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Event Related Potentials (event + relate_potential)
Selected AbstractsERP and RT Delays in Long-Term Abstinent Alcoholics in Processing of Emotional Facial Expressions During Gender and Emotion Categorization TasksALCOHOLISM, Issue 7 2010George Fein Background:, There is considerable evidence that alcoholics differ from nonalcoholics in the processing of stimuli that have emotional content. The current study examines those differences that are present in multi-year abstinent individuals. Methods:, We compared reaction time (RT), accuracy, and Event Related Potentials (ERP) measures in long-term abstinent alcoholics (LTAA, n = 52) with that in age- and gender-comparable nonalcoholic controls (NAC, n = 47). Subjects were presented with male and female faces exhibiting happy, neutral, or sad facial expressions and were instructed to identify the picture gender in 1 task and the emotion being expressed in a subsequent task. Results:, LTAA had slower RTs than NAC when instructed to identify emotion, while RT was comparable when identifying gender. There were no differences between groups on task accuracy. P160 latency was increased in LTAA for both tasks compared to NAC, though P160 amplitude did not differ between groups. The P160 effect was about 5 × as large as the RT effect and was statistically independent of the RT effect, while the RT effect was no longer present after removing variance because of the P160 effect. Conclusions:, Our data demonstrate slower early processing of emotional facial stimuli in alcoholics that is unresolved by long-term abstinence and is most sensitively indexed by delayed P160 latency in LTAA. [source] Effects of task difficulty and time-on-task on mental workloadJAPANESE PSYCHOLOGICAL RESEARCH, Issue 3 2002Shigeru Haga Abstract: Twelve subjects performed a tracking task and a memory search task simultaneously on a computer screen. The dual task continued for approximately 10 min and was repeated three times, interrupted by a short break for subjective ratings: the NASA Task Load Index (NASA-TLX) and the Check List of Mental Condition. Event related potentials (ERP) evoked by the presentation of memory task stimuli were also recorded. All the subjects participated in three experimental sessions, which varied in difficulty of tracking task. Results demonstrated that the NASA-TLX and ERP were sensitive only to the change in task difficulty and were not affected by time-on-task or interaction between task difficulty and time-on-task. [source] Language-Related Potentials in Temporal Lobe Epilepsy Before and After Surgical TreatmentEPILEPSIA, Issue 2000Toshihiko Ito Purpose: Temporal lobectomy has contributed to treatment for medically intractable epilepsies. However, influence of the surgical treatment on cognitive function is not still clear, especially from the electrophysiological viewpoint. N400, an event related potential (ERP) named for its negative polarity and peak latency of 400 ms, is reported to be an electrophysiological sign of neural activities associated with semantic priming in language perception. In the present study, ERPs are applied to evaluate the cognitive function of temporal lobe epilepsy before and after temporal lobectomy. Methods: Two patients with intractable temporal lobe epilepsy participated in this study. Fifteen normal subjects served as controls. The incongruous sentence task (Kutas and Hillyard 1980) was used to record N400 components in an auditory modality. Two types of sentences (40 Japanese sentences for each type) were prepared, in which the terminal words were either semantically congruent or incongruent. The scntences were randomly presented at approximately 65 dB SPL peak intensity. ERPs were recorded according to the international 10,20 system, with a balanced non-cephalic electrode reference and 2 1 channels. The band-pass filter was set from 0.5 to 30 Hz, and the ERPs were sampled at 500 Hz from 200 ms before the onset of terminal words to 824 ms post-stimulus. Waves were calculated by subtracting ERPs in the congruent condition from those in the incongruent condition. N400 was scored as the most negative point between 250 and 450 ms in the subtraction waves. Amplitudes were measured from the baseline of 100 ms before the terminal words. Motor responses were also measured with a right index finger, to estimate the accuracy of understanding sentences. Results: Case I was a 22-year-old male who had intractable epilepsy for 7 years. Magnetic resonance imaging (MRI) showed high-intensity signals in the right amygdalo-hippocampal region. The epileptic seizures were confirmed to originate from the region hy electroencephalography/closed-circuit television monitoring, and single-photon-emission computed tomography. ERPs were recorded I month before and after the right anterior temporal lobectomy. Before the surgery, the rate of correct responses showed