Morfología de los potenciales evocados auditivos de latencia tardía P300 y su rol en la evaluación de la conducta suicida / Morphology of auditory evoked potentials, and its role in the evaluation of suicidal behavior

El suicidio es un problema de salud a nivel mundial, siendo la conducta suicida uno de los predictores de mortalidad por suicidio; sin embargo, su valoración aún sigue siendo compleja. Aunque la cantidad de literatura que ha abordado distintas perspectivas de la conducta suicida es abundante, se requiere ahondar en nuevos métodos que permitan una valoración rápida y objetiva de ésta, proporcionando a los clínicos y pacientes, un sistema de evaluación que registre los cambios de estados emocionales de manera dinámica. El objetivo de este manuscrito fue proporcionar una visión general de la morfología de los potenciales evocados auditivos de latencia tardía p300 y su rol en la evaluación de la conducta suicida.

Suicide is a global health problem, with suicidal behavior being one of the predictors of suicide mortality; however, its assessment is still complex. Although the amount of literature that has addressed different perspectives of suicidal behavior is abundant, it is necessary to deepen new methods that allow a rapid and objective assessment of it, providing clinicians and patients with an evaluation system that allows changes in emotional state to be recorded dynamically. The aim of this manuscript was to provide an overview of morphological patterns of auditory evoked potential P300 latency late in the assessment of suicidal behavior.

Tinnitus and event related potentials: a systematic review / Zumbido e potenciais evocados auditivos relacionados a eventos: uma revisão sistemática

Abstract Introduction Tinnitus is sound perception in the absence of a sound source. Changes in parameters of latency and amplitude on the auditory event related potentials or long latency potentials waves have been cited in tinnitus patients when compared to a control group. Objective To perform an assessment of scientific evidence that verifies the possibility of alterations in latency or amplitude of the waves of event related potentials in individuals with tinnitus. Methods By using SciELO, Lilacs, ISI Web and PubMed, scientific databases, a review was performed. Articles published in English, Portuguese, French and Spanish that correlated tinnitus with changes in event related potentials were included in this review. Results Twelve articles were located, however only eight fulfilled the criteria for inclusion. Conclusion The sample of selected studies demonstrate that the long latency auditory evoked potentials related to events between the control and tinnitus patients showed some changes in latency and or amplitude in tinnitus patients. There are changes in event-related potentials when comparing patients with tinnitus and the control group. These changes take place considering the severity of tinnitus, tinnitus site of lesion, and capacity for changes after interventions. The event related potentials can help to determine the neurotransmitter involved in tinnitus generation and evaluate tinnitus treatments.

Resumo Introdução O zumbido é a percepção de um som na ausência de uma fonte sonora. Mudanças nos parâmetros de latência e amplitude nas ondas dos potenciais evocados auditivos relacionados a eventos ou potenciais de longa latência foram citadas em pacientes com zumbido quando comparados a um grupo controle. Objetivo Realizar uma avaliação de evidências científicas que verifiquem a possibilidade de alterações na latência ou amplitude das ondas de potenciais evocados auditivos relacionados a eventos em indivíduos com zumbido. Método Foi feita uma revisão a partir dos bancos de dados científicos SciELO, Lilacs, ISI Web e PubMed. Artigos publicados em inglês, português, francês e espanhol que correlacionavam zumbido com alterações nos potenciais evocados auditivos relacionados a eventos foram incluídos. Resultados Foram localizados 12 artigos, porém apenas oito preencheram os critérios de inclusão. Conclusão A amostra de estudos selecionados demonstra que os potenciais evocados auditivos de longa latência relacionados a eventos entre os pacientes-controle e com zumbido apresentaram algumas alterações na latência e/ou amplitude nos pacientes com zumbido. Há mudanças nos potenciais relacionados a eventos ao comparar pacientes com zumbido e o grupo controle. Essas alterações consideram a gravidade do zumbido, o local da lesão do zumbido e a capacidade de alterações após as intervenções. Os potenciais evocados auditivos relacionados a eventos podem ajudar a determinar o neurotransmissor envolvido na geração do zumbido e avaliar os tratamentos para o zumbido.

