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Efficient Representation of Natural Visual Input in the Thalamus
Title
Efficient Representation of Natural Visual Input in the Thalamus.
Creator
Dastjerdi, Mohammad, Dong, Dawei, Florida Atlantic University
Abstract/Description
In this dissertat ion, the early visual system is used to explore the role of efficiency in the general organization of the nervous system. Efficient representation theory predicts that neurons dynamically change their responses to changes in the environment in order to maintain their efficiency. To directly test the predication of this theory, a computational model and a neurophysiological experiment are used. Using a computational model, we investigate the sparseness of the response of...
Show moreIn this dissertat ion, the early visual system is used to explore the role of efficiency in the general organization of the nervous system. Efficient representation theory predicts that neurons dynamically change their responses to changes in the environment in order to maintain their efficiency. To directly test the predication of this theory, a computational model and a neurophysiological experiment are used. Using a computational model, we investigate the sparseness of the response of filters at each stage of the model of the visual pathway. We find that the temporal bandpass filter and the rectification in each stage improves the efficiency of the response representation. Moreover, we find that ON/nonlagged responses carry more information than OFF/ lagged responses in signals with low signal-to-noise ratios. In the neurophysiological experiment, the response of LGN cells is measured and compared to their input from the retina in awake cats during free-viewing of natural time-varying images using quasi-intracellular recording technique. We find that the neural responses in the retina and the LGN are efficient. However, the LGN response is more efficient, sparser and less correlated than the retina's response, and it carries less information about eye movements than the retina's. As a result the LGN represents the visual world with fewer spikes. The LGN response changes with the variation of visual input. The temporal correlation of the visual input changes with saccade timing. Accordingly, the temporal receptive field of the LGN also changes in order to maintain the decorrelation of the LGN response regardless of the saccade. The retina-thalamic transmission changes during and after a saccade in order to transmit useful information to the visual cortex and decreases during a saccade in order to eliminate the variation of the visual input during a saccade. However, the transmission increases after a saccade to facilitate the transmission of new information due to the new gaze direction in the visual environment. The temporal receptive field of the LGN, derived from the efficacy of the thalamic transmission, is causal and bimodal. Such a receptive field decorrelates the visual input and improves the sparseness of the LGN response representation.
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Date Issued
2007
PURL
http://purl.flvc.org/fau/fd/FA00000851
Subject Headings
Thalamus--Physiology, Neurotransmitter receptors, Developmental neurobiology, Visual pathways
Format
Document (PDF)
Why rush growing up? A test of the cognitive immaturity hypothesis
Title
Why rush growing up? A test of the cognitive immaturity hypothesis.
Creator
Rosenberg, Justin S., Florida Atlantic University, Bjorklund, David F.
Abstract/Description
This study examined the hypothesis that cognitive immaturity may serve an adaptive purpose for children at a time in ontogeny when they are not capable of ensuring their own survival. Participants were presented pairs of scenarios of 3- and 9-year-old children expressing either immature or mature cognition. Participants were asked to select the child (immature vs. mature) which best reflected each of 11 different psychological traits that were ultimately grouped into 3 trait dimensions: cute,...
Show moreThis study examined the hypothesis that cognitive immaturity may serve an adaptive purpose for children at a time in ontogeny when they are not capable of ensuring their own survival. Participants were presented pairs of scenarios of 3- and 9-year-old children expressing either immature or mature cognition. Participants were asked to select the child (immature vs. mature) which best reflected each of 11 different psychological traits that were ultimately grouped into 3 trait dimensions: cute, deceptive, and smart. Participants received one of 6 pairs of scenarios reflecting examples of either intuitive cognition or nonintuitive cognition. Participants selected the immature child as being more cute and less deceptive than the mature child for the intuitive vignettes, but not for the nonintuitive vignettes. This pattern suggests that some forms of immature cognition do indeed bias adults to feel more favorably toward the children who express them and may foster positive parent-child relationship.
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Date Issued
2006
PURL
http://purl.flvc.org/fcla/dt/13387
Subject Headings
Developmental psychobiology, Developmental neurobiology, Child development--Research, Cognition in children, Individual differences in children, Parent and child
Format
Document (PDF)
Development of a novel assay for in vivo screening of neuromodulatory drugs and targeted disruption of cholinergic synaptic transmission in Drosophila melanogaster
Title
Development of a novel assay for in vivo screening of neuromodulatory drugs and targeted disruption of cholinergic synaptic transmission in Drosophila melanogaster.
Creator
Mejia, Monica, Charles E. Schmidt College of Science, Department of Biological Sciences
Abstract/Description
Finding novel compounds that affect neuronal or muscular function is of great interest, as they can serve as potential pharmacological agents for a variety of neurological disorders. For instance, conopeptides have been developed into powerful drugs like the painkiller PrialtTM. Most conopeptides, however, have yet to be characterized, revealing the need for a rapid and straightforward screening method. We have designed a novel bioassay, which allows for unbiased screening of biological...
Show moreFinding novel compounds that affect neuronal or muscular function is of great interest, as they can serve as potential pharmacological agents for a variety of neurological disorders. For instance, conopeptides have been developed into powerful drugs like the painkiller PrialtTM. Most conopeptides, however, have yet to be characterized, revealing the need for a rapid and straightforward screening method. We have designed a novel bioassay, which allows for unbiased screening of biological activity of compounds in vivo against numerous molecular targets on a wide variety of neurons and muscles in a rapid and straightforward manner. For this, we paired nanoinjection of compounds with electrophysiological recordings from the Giant Fiber System of Drosophila melanogaster, which mediates the escape response of the fly.
