Does the Number of Stimuli Influence the Formation of the Endogenous Components of the Event-Related Auditory Evoked Potentials?

Abstract Introduction The number of stimuli is important to determine the quality of auditory evoked potential records. However, there is no consensus on that number in studies, especially in the sample studied. Objectives To investigate the influence of the number of rare stimuli on forming N2 and P3 components, with different types of acoustic stimuli. Methods Cross-sectional, descriptive, comparative study, approved by the ethics committee of the institution. The sample comprised 20 normal hearing adults of both sexes, aged 18 to 29 years old, with normal scores in the mental state examination and auditory processing skills. The event-related auditory evoked potentials were performed with nonverbal (1 kHz versus 2 kHz) and verbal stimuli (/BA/ versus /DA/). The number of rare stimuli varied randomly in the recordings, with 10, 20, 30, 40, and 50 presentations. Results P3 latency was significantly higher for nonverbal stimuli with 50 rare stimuli. N2 latency did not show any difference between the type and number of stimuli. The absolute P3 and N2-P3 amplitudes showed significant differences for both types of stimuli, with higher amplitude for 10 rare stimuli, in contrast with the other ones. The linear tendency test indicated significance only for the amplitude - as the number of rare stimuli increased, the amplitude tended to decrease. Conclusion The components were identifiable in the different numbers of rare stimuli and types of stimuli. The P3 and N2-P3 latency and amplitude increased with fewer verbal and nonverbal stimuli. Recording protocols must consider the number of rare stimuli.

How Much We Think of Ourselves and How Little We Think of Others: An Investigation of the Neuronal Signature of Self-Consciousness between Different Personality Traits through an Event-Related Potential Study

Background: Previous studies have revealed that self-related tasks (items) receive more attention than non-self-related, and that they elicit event-related potential (ERP) components with larger amplitudes. Since personality has been reported as one of the biological correlates influencing these components, as well as our behavioural differences, it is important to examine how it affects our self-consciousness in relation to tasks of varied relevance and the neurological basis. Methods: A total of 33 male and female undergraduate Malaysian medical students of Universiti Sains Malaysia (USM) participated in the study. The participants were divided into two groups, Ambivert (n = 18) and Extravert (n = 15) groups, using the USM personality inventory questionnaire. In the ERP experiment, squares containing standard stimuli of any word other than self and non-self-related nouns (e.g., Bola, Gigi, Anak, etc.; in English: Ball, Teeth, Kids, etc., respectively), those containing self-related pronouns (Saya, Kami or Kita; in English: I, Us or We, respectively), and non-self-related pronouns (Dia, Anda or Mereka; in English: He/She, You or They, respectively), were shown 58%, 21% and 21% of the time, respectively, in a three-stimulus visual oddball paradigm. All words were presented in Bahasa Melayu. The participants were instructed to press 1 for self and 2 for non-self, and ignore standard stimuli. Results: Comparison of both N200 and P300 amplitudes for self-related and non-selfrelated pronouns in the Extravert group revealed significant differences at seven electrode sites, with self-related having larger amplitude at anterior electrodes and less at posterior. This was not seen in the Ambivert group. Conclusion: The present study suggests that self-relevant pronouns are psychologically more important to extraverts than to ambiverts; hence, they have more self-awareness. This may be due to large amount of dopamine in the brains of extraverts, which is more concentrated in the frontal lobe.

Peculiarities of Cognitive Disorders in Adult Patients with Epilepsy.

