Página 1 dos resultados de 121556 itens digitais encontrados em 0.047 segundos

Fatores associados às alterações morfométricas crânio-encefálicas durante o envelhecimento; Morphometric brain and skull changes during ageing and their related factors

Ferretti, Renata Eloah de Lucena
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 06/10/2008 PT
Relevância na Pesquisa
36.22%
INTRODUÇÃO: Existem alterações na morfologia encefálica durante o envelhecimento, que vão além da atrofia cerebral. Ainda deve ser considerado se essas alterações estão presentes em indivíduos sem comprometimento cognitivo e quais são os fatores associados a elas. OBJETIVO: Identificar se existem alterações morfométricas crânio - encefálicas em indivíduos sem comprometimento cognitivo e se essas alterações podem ser correlacionadas com fatores sócio- demográficos e clínicos, em uma série brasileira de casos autopsiados. METODOLODIA: Foi conduzido um estudo no Serviço de Verificação de Óbitos da Capital, onde 414 indivíduos necropsiados, com 50 anos ou mais de idade, foram submetidos à avaliação clínica completa e à análise morfométrica crânioencefálica (perímetro cefálico, peso, volume e densidade encefálicos). As correlações entre as alterações morfométricas cerebrais e os fatores associados (variáveis sócio demográficas e clínicas) foram obtidos por meio de análise uni e multivariadas. RESULTADOS: Amostra composta por 39,6% de mulheres e 60,4% de homens, com idade média de 68,5 (± 11,9 DP) e 66,2 (± 10,2 DP), respectivamente; maioria branca. Foi observada redução do perímetro cefálico com a idade...

Estudo das alterações microcirculatórias e da evolução do processo inflamatório em modelo de morte encefálica em ratos; Study of microcirculatory alterations and evolution of inflammatory process in a brain death rat model

Simas, Rafael
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 02/05/2013 PT
Relevância na Pesquisa
36.23%
INTRODUÇÃO: Estudos indicam que a morte encefálica está associada com alterações hemodinâmicas, hormonais e inflamatórias, comprometendo a viabilidade dos órgãos para o transplante. Porém, é necessário esclarecer quais destas alterações são decorrentes da morte encefálica e quais são devidas ao trauma associado. Este estudo tem por objetivo avaliar a microcirculação mesentérica, quantificar marcadores sistêmicos da resposta inflamatória, e analisar as alterações histopatológicas em ratos submetidos à morte encefálica comparados com ratos falso-operados. MÉTODOS: Ratos Wistar machos (300 50 g), anestesiados com isoflurano (5-2 %), foram intubados e mecanicamente ventilados (10 mL/kg, 70 ciclos/min). Através de uma trepanação, um cateter Fogarty® 4 F foi inserido no espaço intracraniano e rapidamente insuflado com 500 L de água para indução da morte encefálica. Após a indução da morte encefálica o anestésico foi retirado e os animais receberam solução salina 0,9 % endovenosa (2 mL/h). Animais falso-operados foram apenas trepanados. Pressão arterial média e frequência cardíaca foram monitoradas ao longo de todo tempo de experimento. Após 30, 180 ou 360 min, foram avaliados os seguintes parâmetros: 1) avaliação da perfusão e interação leucócito-endotélio na microcirculação mesentérica por técnica de microscopia intravital; 2) expressão de moléculas de adesão endoteliais (P-selectina e ICAM-1) por imunohistoquímica; 3) quantificação das citocinas (TNF-?...

