Search results for " P300"
showing 10 items of 38 documents
A Confirmatory Study on the Mechanisms Behind Reduced P300 Waves in Depression
2003
A single-trial analysis of event-related potentials (P300) of 21 depressives was performed in comparison with matched controls. The purpose was to confirm previous results revealing an overall reduction of the single-trial P300 amplitude in depression despite fewer elicited single-trial P300 waves in schizophrenics. The result of the present study is in line with our previous investigation implicating a general reduced P300 amplitude on single trials of depressive patients. Therefore, it appears possible to differentiate depressives and schizophrenics by measuring event-related potentials and applying a single-trial analysis of them.
A replication study on P300 single trial analysis in schizophrenia: confirmation of a reduced number of 'true positive' P300 waves.
2000
A single trial analysis of event-related potentials (auditory odd-ball paradigm) of 20 schizophrenics was performed in comparison to matched healthy controls. The purpose of the study was to test the hypothesis that in schizophrenia the well-known P300 amplitude reduction of averaged event-related potentials is due to fewer elicited single trial P300 waves. The results of the present study support this finding of our previous exploratory investigation and point to the view that schizophrenics reveal basal disturbances in information processing due to inadequately elicited electrophysiological responses to target stimuli.
Differential pathophysiological mechanisms of reduced P300 amplitude in schizophrenia and depression: a single trial analysis
1997
In order to address basic mechanisms behind a reduced averaged P300 wave in schizophrenia and depression, 17 unmedicated schizophrenic and 11 unmedicated depressive subjects were tested in an 'oddball paradigm' against healthy controls matched for gender and age. The amplitude distributions of single trials' maximum positive deflections after stimulation (P300) for both target and nontarget stimuli were determined, which served as a basis for calculating the discrimination index d'. This index characterizes differences in the electrophysiological responses to target and nontarget stimuli of a subject being engaged in a discrimination task. As a main result d' was significantly lower for sch…
Neural Correlates of Visual versus Abstract Letter Processing in Roman and Arabic Scripts
2013
In alphabetic orthographies, letter identification is a critical process during the recognition of visually presented words. In the present experiment, we examined whether and when visual form influences letter processing in two very distinct alphabets (Roman and Arabic). Disentangling visual versus abstract letter representations was possible because letters in the Roman alphabet may look visually similar/dissimilar in lowercase and uppercase forms (e.g., c-C vs. r-R) and letters in the Arabic alphabet may look visually similar/dissimilar, depending on their position within a word (e.g., [Formula: see text] - [Formula: see text] vs. [Formula: see text] - [Formula: see text]). We employed a…
Neural mechanisms of training an auditory event‐related potential task in a brain–computer interface context
2019
Effective use of brain-computer interfaces (BCIs) typically requires training. Improved understanding of the neural mechanisms underlying BCI training will facilitate optimisation of BCIs. The current study examined the neural mechanisms related to training for electroencephalography (EEG)-based communication with an auditory event-related potential (ERP) BCI. Neural mechanisms of training in 10 healthy volunteers were assessed with functional magnetic resonance imaging (fMRI) during an auditory ERP-based BCI task before (t1) and after (t5) three ERP-BCI training sessions outside the fMRI scanner (t2, t3, and t4). Attended stimuli were contrasted with ignored stimuli in the first-level fMRI…
Auditory event-related potentials (P300) in epileptic patients.
2001
Auditory event-related potentials (AERPs) were recorded during an auditory oddball paradigm in 108 epileptics and in 32 healthy controls. P300 latency varied in relationship with age only in controls. Symptomatic epileptics had significantly prolonged P300 mean latency compared to those without detectable brain lesion(s) on MR scan. Moreover, these latter patients were compared on the basis of epilepsy duration, type of seizure, seizure frequency and antiepileptic treatment; the application of a multiple regression model showed a significant relationship between P300 latency prolongation and epilepsy duration, seizure frequency and polytherapy.
Don't stop me now: Hampered retrieval of action plans following interruptions
2020
How can we retrieve action plans in working memory (WM) after being distracted or interrupted? The present EEG study investigated this question using a WM task in which a random sequence of single numbers (1-4 and 6-9) was presented. In a given trial, participants had to decide whether the number presented in the preceding trial was odd or even. Additionally, interfering stimuli were randomly presented in 25% of all trials, requiring the participants to either ignore a colored number (distraction) or respond to it (interruption) while maintaining the previously formed action plan in WM. Our results revealed a detrimental impact of interruptions on WM performance in trials after interrupting…
The P300 event-related potential and smoking--a population-based case-control study.
2009
A better understanding of the factors underlying habitual tobacco smoking may further new strategies to go about this major health problem. The P300 event-related potential (ERP) has emerged as a valuable (endo)phenotype in neuropsychiatric research. Previous studies suggested the P300 ERP to be reduced in smokers. The main purpose of the present study was to provide an in-depth description of smoking-related behavioral, biological and electrophysiological phenotypes with an emphasis on the P300 ERP and its mutual relationship with other smoking-related parameters. In this case-control study N=1318 participants (smokers and never-smoking controls) were investigated at 6 German academic inst…
Spectral analysis of P300 generation in depression and schizophrenia.
1997
In the past it was reported in several studies that both depressive and schizophrenic patients exhibit reduced P300 amplitudes compared to healthy controls. In order to elucidate the underlying mechanisms of spectral P300 generation, we analysed P300 responses in depression and schizophrenia by a frequency based approach. Herefore, the amplification (poststimulus/prestimulus) of spectral power in different frequency bands was evaluated for non-target and target epochs. Generally, we found that P300 responses are accompanied by a pronounced frequency amplification in the delta and theta range. For the depressive patients we detected only under target condition a statistically significant red…
Passive exposure to speech sounds modifies change detection brain responses in adults
2019
In early life auditory discrimination ability can be enhanced by passive sound exposure. In contrast, in adulthood passive exposure seems to be insufficient to promote discrimination ability, but this has been tested only with a single short exposure session in humans. We tested whether passive exposure to unfamiliar auditory stimuli can result in enhanced cortical discrimination ability and change detection in adult humans, and whether the possible learning effect generalizes to different stimuli. To address these issues, we exposed adult Finnish participants to Chinese lexical tones passively for 2 h per day on 4 consecutive days. Behavioral responses and the brain's event-related potenti…