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(1 - 15 of 15)
- Title
- Reduced representation of neural networks.
- Creator
- Stefanescu, Roxana A., Charles E. Schmidt College of Science, Department of Physics
- Abstract/Description
-
Experimental and computational investigations addressing how various neural functions are achieved in the brain converged in recent years to a unified idea that the neural activity underlying most of the cognitive functions is distributed over large scale networks comprising various cortical and subcortical areas. Modeling approaches represent these areas and their connections using diverse models of neurocomputational units engaged in graph-like or neural field-like structures. Regardless of...
Show moreExperimental and computational investigations addressing how various neural functions are achieved in the brain converged in recent years to a unified idea that the neural activity underlying most of the cognitive functions is distributed over large scale networks comprising various cortical and subcortical areas. Modeling approaches represent these areas and their connections using diverse models of neurocomputational units engaged in graph-like or neural field-like structures. Regardless of the manner of network implementation, simulations of large scale networks have encountered significant difficulties mainly due to the time delay introduced by the long range connections. To decrease the computational effort, it is common to assume severe approximations to simplify the descriptions of the neural dynamics associated with the system's units. In this dissertation we propose an alternative framework allowing the prevention of such strong assumptions while efficiently representing th e dynamics of a complex neural network. First, we consider the dynamics of small scale networks of globally coupled non-identical excitatory and inhibitory neurons, which could realistically instantiate a neurocomputational unit. We identify the most significant dynamical features the neural population exhibits in different parametric configuration, including multi-cluster dynamics, multi-scale synchronization and oscillator death. Then, using mode decomposition techniques, we construct analytically low dimensional representations of the network dynamics and show that these reduced systems capture the dynamical features of the entire neural population. The cases of linear and synaptic coupling are discussed in detail. In chapter 5, we extend this approach for spatially extended neural networks., We consider the dynamical behavior of a neural field-like network, which incorporates many biologically realistic characteristics such as heterogeneous local and global connectivity as well as dispersion in the neural membrane excitability. We show that in this case as well, we can construct a reduced representation, which may capture well the dynamical features of the full system. The method outlined in this dissertation provides a consistent way to represent complex dynamical features of various neural networks in a computationally efficient manner.
Show less - Date Issued
- 2009
- PURL
- http://purl.flvc.org/FAU/369387
- Subject Headings
- Molecular neurobiology, Neural networks (Neurobiology), Brain, Mathematical models, Cognitive neuroscience, Recognition (Psychology)
- Format
- Document (PDF)
- 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.
Show less - Date Issued
- 2007
- PURL
- http://purl.flvc.org/fau/fd/FA00000851
- Subject Headings
- Thalamus--Physiology, Neurotransmitter receptors, Developmental neurobiology, Visual pathways
- Format
- Document (PDF)
- Title
- A COMPARISON OF TASK RELEVANT NODE IDENTIFICATION TECHNIQUES AND THEIR IMPACT ON NETWORK INFERENCES: GROUP-AGGREGATED, SUBJECT-SPECIFIC, AND VOXEL WISE APPROACHES.
- Creator
- Falco, Dimitri, Bressler, Steven L., Florida Atlantic University, Center for Complex Systems and Brain Sciences, Charles E. Schmidt College of Science
- Abstract/Description
-
The dissertation discusses various node identification techniques as well as their downstream effects on network characteristics using task-activated fMRI data from two working memory paradigms: a verbal n-back task and a visual n-back task. The three node identification techniques examined within this work include: a group-aggregated approach, a subject-specific approach, and a voxel wise approach. The first chapters highlight crucial differences between group-aggregated and subject-specific...