Avaliação dos efeitos da anestesia peridural torácica sobre as alterações miocárdicas associadas à morte encefálica: estudo experimental; Assessment of the effects of thoracic epidural anesthesia on myocardial changes associated with brain death: an experimental study

Silva, Isaac Azevedo
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 03/05/2013 PT
Relevância na Pesquisa
36.21%
INTRODUÇÃO: Atualmente, a maior limitação ao transplante cardíaco, em todo o mundo, é a escassez de doadores cujo número está sempre aquém do número de pacientes portadores de doença cardíaca terminal, e esse hiato fica ainda maior pelo fato de cerca de 25 % dos corações doados não serem utilizados, por estarem acometidos por acentuada disfunção. A descarga catecolaminérgica associada à morte encefálica poderia ser um dos elementos implicados nesta disfunção. Assim, intervenções terapêuticas com intuito de minimizar o exacerbado estímulo simpático visam, em última instância, ampliar a oferta de órgãos para o transplante. OBJETIVOS: Investigar a hipótese de que a anestesia peridural torácica seja capaz de bloquear a tempestade autonômica inerente à morte encefálica por hipertensão intracraniana aguda, minimizando as alterações hemodinâmicas, reduzindo a resposta inflamatória e, por conseguinte, melhorando a condição do enxerto. MÉTODOS: Ratos Wistar machos (250-350 g) anestesiados (isoflurano 5 %) e monitorados continuamente para o registro da pressão arterial média foram submetidos à inserção de cateter no espaço peridural em nível torácico e, em seguida, submetidos à morte encefálica por hipertensão intracraniana aguda pela xxi insuflação de um cateter de Fogarty® introduzido por trepanação. Os animais (n = 28) foram alocados em 4 grupos: grupo salina - infusão de 20 uL de solução salina pelo cateter peridural antes da indução da morte encefálica; grupo bupi-pré - infusão de 20 uL de solução de bupivacaína a 0...

Influência do hemisfério cerebral lesado e de déficits sensoriais sobre o equilíbrio corporal pós-acidente vascular encefálico; Influence of the injured brain hemisphere and of sensory deficits on body balance post-stroke

Fernandes, Corina Aparecida
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 12/12/2014 PT
Relevância na Pesquisa
36.21%
A influência do hemisfério cerebral lesado pós-AVE e da informação visual foram avaliados neste estudo no controle da postura quieta, em perturbação sensorial e mecânica. Também foram avaliados o efeito da informação tátil durante perturbação sensorial e respostas posturais após perturbação postural externa imprevisível. Participaram deste estudo 11 indivíduos pós- AVE no hemisfério cerebral direito, 11 indivíduos pós-AVE no hemisfério cerebral esquerdo e 24 indivíduos sem doenças neurológicas. O desempenho do equilíbrio corporal foi avaliado na postura quieta, na postura ereta com superfície maleável (almofada de espuma) e após perturbação mecânica provocada pela liberação de carga inesperada. A avaliação foi feita sob as condições de visão plena e de oclusão visual. Os resultados da postura quieta revelaram aumento e maior variabilidade de oscilação postural no plano mediolateral de indivíduos pós- AVE em comparação aos sem doenças neurológicas. Indivíduos pós-AVE no hemisfério cerebral direito apresentaram aumento da oscilação postural no plano anteroposterior em comparação aos indivíduos pós-AVE no hemisfério cerebral esquerdo e sem doenças neurológicas. A condição de oclusão visual levou ao aumento da oscilação postural nos indivíduos pós-AVE em comparação aos indivíduos sem doenças neurológicas...

Implications of ischemic penumbra for the diagnosis of brain death

Coimbra,C.G.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/1999 EN
Relevância na Pesquisa
36.21%
The data reviewed here suggest the possibility that a global reduction of blood supply to the whole brain or solely to the infratentorial structures down to the range of ischemic penumbra for several hours or a few days may lead to misdiagnosis of irreversible brain or brain stem damage in a subset of deeply comatose patients with cephalic areflexia. The following proposals are advanced: 1) the lack of any set of clinically detectable brain functions does not provide a safe diagnosis of brain or brain stem death; 2) apnea testing may induce irreversible brain damage and should be abandoned; 3) moderate hypothermia, antipyresis, prevention of arterial hypotension, and occasionally intra-arterial thrombolysis may contribute to good recovery of a possibly large subset of cases of brain injury currently regarded as irreversible; 4) confirmatory tests for brain death should not replace or delay the administration of potentially effective therapeutic measures; 5) in order to validate confirmatory tests, further research is needed to relate their results to specific levels of blood supply to the brain. The current criteria for the diagnosis of brain death should be revised.