Auditory training in autism spectrum disorder: a case report / Treinamento auditivo no transtorno do espectro autista: relato de caso

ABSTRACT This study aimed to measure the effects of a Computer-based Auditory Training Program (CBATP) on an adolescent diagnosed with Autism Spectrum Disorder (ASD) and Central Auditory Processing Disorder (CAPD). This is the case report of a male, 14-year-old adolescent diagnosed with ASD. The individual was submitted to basic audiological evaluation, central auditory processing assessment and hearing electrophysiology (EP), pre- and post-therapeutic intervention. Central auditory processing (CAP) was assessed by means of the following instruments: Time-compressed Speech Test (TCST), Random Gap Detection Test (RGDT), Staggered Spondaic Word Test (SSWT), Frequency (Pitch) Pattern Sequence Test (FPST), and Duration Pattern Test (DPT). The P300 component of the Event-related Potential (ERP) was used in the hearing EP. Pre-intervention assessment of CAP showed changes in the auditory skills of closure, figure-ground and temporal ordering, but normal temporal resolution ability. Post-intervention evaluation of CAP showed improvement in all previously mentioned auditory skills, except for the figure-ground ability, which remained unchanged. Regarding the findings of the hearing EP, a decrease in the latency of the P300 component was observed pre- and post-intervention. This study demonstrated that the use of a CBATP resulted in improvement in the hearing abilities assessed in an adolescent diagnosed with ASD.

RESUMO O objetivo deste estudo foi mensurar o efeito do treinamento auditivo computadorizado em um adolescente diagnosticado com Transtorno do Espectro Autista e Transtorno do Processamento Auditivo. Participou do estudo um adolescente de 14 anos, do sexo masculino, diagnosticado com Transtorno do Espectro Autista. O sujeito foi submetido à avaliação audiológica básica, avaliação do processamento auditivo central e avaliação eletrofisiológica da audição pré e pós-intervenção. A avaliação do processamento auditivo foi composta do Teste de Fala Comprimida (FC), Randon Gap Detection Test (RGDT), Staggered Spondaic Words (SSW), Teste de Padrão de Frequência (TPF) e Teste de Padrão de Duração (TPD). Na avaliação eletrofisiológica, utilizou-se o Potencial Evocado Auditivo Cognitivo (P300). Na avaliação do processamento auditivo central pré-intervenção terapêutica, observou-se alteração nas habilidades de fechamento auditivo, figura-fundo e ordenação temporal. Na habilidade auditiva de resolução temporal, o sujeito da pesquisa demonstrou desempenho dentro dos padrões de normalidade. Na realização do processamento auditivo central, foi possível observar melhora nos resultados de todas as habilidades auditivas citadas anteriormente, exceto na habilidade de figura-fundo, que permaneceu alterada. Quantos aos achados da avaliação eletrofisiológica da audição, verificou-se diminuição da latência do componente P300 na comparação dos resultados pré e pós-treinamento auditivo. Este estudo demonstrou que a utilização de treinamento auditivo trouxe como efeito uma melhora das habilidades auditivas avaliadas de um adolescente diagnosticado com Transtorno do Espectro Autista.

P3 Cognitive Potential in Cochlear Implant Users

Abstract Introduction The P3 cognitive evoked potential is recorded when a subject correctly identifies, evaluates and processes two different auditory stimuli. Objective to evaluate the latency and amplitude of the P3 evoked potential in 26 cochlear implant users with post-lingual deafness with good or poor speech recognition scores as compared with normal hearing subjects matched for age and educational level. Methods In this prospective cohort study, auditory cortical responses were recorded from 26 post-lingual deaf adult cochlear implant users (19 with good and 7 with poor speech recognition scores) and 26 control subjects. Results There was a significant difference in the P3 latency between cochlear implant users with poor speech recognition scores (G-) and their control group (CG) (p= 0.04), and between G- and cochlear implant users with good speech discrimination (G+) (p= 0.01). We found no significant difference in the P3 latency between the CG and G+. In this study, all G- patients had deafness due to meningitis, which suggests that higher auditory function was impaired too. Conclusion Post-lingual deaf adult cochlear implant users in the G- group had prolonged P3 latencies as compared with the CG and the cochlear implant users in the G+ group. The amplitudes were similar between patients and controls. All G- subjects were deaf due to meningitis. These findings suggest that meningitis may have deleterious effects not only on the peripheral auditory system but on the central auditory processing as well.

