RESUMO
The aim of this study was to determine whether non-invasive brain stimulation (NIBS) techniques improve fine motor performance in stroke. We searched PubMed, EMBASE, Web of Science, SciELO and OpenGrey for randomized clinical trials on NIBS for fine motor performance in stroke patients and healthy participants. We computed Hedges' g for active and sham groups, pooled data as random-effects models and performed sensitivity analysis on chronicity, montage, frequency of stimulation and risk of bias. Twenty-nine studies (351 patients and 152 healthy subjects) were reviewed. Effect sizes in stroke populations for transcranial direct current stimulation and repeated transcranial magnetic stimulation were 0.31 [95% confidence interval (CI), 0.08-0.55; P = 0.010; Tau2 , 0.09; I2 , 34%; Q, 18.23; P = 0.110] and 0.46 (95% CI, 0.00-0.92; P = 0.05; Tau2 , 0.38; I2 , 67%; Q, 30.45; P = 0.007). The effect size of non-dominant healthy hemisphere transcranial direct current stimulation on non-dominant hand function was 1.25 (95% CI, 0.09-2.41; P = 0.04; Tau2 , 1.26; I2 , 93%; Q, 40.27; P < 0.001). Our results show that NIBS is associated with gains in fine motor performance in chronic stroke patients and healthy subjects. This supports the effects of NIBS on motor learning and encourages investigation to optimize their effects in clinical and research settings.
Assuntos
Destreza Motora , Reabilitação do Acidente Vascular Cerebral/métodos , Acidente Vascular Cerebral/psicologia , Estimulação Transcraniana por Corrente Contínua/métodos , Estimulação Magnética Transcraniana/métodos , Humanos , Ensaios Clínicos Controlados Aleatórios como Assunto , Acidente Vascular Cerebral/fisiopatologia , Resultado do TratamentoRESUMO
Rhythms and timing control of sequential activity in the brain is fundamental to cognition and behavior. Although experimental and theoretical studies support the understanding that neuronal circuits are intrinsically capable of generating different time intervals, the dynamical origin of the phenomenon of functionally dependent timing control is still unclear. Here, we consider a new mechanism that is related to the multi-neuronal cooperative dynamics in inhibitory brain motifs consisting of a few clusters. It is shown that redundancy and diversity of neurons within each cluster enhances the sensitivity of the timing control with the level of neuronal excitation of the whole network. The generality of the mechanism is shown to work on two different neuronal models: a conductance-based model and a map-based model.
Assuntos
Encéfalo/fisiologia , Modelos Neurológicos , Rede Nervosa/fisiologia , Animais , HumanosRESUMO
La población mundial y nacional está en proceso de envejecimiento. Las enfermedades dermatológicas son frecuentes en todos los grupos etarios y en el adulto mayor no es la excepción. Se realizó un estudio retrospectivo del principal motivo de consulta en los mayores de 60 años, atendidos en el periodo de 3 décadas (1984 a 2013) en una consulta privada de la ciudad de Antofagasta, Chile. Antofagasta exhibe un alto índice de radiación ultravioleta durante todo el año y hasta la década del 70 las aguas de consumo humano contenían arsénico. 4360 fichas de adultos mayores (60 años o más) ingresaron al estudio, 2.626 mujeres (60.2 por ciento) y 1734 hombres (39.8 por ciento). El 75,5 por ciento de los pacientes eran beneficiarios de Fonasa o fueron atendidos gratuitamente. Los diferentes motivos de consulta determinaron 191 diagnósticos diferentes, que fueron agrupados bajo 18 items. Los 3 items más frecuentes de consulta fueron tumores cutáneos (38,1 por ciento de los casos), dermatosis inflamatorias(26 por ciento) e infecciones cutáneas (15,3 por ciento). O sea, en esos 3 items se encasillaron casi el 80 por ciento de los pacientes. Los siete diagnósticos individuales más frecuentes fueron: queratosis seborreicas (9,6 por ciento de los casos), carcinomas basocelulares (6,7 por ciento), dermatitis aguda(5,7 por ciento), herpes zoster (4,3 por ciento), rosácea y condiciones afines (4,2 por ciento), enfermedad de Bowen (4 por ciento) y queratosis actínicas (3,9 por ciento). El alto porcentaje de tumores premalignos y malignos encontrados en los adultos mayores en el estudio, probablemente se relaciona con el daño provocado por la luz ultravioleta y el arsénico.