Brain Inflammation and Microglia: Facts and Misconceptions

Jeong, Hey-Kyeong; Ji, Kyungmin; Min, Kyungjin; Joe, Eun-Hye
Fonte: The Korean Society for Brain and Neural Science Publicador: The Korean Society for Brain and Neural Science
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.21%
The inflammation that accompanies acute injury has dual functions: bactericidal action and repair. Bactericidal functions protect damaged tissue from infection, and repair functions are initiated to aid in the recovery of damaged tissue. Brain injury is somewhat different from injuries in other tissues in two respects. First, many cases of brain injury are not accompanied by infection: there is no chance of pathogens to enter in ischemia or even in traumatic injury if the skull is intact. Second, neurons are rarely regenerated once damaged. This raises the question of whether bactericidal inflammation really occurs in the injured brain; if so, how is this type of inflammation controlled? Many brain inflammation studies have been conducted using cultured microglia (brain macrophages). Even where animal models have been used, the behavior of microglia and neurons has typically been analyzed at or after the time of neuronal death, a time window that excludes the inflammatory response, which begins immediately after the injury. Therefore, to understand the patterns and roles of brain inflammation in the injured brain, it is necessary to analyze the behavior of all cell types in the injured brain immediately after the onset of injury. Based on our experience with both in vitro and in vivo experimental models of brain inflammation...

cpg2 encodes a brain- and synapse-specific protein that regulates the endocytosis of glutamate receptors; Candidate plasticity gene 2 encodes a brain- and synapse-specific protein that regulates the endocytosis of glutamate receptors

Cottrell, Jeffrey Richard, 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 113 leaves; 4695448 bytes; 4695255 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
46.09%
Synaptic plasticity is the rearrangement of neuronal connections that likely underlies learning and memory. It requires the expression of a set of genes essential for the synaptic changes that occur during plasticity, candidate plasticity gene 2 (cpg2) was isolated in a screen for genes that effect synaptic plasticity. In this thesis, I analyze the regulation and function of cpg2 in neurons. I find that cpg2 is a splice-variant of the syne-1 gene that is expressed only in brain regions capable of plasticity and encodes a protein specifically localized to a postsynaptic endocytic zone of excitatory synapses, often in the vicinity of clathrin-coated pits. I further show that, through its C-terminal coiled-coil motifs, CPG2 binds to the actin cytoskeleton and to endophilin B2, a member of a family of proteins involved in membrane trafficking. RNAi-mediated knock-down of CPG2 increased the number of postsynaptic clathrin-coated vesicles, some of which trafficked NMDA receptors, and disrupted the internalization of glutamate receptors. In addition, alterations in its protein levels affected dendritic spine size, supporting a role for CPG2 in regulating membrane trafficking. These data suggest that CPG2 organizes a network of proteins at the postsynaptic endocytic zone critical for glutamate receptor internalization. Due to its unique expression profile and subcellular localization...

Memory systems of the human brain : dissociations among learning capacities in amnesia

Gabrieli, John D. E. (John David Elemer), 1955-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 2 v. (340 leaves); 14508460 bytes; 14548931 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
46.01%
by John D. E. Gabrieli.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Whitaker College of Health Sciences, Technology, and Management, Dept. of Brain and Cognitive Sciences, 1987.; MICROFICHE COPY AVAILABLE IN ARCHIVE AND SCIENCE.; Vita.; Bibliography: leaves 295-325.