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Date Issued
2013
PURL
http://purl.flvc.org/fcla/dt/3362560
Subject Headings
Drosophila melanogaster, Genetics, Drosophila melanogaster, Life cycles, Insects, Physiology, Developmental neurobiology, Neural transmission, Cholinergic mechanisms
Format
Document (PDF)
Maternal neuroendocrine function and fetal development
Title
Maternal neuroendocrine function and fetal development.
Creator
Diego, Miguel Angel, Florida Atlantic University, Jones, Nancy Aaron
Abstract/Description
Maternal neuroendocrine function during pregnancy has been related to a number of pregnancy outcomes including less optimal fetal growth patterns. Animal models have consistently demonstrated that glucocorticoid infusions to the mother result in fetal growth restriction and norepinephrine infusions in reduced blood flow to the fetus. Similarly, human studies reveal that elevated maternal HPA axis and adrenal function (associated with stress anxiety and depression) during pregnancy is related...
Show moreMaternal neuroendocrine function during pregnancy has been related to a number of pregnancy outcomes including less optimal fetal growth patterns. Animal models have consistently demonstrated that glucocorticoid infusions to the mother result in fetal growth restriction and norepinephrine infusions in reduced blood flow to the fetus. Similarly, human studies reveal that elevated maternal HPA axis and adrenal function (associated with stress anxiety and depression) during pregnancy is related to prematurity and low birthweight. The present study examined the relationship between maternal cortisol and norepinephrine and fetal growth measures during mid-gestation. Correlation analyses revealed that both maternal psychological (daily hassles, depression and anxiety) and biochemical (cortisol and norepinephrine) variables were negatively related to fetal growth measures. Hierarchical multiple regression analyses further revealed that maternal cortisol was the best single maternal predictor of fetal growth accounting for a significant portion of the variance even after controlling for gestational age and fetal gender. Results from the structural equation model indicate that the effects of maternal psychological distress on fetal growth are mediated by maternal cortisol. Potential mechanisms of action are discussed.
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Date Issued
2004
PURL
http://purl.flvc.org/fcla/dt/12100
Subject Headings
Neuroendocrinology, Pregnancy, Fetus--Growth, Maternal-fetal exchange, Developmental psychobiology, Comparative neurobiology
Format
Document (PDF)
Theoretical and experimental studies of multisensory integration as a coupled dynamical system
Title
Theoretical and experimental studies of multisensory integration as a coupled dynamical system.
Creator
Assisi, Collins G., Florida Atlantic University, Kelso, J. A. Scott, Jirsa, Viktor K.
Abstract/Description
Perception and behavior are mediated by a widely distributed network of brain areas. Our main concern is, how do the components of the network interact in order to give us a variety of complex coordinated behavior? We first define the nodes of the network, termed functional units, as a strongly coupled ensemble of non-identical neurons and demonstrate that the dynamics of such an ensemble may be approximated by a low dimensional set of equations. The dynamics is studied in two different...
Show morePerception and behavior are mediated by a widely distributed network of brain areas. Our main concern is, how do the components of the network interact in order to give us a variety of complex coordinated behavior? We first define the nodes of the network, termed functional units, as a strongly coupled ensemble of non-identical neurons and demonstrate that the dynamics of such an ensemble may be approximated by a low dimensional set of equations. The dynamics is studied in two different contexts, sensorimotor coordination and multisensory integration. First, we treat movement coupled to the environment as a driven functional unit. Our central hypothesis is that this coupling must be minimally parametric. We demonstrate the experimental validity of this hypothesis and propose a theoretical model that explains the results of our experiment. A second example of the dynamics of functional units is evident in the domain of multisensory integration. We employ a novel rhythmic multisensory paradigm designed to capture the temporal features of multisensory integration parametrically. The relevant parameters of our experiment are the inter-onset interval between pairs of rhythmically presented stimuli and the frequency of presentation. We partition the two dimensional parameter space using subjects perception of the stimulus sequence. The general features of the partitioning are modality independent suggesting that these features depend on the coupling between the unisensory subsystems. We develop a model with coupled functional units and suggest a candidate coupling scheme. In subsequent chapters we probe the neural correlates of multisensory integration using fMRI and EEG. The results of our fMRI experiment demonstrate that multisensory integration is mediated by a network consisting of primary sensory areas, inferior parietal lobule, prefrontal areas and the posterior midbrain. Different percepts lead to the recruitment of different areas and their disengagement for other percepts. In analyzing the EEG data, we first develop a mathematical framework that allows us to differentiate between sources activated for both unisensory and multisensory stimulation from those sources activated only for multisensory stimulation. Using this methodology we show that the influences of multisensory processing may be seen at an early (40--60 ms) stage of sensory processing.
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Date Issued
2005
PURL
http://purl.flvc.org/fcla/dt/12167
Subject Headings
Intersensory effects, Perceptual-motor processes, Sensorimotor integration, Psychology, Comparative, Developmental neurobiology
Format
Document (PDF)