World and national population is in process of aging. Dermatological diseases are frequent in every age group and senior citizens are not an exception. We performed a retrospective study about the main reason of consultation in adults over the age of 60 in the period of 3 decades (1984 to 2013) in a private practice of the city of Antofagasta, Chile. Antofagasta exhibits a high UV index all the year round and until the 70s the water for human consumption contains arsenic. 4360 medical records of patients older than 60 years old were analyzed, 2626 female (60, 2 percent) and 1734 male (39, 8 percent). The different reasons of consultation determined 191 different diagnoses, which were grouped under 18 items. The 3 most frequent items of consultation were cutaneous tumors (38,1 percent of the cases), inflammatory dermatosis (26 percent) and cutaneous infections (15,3 percent), Almost an 80 percent of the patients were classified in these three items. The seven most frequent individual diagnoses were: seborrheic keratosis (9,6 percent of the cases), basal cell carcinoma (6,7 percent), acute dermatitis (5,7 percent), herpes zoster (4,3 percent), rosacea and related conditions (4,2 percent), Bowen disease (4 percent) and actinic keratosis (3,9 percent). The high percentage of premalignant and malignant tumors found among elders in this study is probably related with the damage induced by ultraviolet radiation and arsenic.
Assuntos
Humanos , Masculino , Feminino , Pessoa de Meia-Idade , Envelhecimento , Dermatopatias/epidemiologia , Distribuição por Idade e Sexo , Chile , Neoplasias Cutâneas/epidemiologia , Estudos RetrospectivosRESUMO
BACKGROUND: A previous survey on allergens used by Mexican allergists in their skin prick test (SPT) panel showed wide variation. Humidity varies in different zones of Mexico. This might lead to differences in natural exposure and allergic sensitisation throughout the country. We aim to describe the SPT sensitivity patterns in the different climatic zones in Mexico and to show the usefulness of a structured SPT chart-review including multiple clinics in obtaining these allergen sensitisation patterns. METHODS: A retrospective, structured chart-review of SPT results was undertaken in allergy clinics throughout Mexico. Ratios of SPT positivity were calculated for individual allergens, per climatic zone and nation-wide. Per allergen group the most important allergens were identified. Statistically significant differences between zones and the nation-wide data were tested with Pearson's Chi-squares test. RESULTS: 4169 skin test charts were recollected. The most important allergens causing sensitisation were very similar in different zones, despite climate variation. The allergen with highest ratio of SPT positivity was Dermatophagoides pteronyssinus (51%), with trees (Ash-27%, Alder-22%, Oak19%), and Bermuda grass (26%) as second and third. In the hot zones (humid and dry) Aspergillus was statistically significant more frequently than in more temperate zones. Cockroaches thrive in big cities and humid zones and Mesquite and Poplar in dry zones. Weeds are less important. CONCLUSION: Mexico has its own SPT sensitisation pattern, which is different from America and Europe. A structured chart-review of SPT results is able to show this and might be a tool for allergists in other countries.