Multiple spatial memories in the brain : decoding and modification using microstimulation

Histed, Mark H
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 97 leaves; 1510235 bytes; 1508087 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
46.01%
Sequential processing --- using multiple sensory stimuli to plan and control a set of ordered movements --- is a central aspect of human behavior. Because previous and future movements must be stored during the execution of any movement in a sequence, memory is an indispensable aspect of sequential behavior. To study how memory is used to link sensory inputs to sequential motor outputs, we have used the oculomotor system as a model. We trained monkeys to remember the location of two spatial cues over a brief delay, and then make two eye movements to the remembered locations in the order that they appeared. We explored the role of two different frontal eye movement areas, the frontal and supplementary eye fields (FEF and SEF) during this memory delay. While both the FEF and SEF have shown to be important for sequential behavior, their individual roles are unknown. Here, using physiology, we show that the FEF is important for storing the location of multiple cues and their order in memory. In the SEF, we show that memory period stimulation can affect the order of a sequence, changing the goal of the entire sequence but not the individual movement components.; (cont.) Thus, both areas appear to play complementary roles in sequential planning: the FEF stores target locations...

Increased brain lactate is central to the development of brain edema in rats with chronic liver disease

Bosoi, Cristina R.; Zwingmann, Claudia; Marin, Helen A.; Parent-Robitaille, Christian; Huynh, Jimmy; Tremblay, Mélanie; Rose, Christopher F.
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
36.21%
The pathogenesis of brain edema in patients with chronic liver disease (CLD) and minimal hepatic encephalopathy (HE) remains undefined. This study evaluated the role of brain lactate, glutamine and organic osmolytes, including myo-inositol and taurine, in the development of brain edema in a rat model of cirrhosis.Six-week bile-duct ligated (BDL) rats were injected with (13)C-glucose and de novo synthesis of lactate, and glutamine in the brain was quantified using (13)C nuclear magnetic resonance spectroscopy (NMR). Total brain lactate, glutamine, and osmolytes were measured using (1)H NMR or high performance liquid chromatography. To further define the interplay between lactate, glutamine and brain edema, BDL rats were treated with AST-120 (engineered activated carbon microspheres) and dichloroacetate (DCA: lactate synthesis inhibitor).Significant increases in de novo synthesis of lactate (1.6-fold, p<0.001) and glutamine (2.2-fold, p<0.01) were demonstrated in the brains of BDL rats vs. SHAM-operated controls. Moreover, a decrease in cerebral myo-inositol (p<0.001), with no change in taurine, was found in the presence of brain edema in BDL rats vs. controls. BDL rats treated with either AST-120 or DCA showed attenuation in brain edema and brain lactate. These two treatments did not lead to similar reductions in brain glutamine.Increased brain lactate...

The role of substance P in the progression and complications of secondary brain tumours.

Lewis, Kate
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2012
Relevância na Pesquisa
36.22%
Secondary brain tumours occur when cancer cells enter the circulation from their primary site and colonise the brain, previously shown to occur across the blood-brain barrier (BBB). Substance P (SP), a neurogenic inflammatory mediator, acting predominantly through NK1 receptors plays a role in opening the BBB and in the formation of oedema following stroke and brain trauma. It is hypothesised that SP may also promote the extravasation of tumour cells through the BBB, formation of peritumoral oedema and progression of secondary brain tumours. Walker 256 rat breast carcinoma cells obtained from the Centre for Medical Research, Tohoku University had superior tumorigenic properties compared to cells from the American Type Culture Collection, and were therefore subsequently used in two albino Wistar rat models of tumorigenesis. Firstly, internal carotid artery tumour cell injection was used to establish the effect of tumour cell extravasation across the BBB on brain albumin, endothelial barrier antigen (EBA) and SP immunoreactivity. I then determined if NK1 receptor antagonists could prevent tumour cell extravasation, by evaluating tumour incidence and volume. Secondly, a stereotaxic direct inoculation model was used to investigate the effect of NK1 receptor antagonists on brain tumour growth and peritumoral oedema...

Characterising the role of substance P in human and experimental brain tumours.