no difference between the patient (96 %) and the controls (96 %). The amplitudes of N400 for the patient reduced in the right frontal and central areas (F4, C4), comparing to 99 % confidence limit for control subjects. After the surgery, the rate of correct responses was 97 %, and the amplitudes reduced in the right central, parietal, and posterior temporal areas (C4, P4, 0 2, T6). Case 2 (37-year-old female) had intractable epilepsy for 30 years. MRI showed brain atrophy in the right hippocampal region. The epileptic seizures were confirmed to originate from the region. N400 was recorded 3 months after the resection. The rate of correct responses was 95 %. The amplitudes of N400 were lower in the right frontal, parietal, and temporal areas (electrodes Fp2, F4, P4, T6, Pz), comparing to 99 % confidence limit of controls. Conclusions: Before the lpbectomy, the reduction of amplitudes of N400 indicated that the pathogenesis of intractable temporal lobe epilepsy would influence the process of semantic priming in language perception. After the resection, it was suggested that the right temporal lobectomy might affect the cognitive function in the brain from electrophysiological aspects. We could benefit from further study including analysis of the discrepancy between the amplitudes of N400 and behavioral responses. [source] Visual P3 in Female AlcoholicsALCOHOLISM, Issue 4 2001V. Radha Prabhu Background: The P300 (P3) component of the event related potential has been established as a sensitive risk marker of vulnerability to alcoholism. Most alcoholism studies have focused on men; recent studies indicate that women are equally vulnerable to developing alcoholism. Methods: Visual P3 recorded from 31 electrode positions was evaluated in 44 alcoholic and 60 control women, 24,50 years of age. P3 amplitudes and latencies of the two groups were statistically compared using Analysis of Variance; source localization of surface amplitude values from each group were plotted using a low-resolution brain electromagnetic tomography. Results: The results indicated that alcoholic women had significantly smaller P3 amplitudes in the frontal and central regions compared with controls. Source localization showed lowered activation in alcoholic women in right dorso-lateral prefrontal cortex and the ventro-medial fronto-central regions. Conclusions: The results suggest that P3 is an equally sensitive endophenotypic marker of vulnerability to alcoholism in women. The findings are discussed in terms of functional and physiologic significance of the P3 amplitude in alcoholic women and its relationship to drinking behaviors. [source] The sensitivity of human event-related potentials and reaction time to mobile phone emitted electromagnetic fieldsBIOELECTROMAGNETICS, Issue 4 2006D.L. Hamblin Abstract There is some evidence to suggest that exposure to mobile phones (MPs) can affect neural activity, particularly in response to auditory stimuli. The current investigation (n,=,120) aimed to test recent findings in this area, namely that N100 amplitude and latency would decrease, and that P300 latency and reaction time (RT) would increase under active relative to sham exposure during an auditory task. Visual measures were also explored. A double blind, counterbalanced, crossover design was employed where subjects attended two sessions 1 week apart. In both sessions participants (1) performed auditory and visual oddball tasks while electroencephalogram (EEG) was recorded with a MP set to sham exposure mounted over the temporal region, and (2) performed the same tasks while the handset was set to active/sham. When active, the MP transmitted for 30 min at 895 MHz (average power 250 mW, pulse modulated at 217 Hz, average SAR 0.11 W/kg). Paired t -tests compared difference scores from the sham/sham session to those from the sham/active condition. The study was designed to detect differences of of a standard deviation with a power of 0.80. There was no significant difference between exposure conditions for any auditory or visual event related potential (ERP) component or RT. As previous positive findings were not replicated, it was concluded that there is currently no evidence that acute MP exposure affects these indices of brain activity. Bioelectromagnetics 27:265,273, 2006. © 2006 Wiley-Liss, Inc. [source] Multi-level analysis of cultural phenomena: The role of ERPs approach to prejudiceJOURNAL FOR THE THEORY OF SOCIAL BEHAVIOUR, Issue 1 2009AGUSTÍN IBÁÑEZ Brain processes and social processes are not as separated as many of our Social Psychology and Neuroscience departments. This paper discusses the potential contribution of social neuroscience to the development of a multi-level, dynamic, and context-sensitive approach to prejudice. Specifically, the authors review research on event related potentials during social bias, stereotypes, and social attitudes measurements, showing that electrophysiological