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Biomedical subjects

R W Neufeld

Publications and source records attributed to R W Neufeld.

At least 19 recordsLinked to original sources
PubMed1994

A formal analysis of stressor and stress-proneness effects on simple information processing.

This study examined visual information processing under a stressor of recurring loud sound among groups divided according to psychometrically identified stress susceptibility. Formal models of task performance were employed to address several issues concerning stress effects on cognitive functioning. Examined were effects on parallel versus serial processing structure, task-wise processing capacity, strategies of allocating processing resources to task components, and curtailment of processing of relevant task elements. Contrary to prediction, stressor presence generated slightly more rather than less evidence of a parallel versus serial processing structure. There was some suggestion of central-task capacity depletion among more susceptible subjects, in line with certain theoretical positions. Evidence of curtailed exhaustive processing of relevant stimulus items was negative. Most notable was the disruption by stress among susceptible subjects of performance-enhancing strategies of deploying processing resources across the different task components (elements of the visual display and within-trial stages of processing). Such effects have received relatively little attention in this research domain; their investigation is shown to be made tractable, however, through the application of selected formal models of information processing.

Acoustic Stimulation↗
PubMed1993

Classification of the schizophrenias according to symptomatology: a two-factor model.

Various methods of subtyping schizophrenia are briefly reviewed. It is concluded that the paranoid-nonparanoid dichotomy has been the most consistently supported both clinically and in experimental research. In an attempt to deal with its limitations, a tentative reconceptualization is proposed for schizophrenia. This new model is based on two independent factors: severity of disorder and severity of symptom. The present dimensional approach is shown to be consistent with a number of empirical findings regarding differences and associations between paranoid and nonparanoid symptomatology. The relative advantages of dimensional and categorical descriptions, as well as their combination, are presented.

Cluster Analysis↗
PubMed1992

Disruption of saccade production during oculomotor tracking in schizophrenia and the use of its changes across target velocity as a discriminator of the disorder.

A clear measure of eye movement disorder (EMD) that reliably separated schizophrenic individuals from others would both give insight into the brain control of the disorder and provide an aid in diagnosis. In the present study, a detailed analysis was carried out of the interactions between the pursuit and saccadic components of eye movements at different target velocities. The subjects comprised schizophrenic patients, unipolar depressed patients, and normal controls. The speed of the slow pursuit component did not differ among the groups, but schizophrenic subjects made more saccadic movements at low target velocities, though they started further away from the target at high target velocities. On the basis of these differences, a slope was computed of the linear function that related the number of saccadic eye movements to the velocity of a ramp visual target. Slope direction was negative for schizophrenic subjects but positive for unipolar depressive and normal subjects, and the correct classification rate for subjects was 84%.

Adolescent↗
PubMed1992

A dynamic vulnerability perspective on stress and schizophrenia.

Previous vulnerability models of schizophrenia, while strong, have serious limitations. To deal with the main areas of concern, a multifactor transactional conceptual framework of stress and schizophrenia, which builds on earlier models and incorporates recent research findings, is proposed. Research implications deriving from this framework are discussed.

Adaptation, Psychological↗
PubMed1990

Schizophrenic performance on line bisection: no simple lateralization defects.

Many studies have assessed the possible lateralization deficits of schizophrenics, and the results usually suggest left hemisphere dysfunction. Nevertheless, they have been variable. This may have been due to cognitive demand of the different tasks, not to changes in brain lateralization itself. In order to circumvent this problem, the present study evaluates the performance of schizophrenics on a simple but lateralized task, line bisection. Subjects bisected a line using either visual or tactile information, with the left or right hand, when it was placed in their left or right hemispace or directly in front of them. Schizophrenic subjects were not more erroneous than normals (variable error), nor were they biased differently from normals in either direction with either modality of sensory input (constant error). There were only two significant effects of group on the tactile line bisection, one of position x length x group and one of position x hand x end x length x group, both on constant error (directional bias). The lack of main effects and presence of interactions on these basic tasks suggests that apparent lateralization differences found in schizophrenic subjects are due not to a simple defect of brain lateralization but may stem from task demands and attention allocation.

Attention↗
PubMed1989

Release of saccades in schizophrenics: inattention or inefficiency?