Monitoring auditory cortical plasticity in hearing aid users with long latency auditory evoked potentials: a longitudinal study

OBJECTIVE: The objective of this study was to compare long-latency auditory evoked potentials before and after hearing aid fittings in children with sensorineural hearing loss compared with age-matched children with normal hearing. METHODS: Thirty-two subjects of both genders aged 7 to 12 years participated in this study and were divided into two groups as follows: 14 children with normal hearing were assigned to the control group (mean age 9 years and 8 months), and 18 children with mild to moderate symmetrical bilateral sensorineural hearing loss were assigned to the study group (mean age 9 years and 2 months). The children underwent tympanometry, pure tone and speech audiometry and long-latency auditory evoked potential testing with speech and tone burst stimuli. The groups were assessed at three time points. RESULTS: The study group had a lower percentage of positive responses, lower P1-N1 and P2-N2 amplitudes (speech and tone burst), and increased latencies for the P1 and P300 components following the tone burst stimuli. They also showed improvements in long-latency auditory evoked potentials (with regard to both the amplitude and presence of responses) after hearing aid use. CONCLUSIONS: Alterations in the central auditory pathways can be identified using P1-N1 and P2-N2 amplitude components, and the presence of these components increases after a short period of auditory stimulation (hearing aid use). These findings emphasize the importance of using these amplitude components to monitor the neuroplasticity of the central auditory nervous system in hearing aid users.

Temporal processing and long-latency auditory evoked potential in stutterers / Processamento temporal e potencial evocado auditivo de longa latência em indivíduos gagos

Abstract Introduction: Stuttering is a speech fluency disorder, and may be associated with neuroaudiological factors linked to central auditory processing, including changes in auditory processing skills and temporal resolution. Objective: To characterize the temporal processing and long-latency auditory evoked potential in stutterers and to compare them with non-stutterers. Methods: The study included 41 right-handed subjects, aged 18-46 years, divided into two groups: stutterers (n = 20) and non-stutters (n = 21), compared according to age, education, and sex. All subjects were submitted to the duration pattern tests, random gap detection test, and long-latency auditory evoked potential. Results: Individuals who stutter showed poorer performance on Duration Pattern and Random Gap Detection tests when compared with fluent individuals. In the long-latency auditory evoked potential, there was a difference in the latency of N2 and P3 components; stutterers had higher latency values. Conclusion: Stutterers have poor performance in temporal processing and higher latency values for N2 and P3 components.

Resumo Introdução: A gagueira é um distúrbio da fluência da fala e pode estar associada a fatores neuroaudiológicos ligados ao processamento auditivo central, entre eles as alterações das habilidades auditivas de processamento e resolução temporal. Objetivo: Caracterizar o processamento temporal e o potencial evocado auditivo de longa latência em indivíduos gagos e compará-los com indivíduos sem gagueira. Método: Participaram do estudo 41 indivíduos destros, de 18 a 46 anos, distribuídos em dois grupos: 20 com gagueira e 21 sem gagueira, comparados segundo idade, escolaridade e gênero. Todos os indivíduos foram submetidos aos testes de padrão de duração, teste de identificação de intervalos aleatórios e o potencial evocado auditivo de longa latência. Resultados: Indivíduos com gagueira apresentaram pior desempenho nos testes de padrão de duração e Random Gap Detection, quando comparados com os indivíduos fluentes. No potencial evocado auditivo de longa latência, houve diferença na latência dos componentes N2 e P3, os indivíduos gagos apresentaram maiores valores de latência. Conclusão: Os indivíduos com gagueira apresentaram processamento temporal com desempenho abaixo do esperado e um maior valor de latência para os componentes N2 e P3.

Caracterização eletrofisiológica da audição em indivíduos com Síndrome de Down / Electrophysiological characterization of hearing in individuals with Down syndrome

