Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
The Effect of Threat on Novelty Evoked Amygdala Responses  [PDF]
Nicholas L. Balderston, Doug H. Schultz, Fred J. Helmstetter
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0063220
Abstract: A number of recent papers have suggested that the amygdala plays a role in the brain’s novelty detection circuit. In a recent study, we showed that this role may be specific to certain classes of biologically-relevant stimuli, such as human faces. The purpose of the present experiment was to determine whether other biologically-relevant stimuli also evoke novelty specific amygdala responses. To test this idea, we presented novel and repeated images of snakes and flowers while measuring BOLD. Surprisingly, we found that novel images of snakes and flowers evoke more amygdala activity than repeated images of snakes and flowers. Our results further confirm the robustness of the novelty evoked amygdala responses, even when compared with effects more traditionally associated with the amygdala. In addition, our results suggest that threatening stimuli may prime the amygdala to respond to other types of stimuli as well.
Recording Visual Evoked Potentials and Auditory Evoked P300 at 9.4T Static Magnetic Field  [PDF]
Jorge Arrubla, Irene Neuner, David Hahn, Frank Boers, N. Jon Shah
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0062915
Abstract: Simultaneous recording of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) has shown a number of advantages that make this multimodal technique superior to fMRI alone. The feasibility of recording EEG at ultra-high static magnetic field up to 9.4T was recently demonstrated and promises to be implemented soon in fMRI studies at ultra high magnetic fields. Recording visual evoked potentials are expected to be amongst the most simple for simultaneous EEG/fMRI at ultra-high magnetic field due to the easy assessment of the visual cortex. Auditory evoked P300 measurements are of interest since it is believed that they represent the earliest stage of cognitive processing. In this study, we investigate the feasibility of recording visual evoked potentials and auditory evoked P300 in a 9.4T static magnetic field. For this purpose, EEG data were recorded from 26 healthy volunteers inside a 9.4T MR scanner using a 32-channel MR compatible EEG system. Visual stimulation and auditory oddball paradigm were presented in order to elicit evoked related potentials (ERP). Recordings made outside the scanner were performed using the same stimuli and EEG system for comparison purposes. We were able to retrieve visual P100 and auditory P300 evoked potentials at 9.4T static magnetic field after correction of the ballistocardiogram artefact using independent component analysis. The latencies of the ERPs recorded at 9.4T were not different from those recorded at 0T. The amplitudes of ERPs were higher at 9.4T when compared to recordings at 0T. Nevertheless, it seems that the increased amplitudes of the ERPs are due to the effect of the ultra-high field on the EEG recording system rather than alteration in the intrinsic processes that generate the electrophysiological responses.
Effects of caffeine on visual evoked potencial (P300) and neuromotor performance
Deslandes, Andréa Camaz;Veiga, Heloisa;Cagy, Maurício;Piedade, Roberto;Pompeu, Fernando;Ribeiro, Pedro;
Arquivos de Neuro-Psiquiatria , 2004, DOI: 10.1590/S0004-282X2004000300002
Abstract: the stimulant effects of caffeine on cognitive performance have been widely investigated. the visual evoked potential, specially the p300 component, has been used in studies that explain the stimulant mechanisms of caffeine through neurophysiological methods. in this context, the present study aimed to investigate electrophysiological changes (p300 latency) and modification of cognitive and motor performance produced by caffeine. fifteen healthy volunteers, 9 women and 6 men (26 ± 5 years, 67 ± 12.5kg) were submitted three times to the following procedure: electroencefalographic recording, word color stroop test, and visual discrimination task. subjects took a gelatin caffeine capsule (400 mg) or a placebo (p1 and p2), in a randomized, crossover, double-blind design. a one-factor anova and tukey? post hoc test were used to compare dependent variables on the c, p1 and p2 moments. the statistical analyses indicated a non-significant decrease in reaction time, stroop execution time and latency at cz on the caffeine moment when compared to the others. moreover, a non-significant increase in stroop raw score and latency at pz could be observed. the only significant result was found at fz. these findings suggest that the positive tendency of caffeine to improve cognitive performance is probably associated with changes in the frontal cortex, a widely recognized attention area.