This paper attempts to distinguish between inattention and inefficiency as the cause of the eye movement problems of schizophrenic subjects. It focuses on their release of fast saccadic eye movements in four different situations: interrupting smooth tracking, as double-jumps in refixation, and as inadvertent departures from steady fixation or too-early prediction moves. If an attention deficit causes saccades during tracking, they should be reduced only for schizophrenic subjects in the dark, when there is no contrasting background. Instead the reduction was present for all groups. If double-jumps in saccadic refixations were caused by inattentional instability, they should increase in schizophrenic subjects when the target is a temporary flash of light. Instead, they were reduced in all groups to almost none, suggesting a perceptual processing cause for the excess double jumps. If a global attentional problem of schizophrenia caused saccade release, saccade number should be correlated across the four situations. Instead, there were significant correlations only between departures and predictions in paranoid schizophrenic subjects (r = 0.728) and between predictions and looking in nonparanoid schizophrenic subjects (r = -0.855). This lack of over-all correlations suggests that a common inattentional problem does not produce these eye movement deficiencies. Instead, the perceptual influence on tracking and looking suggests that processing inefficiency is responsible for at least part of the deficit.

Adolescent↗
PubMed1987

Span of apprehension among remitted schizophrenics using small visual angles.

Evidence concerning span of apprehension (SOA) performance as a potential marker of vulnerability to schizophrenia has been the subject of several recent investigations. There is agreement that earlier findings of performance deficits among offspring of schizophrenics and among schizophrenics in remission may not extend to more foveal, as opposed to peripheral, presentations of visual arrays of the SOA task. Using the former format of presentation, the current study found that performance of episodic patients was distinguishable from that of nonpatient controls but performance of remitted patients was not. Readings of psychophysiological activity (heart rate) obtained during SOA task performance were higher among episodic patients than among others, suggesting that such measures may be promising markers of episodes of schizophrenia.

Adolescent↗
PubMed1987

Attentional resources and hemispheric functional asymmetry in schizophrenia.

Inconsistent findings within certain areas of schizophrenia research--processing of verbal and pictorial stimuli, and hemispheric functional asymmetry--suggest the importance of examining the attentional resources associated with the cerebral hemispheres among schizophrenics. A cognitive task battery was developed which assessed the functioning of the left and right hemispheres under varying attentional loads. This battery was administered to paranoid and non-paranoid schizophrenics, and three control groups. Error rate and response latencies were monitored. It was found that the schizophrenics, particularly the non-paranoids, displayed evidence of a generalized decrease in available resources across attentional pools. In addition, response latencies were indicative of a complex interaction involving loads and visual field of stimulus presentation, which differed across schizophrenic subtypes. These lateralized effects among the schizophrenics did not interact with the differential sensitivity of the hemispheres to stimulus characteristics.

Adolescent↗
PubMed1986

The interactional model of anxiety: an evaluation of the differential hypothesis.

The interactional model of anxiety states that individuals who score high on trait anxiety measure for a specific situation dimension will respond with elevated state anxiety only in reaction to encounters with congruent situations. We tested this model by presenting subjects who scored high or low on ego threat, physical danger, novelty ambiguity, and daily routine trait measures with stressors representative of the four situation dimensions. The interactional model was partially supported for ego threat trait anxiety. However, results generally supported the influence of situation rather than the trait or interaction on anxiety response. The lack of trait factor independence for the novelty ambiguity and daily routine trait dimensions is discussed as a potential reason for the nonsupport of the interactional model. Finally, we suggest that the experimental design used in this study is a more accurate and vigorous test of the differential hypothesis than past research.

Adaptation, Psychological↗
PubMed1985

Heart beat interoception: a study of individual differences.

There were two principal aims of the study: to carry out preliminary evaluation of a novel heartbeat tracking technique for objectively measuring cardiac interoception; and to determine whether good and poor heartbeat perceivers could be differentiated with respect to other parameters reflecting individual differences in emotionality, including gender and 'emotional character'. Subjects first completed a battery of self-report questionnaires designed to measure characteristics of emotional experience, and then underwent a series of heartbeat tracking trials in which they used the index finger to tap in synchrony with their ongoing heartbeat activity (interoceptive tracking) and also with an audiotape of pre-recorded heartbeat sounds (exteroceptive tracking). The perceptual index was based on the variability of beat to tap latency. Concurrent validity findings suggested that the tracking index reflects a promising measure of cardiac interoceptive acuity. Good perceivers were found to have higher heart-rate measures than poor perceivers. With regard to 'emotional character' good perceivers had higher state anxiety, and were less emotionally expressive, although these differences were only marginally significant (P less than 0.08) with multivariate testing. Applications of the heartbeat tracking technique for further empirical evaluation of the role of interoception in emotion are discussed.

Adolescent↗
PubMed1985

Cognition and symptomatology in schizophrenia.

The experimental work on cognitive processes in schizophrenia is critically reviewed with respect to its relevance in understanding schizophrenic symptomatology. Several logical and empirical issues that complicate any comprehensive attempt to relate schizophrenic symptoms and information processing are discussed. Studies germane to schizophrenic sensory/perceptual, cognitive, affective, and motor anomalies are examined, and it is concluded that the cognitive approach to these areas is promising, but further research and theory elaboration will be required in order to provide a firm basis for cognitively oriented intervention attempts.

Affect↗