Aim: The basic aim of the article is to study the state of cognitive functions in patients with epilepsy due to clinical characteristics and a pharmacological group of received anticonvulsive medicines using MMSE test and examination of cognitive induced potential P300. Place and Duration of Study: The Department of Neurology at Tashkent Institute of Postgraduate Medical Education, Tashkent, Uzbekistan, between April 2012 and April 2013. Methodology and Study Design: The study was conducted on the basis of the neurological department of the city hospital number 7 in Tashkent (Uzbekistan). 75 patients with epilepsy at the age from 21 to 42 being under treatment at hospital were examined. The average age of patients in the debut of the disease was 32±9.3 years. The clinical form of the disease and epileptic seizures were determined based on the International Classification of epileptic seizures and the International Classification of epilepsy and seizures. Clinical assessment of cognitive functions was performed using MMSE (Mini Mental State Examination) test. Besides this method of research of cognitive evoked EEG potential to acoustic stimulation, and the assessment of potential latencies of P300, which reflects the cognitive processes of attention and perception, N200 was used, reflecting the process of initial identification of the stimulus. Results: The results indicated the presence of more severe cognitive disorders in patients who were sick for more than 5 years, with symptomatic epilepsy, generalized convulsive seizures and taking barbiturates. It was established by assessing cognitive function method, that examination of potential P300 is more sensitive in comparison with MMSE test. Conclusion: Our results clearly demonstrate the extension of the latent period of the components of P300 complex at all examined patients, shows a decline in the integral functions of the central nervous system and the mechanisms of information processing occurring in epilepsy. While taking AEDs, cognitive deficit increases in the following order valproates – carbamazepine – barbiturates.

Delayed latencies of auditory evoked potential P300 are associated with the severity of Parkinson's disease in older patients / O atraso das latências do potencial evocado auditivo P300 está associado à gravidade da doença de Parkinson em pacientes mais velhos

Electrophysiological methods could provide important information about the neurophysiological status in Parkinson's disease (PD). Objective: To investigate the prolonged auditory P300 latency in PD and its association with the disease clinical stage. Method: Clinical profiles of 44 patients were evaluated and those in initial and advanced stages of PD were identified. The frequency of altered latencies, median of latencies in each stage, and correlation between latencies and motor and non-motor clinical features were analyzed. Latencies were considered altered when they were more than two standard deviations from the mean of controls, per age group. Results: It was verified 10% of alterations in initial stages and 31% in advanced. There was correlation between latencies and non-motor clinical features. Subjects older than 65, in advanced stages, presented a significant increase of latencies. Conclusion: There was an association between PD severity and P300 prolonged latencies among subjects 65 years old or older. .

Exames eletrofisiológicos podem fornecer informações sobre o status neurofisiológico na doença de Parkinson (DP). Objetivo: Investigar o prolongamento das latências do P300 auditivo na DP e sua associação com o estágio da doença. Método: Foi avaliado o quadro clínico de 44 pacientes e identificados aqueles em estágio inicial e avançado da DP. Analisou-se a frequência de latências alteradas, mediana das latências em cada estágio e a correlação entre latências e quadro clínico motor e não motor da DP. As latências foram consideradas alteradas quando superiores a dois desvios-padrão da média dos controles, por grupo etário. Resultados: Verificaram-se 10% de alterações no estágio inicial e 31% no avançado. Houve correlação entre as latências e o quadro clínico não motor. Sujeitos com mais de 65 anos, em estágio avançado, apresentaram significativo aumento das latências. Conclusão: Existe associação entre gravidade da DP e prolongamento das latências do P300 nos sujeitos acima de 65 anos. .

The Assessment of Reliability of Cognitive Evoked Potential in Normal Person

OBJECTIVE: To evaluate intra-tester reliability of P300 more precisely, this study was designed. Event-related potential (ERP) is the result of endogenous brain response following cognitive stimulus. The P300 component of the human ERP is a positive wave with a latency of 300 ms or greater. Our purpose of this study was to estimate reliability of P300 latency and amplitude with 30 normal persons without head injury, as well as to set up them as the reference values in the event that they would be found to be highly reliable. METHODS: ERP was performed at three separate times on 30 normal adults in their 20s and 30s. We measured P300 latency and amplitude among ERP. RESULTS: P300 latency show excellent reliability with intraclass correlation coefficient (ICC) of 0.81. As to P300 amplitude, reliability was good to fair with ICC of 0.53. Average value of P300 latency was 311.3+/-37.0 ms, shorter than reference value of previous study in Korea. CONCLUSION: P300 latency revealed higher reliability than P300 amplitude, although reliability of P300 was confirmed in both component. After further study including precise mechanism, influence factor on measurement and method standardization, it is expected to be an objective indicator to assess the cognitive state and predict prognosis.