Harford-Wright, Elizabeth Asha
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2013
Relevância na Pesquisa
36.21%
Currently within Australia, brain tumours account for one death every eight hours. They are inherently difficult to treat, and even with the best current treatments, prognosis for these patients remains extremely poor. At present, treatment options for patients with either primary or secondary brain tumours are limited. Indeed most brain metastasis patients have a short survival time, despite the fact that initial treatment is often effective in reducing neurological deficits and tumour size. One of the most serious complications of brain tumours is cerebral oedema, which is typically vasogenic in nature due to disruption of normal blood brain barrier function. Cerebral oedema is associated with many life-threatening complications such as raised intracranial pressure, reduction in cerebral perfusion pressure and in severe cases can result in brain herniation and death. Although treatments for cerebral oedema currently exist, they are associated with many deleterious side effects, prompting the search for alternative treatments. The neuropeptide substance P and its NK1 receptor are reported to be upregulated in a number of different cancer types. This increase is thought to correspond with SP mediated increases in cellular proliferation...

Wachstum von Meningeomen an der Hirn-Tumor-Grenze: eine immunhistochemische Studie; Growth of meningiomas at the brain-tumour-interface: an immunohistochemical study

Fritz, Jasmin Caterina
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
36.22%
Wir untersuchten 49 Gewebeproben von meningotheliomatösen, benignen WHO Grad I Meningeomen und verglichen hirninvasive (n=21) mit nicht-invasiven Exemplaren. Dabei unterschieden wir nicht-invasive Meningeome mit anhängendem Hirngewebe (n=20) von solchen ohne Hirngewebe im Präparat (n=8). Mittels immunhistochemischer Methoden konnten wir in der Kollagen IV-Färbung Neubildung von Basalmembran durch das Meningeom und Zerstörung der pial-glialen Grenzbasalmembran nachweisen. Zerstörung der pial-glialen Grenzbasalmembran konnte in allen hirninvasiven Fällen (100%) und 17 nicht-invasiven Meningeomen (61%) nachgewiesen werden. Hirninvasion tritt in folgenden Mustern auf: kleine Ausstülpungen, die fokal die pial-gliale Basalmembran durchbrechen, Tumorzapfen, die zum Teil ganz von Hirngewebe ummauert sind, aber auch Verlust der pial-glialen Basalmembran über weite Strecken ohne direkten Einfluss von invasiven Meningeomanteilen. Diese Degradation ist in verschiedenen Graden bei allen Meningeomen festzustellen und unterscheidet nicht zwischen hirninvasiven und nicht-invasiven Exemplaren. Weiterführende Studien mit Bestimmung von Proteasen sind notwendig, um den Invasionsmechanismus zu erforschen. Zusätzlich fanden wir Neubildung von Basalmembran an der Hirn-Tumor-Grenze in 37 Fällen. Das Invasionsverhalten korreliert nicht mit dem Proliferationsindex MIB-1. Die EMA-Färbung sollte aufdecken...

Mikrogliale Reaktion auf hirninvasive Meningeome; Microglial reaction on brain invasive meningioma

Grund, Stephanie Isabelle
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
36.21%
Hirninvasion von Meningeomen stellt ein seltenes, aber prognostisch ungünstiges Verhalten dieser Tumore dar. Die Mikroglia ist ein empfindlicher Sensor für pathologische Prozesse im ZNS und mitverantwortlich für deren Abwehr. Da die genauen Vorgänge bei Hirninvasion nur wenig untersucht sind und keine Arbeiten zur mikroglialen Reaktion dabei bestanden, war das Ziel unserer Studie die Reaktion der Mikroglia an der Hirn-Tumorgrenze und im anliegenden Hirnparenchym zu untersuchen. Als Probengut wählten wir 18 invasive Meningeome des WHO-Grads I, 13 invasive Meningeome des WHO-Grads II und 7 invasive Meningeome des WHO-Grades III und untersuchten diese Präparate immunhistochemisch auf Reaktionen der Mikroglia an der Hirn-Tumorgrenze und im darauf folgenden ZNS-Gewebe. Färbungen mit Anti-CD68 und -CD45 dienten der Detektion ruhender Mikroglia, während Anti-CD14 und -MRP8 aktivierte Mikroglia anfärbten. MHCII nahm als Oberflächenmolekül auf ruhender und aktivierter Mikroglia eine Zwischenstellung ein. Um eine Korrelation mit dem Vorhandensein von Basalmembran an der Hirn-Tumorgrenze und dem Vorhandensein von Mikrogliazellen zu ermöglichen wiesen wir Basalmembran anhand Färbungen mit Anti-Collagen 4 Antikörpern nach. Dabei stellten wir fest...