Correla o do potencial evocado P300 com aspectos cognitivos e depressivos do envelhecimento Correlation of the P300 evoked potential in depressive and cognitive aspects of aging  [cached]
Elisiane Crestani de Miranda,Maria Madalena Canina Pinheiro,Liliane Desgualdo Pereira,Maria Cecília Martineli Iorio
Brazilian Journal of Otorhinolaryngology , 2012, DOI: 10.5935/1808-8694.20120013
Abstract: O P300 é um potencial evocado auditivo de longa latência dependente das habilidades cognitivas. Acredita-se que altera es cognitivas decorrentes ou n o por sintomas depressivos possam interferir no P300. OBJETIVO: Verificar a influência do envelhecimento, dos aspectos cognitivos e depressivos na latência do P300 em idosos. MéTODO: Estudo clínico e experimental com 60 idosos com perda auditiva neurossensorial de grau leve a moderadamente grave, sendo 20 do sexo masculino e 40 feminino e idade média de 71,1 anos. Os participantes realizaram o potencial evocado auditivo de longa latência, no qual foi estudada a latência do P300 (milissegundos). Os aspectos cognitivos foram avaliados por meio do Miniexame do Estado Mental (MEEM) e Escala de Avalia o da Doen a de Alzheimer (ADAS-Cog). Na avalia o da sintomatologia depressiva, foi aplicada a Escala de Depress o Geriátrica (EDG-15). RESULTADOS: Observou-se uma correla o positiva significante entre a Latência e Idade (p = 0,031). Entretanto, n o houve diferen a significante entre a latência do P300 e as categorias do ADAS-Cog (p = 0,584), MEEM (p = 0,199) e EDG (p = 0,541). CONCLUS O:O avan o da idade ocasionou um aumento da latência do P300, porém, o desempenho cognitivo e a presen a de sintomatologia depressiva n o influenciaram os resultados do P300 nesta popula o de idosos. The P300 is a long-latency auditory evoked potential highly dependent on cognitive skills. It is believed that cognitive changes caused or not by depressive symptoms may interfere with the P300. AIM: To investigate the influence of aging, cognitive and depression aspects of the P300 latency in elderly people. METHODS: Clinical and experimental study with 60 elderly patients with sensorineural hearing loss of mild to moderately severe level, 20 males and 40 females, average age of 71.1. Participants were submitted to the long latency auditory evoked potential, in which the P300 latency (milliseconds) was studied. The cognitive aspects were assessed using the Mini-Mental State Examination (MMSE) and Alzheimer's Disease Assessment Scale (ADAS-Cog). In the assessment of depressive symptoms the Geriatric Depression Scale (GDS-15) was applied. RESULTS: We found a significant positive correlation between latency and age (p = 0.031). There were no significant differences among the P300 latency and the ADAS-Cog (p = 0.584), MMSE (p = 0.199) and GDS (p = 0.541) categories. CONCLUSION: Aging caused an increase in the P300 latency; however, cognitive performance and the presence of depressive symptoms did not influence the P300 results in this
Bayesian Odds-Ratio Filters: A Template-Based Method for Online Detection of P300 Evoked Responses  [PDF]
Asim M. Mubeen,Kevin H. Knuth
Physics , 2013,
Abstract: Template-based signal detection most often relies on computing a correlation, or a dot product, between an incoming data stream and a signal template. While such a correlation results in an ongoing estimate of the magnitude of the signal in the data stream, it does not directly indicate the presence or absence of a signal. Instead, the problem of signal detection is one of model-selection. Here we explore the use of the Bayesian odds-ratio (OR), which is the ratio of posterior probabilities of a signal-plus-noise model over a noise-only model. We demonstrate this method by applying it to simulated electroencephalographic (EEG) signals based on the P300 response, which is widely used in both Brain Computer Interface (BCI) and Brain Machine Interface (BMI) systems. The efficacy of this algorithm is demonstrated by comparing the receiver operating characteristic (ROC) curves of the OR-based (logOR) filter to the usual correlation method where we find a significant improvement in P300 detection. The logOR filter promises to improve the accuracy and speed of the detection of evoked brain responses in BCI/BMI applications as well the detection of template signals in general.
Analysis of the influence of bromazepam on cognitive performance through the visual evoked potential (P300)
Puga, Fernanda;Veiga, Heloisa;Cagy, Maurício;McDowell, Kaleb;Piedade, Roberto;Ribeiro, Pedro;
Arquivos de Neuro-Psiquiatria , 2005, DOI: 10.1590/S0004-282X2005000200008
Abstract: benzodiazepines have been used in the pharmacological treatment of anxiety for over four decades. however, very few studies have combined bromazepam and event-related potentials (erp). the present study aimed at investigating the modulatory effects of this drug on brain dynamics. specifically, the effects of bromazepam (3mg) on the p300 component of the erp were tested in a double-blind experiment. the sample, consisting of 15 healthy subjects (7 male and 8 female), was submitted to a visual discrimination task, which employed the "oddball" paradigm. electrophysiological (p300) and behavioral measures (stroop, digit span, and reaction time) were analyzed across three experimental conditions: placebo 1, placebo 2, and bromazepam. results suggest that the effects of bromazepam (3mg) on cognitive processes are not apparent. in spite of what seems irrefutable in current literature, bromazepam did not produce evident effects on the behavioral and electrophysiological variables analyzed.