Show moreThe dissertation discusses various node identification techniques as well as their downstream effects on network characteristics using task-activated fMRI data from two working memory paradigms: a verbal n-back task and a visual n-back task. The three node identification techniques examined within this work include: a group-aggregated approach, a subject-specific approach, and a voxel wise approach. The first chapters highlight crucial differences between group-aggregated and subject-specific methods of isolating nodes prior to undirected functional connectivity analysis. Results show that the two techniques yield significantly different network interactions and local network characteristics, despite having their network nodes restricted to the same anatomical regions. Prior to the introduction of the third technique, a chapter is dedicated to explaining the differences between a priori approaches (like the previously introduced group-aggregated and subject-specific techniques) and no a priori approaches (like the voxel wise approach). The chapter also discusses two ways to aggregate signal for node representation within a network: using the signal from a single voxel or aggregating signal across a group of neighboring voxels. Subsequently, a chapter is dedicated to introducing a novel processing pipeline which uses a data driven voxel wise approach to identify network nodes. The novel pipeline defines nodes using spatial temporal features generated by a deep learning algorithm and is validated by an analysis showing that the isolated nodes are condition and subject specific. The dissertation concludes by summarizing the main takeaways from each of the three analyses as well as highlighting the advantages and disadvantages of each of the three node identification techniques.
Show less - Date Issued
- 2020
- PURL
- http://purl.flvc.org/fau/fd/FA00013553
- Subject Headings
- Functional magnetic resonance imaging, Brain mapping, Working memory, Neural networks (Neurobiology), Neuroimaging--methods
- Format
- Document (PDF)
- 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.
Show less - 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)
- Title
- Functional roles of L1-Cam/Neuroglian in the nervous system of Drosophila Melanogaster.
- Creator
- Kudumala, Sirisha, Godenschwege, Tanja A., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Biological Sciences
- Abstract/Description
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Neuronal cell adhesion molecules of L1 family play a critical role in proper nervous system development. Various mutations on human L1-CAM that lead to severe neurodevelopmental disorders like retardation, spasticity etc. termed under L1 syndrome. The vertebrr their roles in axon pathfinding, neurite extension and cell migration, howeverate L1CAM and its homolog in Drosophila, neuroglian (nrg) have been well studied fo, much less is known about the mechanisms by which they fine tune synaptic...
Show moreNeuronal cell adhesion molecules of L1 family play a critical role in proper nervous system development. Various mutations on human L1-CAM that lead to severe neurodevelopmental disorders like retardation, spasticity etc. termed under L1 syndrome. The vertebrr their roles in axon pathfinding, neurite extension and cell migration, howeverate L1CAM and its homolog in Drosophila, neuroglian (nrg) have been well studied fo, much less is known about the mechanisms by which they fine tune synaptic connectivity to control the development and maintenance of synaptic connections within neuronal circuits. Here we characterized the essential role of nrg in regulating synaptic structure and function in vivo in a well characterized Drosophila central synapse model neuron, the Giant Fiber (GF) system. Previous studies from our lab revealed that the phosphorylation status of the tyrosine in the Ankyrin binding FIGQY motif in the intracellular domain of Nrg iscrucial for synapse formation of the GF to Tergo-Trochanteral Motor neuron (TTMn) synapse in the GF circuit. The present work provided us with novel insights into the role of Nrg-Ank interaction in regulating Nrg function during synapse formation and maintenance. By utilizing a sophisticated Pacman based genomic rescue strategy we have shown that dynamic regulation of the Neuroglian–Ankyrin interaction is required to coordinate transsynaptic development in the GF–TTMn synapse. In contrast, the strength of Ankyrin binding directly controls the balance between synapse formation and maintenance at the NMJ. Human L1 pathological mutations affect different biological processes distinctively and thus their proper characterization in vivo is essential to understand L1CAM function. By utilizing nrg14;P[nrg180ΔFIGQY] mutants that have exclusive synaptic defects and the previously characterized nrg849 allele that affected both GF guidance and synaptic function, we were able to analyze pathological L1CAM missense mutations with respect to their effects on guidance and synapse formation in vivo. We found that the human pathological H210Q, R184Q and Y1070C, but not the E309K and L120V L1CAM mutations affect outside-in signaling via the FIGQY Ankyrin binding domain which is required for synapse formation and not for axon guidance while L1CAM homophilic binding and signaling via the ERM motif is essential for axon guidance in Drosophila.
Show less - Date Issued
- 2014
- PURL
- http://purl.flvc.org/fau/fd/FA00004131, http://purl.flvc.org/fau/fd/FA00004131
- Subject Headings
- Cell adhesion molecules, Cellular signal transduction, Cognitive neuroscience, Cognitive neuroscience, Drosophila melanogaster, Molecular neurobiology
- Format
- Document (PDF)
- Title
- The "Stop-It anti-fidgeting device.