Metabolic Brain-Computer Interfaces; Metabolische Gehirn-Komputer Schnittstelle

Sitaram, Ranganatha
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
36.23%
Brain-Computer Interfaces (BCI) utilise neurophysiological signals originating in the brain to activate or deactivate external devices or computers (Donoghue 2002; Wolpaw, Birbaumer et al. 2002; Nicolelis 2003; Birbaumer and Cohen 2007). The neuronal signals can be recorded from inside the brain (invasive BCIs) or outside (non-invasive BCIs) of the brain. Most BCIs developed so far have used operant training of direct neuroelectric responses, Electroencephalography (EEG) waves, event-related potentials and brain oscillations (Birbaumer, Weber et al. 2006; Birbaumer and Cohen 2007). Compared to neuroelectric studies on regulation of brain activity, there have been fewer studies with metabolic signals from the brain (Sitaram, Caria et al. 2007; Weiskopf, Sitaram et al. 2007; Sitaram, Weiskopf et al. 2008). Near Infrared Spectroscopy (NIRS) and Functional magnetic resonance imaging (fMRI) present themselves as attractive methods of acquiring hemodynamic activity of the brain for a developing a BCI. In this study, we exploit NIRS and fMRI for the implementation of BCIs for the investigation of regulation of hemodynamic signals in the brain and their behavioural consequences. We propose that these methods could be used not only for communication and control in paralysis...

Brain Gain : Claims about its Size and Impact on Welfare and Growth Are Greatly Exaggerated

Schiff, Maurice
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Tipo: Publications & Research :: Policy Research Working Paper; Publications & Research
ENGLISH
Relevância na Pesquisa
36.23%
Based on static partial equilibrium analysis, the "new brain drain" literature argues that, by raising the return to education, a brain drain generates a brain gain that is, under certain conditions, larger than the brain drain itself, and that such a net brain gain results in an increase in welfare and growth due to education's positive externalities. This paper argues that these claims are exaggerated. In the static case, and based on both partial and general equilibrium considerations, the paper shows that (1) the size of the brain gain is smaller than suggested in that literature; (2) the impact on welfare and growth is smaller as well (for any brain gain size); (3) a positive brain gain is likely to result in a smaller, possibly negative, human capital gain; (4) an increase in the stock of human capital may have a negative impact on welfare and growth; and (5) in a dynamic framework, the paper shows that the steady-state brain gain is equal to the brain drain so that a 'beneficial brain drain' cannot take place, and a net brain loss is likely during the transition.

Assessing brain plasticity across the lifespan with transcranial magnetic stimulation: why, how, and what is the ultimate goal?

Freitas, Catarina; Farzan, Faranak; Pascual-Leone, Alvaro
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
36.22%
Sustaining brain and cognitive function across the lifespan must be one of the main biomedical goals of the twenty-first century. We need to aim to prevent neuropsychiatric diseases and, thus, to identify and remediate brain and cognitive dysfunction before clinical symptoms manifest and disability develops. The brain undergoes a complex array of changes from developmental years into old age, putatively the underpinnings of changes in cognition and behavior throughout life. A functionally “normal” brain is a changing brain, a brain whose capacity and mechanisms of change are shifting appropriately from one time-point to another in a given individual's life. Therefore, assessing the mechanisms of brain plasticity across the lifespan is critical to gain insight into an individual's brain health. Indexing brain plasticity in humans is possible with transcranial magnetic stimulation (TMS), which, in combination with neuroimaging, provides a powerful tool for exploring local cortical and brain network plasticity. Here, we review investigations to date, summarize findings, and discuss some of the challenges that need to be solved to enhance the use of TMS measures of brain plasticity across all ages. Ultimately, TMS measures of plasticity can become the foundation for a brain health index (BHI) to enable objective correlates of an individual's brain health over time...

