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Articles 1 - 13 of 13
Full-Text Articles in Life Sciences
Ultrastructural Correlates Of Axons And Synapses Belonging To Different Circuits In Ferret Primary Visual Cortex, Anjelique Sawh
Ultrastructural Correlates Of Axons And Synapses Belonging To Different Circuits In Ferret Primary Visual Cortex, Anjelique Sawh
Dissertations and Theses
The goal of this study was to determine differences in distinctive layers of mammalian primary visual cortex through analysis of their ultrastructural characteristics. Characterizing brain circuitry using 3-dimensional reconstruction of electron microscopy images, and subsequent ultrastructural analysis of axonal populations provides us with a better understanding of the connectivity of the neural circuits. By quantifying ultrastructural differences in axonal processes such as synaptic densities, types of synapses and their post-synaptic densities (PSDs), mitochondrial volumes, synaptic vesicle aggregates, dendritic targets, and bouton volumes, we aimed to understand whether differences in anatomical specializations among different cortical layers could underlie differences in function …
Neural Processing Of Semantic Content In Movies, Maximilian Nentwich
Neural Processing Of Semantic Content In Movies, Maximilian Nentwich
Dissertations and Theses
Naturalistic stimuli, such as movies, contain interacting, multimodal and semantic features and allow for free exploration through eye movements. The full extent of neural responses to features such as motion, film cuts and eye movement behavior has not been established. The main hypothesis of this thesis is that complex multimodal and semantic stimuli in naturalistic movies engage a widespread ensemble of locations across the entire brain. To address this question I analyzed simultaneous intracranial and eyetracking data from over 6,000 electrodes across 23 patients with intractable epilepsy. Responses to fast eye movements – saccades – and film cuts are widespread …
When The Brain Plays A Game: Neural Responses To Visual Dynamics During Naturalistic Visual Tasks, Jason Ki
When The Brain Plays A Game: Neural Responses To Visual Dynamics During Naturalistic Visual Tasks, Jason Ki
Dissertations and Theses
Many day-to-day tasks involve processing of complex visual information in a continuous stream. While much of our knowledge on visual processing has been established from reductionist approaches in lab-controlled settings, very little is known about the processing of complex dynamic stimuli experienced in everyday scenarios. Traditional investigations employ event-related paradigms that involve presentation of simple stimuli at select locations in visual space and discrete moments in time. In contrast, visual stimuli in real-life are highly dynamic, spatially-heterogeneous, and semantically rich. Moreover, traditional experiments impose unnatural task constraints (e.g., inhibited saccades), thus, it is unclear whether theories developed under the reductionist …
Analyzing Ultrastructural Characteristics Of Post-Synaptic Targets Of Pre-Identified Presynaptic Boutons In Layer 3 And Layer 4 Of The Ferret Primary Visual Cortex, Donia Shehab
Dissertations and Theses
The purpose of this study was to analyze the size and ultrastructural characteristics of post-synaptic elements apposed to previously characterized pre-synaptic elements in layers 3 and 4 of the primary visual cortex (PVC). We are aiming to quantify a range of values for synaptic element morphologies as well as to correlate pre- and post-synaptic elements to find a set of rules that is prevalent in the visual cortex that can also be upheld in other mammals. We hypothesize that bigger pre-synaptic elements correlate to bigger synapses and bigger post-synaptic elements. We compared these two different layers because they receive synaptic …
Cloning And Characterization Of The Vasopressin-Oxytocin Neuropeptide Signaling System In The Vocal Control System Of The Zebra Finch (Taeniopygia Guttata), Emily R. Tortora
Cloning And Characterization Of The Vasopressin-Oxytocin Neuropeptide Signaling System In The Vocal Control System Of The Zebra Finch (Taeniopygia Guttata), Emily R. Tortora
Dissertations and Theses
Vasopressin (VP) and Oxytocin (OT) are neuropeptides produced in the hypothalamus and expressed in the cerebrum and pituitary gland of the brain. Studies of VP and OT have long demonstrated their influence on social behaviors in mammals. Comparative analyses of these neuropeptides and in-depth analyses in non-mammalian species may reveal the specific mechanistic roles these hormones play in social behavioral functioning. The acquisition of complex behavioral patterns involves sensory-motor functions. How social interactions modulate sensory-motor mechanisms that promote complex behavior acquisition and maintenance can be well study in vocal learning birds. Here, in addition to reviewing the pertinent literature, I …
Lateralized Temporal Integration Properties Of The Mouse Auditory Cortex, Demetrios Neophytou
Lateralized Temporal Integration Properties Of The Mouse Auditory Cortex, Demetrios Neophytou
Dissertations and Theses
Social communication calls are fleeting, rapidly modulating signals and the ability of the auditory system to perceive such transient signals is a remarkable phenomenon. The mechanism by which the auditory cortex (ACx) is believed to be capable of processing these signals is through recurrent connectivity in the cortical circuits. Recurrent connectivity is proposed to be a possible circuit motif that aids in the processing of these transient signals. Recurrent connectivity is believed to have an effect on the temporal fidelity, the ability to follow a modulating signal, and the recurrent activity, sustained activity following stimulus offset, at the level of …
