Biomedical subjects

M Eimer

Publications and source records attributed to M Eimer.

47 records · Page 3Linked to original sources

PubMed1995

Stimulus-response compatibility and automatic response activation: evidence from psychophysiological studies.

Effects of dimensional overlap between stimuli and responses on partial response activation were investigated within a priming paradigm with the help of event-related potentials. The likely position of a target stimulus (requiring a left or a right reaction) was indicated by an arrow precue. To test whether automatic response activation processes are triggered by the cue, the lateralized readiness potential was computed. It was found that responses congruent to the direction of the cue were activated about 200 ms after cue onset. This early process was unaffected by specific cue-response contingencies and was completely missing when a nonspatial (color) cue was used. A second response activation phase was observed, which was partially controlled by specific response instructions and subjective expectancies. It is concluded that when stimuli and responses overlap with respect to spatial attributes, automatic response activation process are triggered, which may later be replaced by the activation of an expected response.

Adult↗

PubMed1994

An ERP study on visual spatial priming with peripheral onsets.

Visual event-related potentials were measured for peripheral target stimuli that were preceded by a peripheral square. Targets appeared either at the same location as the square or in the opposite visual hemifield. In Experiment 1, 75% of the trials were same-location trials, and in Experiment 2, same- and opposite-location trials were equiprobable. The subject's overt response was dependent either on the identity or on the location of the target. In both experiments, opposite-location targets elicited an enhanced P1 at posterior electrodes ipsilateral to the position of the letter. This enhancement may be due to a sensory inhibition of same-location targets. Same-location targets elicited an enhanced negativity between 130 and 300 ms, with a first peak located parietally and a second peak broadly distributed over midline electrodes. This effect was larger in Experiment 1 than in Experiment 2 and is interpreted as enhanced processing of same-location targets due to an attentional orienting process elicited by the peripheral square.

Adult↗

PubMed1994

"Sensory gating" as a mechanism for visuospatial orienting: electrophysiological evidence from trial-by-trial cuing experiments.

Stimuli attended-to locations in visual space are usually detected with higher speed and accuracy than stimuli at unattended positions. It has been argued that this effect is due to "sensory gating" mechanisms that modulate the flow of perceptual information from attended and unattended positions. In the present experiments, event-related potentials (ERPs) were recorded to stimuli that were preceded either by a valid or by an invalid positional cue (trial-by-trial cuing). When overt responses were required only to infrequent target stimuli on valid trials (Experiment 1) or to all validly cued stimuli (Experiment 2B), but not to invalid trials, systematic enhancements of early sensory-evoked potentials were found. These effects were smaller when both validly and invalidly cued stimuli required a response (Experiment 2A). These findings are interpreted as evidence that sensory gating processes are activated during the trial-by-trial cuing of spatial attention. Furthermore, valid stimuli elicited a greater negativity than invalid stimuli at midline electrodes following the early enhancements of sensory-evoked potentials. This possibly reflects an additional enhanced processing of attended-to locations.

Adult↗

PubMed1993

Effects of attention and stimulus probability on ERPs in a Go/Nogo task.

Event-related potentials were measured to letters presented either to the left or the right of a fixation point that were preceded by a precue that indicated the position of the upcoming letter either correctly (valid trials) or incorrectly (invalid trials). One letter required a response (Go stimulus), while the other letter required no response (Nogo stimulus). In experiment I, Nogo letters occurred only on 25% of the trials, while in experiment II, Go and Nogo letters were equiprobable. In both experiments, Nogo stimuli elicited larger N2 components and P3s with a more anterior topography than did Go stimuli. The N2 enhancement elicited by Nogo stimuli showed a frontal maximum (most markedly when Go and Nogo stimuli were equiprobable) and was significantly influenced by precue validity. These results are discussed in terms of "Response Mismatch" and action inhibition processes.

Adult↗

PubMed1993

Effects of transient spatial attention on auditory event-related potentials.

Event-related potentials (ERPs) were recorded in subjects receiving left- and right-ear tones while they shifted attention to the left or right on a trial-by-trial basis. ERPs at attended compared with unattended tones revealed an enhanced negativity consisting of an early part that was parietally distributed and a later part with a frontocentral distribution. It may be concluded that these ERP modulations reflect the selection of auditory stimuli according to spatial criteria within a transient spatial attention situation. Furthermore, the attention-related negativity was not reduced for long inter-stimulus intervals (10 s) suggesting that prior stimulus exposure is not a basic requirement for eliciting attention-related negativity in the auditory modality.

Adult↗

PubMed1993

Adverse events related to drugs and drug withdrawal in nursing home residents.