Assuntos
Clima , Inquéritos Epidemiológicos , Hipersensibilidade/diagnóstico , Hipersensibilidade/epidemiologia , Testes Cutâneos , Adolescente , Adulto , Idoso , Animais , Antígenos de Dermatophagoides/efeitos adversos , Antígenos de Dermatophagoides/imunologia , Antígenos de Plantas/efeitos adversos , Antígenos de Plantas/imunologia , Criança , Pré-Escolar , Cynodon , Feminino , Humanos , Hipersensibilidade/imunologia , Masculino , México , Pessoa de Meia-Idade , Pyroglyphidae , Estudos Retrospectivos , ÁrvoresRESUMO
OBJECTIVE: The aims of this study were to validate BOD POD in a wide sample of healthy and independent Mexican elderly men and women subjects using the 4 compartment (4C) model as the reference method, and to evaluate the assumptions of the densitometric two-compartment (2C) model. DESIGN: Cross-sectional study designed to assess body composition and validation of a method based on 2C model (BOD POD). SETTING: Urban and rural regions of Sonora, Mexico. SUBJECTS: Two hundred and two free-living subjects >or=60 years old were completed in this study. METHODS: Body density and body fat were measured by the BOD POD, total body water by deuterium dilution and total body bone ash by dual energy X-ray absorptiometry. Body composition was determined using Baumgartner's equation. RESULTS: Percent body fat by the 4C model was 31.2 and 42.5% in men and women, respectively (P<0.001). Group mean accuracy of body fat by BOD POD against that of the 4C model showed an effect of sex (P<0.001), but not the method (P=0.27). Results of individual accuracy showed no significant difference with the identity line and the slope was significantly different from zero or a slope similar to one. Precision assessed by model R (2) was high for all subjects and for men and women by separate. The standard error of the estimate was low for all and for men and women by separate. Bland and Altman analysis showed no significant bias. CONCLUSION: The BOD POD technique is a valid and reliable method compared to the 4C model and it could be applied in subjects with similar physical and anthropometric characteristics to subjects of this study.
Assuntos
Absorciometria de Fóton/normas , Tecido Adiposo/anatomia & histologia , Composição Corporal , Modelos Teóricos , Absorciometria de Fóton/métodos , Idoso , Idoso de 80 Anos ou mais , Composição Corporal/fisiologia , Água Corporal/fisiologia , Peso Corporal/fisiologia , Densidade Óssea/fisiologia , Estudos Transversais , Feminino , Humanos , Técnicas de Diluição do Indicador , Masculino , México , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Fatores SexuaisRESUMO
The impedance spectroscopy technique (IST) was used for studying the effect of a 0.5 T magnetic field on the electrical properties of whole human blood. A Solartron SI 1260 spectrometer was used to measure the impedance spectra of magnetic field exposed blood samples compared to non-exposed samples. An equivalent electrical circuit model, consisting in a resistance Rs in series with a parallel circuit formed by a constant phase element (CPE) and another resistance Rp, is proposed to fit the data in both cases. The experiment used 3 ml human blood samples from 160 healthy donors. A Wilcoxon matched pairs statistical test was applied to the data. The data analysis seems to show a statistically significant increase of the values of resistance Rp (Z = 5.06, P < 0.001) and capacitance CT (Z = 3.32, P < 0.001) of the blood exposed to magnetic field, by approximately 10.4% and 1.9%, respectively.
Assuntos
Fenômenos Fisiológicos Sanguíneos/efeitos da radiação , Campos Eletromagnéticos , Magnetismo , Análise Espectral/métodos , Adolescente , Adulto , Capacitância Elétrica , Impedância Elétrica , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Doses de RadiaçãoAssuntos
Toxicologia , Toxicologia , Venenos , Intoxicação , Toxinas Biológicas , Toxicologia , Alergia e ImunologiaRESUMO
In any scientific theory, the conceptual framework already determines the nature and possible scope of the results. Oversimplification prevents an adequate description of the system, whereas too detailed a description obscures the fundamental principles behind the observed phenomena in addition to misspending time and resources. In theoretical neuroscience, this is an important issue because the description level varies widely from detailed biophysical descriptions to abstract computational models. We discuss the question of the appropriate modeling level in the context of a recent report on synchrony in iteratively constructed feed-forward networks of rat cortex pyramidal neuron somata (Reyes, 2003).
Assuntos
Sincronização Cortical/métodos , Redes Neurais de Computação , Neurônios/fisiologia , Potenciais de Ação/fisiologiaRESUMO
We discuss a biophysical model of synaptic plasticity that provides a unified view of the outcomes of synaptic modification protocols, including: (1) prescribed time courses of postsynaptic intracellular Ca(2+) release, (2) postsynaptic voltage clamping with presentation of presynaptic spike trains at various frequencies, (3) direct postsynaptic response to presynaptic spike trains at various frequencies, and (4) LTP/LTD as a response to precisely timed presynaptic and postsynaptic spikes.