- Creator
- Barnard, Scott A., College of Engineering and Computer Science, Department of Computer and Electrical Engineering and Computer Science
- Abstract/Description
-
Fidgeting and otherwise constant movements in individuals can be beneficial in those who suffer from Attention Deficit/Hyperactivity Disorder or Generalized Anxiety Disorder as well as others. However this constant movement can also be a distraction to others as well as protrude an air of no self confidence. It is the drawbacks from these actions that we wish to address. By developing an intelligent system that can detect these motions and alert the user, it will allow the wearer of the...
Show moreFidgeting and otherwise constant movements in individuals can be beneficial in those who suffer from Attention Deficit/Hyperactivity Disorder or Generalized Anxiety Disorder as well as others. However this constant movement can also be a distraction to others as well as protrude an air of no self confidence. It is the drawbacks from these actions that we wish to address. By developing an intelligent system that can detect these motions and alert the user, it will allow the wearer of the device to self correct. It is in this self control that one may exhibit more confidence or simply reduce the level of irritation experienced by those in the immediate vicinity. We have designed and built a low cost, mobile, lightweight, untethered, wearable prototype device. It will detect these actions and deliver user selectable biofeedback through a light emitting diode, buzzer, vibromotor or an electric shock to allow for self control.
Show less - Date Issued
- 2009
- PURL
- http://purl.flvc.org/FAU/368612
- Subject Headings
- Restless legs syndrome, Treatment, Technological innovations, Agitation (Psychology), Biomedical engineering, Neural networks (Neurobiology)
- Format
- Document (PDF)
- Title
- Potential therapies and neuroprotective cascades in anoxia tolerant freshwater turtle Trachemys scripta ellegans.
- Creator
- Nayak, Gauri., Charles E. Schmidt College of Science, Department of Biomedical Science
- Abstract/Description
-
Mammalian neurons exhibit extreme sensitivity to oxygen deprivation and undergo rapid and irreversible degeneration when oxygen supply is curtailed. Though several neuroprotective pathways are activated during oxygen deprivation, their analyses are masked by the complex series of pathological events which are triggered simultaneously. Such events can be analyzed in the anoxia tolerant fresh water turtle, which can inherently survive the conditions of oxygen deprivation and post-anoxic...
Show moreMammalian neurons exhibit extreme sensitivity to oxygen deprivation and undergo rapid and irreversible degeneration when oxygen supply is curtailed. Though several neuroprotective pathways are activated during oxygen deprivation, their analyses are masked by the complex series of pathological events which are triggered simultaneously. Such events can be analyzed in the anoxia tolerant fresh water turtle, which can inherently survive the conditions of oxygen deprivation and post-anoxic reoxygenation without brain damage. It is likely in such a model that modulation of a particular molecular pathway is adaptive rather than pathological. The major objective behind this study was to analyze the intracellular signaling pathways mediating the protective effects of adenosine, a potential neuromodulator, and its effect on cell survival by influencing the key prosurvival proteins that prevent apoptosis. In vivo and in vitro studies have shown that adenosine acts as a neuroprotective metabolite and its action can be duplicated or abrogated using specific agonist and antagonists. Stimulating the adenosine receptors using selective A1 receptor agonist N6-cyclopentyladenosine (CPA) activated the presumed prosurvival ERK and P13-K/AKT cascade promoting cell survival, and suppression of the receptor using the selective antagonist DPCPX (8- cyclopentyl-1,3-dipropylxanthine) activated the prodeath JNK and P38 pathways. The complex regulation of the MAPK's/AKT signaling cascades was also analyzed using their specific inhibitors. The inhibiton of the ERK and AKT pathway increased cell death, indicating a prosurvival role, whereas inhibiton of the JNK and p38 pathway increased cell survival in this model. In vitro studies have also shown a high Bcl-2/BAX ratio during anoxia and reoxygenation, indicating a strong resistance to cell death via apoptosis., Silencing of the anti-apoptotic Bcl-2 gene using specific siRNA upregulated levels of prodeath BAX, thus altering the Bcl-2/BAX ratio and elevating cleaved Caspase-3 levels leading to increased cell death. Another promising neuroprotective target which we analyzed was Neuroglobin, which was induced during oxygen crisis and silencing this gene indicated that its plays a major role in modulation of ROS. This study strongly emphasizes the advantages of an alternate animal model in elucidating neuroprotective mechanisms and revealing novel therapeutic targets which could eventually help clinicians to design new stroke therapies based on naturally tolerant organisms.