OBJECTIVE: To (1) develop and standardize explicit criteria to link clinical adverse events to drug withdrawal, (2) determine the incidence and severity of Adverse Drug Events (ADEs) and Adverse Drug Withdrawal Events (ADWEs) in a nursing home population, and (3) establish the contribution of demographic, clinical, and functional characteristics to ADEs and ADWEs. DESIGN: Retrospective record review of an admission cohort. SETTING AND SUBJECTS: Consecutive admissions of residents of an academic Veterans Affairs nursing home with available records and lengths of stay > 30 days (n = 175). Subjects were 96% men, aged 70 +/- 12 years, and took 7.0 +/- 3.4 medications. METHODS: We applied standardized algorithms to determine incidence, probability, and severity of ADEs and ADWEs. Multiple regression techniques were used to identify factors associated with frequency and risk of events. RESULTS: Ninety five residents experienced 201 ADEs. Twelve required hospitalization or prolonged hospitalization, and one resident died. Sixty two persons had 94 ADWEs. None were associated with death and one with hospitalization. The four most commonly prescribed drug classes accounted for 72% of ADEs and 80% of ADWEs. Results of multivariate analyses showed common risk factors for both ADEs and ADWEs: number of diagnoses, number of medications, and hospitalization during the nursing home stay. CONCLUSIONS: ADEs and ADWEs were common in nursing home residents in this Veteran's Affairs setting. Explicit criteria developed and applied in this study should be applied prospectively in other settings, both to further define risk of drug discontinuation and to assist in development of specific drug discontinuation guidelines.

Aged↗

PubMed1990

Representational content and computation in the human visual system.

Information-processing systems can be characterized by their ability to transform systematically certain internal representational states (symbols) into one another. The presence of such an information-processing capacity calls for an explanation. How could such an explanation in principle be formulated? How is it possible to specify internal representational states and to ascribe to them certain representational contents? What has to be demonstrated by such explanations is how an information-processing capacity is actually instantiated in a system. In this paper, the outlines of an explanation by instantiation are sketched for a specific human visual capacity. In addition, some fundamental problems facing the development of this explanation will be discussed.

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PubMed1989

Management of the behavioral symptoms associated with dementia.

Dementia-related behavioral symptoms present a difficult management problem for caregivers and health care providers. The first step in the treatment of behavioral symptoms in the elderly should involve nonpharmacologic measures. This should include the exclusion of medication-induced dementia and delirium, which is an important consideration in the elderly owing to multiple medication use and alterations in pharmacokinetics and pharmacodynamics. Other measures involve relatively simple environmental changes. If these are unsuccessful, pharmacologic management is often tried. Numerous concerns surround the use of antipsychotics, which are the primary agents used to treat behavioral symptoms in demented elderly. The public is concerned about their inappropriate use as chemical restraints. Another concern involves the efficacy of these agents. Most well-designed studies demonstrate an overall modest effect from the antipsychotics that is often similar to that seen with placebo. There may be a small number of patients who respond markedly, whereas the majority do not receive great benefit. Unfortunately, all are exposed to the numerous side effects of these agents, including some irreversible movement disorders. If these agents are believed to be necessary, efforts should be made to use them in a manner that reduces the associated risks. A few other agents have been noted to successfully treat the problem behaviors associated with dementia, but most have been in the form of case reports. It appears that the optimal treatment of these problems relies on future research in the area of nonantipsychotic modalities that will be efficacious and have a rather benign side effect profile.

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PubMed1987

Elevated serum carbamazepine concentrations following diltiazem initiation.

A case of carbamazepine neurotoxicity following the addition of diltiazem is reported. A patient with previously stable carbamazepine serum concentrations was treated with diltiazem for atrial fibrillation and a rapid ventricular response. After three days on the combined regimen, the patient developed neurological symptoms resulting in hospitalization. After a review of the patient's medication usage and carbamazepine concentrations, an interaction between diltiazem and carbamazepine was suspected. Carbamazepine's elimination appears to have been decreased, resulting in neurotoxicity. The toxicity resolved when the carbamazepine dosage was decreased 62 percent.

Aged↗

PubMed1985

Effects of clorazepate on breathlessness and exercise tolerance in patients with chronic airflow obstruction.

Five patients with severe chronic lung disease were given placebo or 7.5 mg of clorazepate, a benzodiazepine, at bedtime for two weeks using a double-blind cross-over study design. Exercise tolerance, arterial blood gases, pulmonary function tests, self-rated breathlessness, and self-administered depression and anxiety scores were similar during drug treatment, placebo treatment, and washout periods. Higher doses of clorazepate were not tolerated by three of five patients. Nonanxious patients with chronic lung disease seem not to benefit subjectively or objectively from a low-dose benzodiazepine regimen.

Aged↗

PubMedDate not supplied

Spatial cueing, sensory gating and selective response preparation: an ERP study on visuo-spatial orienting.

Event-related brain potentials (ERPs) were recorded in a visuo-spatial attention task where the position of an imperative stimulus was indicated either validly or invalidly by a central arrow (trial-by-trial cueing). Subjects had to perform choice RT tasks with the response being dependent either on the identity of the target stimulus or on its position. When target identity was relevant for response selection, validly cued stimuli elicited amplitude enhancements of the early, sensory-evoked P1 and N1 components at lateral posterior sites. The N1 validity effect was limited to scalp sites ipsilateral to the visual field of stimulus presentation. Although these effects were found only when the sensory discrimination task was considerably difficult, they are in line with models assuming that modulations of sensory-perceptual processing ("sensory gating") are induced by spatial cueing. However, when target location was response-relevant, N1 amplitude enhancements were consistently elicited by invalidly cued letters. CNV and LRP measures indicated that the arrow elicited response-related processing in the cue-target interval. Such processes occurred even when the cue contained no information about an upcoming response. Two consecutive lateralization phases were distinguishable in the LRP, with experimentally induced response assignments becoming effective only during the second phase.

Adult↗