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Search Results: 1 - 10 of 463394 matches for " Sam A Deadwyler "
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Facilitation of Task Performance and Removal of the Effects of Sleep Deprivation by an Ampakine (CX717) in Nonhuman Primates
Linda J. Porrino,James B. Daunais,Gary A. Rogers,Robert E. Hampson,Sam A. Deadwyler
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0030299
Abstract: The deleterious effects of prolonged sleep deprivation on behavior and cognition are a concern in modern society. Persons at risk for impaired performance and health-related issues resulting from prolonged sleep loss would benefit from agents capable of reducing these detrimental effects at the time they are sleep deprived. Agents capable of improving cognition by enhancing brain activity under normal circumstances may also have the potential to reduce the harmful or unwanted effects of sleep deprivation. The significant prevalence of excitatory α-amino-3-hydroxy-5-methyl-4-isoxazolepr?opionicacid (AMPA) glutamatergic receptors in the brain provides a basis for implementing a class of drugs that could act to alter or remove the effects of sleep deprivation. The ampakine CX717 (Cortex Pharmaceuticals), a positive allosteric modulator of AMPA receptors, was tested for its ability to enhance performance of a cognitive, delayed match-to-sample task under normal circumstances in well-trained monkeys, as well as alleviate the detrimental effects of 30–36 h of sleep deprivation. CX717 produced a dose-dependent enhancement of task performance under normal alert testing conditions. Concomitant measures of regional cerebral metabolic rates for glucose (CMRglc) during the task, utilizing positron emission tomography, revealed increased activity in prefrontal cortex, dorsal striatum, and medial temporal lobe (including hippocampus) that was significantly enhanced over normal alert conditions following administration of CX717. A single night of sleep deprivation produced severe impairments in performance in the same monkeys, accompanied by significant alterations in task-related CMRglc in these same brain regions. However, CX717 administered to sleep-deprived monkeys produced a striking removal of the behavioral impairment and returned performance to above-normal levels even though animals were sleep deprived. Consistent with this recovery, CMRglc in all but one brain region affected by sleep deprivation was also returned to the normal alert pattern by the drug. The ampakine CX717, in addition to enhancing cognitive performance under normal alert conditions, also proved effective in alleviating impairment of performance due to sleep deprivation. Therefore, the ability to activate specific brain regions under normal alert conditions and alter the deleterious effects of sleep deprivation on activity in those same regions indicate a potential role for ampakines in sustaining performance under these types of adverse conditions.
Facilitation of Task Performance and Removal of the Effects of Sleep Deprivation by an Ampakine (CX717) in Nonhuman Primates
Linda J Porrino,James B Daunais,Gary A Rogers,Robert E Hampson,Sam A Deadwyler
PLOS Biology , 2005, DOI: 10.1371/journal.pbio.0030299
Abstract: The deleterious effects of prolonged sleep deprivation on behavior and cognition are a concern in modern society. Persons at risk for impaired performance and health-related issues resulting from prolonged sleep loss would benefit from agents capable of reducing these detrimental effects at the time they are sleep deprived. Agents capable of improving cognition by enhancing brain activity under normal circumstances may also have the potential to reduce the harmful or unwanted effects of sleep deprivation. The significant prevalence of excitatory α-amino-3-hydroxy-5-methyl-4-isoxazolepr?opionicacid (AMPA) glutamatergic receptors in the brain provides a basis for implementing a class of drugs that could act to alter or remove the effects of sleep deprivation. The ampakine CX717 (Cortex Pharmaceuticals), a positive allosteric modulator of AMPA receptors, was tested for its ability to enhance performance of a cognitive, delayed match-to-sample task under normal circumstances in well-trained monkeys, as well as alleviate the detrimental effects of 30–36 h of sleep deprivation. CX717 produced a dose-dependent enhancement of task performance under normal alert testing conditions. Concomitant measures of regional cerebral metabolic rates for glucose (CMRglc) during the task, utilizing positron emission tomography, revealed increased activity in prefrontal cortex, dorsal striatum, and medial temporal lobe (including hippocampus) that was significantly enhanced over normal alert conditions following administration of CX717. A single night of sleep deprivation produced severe impairments in performance in the same monkeys, accompanied by significant alterations in task-related CMRglc in these same brain regions. However, CX717 administered to sleep-deprived monkeys produced a striking removal of the behavioral impairment and returned performance to above-normal levels even though animals were sleep deprived. Consistent with this recovery, CMRglc in all but one brain region affected by sleep deprivation was also returned to the normal alert pattern by the drug. The ampakine CX717, in addition to enhancing cognitive performance under normal alert conditions, also proved effective in alleviating impairment of performance due to sleep deprivation. Therefore, the ability to activate specific brain regions under normal alert conditions and alter the deleterious effects of sleep deprivation on activity in those same regions indicate a potential role for ampakines in sustaining performance under these types of adverse conditions.