Show less - Date Issued
- 2009
- PURL
- http://purl.flvc.org/FAU/186762
- Subject Headings
- Turtles, Physiology, Adenosine, Receptors, Cellular signal transduction, Molecular neurobiology, Apoptosis, Research, Cellular control mechanisms
- Format
- Document (PDF)
- Title
- The neural correlates of endogenously cued covert visuospatial attentional shifting in the cue-target interval: an electroencephalographic study.
- Creator
- Modestino, Edward Justin., Charles E. Schmidt College of Science, Center for Complex Systems and Brain Sciences
- Abstract/Description
-
This study investigated electroencephalographic differences related to cue (central left- or right-directed arrows) in a covert endogenous visual spatial attention task patterned after that of Hopf and Mangun (2000). This was done with the intent of defining the timing of components in relation to cognitive processes within the cue-target interval. Multiple techniques were employed to do this. Event-related potentials (ERPs) were examined using Independent Component Analysis. This revealed a...
Show moreThis study investigated electroencephalographic differences related to cue (central left- or right-directed arrows) in a covert endogenous visual spatial attention task patterned after that of Hopf and Mangun (2000). This was done with the intent of defining the timing of components in relation to cognitive processes within the cue-target interval. Multiple techniques were employed to do this. Event-related potentials (ERPs) were examined using Independent Component Analysis. This revealed a significant N1, between 100:200 ms post-cue, greater contralateral to the cue. Difference wave ERPs, left minus right cue-locked data, divulged significant early directing attention negativity (EDAN) at 200:400 ms post-cue in the right posterior which reversed polarity in the left posterior. Temporal spectral evolution (TSE) analysis of the alpha band revealed three stages, (1) high bilateral alpha precue to 120 ms post-cue, (2) an event related desynchronization (ERD) from approximately 120 ms: 500 ms post-cue, and (3) an event related synchronization (ERS) rebound, 500: 900 ms post-cue, where alpha amplitude, a measure of activity, was highest contralateral to the ignored hemifield and lower contralateral to the attended hemifield. Using a combination of all of these components and scientific literature in this field, it is possible to plot out the time course of the cognitive events and their neural correlates.
Show less - Date Issued
- 2009
- PURL
- http://purl.flvc.org/FAU/369199
- Subject Headings
- Brain mapping, Neural networks (Neurobiology), Cognitive neuroscience, Recognition (Psychology), Cognition, Research, Methodology
- Format
- Document (PDF)
- Title
- Molecular mechanisms of neuroprotection in the anoxia tolerant freshwater turtle.
- Creator
- Kesaraju, Shailaja., Charles E. Schmidt College of Science, Department of Biological Sciences
- Abstract/Description
-
Cardiac ischemia, stroke and some neurodegenerative disorders are all characterized by cell damage and death due to low oxygen levels. Comparative studies show that anoxia tolerant model systems present a unique opportunity to study "survival" instead of death in the complete absence of oxygen. The freshwater turtle (Trachemys scripta elegans) is unique in its ability to survive total oxygen deprivation for hours to days, as well as reoxygenation insult after anoxia. The broad objective of...