methods are powerful tools for analyzing the temporal fine-dynamics of psychological processes involved in implicit and explicit prejudice. Meta-theoretical implications are drawn regarding the social psychological modeling of social attitudes, and for the integration of social neuroscience into a multi-level account of cultural behavior. [source] Electrophysiological and neuropsychological tests for the diagnosis of subclinical hepatic encephalopathy and prediction of overt encephalopathyLIVER INTERNATIONAL, Issue 3 2002Nandini Saxena Abstract: Background: Subclinical hepatic encephalopathy (SHE) features in 30,84% of patients with cirrhosis of the liver. Its clinical significance with regards to progression to overt encephalopathy has however, not been established. Aims: The present study was conducted (i) to compare the diagnostic usefulness of neuropsychological tests with that of electrophysiological (EP) tests in detection of SHE, and (ii) to examine the natural course of SHE. Methods: Seventy-five-nonencephalopathic cirrhotics (11 females, 64 males; mean (± SD) age 43.6 (± 11.7) years; mean (± SD) education 11(± 3) years) were studied using a battery of tests for intelligence and memory, the number connection test (NCT), and EP tests viz. electroencephalogram (EEG) and auditory P300 event related potentials (P3ERP). All the patients were followed up for a period of 6 months to 2 years for development of overt encephalopathy. Results: Thirty-five out of 75(47%) patients were diagnosed to have SHE based on at least one abnormal test result. The P3ERP latencies detected SHE in maximum number of patients (23%) followed by EEG (21%). Nearly 59% of patients with SHE progressed to overt encephalopathy within a mean duration of 4 months. Multivariate analysis showed that prior episode of encephalopathy (RR = 6.3; 95% CI = 2.0,19.7), abnormality on EEG (RR = 7.5; 95% CI = 2.2,25.3), abnormal performance on psychometric battery of tests (RR = 35.2; 95% CI = 4.3,287.3), occurrence of gastrointestinal bleed (RR = 19.3; 95% CI = 4.1,88.9), occurrence of dehydration (RR = 10.7; 95% CI = 2.5,45.4) and infection (RR = 11.4; 95% CI = 2.0,64.4) had significantly higher risk for development of overt encephalopathy. Conclusions: EP methods were more sensitive in detection of SHE. Amongst all the tests used, presence of only an abnormal EEG was significantly associated with development of overt encephalopathy along with the precipitating factors. [source] The selective processing of briefly presented affective pictures: An ERP analysisPSYCHOPHYSIOLOGY, Issue 3 2004Harald T. Schupp Abstract Recent event-related potential (ERP) studies revealed the selective processing of affective pictures. The present study explored whether the same phenomenon can be observed when pictures are presented only briefly. Toward this end, pleasant, neutral, and unpleasant pictures from the International Affective Pictures Series were presented for 120 ms while event related potentials were measured by dense sensor arrays. As observed for longer picture presentations, brief affective pictures were selectively processed. Specifically, pleasant and unpleasant pictures were associated with an early endogenous negative shift over temporo-occipital sensors compared to neutral images. In addition, affective pictures elicited enlarged late positive potentials over centro-parietal sensor sites relative to neutral images. These data suggest that a quick glimpse of emotionally relevant stimuli appears sufficient to tune the brain for selective perceptual processing. [source] Comprehension skill and word-to-text integration processesAPPLIED COGNITIVE PSYCHOLOGY, Issue 3 2008Charles Perfetti We examine comprehension skill differences in the processes of word-to-text integration, the connection of the meaning of a word, as it is read, to a representation of the text. We review two ,on-line' integration studies using event related potentials (ERPs) to provide fine-grain temporal data on the word-to-text processes of adult readers. The studies demonstrate indicators for word-to-text integration and show differences in these indicators as a function of adult reading comprehension skill. For skilled comprehenders, integration processes were reflected in N400 indicators when a critical word had an explicit link to a word in the prior text and by both N400 and P300 indicators when its meaning was a paraphrase of a prior word. When forward inferences were required for subsequent word-to-text integration, effects for skilled comprehenders were not reliable. Less skilled comprehenders showed delayed and less robust ERP effects, especially when meaning paraphrase was the basis of the integration. We discuss the significance of skill differences in integration processes with a focus on the use of context-dependent word meaning as a possible source of these differences. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||