Plasticity of brain wave network interactions and evolution across physiologic states

Liu, Kang K. L.; Bartsch, Ronny P.; Lin, Aijing; Mantegna, Rosario N.; Ivanov, Plamen Ch.
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
36.24%
Neural plasticity transcends a range of spatio-temporal scales and serves as the basis of various brain activities and physiologic functions. At the microscopic level, it enables the emergence of brain waves with complex temporal dynamics. At the macroscopic level, presence and dominance of specific brain waves is associated with important brain functions. The role of neural plasticity at different levels in generating distinct brain rhythms and how brain rhythms communicate with each other across brain areas to generate physiologic states and functions remains not understood. Here we perform an empirical exploration of neural plasticity at the level of brain wave network interactions representing dynamical communications within and between different brain areas in the frequency domain. We introduce the concept of time delay stability (TDS) to quantify coordinated bursts in the activity of brain waves, and we employ a system-wide Network Physiology integrative approach to probe the network of coordinated brain wave activations and its evolution across physiologic states. We find an association between network structure and physiologic states. We uncover a hierarchical reorganization in the brain wave networks in response to changes in physiologic state...

Diffusion Tensor Imaging Biomarkers of Brain Development and Disease

Calabrese, Evan Darcy Cozzens
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2014
Relevância na Pesquisa
36.24%

Understanding the structure of the brain has been a major goal of neuroscience research over the past century, driven in part by the understanding that brain structure closely follows function. Normative brain maps, or atlases, can be used to understand normal brain structure, and to identify structural differences resulting from disease. Recently, diffusion tensor magnetic resonance imaging has emerged as a powerful tool for brain atlasing; however, its utility is hindered by image resolution and signal limitations. These limitations can be overcome by imaging fixed ex-vivo specimens stained with MRI contrast agents, a technique known as diffusion tensor magnetic resonance histology (DT-MRH). DT-MRH represents a unique, quantitative tool for mapping the brain with unprecedented structural detail. This technique has engendered a new generation of 3D, digital brain atlases, capable of representing complex dynamic processes such as neurodevelopment. This dissertation explores the use of DT-MRH for quantitative brain atlasing in an animal model and initial work in the human brain.

Chapter 1 describes the advantages of the DT-MRH technique, and the motivations for generating a quantitative atlas of rat postnatal neurodevelopment. The second chapter covers optimization of the DT-MRH hardware and pulse sequence design for imaging the developing rat brain. Chapter 3 details the acquisition and curation of rat neurodevelopmental atlas data. Chapter 4 describes the creation and implementation of an ontology-based segmentation scheme for tracking changes in the developing brain. Chapters 5 and 6 pertain to analyses of volumetric changes and diffusion tensor parameter changes throughout rat postnatal neurodevelopment...

Numerical Simulation of Primary Blast Brain Injury

Panzer, Matthew Brian
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2012
Relevância na Pesquisa
36.23%

Explosions are associated with more than 80% of the casualties in the Iraq and Afghanistan wars. Given the widespread use of thoracic protective armor, the most prevalent injury for combat personnel is blast-related traumatic brain injury (TBI). Almost 20% of veterans returning from duty had one or more clinically confirmed cases of TBI. In the decades of research prior to 2000, neurotrauma was under-recognized as a blast injury and the etiology and pathology of these injuries remains unclear.

This dissertation used the finite element (FE) method to address many of the biomechanics-based questions related to blast brain injuries. FE modeling is a powerful tool for studying the biomechanical response of a human or animal body to blast loading, particularly because of the many challenges related to experimental work in this field. In this dissertation, novel FE models of the human and ferret head were developed for blast and blunt impact simulation, and the ensuing response of the brain was investigated. The blast conditions simulated in this research were representative of peak overpressures and durations of real-world explosives. In general, intracranial pressures were dependent on the peak pressure of the impinging blast wave...