RESUMO Introdução Poucos estudos realizaram, concomitantemente, o potencial evocado auditivo de tronco encefálico (PEATE) e o P300 na Síndrome de Down (SD), em indivíduos audiologicamente normais, para a avaliação da via auditiva central, principalmente pela dificuldade de realizar estes procedimentos nesta população. Estudos anteriores sugeriram que indivíduos com SD podem apresentar padrões de respostas diferentes das encontradas em indivíduos com desenvolvimento típico, sendo que a identificação destes seria fundamental para o estabelecimento de um diagnóstico audiológico preciso. Objetivo Caracterizar o PEATE e o P300 em indivíduos com SD audiologicamente normais. Método Foram analisados o PEATE e o P300 de 17 indivíduos com SD e 21 com desenvolvimento típico de sete a 15 anos. A análise foi quantitativa e qualitativa, utilizando medidas descritivas e os testes de hipótese. Resultados Os valores de latência foram menores no PEATE para o grupo SD, com diferença estatisticamente significante para a onda V, interpicos III-V e I-V; não foram encontradas diferenças significantes nos valores de latência do P300. Observou-se maior número de indivíduos com valores precoces para as latências do PEATE e com latências atrasadas para o P300 no grupo SD; ambas as comparações mostraram diferenças significantes. Conclusão Crianças e adolescentes com SD podem apresentar respostas precoces para os componentes do PEATE, sugerindo que a via auditiva destes necessita de menor tempo para a transmissão neural do estímulo acústico até o tronco encefálico. Quanto ao P300, indivíduos com SD podem apresentar latências aumentadas, sugerindo comprometimento na via auditiva central quanto ao processamento cortical da informação auditiva.

ABSTRACT Introduction Few studies have performed Brainstem (BAEP) and P300 Auditory Evoked Potentials simultaneously to assess central auditory pathways in normal hearing individuals with Down syndrome (DS), mainly because of the difficulty in applying these procedures to this population. Previous studies have suggested that individuals with DS might present different patterns of response compared with those of individuals with typical development; nevertheless, the identification of these potentials would be crucial for the establishment of an accurate audiological diagnosis. Purpose To characterize BAEP and P300 in normal-hearing individuals with DS. Methods BAEP and P300 were analyzed in 17 individuals with DS and in 21 individuals with typical development aged 7 to 15 years. The results were quantitatively and qualitatively analyzed using descriptive measures and hypothesis tests. Results In the quantitative analysis, latency values were lower in the BAEP for the DS group, with statistically significant difference for wave V and interpeaks III-V and I-V; there were no significant differences in the P300 latency values. In the qualitative analysis, there were a larger number of individuals with early values for BAEP latencies and late latencies for P300 in the DS group; both comparisons showed statistically significant differences. Conclusion Children and adolescents with DS can present early responses to the components of BAEP, suggesting that their auditory pathway requires less time for the neural transmission of acoustic stimuli to the brainstem. Concerning P300, individuals with DS may present increased latencies, suggesting impairment in the central auditory pathway for the cortical processing of auditory information.

Sleep disorder investigation might be considered to be mandatory in attention deficit/hyperactivity disorder guideline / Investigação de distúrbio do sono deve ser considerada obrigatória e incluída no manejo de distúrbios do déficit de atenção/hiperatividade

ABSTRACT Objective To determine the prevalence of obstructive sleep apnea (OSA) in children with attention deficit/hyperactive disorder (ADHD) and compare amplitude and latency of the P300 potential among children with and without OSA. Method Sixty-one children with ADHD underwent oddball auditory attention tests for detection of P300 (ERPs) followed by an all-night polysomnography. The children were divided in two groups, those with and without OSA. Results Significant decreased amplitude of the P300 potential was observed in children with OSA when compared with children without OSA. Conclusion The study showed that sleep fragmentation as a result of OSA can exacerbate the attention disorder that characterizes ADHD, and highlights the importance of assessing the presence of OSA in the differential diagnosis of children with attention deficits.

RESUMO Objetivo determinar a prevalência de apneia obstrutiva do sono (AOS) em crianças com déficit de atenção / hiperatividade (TDAH) e comparar amplitude e latência do potencial P300 entre as crianças com e sem AOS. Método Sessenta e uma crianças com TDAH foram submetidos a testes de atenção auditiva com o paradigma oddball para a detecção de potenciais relacionados a eventos (PREs) do tipo P300, seguidos por polissonografia de noite inteira. As crianças foram divididas em dois grupos, crianças com e sem AOS. Resultados Foi observada redução significativa da amplitude do potencial P300 em crianças com AOS quando comparadas com crianças sem AOS. Conclusão O estudo mostrou que a fragmentação do sono, consequente a AOS, pode exacerbar o déficit de atenção, que caracteriza o TDAH, e destacou a importância de avaliar a presença de AOS no diagnóstico diferencial de crianças com déficit de atenção.