Pain-related somatosensory evoked potentials and functional brain magnetic resonance in the evaluation of neurologic recovery after cardiac arrest: a case study of three patients
Paolo Zanatta, Simone Messerotti Benvenuti, Fabrizio Baldanzi, Matteo Bendini, Marsilio Saccavini, Wadih Tamari, Daniela Palomba, Enrico Bosco
Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine , 2012, DOI: 10.1186/1757-7241-20-22
Abstract: Early and accurate prognostic assessment of neurological functional outcomes in comatose patients after cardiac arrest is a relevant medical, ethical, and economic issue. It has been shown that beyond the Glasgow Coma Scale (GCS), a patient's pupil light reactivity, corneal reflexes, myoclonus status epilepticus, and serum neuron-specific enolase, short latency somatosensory-evoked potentials (SEPs) (N20/P25) improve the accuracy of neurological prognosis in comatose patients after cardiac arrest [1]. SEPs have shown high sensitivity and specificity in predicting poor outcomes. Indeed, that the bilateral disappearance of cortical N20/P25 is well-established to be associated with adverse outcomes such as death or survival in a vegetative state. Nonetheless, the presence of N20/P25 may not be sensitive enough to predict a good neurological outcome [2]. In fact, only the event-related evoked potentials (i.e., mismatched negativity and novelty P300), middle latency cortical somatosensory-evoked potentials (MLCEPs), and reactivity electroencephalogram (EEG) background have been associated with a favourable neurological prognosis [3-7].In recent years, brain functional neuroimaging has been used in order to clarify the diagnosis of the vegetative state, suggesting that brain activation imaging may reflect awareness and/or cognition and provide reliable prognostic information [8,9]. However, given that this methodology is based on imagery and communication task paradigms, this approach is only feasible in the chronic phase of consciousness disorders. Moreover, studies using positron emission tomography have shown that minimally conscious state patients, compared to vegetative state patients, may show brain processing activation elicited by noxious electrical stimulation of the median nerves similar to that seen in healthy controls, suggesting a possible cortical processing of pain [10-12]. However, the intensity of electrical stimuli applied in vegetative patients (i.e., 1
P300 brain computer interface: current challenges and emerging trends  [PDF]
Reza Fazel-Rezai,Brendan Z. Allison,Christoph Guger,Eric W. Sellers,Sonja C. Kleih,Andrea Kübler
Frontiers in Neuroengineering , 2012, DOI: 10.3389/fneng.2012.00014
Abstract: A brain-computer interface (BCI) enables communication without movement based on brain signals measured with electroencephalography (EEG). BCIs usually rely on one of three types of signals: the P300 and other components of the event-related potential (ERP), steady state visual evoked potential (SSVEP), or event related desynchronization (ERD). Although P300 BCIs were introduced over twenty years ago, the past few years have seen a strong increase in P300 BCI research. This closed-loop BCI approach relies on the P300 and other components of the ERP, based on an oddball paradigm presented to the subject. In this paper, we overview the current status of P300 BCI technology, and then discuss new directions: paradigms for eliciting P300s; signal processing methods; applications; and hybrid BCIs. We conclude that P300 BCIs are quite promising, as several emerging directions have not yet been fully explored and could lead to improvements in bit rate, reliability, usability, and flexibility.
Auditory evoked potentials in peripheral vestibular disorder individuals  [cached]
Matas, Carla Gentile,Silva, Sara Manami,Wen, Débora Dong Mei,Nunes, Cristiane da Silva
International Archives of Otorhinolaryngology , 2011,
Abstract: Introduction: The auditory and vestibular systems are located in the same peripheral receptor, however they enter the CNS and go through different ways, thus creating a number of connections and reaching a wide area of the encephalon. Despite going through different ways, some changes can impair both systems. Such tests as Auditory Evoked Potentials can help find a diagnosis when vestibular alterations are seen. Objective: describe the Auditory Evoked Potential results in individuals complaining about dizziness or vertigo with Peripheral Vestibular Disorders and in normal individuals having the same complaint. Methods: Short, middle and long latency Auditory Evoked Potentials were performed as a transversal prospective study. Conclusion: individuals complaining about dizziness or vertigo can show some changes in BAEP (Brainstem Auditory Evoked Potential), MLAEP (Medium Latency Auditory Evoked Potential) and P300.
ABR and auditory P300 findings inchildren with ADHD
Schochat, Eliane;Scheuer, Claudia Ines;Andrade, ênio Roberto de;
Arquivos de Neuro-Psiquiatria , 2002, DOI: 10.1590/S0004-282X2002000500012
Abstract: auditory processing disorders (apd), also referred as central auditory processing disorders (capd) and attention deficit hyperactivity disorders (adhd) have become popular diagnostic entities for school age children. it has been demonstrated a high incidence of comorbid adhd with communication disorders and auditory processing disorder. the aim of this study was to investigate abr and p300 auditory evoked potentials in children with adhd, in a double-blind study. twenty-one children, ages between 7 and 10 years, with a primary diagnosis of adhd, participated in this experiment. results showed that all children had normal abr with normal latency for wave v. results also showed that among 42 ears combined 52.38% did not have p300. for the medicated subjects we observed that among 28 ears, 42.85% did not have p300 and for the non-medicated 71.43% (n = 14 ears) did not have p300. our results suggest that the medicated subjects had more presence of p300 (57.15%) than the non-medicated group (28.57%), though the absence of these potentials were high among the group - 52.38%.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.