Assuntos
Modelos Biológicos , Plasticidade Neuronal/fisiologia , Dinâmica não Linear , Sinapses/fisiologia , Animais , Cálcio/metabolismo , Canais de Cálcio/fisiologia , Relação Dose-Resposta a Droga , Estimulação Elétrica , Potenciais Pós-Sinápticos Excitadores , Hipocampo/efeitos dos fármacos , Hipocampo/fisiologia , Magnésio/farmacologia , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Terminações Pré-Sinápticas/fisiologia , Tempo de Reação/fisiologia , Receptores de AMPA/fisiologia , Receptores de N-Metil-D-Aspartato/fisiologia , Sinapses/efeitos dos fármacos , Transmissão Sináptica , Fatores de TempoRESUMO
The aim of the study was to evaluate the association between hyperprolactinemia and T lymphocyte activation through the soluble IL-2 receptor (sIL-2R) in systemic lupus erythematosus (SLE) patients. Seventy SLE patients, 18 of them with hyperprolactinemia (HPRL), were compared with 18 normoprolactinemic (NPRL) patients and 10 age-matched healthy blood-bank donor women. Patients were evaluated by means of the SLE activity index (SLEDAI). Total serum IgG and sIL-2R levels were determined by an ELISA assay. Differences between sIL-2R and IgG serum levels in patients and controls were examined by Kruskal-Wallis analysis and a Spearman r correlation to determine the association between sIL-2R, IgG and prolactin (PRL) levels. IgG and sIL-2R serum levels did not differ significantly between HPRL and NPRL patients: 1827.3 (1428-2226) vs 2028.8 (1586-2467) mg/dl and 882.2 (511-1254) vs 740.1 (534-946.4) U/ml, respectively (confidence interval 95%). In the total SLE group, sIL-2R and IgG serum levels were positively associated (P = 0.0009), however, this was not the case for sIL-2R and PRL (P > 0.49). We did not demonstrate an association between HPRL and lymphocyte activation measured through serum sIL-2R in female patients with SLE.
Assuntos
Hiperprolactinemia/imunologia , Lúpus Eritematoso Sistêmico/imunologia , Ativação Linfocitária/imunologia , Receptores de Interleucina-2/imunologia , Adolescente , Adulto , Biomarcadores/sangue , Feminino , Humanos , Hiperprolactinemia/etiologia , Imunoglobulina G/imunologia , Lúpus Eritematoso Sistêmico/complicações , Linfócitos T/imunologiaRESUMO
We study the synchronization of two model neurons coupled through a synapse having an activity-dependent strength. Our synapse follows the rules of spike-timing dependent plasticity. We show that this plasticity of the coupling between neurons produces enlarged frequency-locking zones and results in synchronization that is more rapid and much more robust against noise than classical synchronization arising from connections with constant strength. We also present a simple discrete map model that demonstrates the generality of the phenomenon.
Assuntos
Biofísica , Neurônios/patologia , Animais , Fenômenos Biofísicos , Modelos Teóricos , Distribuição Normal , Fatores de TempoRESUMO
Using a modified version of a phenomenological model for the dynamics of synaptic plasticity, we examine some recent experiments of Wu et al. [(2001) J Physiol 533:745-755]. We show that the model is quantitatively consistent with their experimental protocols producing long-term potentiation (LTP) and long-term depression (LTD) in slice preparations of rat hippocampus. We also predict the outcome of similar experiments using different frequencies and depolarization levels than reported in their results.
Assuntos
Hipocampo/fisiologia , Potenciação de Longa Duração/fisiologia , Vias Neurais/fisiologia , Neurônios/fisiologia , Sinapses/fisiologia , Potenciais de Ação/fisiologia , Animais , Hipocampo/citologia , Depressão Sináptica de Longo Prazo/fisiologia , Modelos Neurológicos , Vias Neurais/citologia , Neurônios/citologia , Dinâmica não Linear , Valor Preditivo dos Testes , Ratos , Reprodutibilidade dos Testes , Transmissão Sináptica/fisiologiaRESUMO
The role of synaptic dynamics in processing neural information is investigated in a neural information channel with realistic model neurons having chaotic intrinsic dynamics. Our neuron models are realized in simple analogue circuits, and our synaptic connections are realized both in analogue circuits and through a dynamic clamp program. The information which is input to the first chaotic neuron in the channel emerges partially absent and partially 'hidden'. Part is absent because of the dynamical effects of the chaotic oscillation that effectively acts as a noisy channel. The 'hidden' part is recoverable. We show that synaptic parameters, most significantly receptor binding time constants, can be tuned to enhance the information transmission by the combination of a neuron plus a synapse. We discuss how the dynamics of the synapse can be used to recover 'hidden' information using average mutual information as a measure of the quality of information transport.