Variables in P300 recording: task type and electrode position

ABSTRACT Purpose To analyze the latency and amplitude of P300 responses obtained with electrodes positioned at Cz and Fz and in different tasks of infrequent stimulus identification in normal hearing individuals. Methods Forty adults of both genders participated in the study. Three recordings with three different tasks were obtained for the identification of the infrequent stimulus; simultaneous recordings were obtained from Cz and Fz positions. Results Cz position showed significantly greater amplitudes and lower latencies than Fz. Regarding the three tasks, only “pronouncing the word ’thin’” was different from “raising a finger”, with lowest latencies for the verbal task. Regarding amplitude, significantly higher values were observed for “raising a finger”, followed by “pronouncing the word ‘thin’” and mental counting. Conclusion Cz obtained the best values, highest amplitude and lowest latency. Lowest latencies were obtained for the task of “pronouncing the word ‘thin’” and the highest amplitudes were obtained for “raising a finger”.

Auditory evoked potential P300 in adults: reference values / Potencial evocado auditivo P300 em adultos: valores de referência

ABSTRACT Objective To establish reference intervals for cognitive potential P300 latency using tone burst stimuli. Methods This study involved 28 participants aged between 18 and 59 years. P300 recordings were performed using a two-channel device (Masbe, Contronic). Electrode placement was as follows: Fpz (ground electrode), Cz (active electrode), M1 and M2 (reference electrodes). Intensity corresponded to 80 dB HL and frequent and rare stimulus frequencies to 1,000Hz and 2,000Hz, respectively. Stimuli were delivered binaurally. Results Mean age of participants was 35 years. Average P300 latency was 305ms. Conclusion Maximum acceptable P300 latency values of 362.5ms (305 + 2SD 28.75) were determined for adults aged 18 to 59 years using the protocol described.

RESUMO Objetivo Estabelecer valores de referência para a latência do potencial cognitivo P300 com estímulos tone burst. Métodos Participaram do estudo 28 indivíduos entre 18 e 59 anos. O registro do P300 foi realizado no equipamento Masbe da marca Contronic. Os eletrodos foram fixados nas posições Fpz (eletrodo terra), Cz (eletrodo ativo), M1 e M2 (eletrodos referência). A intensidade foi de 80 dB NA. A frequência do estímulo frequente foi de 1.000Hz e a do estímulo raro de 2.000Hz. Os estímulos foram apresentados na forma binaural. Resultados A média de idade dos indivíduos foi de 35 anos. A média de latência para P300 de 305ms. Conclusão Usando o protocolo descrito, o valor máximo de latência aceitáveis para P300 foram de 362,5ms (305 + 2DP 28,75) na faixa etária do adulto de 18 a 59 anos.

P300 in individuals with sensorineural hearing loss / P300 em indivíduos com perda auditiva sensorioneural

INTRODUCTION: Behavioral and electrophysiological auditory evaluations contribute to the understanding of the auditory system and of the process of intervention. OBJECTIVE: To study P300 in subjects with severe or profound sensorineural hearing loss. METHODS: This was a descriptive cross-sectional prospective study. It included 29 individuals of both genders with severe or profound sensorineural hearing loss without other type of disorders, aged 11 to 42 years; all were assessed by behavioral audiological evaluation and auditory evoked potentials. RESULTS: A recording of the P3 wave was obtained in 17 individuals, with a mean latency of 326.97 ms and mean amplitude of 3.76 V. There were significant differences in latency in relation to age and in amplitude according to degree of hearing loss. There was a statistically significant association of the P300 results with the degrees of hearing loss (p = 0.04), with the predominant auditory communication channels (p < 0.0001), and with time of hearing loss. CONCLUSIONS: P300 can be recorded in individuals with severe and profound congenital sensorineural hearing loss; it may contribute to the understanding of cortical development and is a good predictor of the early intervention outcome. .

INTRODUÇÃO: As avaliações comportamentais e eletrofisiológicas auditivas contribuem para o entendimento do sistema auditivo e do processo de intervenção. OBJETIVO: Estudar P300 em indivíduos com perda auditiva sensorioneural severa ou profunda. MÉTODO: Estudo prospectivo transversal descritivo. Participaram 29 indivíduos, de ambos os sexos, com idade entre 18 e 45 anos com perda auditiva sensorioneural, congênita severa ou profunda e sem comorbidades, avaliados por meio de avaliação audiológica comportamental e potencial evocado auditivo de longa latência. RESULTADOS: O registro da onda P3 foi obtido em 17 indivíduos, com latência e amplitude média de 326,97 ms e 3,76V, respectivamente. Houve diferenças significativas da medida de latência em relação à idade e da amplitude segundo o grau da perda auditiva. Evidenciou-se associação do resultado do P300 aos graus de perda auditiva (p = 0,04) e ao canal de comunicação auditiva predominante (p = 0,0001) e ao tempo de privação auditiva (teste exato de Fisher). CONCLUSÕES: P300 pode ser registrado em indivíduos com perda auditiva sensorioneural congênita e colaborar para a compreensão do desenvolvimento cortical auditivo e ser preditor do resultado da intervenção. .

