Biomedical subjects

A Litke

Publications and source records attributed to A Litke.

5 recordsLinked to original sources

PubMed1997

Electrophysiological evidence of memory impairment in alcoholic patients.

In a series of event-related potential (ERP) studies, we have consistently demonstrated an ERP component correlate of visual short-term memory. There have been frequent reports on the deficits of information encoding, retention, and retrieval in chronic alcoholics. In the present study, we investigated that the ERP mnemonic effects could be influenced by long-term alcohol abuse. ERP data were recorded from 48 controls and 77 alcoholics while the subjects performed a modified delayed matching to sample paradigm using a series of object pictures as stimuli. The alcoholics completed the task with more errors and longer response times than the controls. The major differences in the evoked potentials between the two groups are found at the temporo-occipital and frontal regions in the sample and nonmatching trials, and mostly prominent in the right hemisphere. The current study indicates that the ERP technique can be a useful tool to index short-term memory. The ERP mnemonic effect difference between the two groups may be a reflection of a working memory deficit caused by long-term alcohol abuse. Our data also suggest right hemisphere dysfunction in alcoholics, with deficits in information encoding.

Adult↗

PubMed1997

Visual object priming differs from visual word priming: an ERP study.

Implicit memory is inferred from repetition priming effects in tasks such as word identification, word fragment completion, and perceptual recognition with masking or brief exposures. In this experiment, we explored whether the visual word and object repetition priming effects can be reflected by features of ERP and whether visual word repetition priming differs from visual object repetition priming. We have observed that (1) pre-exposure to recognizable stimuli (both word and object picture) shortened the response time in identifying their repetitions; (2) repetition of unrecognized scrambles of words or object pictures did not show any effects on ERP patterns; (3) ERPs distinguished recognizable from unrecognizable stimuli; and, (4) repetitions of both words and pictures strongly influenced the patterns of ERPs, though the ERPs to word stimuli differed from the ERPs to picture stimuli.

Adult↗

PubMed1997

Reflection of working memory: ERP mnemonic effects.

The study of working memory often utilizes a delayed matching to sample paradigm (DMS). Typically in the matching condition, the test and sample stimuli are identical, raising the possible confound of retinotopic projections for the matching stimuli in contrast to the non-matching stimuli. In the present study, 65 healthy subjects performed a modified delayed matching to sample task while monitoring their ERP waveforms. The stimuli consisted of 60 different sample stimuli (S1) and 60 different test stimuli (S2). Half of the S2s were complementary to the sample stimuli (Fit), the other half of the S2s were not complementary (Nonfit). After S2, the subjects pressed one of the buttons to indicate whether the test stimulus fits the sample stimulus. Our statistical results indicated that the ERPs to sample stimuli differed from the ERPs to test stimuli from 200 ms poststimulus to the end of the recording epoch. The ERPs to fitting stimuli were significantly different from those to non-fitting stimuli from 200 to 400 ms poststimulus. The ERP patterns in the present study may reflect ERP mnemonic effect for working memory. Our results ruled out the retinotopic confound as a potential mediator variable, and are in agreement with other animal or human neurophysiological studies on memory.

Adult↗

PubMed1996

A simple auditory oddball task in young adult males at high risk for alcoholism.

The reduction in the amplitude of the auditory P300 in young adult males at high risk for alcoholism has not been as consistently replicated as has been the reduction in the visual P300 amplitude in the same group. The easier nature of the auditory task was thought to be responsible for the inconsistency. We examined the auditory P300 amplitude in a group that has not yet been studied, young adult sons of alcoholics (mean age = 24.9 years, n = 48), and compared them with age and sex-matched controls (mean age = 27.8 years, n = 23). We found the auditory P300 amplitude to be reduced in the high-risk group and this reduction to be the greatest over the posterior centroparietal and occipital areas when individual leads were examined. We further analyzed the data using current source density, a mathematical transformation that circumvents some of the errors inherent in measuring scalp-evoked potentials, and found reduced current source density in the high-risk group in the posterior central and parietal areas. Thus, we found that a simple auditory oddball task was effective in eliciting P300 differences in groups at high and low risk for alcoholism. The clinical significance of the P300 is discussed, as well as the relevance of task difficulty in eliciting auditory P300 differences in young males at high risk for alcoholism.

Adult↗

PubMed1995

Event related potentials during object recognition tasks.

In our previous studies, we have demonstrated an ERP correlate of visual memory with a modified delayed matching-to-sample paradigm using a series of nonsense line drawings or faces as stimuli. In this experiment, we employed pictures of objects to determine whether the ERP can reflect the object recognition process and whether visual stimuli with a verbal label would result in a different topographic distribution from past topography obtained with visual stimuli without a verbal label. The results of this study suggest that the amplitude of the ERP component (c247) to repeated (primed) pictures of common objects was significantly decreased as compared to the unrepeated (unprimed) pictures; the latency for the peak of c247 was decreased for the repeated compared to the unrepeated, and the response time was also significantly shorter to the repeated picture stimuli than to the unrepeated; the topographical distribution of c247 was mainly located in the occipitotemporal areas of the brain. However, the source energy density map showed that the topographic involvement of the brain regions to the c247 was different in the matching and nonmatching trials.

Adult↗