Closing the loop in primate prefrontal cortex: inter-laminar processing
Ioan Opris,Peter F. Huettl,Theodore W. Berger,Robert E. Hampson,Sam A. Deadwyler
Frontiers in Neural Circuits , 2012, DOI: 10.3389/fncir.2012.00088
Abstract: Prefrontal cortical (PFC) activity in the primate brain emerging from minicolumnar microcircuits plays a critical role in cognitive processes dealing with executive control of behavior. However, the specific operations of columnar laminar processing in prefrontal cortex (PFC) are not completely understood. Here we show via implementation of unique microanatomical recording and stimulating arrays, that minicolumns in PFC are involved in the executive control of behavior in rhesus macaque nonhuman primates (NHPs) performing a delayed-match-to-sample (DMS) task. PFC neurons demonstrate functional interactions between pairs of putative pyramidal cells within specified cortical layers via anatomically oriented minicolumns. Results reveal target-specific, spatially tuned firing between inter-laminar (layer 2/3 and layer 5) pairs of neurons participating in the gating of information during the decision making phase of the task with differential correlations between activity in layer 2/3 and layer 5 in the integration of spatial vs. object-specific information for correct task performance. Such inter-laminar processing was exploited by the interfacing of an online model which delivered stimulation to layer 5 locations in a pattern associated with successful performance thereby closing the columnar loop externally in a manner that mimicked normal processing in the same task. These unique technologies demonstrate that PFC neurons encode and process information via minicolumns which provides a closed loop form of “executive function,” hence disruption of such inter-laminar processing could form the bases for cognitive dysfunction in primate brain.
Extraction and restoration of hippocampal spatial memories with non-linear dynamical modeling
Dong Song,Vasilis Z. Marmarelis,Robert E. Hampson,Sam A. Deadwyler,Theodore W. Berger
Frontiers in Systems Neuroscience , 2014, DOI: 10.3389/fnsys.2014.00097
Abstract: To build a cognitive prosthesis that can replace the memory function of the hippocampus, it is essential to model the input-output function of the damaged hippocampal region, so the prosthetic device can stimulate the downstream hippocampal region, e.g., CA1, with the output signal, e.g., CA1 spike trains, predicted from the ongoing input signal, e.g., CA3 spike trains, and the identified input-output function, e.g., CA3-CA1 model. In order for the downstream region to form appropriate long-term memories based on the restored output signal, furthermore, the output signal should contain sufficient information about the memories that the animal has formed. In this study, we verify this premise by applying regression and classification modelings of the spatio-temporal patterns of spike trains to the hippocampal CA3 and CA1 data recorded from rats performing a memory-dependent delayed non-match-to-sample (DNMS) task. The regression model is essentially the multiple-input, multiple-output (MIMO) non-linear dynamical model of spike train transformation. It predicts the output spike trains based on the input spike trains and thus restores the output signal. In addition, the classification model interprets the signal by relating the spatio-temporal patterns to the memory events. We have found that: (1) both hippocampal CA3 and CA1 spike trains contain sufficient information for predicting the locations of the sample responses (i.e., left and right memories) during the DNMS task; and more importantly (2) the CA1 spike trains predicted from the CA3 spike trains by the MIMO model also are sufficient for predicting the locations on a single-trial basis. These results show quantitatively that, with a moderate number of unitary recordings from the hippocampus, the MIMO non-linear dynamical model is able to extract and restore spatial memory information for the formation of long-term memories and thus can serve as the computational basis of the hippocampal memory prosthesis.
Donor/recipient enhancement of memory in rat hippocampus
Sam A. Deadwyler,Theodore W. Berger,Andrew J. Sweatt,Dong Song,Rosa H. M. Chan,Ioan Opris,Vasilis Z. Marmarelis,Robert E. Hampson
Frontiers in Systems Neuroscience , 2013, DOI: 10.3389/fnsys.2013.00120
Abstract: The critical role of the mammalian hippocampus in the formation, translation and retrieval of memory has been documented over many decades. There are many theories of how the hippocampus operates to encode events and a precise mechanism was recently identified in rats performing a short-term memory task which demonstrated that successful information encoding was promoted via specific patterns of activity generated within ensembles of hippocampal neurons. In the study presented here, these “representations” were extracted via a customized non-linear multi-input multi-output (MIMO) mathematical model which allowed prediction of successful performance on specific trials within the testing session. A unique feature of this characterization was demonstrated when successful information encoding patterns were derived online from well-trained “donor” animals during difficult long-delay trials and delivered via online electrical stimulation to synchronously tested na?ve “recipient” animals never before exposed to the delay feature of the task. By transferring such model-derived trained (donor) animal hippocampal firing patterns via stimulation to coupled na?ve recipient animals, their task performance was facilitated in a direct “donor-recipient” manner. This provides the basis for utilizing extracted appropriate neural information from one brain to induce, recover, or enhance memory related processing in the brain of another subject.
STCP-Timestamp: Bandwidth Estimation Algorithm to Improve TCP Performance in Integrated Wireless Communication Networks
Ezil Sam Leni A.