Progress on neuropsychology and event-related potentials in patients with brain trauma / 法医学杂志

With the development of information technology, as one of the research frontiers in neurophysiology, event-related potentials (ERP) is concerned increasingly by international scholars, which provides a feasible and objective method for exploring cognitive function. There are many advances in neuropsychology due to new assessment tool for the last years. The basic theories in the field of ERP and neuropsychology were reviewed in this article. The research and development in evaluating cognitive function of patients with syndrome after brain trauma were focused in this review, and the perspectives for the future research of ERP was also explored.

Auditory P300 in the patients with traumatic brain injury / 法医学杂志

OBJECTIVE@#To assess the cognitive dysfunction in patients with the traumatic brain injury (TBI) by auditory P300.@*METHODS@#Auditory P300 was recorded in the normal subjects and patients with TBI at the active (foot pedal) and passive task.@*RESULTS@#In healthy persons, N2 and P3 in active task state showed higher amplitude than that in passive task state, and no significant prolongation of the latency. The amplitude of N1 and P2 at Cz was higher than that at Pz. In passive task state, N2 and P3 showed higher amplitude and longer latency in the patients than that in the healthy persons. N2 and P3 of the patients in the active task showed higher amplitude and longer latency than that in the passive task. Obvious change of P3 latency was observed in the patients with attention disorder.@*CONCLUSION@#The type of task mainly affect the amplitude of N2 and P3. The latency of N2 and P3 in passive task can be used as an indication for evaluating cognitive function in patients with diffuse brain injury.

Technical development of detecting deception / 法医学杂志

Polygraph, as a traditional lie detector, is used to detect lies by some changes of human peripheral neuro-vegetative responses. The reliability of this technique, which depends on some other none-instrumental factors to a great extent, has drawn lots of attention and question. Event related potentials (ERPs) have good specificity and time resolution and can monitor instant cognitive processing and brain electric activity. However, its space resolution is poorer than brain function nuclear magnetic resonance imaging (fMRI) relatively. Brain fMRI can show the brain functional changes directly. It has good space resolution but bad time resolution, and all images of fMRI are just the final results of brain changes after lying. So, fMRI technique for detecting deception is still in the basic research phase at present. Contrary to other techniques, psychometrics has been used and studied more in detecting deception or malingery in practice.

Post-task changes in visual P300 and their reversibility through brief hyperventilation.

Long hours of continuous, mental task reportedly increase the average auditory P3 latency of the normal subjects significantly, a change that is thought to be related to mental fatigue. We have tried out several protocols of varying task difficulty and duration in an effort to study the onset of the assumed fatigue-related changes. The present study shows that changes in visual event-related potential occur in less than two minutes if the task is sufficiently rigorous. The changes occur both in latency and in amplitude. Moreover, the changes are reversible with a brief (30 second) period of hyperventilation. The changes were most marked at Fz. Following the difficult task, the P3 amplitude at Fz decreased from 8.588 micro/V +/- 0.966 to 5.800 microV +/- 0.795 and the P3 latency increased from 368 +/- 4 ms to 380 +/- 3. Following hyperventilation, the P3 amplitude at Fz reverted to 8.457 +/- 5 and the P3 latency reverted to 371 +/- 5 ms. These observations call for further investigations on the cause of the post-task changes and their quick reversibility.

Effect of chronic hypobaric hypoxia on components of the human event related potential.

