validated antibodies for use in the bottlenose dolphin and the techniques used to assess them in a multimodal, quantitative way. 7T-MRI and stereology were implemented to assess the neuronal, axonal, glial and fiber tract counts in the inferior colliculus and ventral cochlear nucleus of a healthy bottlenose dolphin, which created a baseline understanding of protein expression in these structures, and the influence of tissue processing. This will make a valuable comparison for when positive controls of acoustic trauma would become available. Furthermore, we explored the connectome and neuronal morphology of auditory nuclei and experimented with probe designs and machine learning algorithms to quantify structures of interest. Comparisons with pathological human brains revealed similarities in the configuration of extracellular matrix components to those of a healthy dolphin, in line with existing knowledge on the tolerance to hypoxia in these diving animals. This could have interesting implications in future investigation of the evolutionary development of marine mammal brains, as well as help diversify out-of-the-box approaches to researching human neurodegenerative disease, as is being done with hibernating species. The data and methodologies described herein contribute to the knowledge on neurochemical signature of the cetacean central nervous system. They are intended to facilitate understanding of auditory and non-auditory pathology and build an evidence-based backbone to future policies regarding noise and other form of anthropogenic threats to the marine environment

    New advances in the neurobiological mechanisms regulating fear extinction.

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    Brain Computations and Connectivity [2nd edition]

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    This is an open access title available under the terms of a CC BY-NC-ND 4.0 International licence. It is free to read on the Oxford Academic platform and offered as a free PDF download from OUP and selected open access locations. Brain Computations and Connectivity is about how the brain works. In order to understand this, it is essential to know what is computed by different brain systems; and how the computations are performed. The aim of this book is to elucidate what is computed in different brain systems; and to describe current biologically plausible computational approaches and models of how each of these brain systems computes. Understanding the brain in this way has enormous potential for understanding ourselves better in health and in disease. Potential applications of this understanding are to the treatment of the brain in disease; and to artificial intelligence which will benefit from knowledge of how the brain performs many of its extraordinarily impressive functions. This book is pioneering in taking this approach to brain function: to consider what is computed by many of our brain systems; and how it is computed, and updates by much new evidence including the connectivity of the human brain the earlier book: Rolls (2021) Brain Computations: What and How, Oxford University Press. Brain Computations and Connectivity will be of interest to all scientists interested in brain function and how the brain works, whether they are from neuroscience, or from medical sciences including neurology and psychiatry, or from the area of computational science including machine learning and artificial intelligence, or from areas such as theoretical physics

    Cannabidiol regulation of extinction and relapse of learned fear

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    Anxiety- and trauma-related disorders are chronic debilitating mental conditions, characterized by dysregulation of aversive memory processing and its impaired suppression. Current pharmacological and exposure-based psychotherapeutic approaches often produce inadequate responses, resulting in elevated rates of relapse. Cannabidiol (CBD), the non-psychotropic constituent of Cannabis Sativa, demonstrates a promising therapeutic potential for these disorders due to its modulating effects on the expression and extinction of learned fear. In this thesis, the potential effects of systemic CBD on extinction and learned fear relapse over time were initially investigated, after developing a working protocol for spontaneous fear recovery. Rats underwent auditory fear conditioning (day 1), extinction training with CBD administered before or after the session (day 2), and drug-free tests of extinction recall (day 4) and spontaneous recovery (day 24). CBD administration before extinction training was found to acutely reduce the expression of contextual fear, without affecting auditory fear expression or extinction training. Although CBD did not affect extinction recall, it suppressed later spontaneous recovery of auditory fear. Next, the pharmacological mechanisms underlying these CBD effects were investigated by examining the potential involvement of cannabinoid 1 receptor (CB1R) or 5-hydroxytryptamine 1A receptor (5-HT1AR) signaling, molecular targets through which CBD was found to elicit fear-alleviating and anxiolytic-like effects. After performing dose-response studies with the CB1R inverse agonist AM251 and the 5-HT1AR antagonist WAY100,635, these compounds were administered in combination with CBD. However, when CBD was given alone in either study it failed to reproduce the previously observed effects, rendering it impossible to exclude the potential involvement of either transmission mechanism in mediating the effects of CBD on learned fear expression and spontaneous fear recovery. Lastly, the effects of CBD on stress-induced impairments in extinction learning triggered by recent fear conditioning were examined by using an immediate extinction deficit (IED) protocol. Rats were administered with CBD before immediate or no extinction session, and the next day subjected to a drug-free extinction recall test. CBD enhanced recall of extinction to prevent the IED phenomenon, without interfering with the consolidation of learned fear memory. Taken together, CBD induced long-term protection against fear relapse after successful extinction and alleviated stress-induced impairments in extinction learning. Because of the inability to reproduce the effects of CBD on fear relapse while investigating the involvement of CB1R or 5-HT1AR mediated signaling, this necessitates further studies to elucidate the exact pharmacological mechanisms underlying the CBD effects observed in this project. However, these findings add valuable insight into CBD’s potential as a candidate therapeutic for the management of anxiety- and trauma-related disorders

    Molecular Mechanisms of Sensorineural Hearing Loss and Development of Inner Ear Therapeutics

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    The sense of hearing is vulnerable to environmental challenges, such as exposure to noise. More than 1.5 billion people experience some decline in hearing ability during their lifetime, of whom at least 430 million will be affected by disabling hearing loss. If not identified and addressed in a timely way, hearing loss can severely reduce the quality of life at various stages. Some causes of hearing loss can be prevented, for example from occupational or leisure noise. The World Health Organization estimates that more than 1 billion young people put themselves at risk of permanent hearing loss by listening to loud music over long periods of time. Mitigating such risks through public health action is essential to reduce the impact of hearing loss in the community. The etiology of sensorineural hearing loss is complex and multifactorial, arising from congenital and acquired causes. This book highlights the diverse range of approaches to sensorineural hearing loss, from designing new animal models of age-related hearing loss, to the use of microRNAs as biomarkers of cochlear injury and drug repurposing for the therapy of age-related and noise-induced hearing loss. Further investigation into the underlying molecular mechanisms of sensorineural hearing loss and the integration of the novel drug, cell, and gene therapy strategies into controlled clinical studies will permit significant advances in a field where there are currently many unmet needs

    Cerebral Circulation

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    Diagnostics and diseases related to the cerebrovascular system are constantly evolving and updating. 3D augmented reality or quantification of cerebral perfusion are becoming important diagnostic tools in daily practice and the role of the cerebral venous system is being constantly revised considering new theories such as that of “the glymphatic system.” This book provides updates on models, diagnosis, and treatment of diseases of the cerebrovascular system
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