Attention Strongly Modulates Reliability Of Neural Response To Naturalistic Narrative Stimuli, Jason Ki
Attention Strongly Modulates Reliability Of Neural Response To Naturalistic Narrative Stimuli, Jason Ki
Dissertations and Theses
Attentional engagement is a major determinant of how effectively we gather information through our senses. Alongside the sheer growth in the amount and variety of information content we are presented with through modern media, there is increased variability in the degree to which we ‘absorb’ that information. Traditional research on attention has illuminated the basic principles of sensory selection to isolated features or locations, but it provides little insight into the neural underpinnings of our attentional engagement with modern naturalistic content. Here, we show in human subjects that the reliability of an individual's neural responses with respect to a larger …
Mechanisms Of Value-Biased Prioritization In Fast Sensorimotor Decision Making, Kivilcim Afacan-Seref
Mechanisms Of Value-Biased Prioritization In Fast Sensorimotor Decision Making, Kivilcim Afacan-Seref
Dissertations and Theses
In dynamic environments, split-second sensorimotor decisions must be prioritized according to potential payoffs to maximize overall rewards. The impact of relative value on deliberative perceptual judgments has been examined extensively, but relatively little is known about value-biasing mechanisms in the common situation where physical evidence is strong but the time to act is severely limited. This research examines the behavioral and electrophysiological indices of how value biases split-second perceptual decisions and the possible mechanisms underlying the process. In prominent decision models, a noisy but statistically stationary representation of sensory evidence is integrated over time to an action-triggering bound, and value-biases …
Understanding How Sequence Differences Among Glutamate Transporters Might Contribute To Their Differential Function In Glutamate Clearance In C. Elegans, Irving Estevez
Dissertations and Theses
In the nervous system, high circuit resolution requires efficient post-signaling clearance of the neurotransmitter. Glutamate-mediated neurotransmission involves the release of glutamate (Glu) into the synaptic cleft by the presynaptic cell and binding to glutamate receptors (GluR) on the postsynaptic cell, leading to activation of a signal transduction cascade. Neurotransmission is eventually terminated by Glu uptake via glutamate transporters (GluT). Inefficient Glu clearance is detrimental to precise rapid signaling, can lead to blurring of circuit resolution by inadvertent Glu spillover to nearby circuits, and may even be neurotoxic. While classical views depict synapses as insulated by glia, recent technological advances show …
Effects Of Weak Electric Fields On Long-Term Synaptic Plasticity, Gregory Kronberg
Effects Of Weak Electric Fields On Long-Term Synaptic Plasticity, Gregory Kronberg
Dissertations and Theses
Transcranial direct current stimulation (tDCS) is a technique where a weak direct electrical current is applied to the scalp with the goal of stimulating the brain. There is tremendous interest in the use of tDCS for treating brain disorders and improving brain function. However, the effects of tDCS have been highly variable across studies, leading to a debate over its efficacy. A major challenge is therefore to design tDCS protocols that yield predictable effects, which will require a better understanding of its basic mechanisms of action. One commonly discussed mechanism is that tDCS may alter synaptic plasticity, but the biophysics …
Mechanisms Of Microglia Mediated Apolipoprotien E Neurotoxicity, Pardeep Singh
Mechanisms Of Microglia Mediated Apolipoprotien E Neurotoxicity, Pardeep Singh
Dissertations and Theses
No abstract provided.
Using Fundamental Properties Of Light To Investigate Photonic Effects In Condensed Matter And Biological Tissues, Laura A. Sordillo
Using Fundamental Properties Of Light To Investigate Photonic Effects In Condensed Matter And Biological Tissues, Laura A. Sordillo
Dissertations and Theses
Light possesses characteristics such as polarization, wavelength and coherence. The interaction of light and matter, whether in a semiconductor or in a biological sample, can reveal important information about the internal properties of a system. My thesis focuses on two areas: photocarriers in gallium arsenide and biomedical optics. Varying the excitation wavelength can be used to study both biological tissue and condensed matter. I altered the excitation wavelengths to be in the longer near-infrared (NIR) optical windows, in the shortwave infrared (SWIR) range, a wavelength region previously thought to be unusable for medical imaging. With this method, I acquired high …
Defining The Relationship Between Maternal Care Behavior And Hearing Development In Wistar Rats, Jingyun Qiu
Defining The Relationship Between Maternal Care Behavior And Hearing Development In Wistar Rats, Jingyun Qiu
Dissertations and Theses
Previous studies in rodents have demonstrated the profound effects that variations in maternal care play during the postnatal development of the brain. However, much less is known about how maternal care affects hearing development. Recently, manipulations of maternal care have been investigated to accelerate hearing onset. We hypothesized that accelerated hearing development results from changes in maternal care behavior. To test this hypothesis, we used a selection model in which natural variations in maternal care were identified in a large cohort of dams by measuring the frequency of different behaviors including LG followed by selection of dams with LG scores …