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Biomedical subjects

C Meinecke

Publications and source records attributed to C Meinecke.

13 recordsLinked to original sources
PubMed2001

Feature localization and identification.

Theories on visual search differ substantially with respect to the relationship they assume between localization and identification processes. The aim of the present study was to rigorously compare the alternative theoretical notions on how localization and identification processes are related. In two experiments, participants searched for a target with a unique line orientation among distractors containing another orientation. Localization and identification performance were measured in combination, as function of display size and target eccentricity. To compare the alternative theories, formal binomial models were developed and compared with respect to their goodness of fit to the individual data. The formal analyses showed that the model assuming identification processes to be conditioned on localization processes provided the best fit to the individual data. Furthermore, maximum likelihood estimates of the parameter corresponding to identification processes were differently affected by display size than identification performance was. The results were discussed in terms of their implication for current theories on visual search.

Fixation, Ocular↗
PubMed2001

Automaticity and attention: investigating automatic processing in texture segmentation with event-related brain potentials.

The present article deals with the question of automaticity and/or plasticity of processes in early vision. The detection of irregularities in an otherwise homogeneous surrounding, as studied in texture segmentation tasks, is considered an example of an automatic process in the processing of visual information. Participants in texture segmentation experiments are usually instructed to respond to the texture stimuli, i.e. attention is completely allocated towards them. Automaticity, however, would imply that processing takes also place when no attention is allocated to the texture stimuli and participants, e.g. perform another primary task. We investigated the automaticity of texture segmentation by recording Event-related potentials which allow to investigate processing also when no overt response is given. Three experiments investigated the role of attention in texture segmentation by varying task relevance of the texture stimuli. Participants had to either discriminate homogeneous or inhomogeneous textures or had to perform a different primary task of varying complexity. Two components were found to be sensitive to texture segmentation, a posterior N2 and a positivity within the P3 time interval. Both components were also observed when texture segmentation was task-irrelevant. However, while the posterior N2 was not affected by the complexity of the primary task and thus showed some degree of automaticity, the P3 was found to be dependent on the attentional resources left over by the primary task.

Adult↗
PubMed2001

Learning to ignore the mask in texture segmentation tasks.

Although traditionally texture segmentation has been regarded as an automatic, preattentive process, participants confronted with texture segmentation in experimental settings (i.e., with brief presentation time and subsequent masking) are initially unable to perform the task. According to perceptual learning concepts, participants must learn to fine-tune their sensory channels before perception improves under restricted viewing conditions. The present article proposes an alternative perspective that emphasizes the role of the mask. Four experiments showed that the amount of observed learning depends on the structural and temporal homogeneity or heterogeneity of the mask. The authors suggest that learning consists of separating the task-relevant signal stemming from the texture from the task-irrelevant signal of the mask and of ignoring the mask.

Adult↗
PubMed1994

Peripheral and foveal segmentation of angle textures.

Studies of the effects of retinal eccentricity on the visual segmentation of textures are presented. The textures used in these studies were composed of angle elements. These were presented tachistoscopically to college students in three different experiments. Results showed that there were different relationships between segmentation performance and eccentricity, depending on the width of the angles used in the background and target texture. One major difference was that peak performance was found in the fovea in some conditions, and in peripheral areas in other conditions. Performance in the fovea and the periphery seemed to be determined by qualitatively different features. It was assumed that an appropriate explanation is that the system-internal representation of a specific stimulus within the early visual system differs as a function of the retinal location at which it is projected. Thus, the critical features discriminating between target and background texture have to be sought in the system-internal representation of the stimulus instead of in the stimulus itself. The data show that a relatively exact system-internal representation of the stimulus is present in the fovea, where performance is determined by angle width. In the periphery, in contrast, angles seem to be represented as "blobs," and performance is determined by the orientation of the blobs' main axes.

Depth Perception↗
PubMed1993

Adverse clinical events in dependent long-term nursing home residents.

OBJECTIVE: To assess the occurrence, type, and burden of adverse clinical events (ACE) among residents of chronic facilities. An ACE is any acute or subacute change in health status suggesting acute or subacute illness. DESIGN: Survey with face-to-face functional assessment and 3-month retrospective chart review. STUDY POPULATION: One hundred six continuing-care residents with a minimum length of stay of 4 months at an Italian chronic care facility. MEASUREMENTS: Functional assessment and chart review-based classification of ACE burden on care management according to a clinical-functional Severity Rating Scale. MAIN RESULTS: Functional dependence, dementia and concurrent clinical problems were common. Two hundred seventy-three ACEs were detected. Eighty-nine percent of residents experienced at least one ACE. Only 21% of ACEs could be managed by simple medical intervention and monitoring within 1 day; in 23% there was need for more complex care management; 7% of the latter ACEs resulted in residual (new) functional impairment. Cardiovascular and gastrointestinal systems were most commonly involved in ACEs. Neurological ACEs were the most frequent category leading to new functional impairment (22%). ACE occurrence/burden was higher in male residents (P < 0.01) and strongly associated with the number of concurrent medical problems (P < 0.001). Neither cognitive nor functional dependence levels were related to ACE occurrence. CONCLUSIONS: This description of the burden on care management resulting from acute and subacute changes in clinical and functional status of chronic patients emphasizes the continuing and unpredictable nature of medical attention required in a nursing home or chronic care facility. ACEs occur far more frequently among the elderly than is generally recognized. Thus a high level of medical and nursing skill is necessary in chronic care facilities.

Aged↗
PubMed1992

Risk reduction in sexual behavior: a condom giveaway program in a drug abuse treatment clinic.

Just before and 4 months after initiation of a condom giveaway program, a questionnaire regarding sexual behavior and condom acquisition was administered to 103 men attending an outpatient drug abuse treatment clinic. Jars filled with a variety of condoms were placed in every clinic room. Condom taking varied as a function of room. Sixty percent of the subjects reported taking condoms. At follow-up, clients reported increases in condom possession and in use of condoms for vaginal intercourse.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Cognitive deficits associated with human immunodeficiency virus encephalopathy.

The encephalopathy associated with direct nervous system infection by the human immunodeficiency virus (HIV) has been recognized as one of the major debilitating aspects of the acquired immunodeficiency syndrome (AIDS) and of pre-AIDS conditions. A comprehensive neuropsychological examination of symptomatic HIV-infected subjects without opportunistic cerebral disease demonstrated a distinctive pattern of cognitive deficits marked by prominent attentional impairment. Evidence of organizational and reasoning impairments also was observed, but language, visual-spatial, and memory consolidation abilities were relatively preserved. The findings suggest a profile of impairment similar to other cognitive syndromes involving dysfunction of predominantly anterior brain structures and projections and suggest a rationale for psychostimulant drug treatment.

AIDS Dementia Complex↗
PubMed1989

Retinal eccentricity and the detection of targets.

It is known that the detectability of a target depends on its similarity to the individual context elements. This article attempts to show that global properties of the context can also influence detection performance. For example, the detection of an O among several Hs appears to be easier than the detection of an H among several Os, because the context consists of elements that are more angular. However, this angular-context advantage is most apparent when the stimulus projection falls on extrafoveal areas of the retina. The results of two stimulus manipulations suggest that the decreasing ability of the visual system with increasing eccentricity could be responsible for this relationship. Increasing the distance between the single elements, and thus reducing the effect of lateral inhibition, led to a deterioration in performance; and by defocusing the stimulus presentation it was possible to achieve an improvement in performance.

Adult↗