Show moreCardiac ischemia, stroke and some neurodegenerative disorders are all characterized by cell damage and death due to low oxygen levels. Comparative studies show that anoxia tolerant model systems present a unique opportunity to study "survival" instead of death in the complete absence of oxygen. The freshwater turtle (Trachemys scripta elegans) is unique in its ability to survive total oxygen deprivation for hours to days, as well as reoxygenation insult after anoxia. The broad objective of this study is to understand the modulation of key molecular mechanisms involving stress proteins and VEGF that offer neuroprotection and enhance cell survival in the freshwater turtle through anoxia and reoxygenation. In vivo analyses have shown that anoxia induced stress proteins (Hsp72, Hsp60, Grp94, Hsp60, Hsp27, HO-1); modest changes in the Bcl2/Bax ratio and no change in cleaved caspase-3 expression suggesting resistance to neuronal damage. These results were corroborated with immunohistochemical evidence indicating no damage in turtle brain when subjected to the stress of anoxia and A/R. To understand the functional role of Hsp72, siRNA against Hsp72 was utilized to knockdown Hsp72 in vitro (neuronally enriched primary cell cultures established from the turtle). Knockdown cultures were characterized by increased cell death associated with elevated ROS levels. Silencing of Hsp72 knocks down the expression of Bcl2 and increases the expression of Bax, thereby decreasing the Bcl2/Bax ratio. However, there was no increase in cytosolic Cytochrome c or the expression levels of cleaved Caspase-3. Significant increase in AIF was observed in the knockdown cultures that increase through anoxia and reoxygenation, suggesting a caspase independent pathway of cell death., Expression of the master regulator of hypoxia, HIF1 alpha and its target gene, VEGF, were analyzed at the mRNA and protein levels. The results showed no significant increase in HIF-1 alpha levels but anoxia VE GF The levels of stress proteins and VEGF returned to control levels during reoxygenation suggesting robust ROS protection mechanisms through reoxygenation. The present study thereby emphasizes Trachemys scripta as an advantageous model to examine anoxia and reoxygenation survival without major damage to the brain due to it's modulation of molecular mechanisms.
Show less - Date Issued
- 2008
- PURL
- http://purl.flvc.org/FAU/165943
- Subject Headings
- Turtles, Physiology, Anoxemia, Proteins, Chemical modification, Oxygen, Physiological effect, Molecular neurobiology
- Format
- Document (PDF)
- 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.
Show less - 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)
- Title
- The Influence of Alcohol in Chronic Cocaine Abuse: A Follow up Study.
- Creator
- Simmers, Chad Paul, Rosselli, Monica, Florida Atlantic University
- Abstract/Description
-
Background: Alcohol is the substance most commonly abused in combination with cocaine. Few studies have explored the effect of alcohol on memory recovery of chronic cocaine users. Moreover, results from these studies are often contradictory. The current study compared the effects of alcohol in a sample of cocaine dependent individuals, with and without concomitant alcohol abuse, at early and late abstinence. Methods: Verbal and non-verbal memory ability was tested in 18 cocaine only (COC) and...
Show moreBackground: Alcohol is the substance most commonly abused in combination with cocaine. Few studies have explored the effect of alcohol on memory recovery of chronic cocaine users. Moreover, results from these studies are often contradictory. The current study compared the effects of alcohol in a sample of cocaine dependent individuals, with and without concomitant alcohol abuse, at early and late abstinence. Methods: Verbal and non-verbal memory ability was tested in 18 cocaine only (COC) and 30 dual cocaine and alcohol (CA) dependent participants at 2 weeks and around 3 months after admission to a rehabilitation facility. Verbal immediate and delay memory were assessed using the Digit Span subset of the Wechsler Adult Intelligence Scale - Revised (WAIS-R) and the California Verbal Learning test (CVLT); non verbal immediate and delay memory were measured using the Benton Visual Retention Test (BVRT) and the Rey-Osterrieth Complex Figure test (ROCFT). Results: The cocaine participants exhibited a similar memory recovery profile in short term memory tasks independently of their history of alcohol abuse. However, significant group differences emerged in delayed memory tasks. On the ROCFT delayed memory test the CA group performed significantly worse than the COC group with significantly less improvement in scores during abstinence as well. The reduced score enhancement during abstinence in theCA group was also observed in the CVL T delayed memory variables. Conclusions: The present study suggests that the use of alcohol in combination with cocaine may have an effect on memory recovery with specific impact on long-term memory tasks.
Show less - Date Issued
- 2008
- PURL
- http://purl.flvc.org/fau/fd/FA00000829
- Subject Headings
- Cocaine abuse--Psychological aspects, Alcoholism--Psychological aspects, Substance abuse--Physiological aspects, Neurobiology
- Format
- Document (PDF)
- 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.