Asian Journal of Information Technology , 2012,
Abstract: As wireless networks with high data rate get widely deployed, improving the performance of TCP over these networks plays vital role. Wireless link losses have dramatic adverse impact on TCP performance due to the difficulty in distinguishing the congestion losses from wireless link losses. We studied the various existing Bandwidth Estimation Algorithms. Then we proposed a new technique to estimate the available bandwidth using the timestamp option of the TCP Header. The proposed system is evaluated in the integrated wireless environment and the simulated results are also shown.
Unusual Complication Following Spinal Anesthesia for Caesarean Section  [PDF]
A. Antwi-Kusi,W. Sam Awortwi,A. Serwaa Hemeng
Open Journal of Anesthesiology (OJAnes) , 2013, DOI: 10.4236/ojanes.2013.35060
Abstract: Spinal anesthesia involves the introduction of local anesthetics into the subarachnoid space leading to the loss of sensation of pain. Common complications following spinal anesthesia include hypotension leading to nausea and vomiting, failure of the spinal and post dural puncture. Other uncommon complications include high and total spinal and spinal haematoma. In this report the patient experienced uncontrollable jerking of the lower limbs, hypertension, arrhythmias and cardiac arrest refractory to resuscitation.
Unusual Complication Following Spinal Anesthesia for Caesarean Section  [PDF]
A. Antwi-Kusi, W. Sam Awortwi, A. Serwaa Hemeng
Open Journal of Anesthesiology (OJAnes) , 2013, DOI: 10.4236/ojanes.2013.35060
Abstract:

Spinal anesthesia involves the introduction of local anesthetics into the subarachnoid space leading to the loss of sensation of pain. Common complications following spinal anesthesia include hypotension leading to nausea and vomiting, failure of the spinal and post dural puncture. Other uncommon complications include high and total spinal and spinal haematoma. In this report the patient experienced uncontrollable jerking of the lower limbs, hypertension, arrhythmias and cardiac arrest refractory to resuscitation.

A call to arms to reduce premature deaths by using inexpensive resuscitation care
Sam A Warren, Graham Nichol
Critical Care , 2008, DOI: 10.1186/cc6970
Abstract: In this issue of Critical Care, Graf and colleagues [1] describe a long-term cohort study of the costs and consequences of intensive care after resuscitation from cardiac arrest. We took particular interest in this study because health care costs in the US exceed those of any other nation. This study was a programmatic evaluation rather than an assessment of a specific intervention such as therapeutic hypothermia. Thirty-one percent of the cohort that survived to be cared for in the intensive care setting were still alive 5 years after hospital discharge. The health-related quality of life of this group of 5-year survivors was similar to that of matched healthy controls. The cost per quality-adjusted life year (QALY) gained was 14,487 euros (approximately US $22,900 at current rates). The cost per life year gained increased by 18% when it included the 6.4% of 5-year survivors who had severe neurological disability (that is, Glasgow Coma Scale score of less than 6).How much to pay for a health intervention is a poignant question most societies have yet to answer formally. Such decisions are complex and are predicated not only on the absolute and incremental cost of the intervention but also on the quantity and quality of effectiveness data related to the intervention. Countries with a centralized planning process for health care may imply their answer when they approve or disapprove for national formulary a drug designed to extend life in a terminal disease. The UK's National Health Service recently declined approval of bevacizumab (Avastin, with a cost of therapy per year of approximately $100,000) as first-line therapy for lung and breast cancer [2]. In the US, there appears to be a general consensus that $50,000 to $100,000 per year of life gained is acceptable [3]. An analysis based on economic principles suggested that we should be willing to spend up to twice the average annual income on health care [4]. In this light, less than 15,000 euros per QALY for intens
On the placement of the Cretaceous orthopteran Brauckmannia groeningae from Brazil, with notes on the relationships of Schizodactylidae (Orthoptera, Ensifera)
Sam Heads,a Leuzinger
ZooKeys , 2011, DOI: 10.3897/zookeys.77.769
Abstract: The fossil orthopteran Brauckmannia groeningae Martins-Neto (Orthoptera, Ensifera) from the Early Cretaceous Crato Formation of Brazil, currently misplaced at both the genus and family level, is transferred to the family Schizodactylidae and assigned to the extant genus Schizodactylus Brullé; ergo, Brauckmannia enters synonymy under Schizodactylus and Brauckmanniidae enters synonymy under Schizodactylidae. Schizodactylus groeningae (Martins-Neto), comb. n. agrees in size and general habitus with extant members of the genus, but can be readily separated by the robust, subovoid form of the metatibiae and the distinctive morphology of the lateral metabasitarsal processes. This species represents the first fossil occurrence of Schizodactylidae and the only New World record of this ancient lineage. Phylogenetic relationships of the schizodactylids are reviewed and a sister-group relationship with Grylloidea advocated based on a reappraisal of morphological and molecular evidence.
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