Assuntos
Memória/fisiologia , Modelos Neurológicos , Sinapses/fisiologia , AnimaisRESUMO
Long-term synaptic plasticity leading to enhancement in synaptic efficacy (long-term potentiation, LTP) or decrease in synaptic efficacy (long-term depression, LTD) is widely regarded as underlying learning and memory in nervous systems. LTP and LTD at excitatory neuronal synapses are observed to be induced by precise timing of pre- and postsynaptic events. Modification of synaptic transmission in long-term plasticity is a complex process involving many pathways; for example, it is also known that both forms of synaptic plasticity can be induced by various time courses of Ca(2+) introduction into the postsynaptic cell. We present a phenomenological description of a two-component process for synaptic plasticity. Our dynamical model reproduces the spike time-dependent plasticity of excitatory synapses as a function of relative timing between pre- and postsynaptic events, as observed in recent experiments. The model accounts for LTP and LTD when the postsynaptic cell is voltage clamped and depolarized (LTP) or hyperpolarized (LTD) and no postsynaptic action potentials are evoked. We are also able to connect our model with the Bienenstock, Cooper, and Munro rule. We give model predictions for changes in synaptic strength when periodic spike trains of varying frequency and Poisson distributed spike trains with varying average frequency are presented pre- and postsynaptically. When the frequency of spike presentation exceeds approximately 30-40 Hz, only LTP is induced.
Assuntos
Potenciação de Longa Duração , Plasticidade Neuronal/fisiologia , Sinapses/fisiologia , Modelos Neurológicos , Transmissão Sináptica/fisiologiaRESUMO
Methods of objectively assessing the growth rate of hairs in hirsute women have generally required some form of shaving and have focused on studying hairs affecting the face, which has reduced the number of patients willing or able to participate in such studies. A possible solution is to assess the terminal hairs on the lower abdomen (ie, the male escutcheon) because these two body areas are the most frequently affected with excess hair growth in hirsute patients. Nonetheless, it is unclear how the growth characteristics (density, diameter, and growth rate) of the hairs on the abdomen and face differ in these patients. We hypothesize that the growth characteristics of terminal hairs on the abdomen and face are similar and that evaluation of either area may be sufficient in assessing the hair growth rate of these patients. To objectively evaluate hair growth in the face and abdomen in hirsute patients, we developed a computer-aided image analysis system capable of measuring several growth parameters. Twenty hirsute women (12 white and 8 black), aged 31.2 +/- 6.1 years, were studied. Facial and abdominal skin areas were shaved, and 3 to 5 days later the areas were photographed through a calibrated glass plate and 5 terminal hairs were plucked from each area. The daily hair growth rate (assessed by photography and by direct measurement of the plucked hair), the density of hairs (number of hairs per surface area assessed by photography), and hair diameter (of the plucked hairs) were determined. The extent of hirsutism was also measured, albeit subjectively, by a modification of the Ferriman-Gallwey method, with each area given a score of 0 (no terminal hairs seen) to 4 (terminal hairs in a pattern similar to that of a very hirsute man). Facial, abdominal, and total Ferriman-Gallwey scores were 1.3 +/- 0.6, 1.8 +/- 0.9, and 12.5 +/- 5.4, respectively. Our results indicated that facial hairs were distributed in greater density and had a greater diameter than abdominal hairs (15.6 +/- 14.2 hairs/cm(2) vs 5.4 +/- 1.9 hairs/cm(2), and 84.5 +/- 19.5 microm and 66.2 +/- 17.5 microm, respectively, P <.005). Alternatively, the growth rates of facial and abdominal hairs were similar, whether determined photographically (0.36 +/- 0.18 mm/day vs 0.43 +/- 0.19 mm/day, respectively) or from plucked hairs (1.2 +/- +0.2 mm/d vs 1.4 + 0.4 mm/d, respectively). We conclude that although the density and diameter of facial hairs are greater than that of lower abdominal hairs, these areas have very similar growth rates. Hence evaluation of either of the body areas, using an objective method of assessing hair growth, should provide equivalent results.