BACKGROUND & OBJECTIVES: Induction to high altitude (HA) leads to deterioration in cognitive functions. The event related potentials (ERPs) like P300 are reported to be affected by hypoxia and bring about impairments in cognitive performance. The aim of the study was to investigate the effect of hypobaric hypoxia on event related potentials at two different altitudes i.e., 3200 m (HA I) and 4300 m (HA II) in ascending order to see how ERPs change with increasing altitude. METHODS: The study was carried out on 20 healthy male volunteers at sea level (SL) and thereafter at high altitude (HA) in Eastern Himalayas and on return to sea level (RSL). The P300 was recorded by using standard auditory odd ball paradigm with compact -4 (Nicolet, USA). RESULTS: The N1, N2 and P2 latencies were not significantly affected at HA I and HA II in comparison with SL indicating no effect of hypobaric hypoxia on sensory conduction. However, at HA II, most of the subjects showed an increase in latency of P3 component reflecting sensory discrimination and delay in evaluation process at 4300 m. At HA I, only 10 out of 20 subjects showed an increase in P3 wave latency and 3 did not show any change in N2-P3 components. INTERPRETATION & CONCLUSION: The results of the present study showed an increase in P300 wave latency at 3200 and 4300 m of high altitude. The observations suggest that hypoxia causes slowing of the signal processing at 4300 m, and magnitudes of the effects are altitude dependent with higher level of decline observed with increasing altitude.

Post-task P3-changes following a brief, rigorous visual task indicate individual differences in the task-specific ability.

The P3 latency in an auditory oddball ERP paradigm is known to get prolonged after a few hours of mental task. The present study shows that it takes merely a few minutes of challenging visual mental activity to produce significant changes in P3 latency in the visual oddball ERP paradigm. However, the mental activity results in a shortening of P3-latency almost as often as it results in its prolongation. Similarly, the post-task P3 amplitude is higher or lower with nearly equal incidences. Following the task, the reaction time shortens as often as it prolongs. It seems that the P3 changes and their variations through electrode sites signify individual differences in the amount and extent of additional neuronal resources tapped by the subject in coping with the challenging task, and that it leaves an aftereffect for several minutes after the mental workload is withdrawn. These aftereffects get indexed in the P3 wave characteristics of a much simpler ERP paradigm with more change occurring in the better performers. In the clinical context, these observations raise doubts about the diagnostic value of P3 latency or amplitude without knowledge of the immediate history of mental workload.

Correlation between Cognitive Capacity Screening Examination and Cognitive Evoked Potential in Alcohol-Dependent Patients

The aim of this study was to verify the significance of cognitive evoked potentials and the correlation between the auditory event-related potential and the Cognitive Capacity Screening Examination (CCSE) in alcohol dependent patients. The P300 studies using an auditory paradigm were performed on 25 alcohol dependent patients, and then the results were compared with score of the CCSE. 1) The latencies of the P300 were significantly prolonged in the patient group compared with the control group, and the scores of CCSE were significantly reduced in the patient group compared with the control group (p 0.05). 4) There was significant reliability in P300 latency study (alpha=0.9771). These findings suggest that the latency of P300 may be useful as a clinical electrodiagnostic measurement that can objectively reflect cognitive dysfunction in alcohol dependent patients, and it can be used as a quantitative analysis of cognitive dysfunction even for early asymptomatic alcohol dependent patients.

Electrophysiologic evaluation of Sudarshan Kriya: an EEG, BAER, P300 study.

To compare the resting Electroencephalogram (EEG), Brainstem Auditory Evoked Responses (BAER) and P300 amongst trained and regular practitioners of Sudarshan Kriya (SK) GP-I and Controls (GP-II).

Effect of high altitude (HA) on event related brain potentials.

Event Related brain potentials (ERPs) were recorded in 15 subjects using standard auditory odd ball paradigm, in which subjects were presented a sequence of two distinguishable sound stimuli of that occurred frequently (frequently (frequent stimulus-non target) and the other infrequently (rare stimulus-target). These recordings were made at sea level (SL) and then the subjects were air lifted to 3500 m altitude (HA), where they stayed for 3 weeks. Their ERPs were recorded during the first and third week of stay at HA and on return to sea level (RSL). Data indicated impairment in cognitive function as a result of exposure to HA as depicted by increase in the latency of P3 which was significant during the 1st week of stay at HA compared to sea level. The P3 wave latency during the 3rd week of stay at HA showed an increase compared to SL but was not statistically significant. From the results it may be concluded that high altitude hypoxia induced slow processing of stimulus evaluation, may be responsible for increase in P3 latency. The difference in the latent period of P3 waves during the first and third week of stay at HA may be due to continuous stay at HA which might lead to the time dependent adaptive processes occurring with increasing duration of exposure to HA which may induce learning effects.