Show less - 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)
- Title
- Regulation of rapid signaling at the cone ribbon synapse via distinct pre- and postsynaptic mechanisms.
- Creator
- Rowan, Matthew JM., Charles E. Schmidt College of Science, Department of Biological Sciences
- Abstract/Description
-
Background: Light-adaptation is a multifaceted process in the retina that helps adjust the visual system to changing illumination levels. Many studies are focused on the photochemical mechanism of light-adaptation. Neural network adaptation mechanisms at the photoreceptor synapse are largely unknown. We find that large, spontaneous Excitatory Amino Acid Transporter (EAATs) activity in cone terminals may contribute to cone synaptic adaptation, specifically with respect to how these signals...
Show moreBackground: Light-adaptation is a multifaceted process in the retina that helps adjust the visual system to changing illumination levels. Many studies are focused on the photochemical mechanism of light-adaptation. Neural network adaptation mechanisms at the photoreceptor synapse are largely unknown. We find that large, spontaneous Excitatory Amino Acid Transporter (EAATs) activity in cone terminals may contribute to cone synaptic adaptation, specifically with respect to how these signals change in differing conditions of light. EAATs in neurons quickly transport glutamate from the synaptic cleft, and also elicit large thermodynamically uncoupled Cl- currents when activated. We recorded synaptic EAAT currents from cones to study glutamate-uptake events elicited by glutamate release from the local cone, and from adjacent photoreceptors. We find that cones are synaptically connected via EAATs in dark ; this synaptic connection is diminished in light-adapted cones. Methods: Whole-cell patch-clamp was performed on dark- and transiently light-adapted tiger salamander cones. Endogenous EAAT currents were recorded in cones with a short depolarization to -10mV/2ms, while spontaneous transporter currents from network cones were observed while a local cone holding at -70mV constantly. DHKA, a specific transporter inhibitor, was used to identify EAAT2 currents in the cone terminals, while TBOA identified other EAAT subtypes. GABAergic and glycinergic network inputs were always blocked with picrotoxin and strychnine. Results: Spontaneous EAAT currents were observed in cones held constantly at -70mV in dark, indicating that the cones received glutamate inputs from adjacent photoreceptors. These spontaneous EAAT currents disappeared in presence of a strong light, possibly because the light suppressed glutamate releases from the adjacent photoreceptors. The spontaneous EAAT currents were blocked with TBOA, but not DHKA, an inhibitor for EAAT2 subtype, suggesting that a, non-EAAT 2 subtype may reside in a basal or perisynaptic area of cones, with a specialized ability to bind exocytosed glutamate from adjacent cones in dark. Furthermore, these results could be artificially replicated by dual-electrode recordings from two adjacent cones. When glutamate release was elicited from one cone, the TBOA-sensitive EAAT currents were observed from the other cone. Conclusions: Cones appear to act like a meshwork, synaptically connected via glutamate transporters. Light attenuates glutamate release and diminishes the cone-cone synaptic connections. This process may act as an important network mechanism for cone light adaptation.
Show less - Date Issued
- 2011
- PURL
- http://purl.flvc.org/FAU/3337186
- Subject Headings
- Synapses, Neural transmission, VIsual perception, Presynaptic receptors, Molecular neurobiology, Glutamic acid, Neural receptors, Cellular signal transduction, Retina, Cytology
- Format
- Document (PDF)
- Title
- Why rush growing up? A test of the cognitive immaturity hypothesis.
- Creator
- Rosenberg, Justin S., Florida Atlantic University, Bjorklund, David F.
- Abstract/Description
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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.
Show less - 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)
- Title
- Fractal ion-channel behavior generates fractal firing patterns in neuronal models.
- Creator
- Liebovitch, Larry S., Lowen, Steven B., White, John A.
- Date Issued
- 1999-05
- PURL
- http://purl.flvc.org/fau/165477
- Subject Headings
- Biophysics--Research, Fractals, Neural networks (Neurobiology)--Mathematical models, Neurons--Mathematical models, Markov processes--Mathematical models, Ion channels--Mathematical models
- Format
- Document (PDF)