Assuntos
Cabelo/crescimento & desenvolvimento , Hirsutismo/fisiopatologia , Abdome , Adulto , Face , Feminino , Cabelo/anatomia & histologia , Humanos , FotografaçãoRESUMO
Two main classes of excitable neurons are analyzed in terms of connection topology and strength of the coupling in a network of neurons. In both cases, we measure the degree of synchronization and responsiveness of the neural assembly. Class 2 excitability presents a fast wave-like propagation of the activity pattern, strong frequency dependence on the connection topology and a good level of synchronization regardless of the topology. On the other hand, class 1 excitability shows a strong dependence of the wave propagation speed and the synchronization degree on the connection topology, in addition no frequency adaptation is observed. We conclude that both types of neural excitability endow the neural assembly with very different dynamical properties. Although, for simplicity reasons, no inhibition has been included in our study, the emergent properties described in this paper may help to determine the class of excitability underlying a neural assembly.
Assuntos
Potenciais de Ação/fisiologia , Sincronização Cortical , Modelos Neurológicos , Rede Nervosa/fisiologia , Neurônios/fisiologia , Transmissão Sináptica/fisiologia , Animais , Relógios Biológicos/fisiologia , Humanos , Tempo de Reação/fisiologiaRESUMO
An essential question raised after the observation of highly variable bursting activity in individual neurons of Central Pattern Generators (CPGs) is how an assembly of such cells can cooperatively act to produce regular signals to motor systems. It is well known that some neurons in the lobster stomatogastric ganglion have a highly irregular spiking-bursting behavior when they are synaptically isolated from any connection in the CPG. Experimental recordings show that periodic stimuli on a single neuron can regulate its firing activity. Other evidence demonstrates that specific chemical and/or electrical synapses among neurons also induce the regularization of the rhythms. In this paper we present a modeling study in which a slow subcellular dynamics, the exchange of calcium between an intracellular store and the cytoplasm, is responsible for the origin and control of the irregular spiking-bursting activity. We show this in simulations of single cells under periodic driving and in minimal networks where the cooperative activity can induce regularization. While often neglected in the description of realistic neuron models, subcellular processes with slow dynamics may play an important role in information processing and short-term memory of spiking-bursting neurons.
Assuntos
Potenciais de Ação/fisiologia , Gânglios dos Invertebrados/fisiologia , Modelos Neurológicos , Nephropidae/fisiologia , Rede Nervosa/fisiologia , Neurônios/fisiologia , Periodicidade , Transmissão Sináptica/fisiologia , Animais , Sinalização do Cálcio/fisiologia , Nephropidae/citologiaRESUMO
Following studies of olfactory processing in insects and fish, we investigate neural networks whose dynamics in phase space is represented by orbits near the heteroclinic connections between saddle regions (fixed points or limit cycles). These networks encode input information as trajectories along the heteroclinic connections. If there are N neurons in the network, the capacity is approximately e(N-1)!, i.e., much larger than that of most traditional network structures. We show that a small winnerless competition network composed of FitzHugh-Nagumo spiking neurons efficiently transforms input information into a spatiotemporal output.
Assuntos
Modelos Neurológicos , Rede Nervosa/fisiologia , Neurônios/fisiologia , Potenciais de Ação/fisiologia , Animais , Peixes/fisiologia , Gafanhotos/fisiologia , Condutos Olfatórios/fisiologia , Sinapses/fisiologiaRESUMO
The prevalence of infertility has increased in recent years, but the medical services to treat these problems are not available for most of the affected couples. The prognosis for fertility is important in order to determine the therapeutic capacity of each service, and to select the couples that could be treated at a primary level, or to send them to more advanced levels of reproductive technology. In practice, the infertility is treated in primary medical levels and the assisted reproductive technology is available only to a limited sector of the poblation. In general, the managed-care plans do not compensate directly for infertility treatments, but they are indirectly paying some therapeutic procedures for fertility.