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PubMed1997

A topographic study of ERPs elicited by visual feature discrimination.

The functional properties and topographic distribution of event-related potential (ERP) components elicited by visual discrimination of orientation, spatial frequency, spatial location, and color were investigated. ERPs were recorded from 28 electrode sites from 16 adult subjects. Five ERP components were measured: N1 (peak latency = 160 ms), P2 (250 ms), anterior N2 (260 ms), posterior N2 (280 ms), and P3 (400 ms). N1 and P2 were more negative when a stimulus was a target, showing the selection negativity effect. Feature-specific effects on component amplitude or topography varied by component. N1 and P2 were sensitive to stimulus orientation and location. Anterior or posterior N2 was sensitive to orientation, spatial frequency, and location. P3 varied with orientation, but not with other stimulus features. Cross-task comparisons of ERPs to vertical line segments in the color, orientation, and location discrimination tasks indicated that P2 and N2, but not N1 and P3, were sensitive to changes in task-demand. These data provide topographic evidence that ERP components in the 160-400 ms time domain can be differentiated on the basis to processing of specific visual features, and reflect neurophysiologically distinct visual pathways in the human cortex.

Adult↗

PubMed1999

A normed study of face recognition in autism and related disorders.

Although the interpretation of studies of face recognition in older children, adolescents, and adults with autism is complicated by the fact that participating samples and adopted methodologies vary significantly, there is nevertheless strong evidence indicating processing peculiarities even when task performance is not deficient. Much less is known about face recognition abilities in younger children with autism. This study employed a well-normed task of face recognition to measure this ability in 102 young children with autism, pervasive developmental disorder not otherwise specified (PDDNOS), and non-PDD disorders (mental retardation and language disorders) matched on chronological age and nonverbal mental age, and in a subsample of 51 children divided equally in the same three groups matched on chronological age and verbal mental age. There were pronounced deficits of face recognition in the autistic group relative to the other nonverbally matched and verbally matched groups. Performance on two comparison tasks did not reveal significant differences when verbal ability was adequately controlled. We concluded that young children with autism have face recognition deficits that cannot be attributed to overall cognitive abilities or task demands. In contrast to controls, there was a lower correlation between performance on face recognition and nonverbal intelligence, suggesting that in autism face recognition is less correlated with general cognitive capacity. Contrary to our expectation, children with PDDNOS did not show face recognition deficits.

Adult↗

PubMed2006

[How do parents experience the premature birth of their child?].

Advising and guidance of parents of premature children represent an important field of care activity in paediatrics. Nursing personnel are expected to react appropriately and competently to the needs and problematic situations of parents of prematurely born children. Only a restricted basis of sound knowledge is available for the fulfilment of this demanding task. The aim and purpose of the following literature analysis is to collect the knowledge currently available and to make it available to nursing, in theory and practice, in a concise form. In this way, the tasks of nursing personnel in this field can be formulated and future training content can be defined in more detail. Several data banks and the keyword catalogue of the University and Regional Library of Münster and the Central Library for Medicine in Cologne were consulted using the key term "premature birth" and various combinations of terms. A look at the research results makes it clear that the perspective of nursing researchers is particularly restricted to the immediately present and acute problem situations of children and parents during the period of the postnatal stay in hospital. There are only very few studies -that inquire into long-term effects in the parents' experiencing and overcoming of the premature birth. The following literature study shows that mothers in particular display intense emotional reactions as a result of a premature birth. These emotions are expressed in the form of fear concerning the disablement or death of the child as well as in feelings of physical inadequacy and incomplete self-realisation. In view of the life-long increased morbidity of prematurely born children and the hospital stays related to it, nursing personnel could benefit from developing specific insight into and understanding for the difficult life situation of parents of a prematurely born child. Regarding the present state of research, it is striking that the aspects of how the parents of premature children come to terms with their problem situations have to date been predominantly investigated via standardized processes.

Adaptation, Psychological↗

PubMed2000

fMRI during affect discrimination in bipolar affective disorder.

OBJECTIVE: It has been hypothesized that disturbances in affect may represent distinct etiologic factors for bipolar affective disorder. The neural mechanisms mediating affective processes and their relationship to brain development and the pathophysiology of bipolar affective disorder remain to be clarified. Recent advances in neuroimaging techniques have made possible the non-invasive examination of specific brain regions during cortical challenge paradigms. This study reports findings based on fMRI data acquired during fearful and happy affect recognition paradigms in patients with bipolar affective disorder and in healthy adult subjects. METHODS: Prior to the scan, subjects were instructed to view the stimuli and to identify the type of facial expression presented. Echo planar scanning was performed on a 1.5 Tesla scanner which had been retrofitted with a whole body echo planar coil, using a head coil. RESULTS: The data indicate that in adult subjects with bipolar affective disorder, there is a reduction in dorsolateral prefrontal cortex activation and an increase in amygdalar activation in response to fearful facial affect. In a healthy comparison group, signal intensity changes were not found in these regions. In addition, although the patients with bipolar affective disorder completed the task demands, they demonstrated an impaired ability to correctly identify fearful facial affect but not the happy facial affect displayed. CONCLUSION: These findings are consistent with the hypothesis that in some patients with bipolar affective disorder, there may be a reduction of frontal cortical function which may be associated with affective as well as attentional processing deficits.

Adult↗

PubMed1993

Hypnotic analgesia: dissociated experience or dissociated control?

High-hypnotizable subjects (n = 18) were superior to low-hypnotizable subjects (n = 18) in the extent of pain reduction produced by hypnotic analgesia and by a stress-inoculation procedure. However, stress inoculation but not hypnotic analgesia impaired performance on a cognitively demanding task that competed with pain reduction for cognitive resources. This outcome implies that hypnotic analgesia occurs with little or no cognitive effort to reduce pain and challenges the social psychological model of hypnosis. The findings are also inconsistent with the notion of dissociated experience, which proposes that pain and the cognitive efforts to reduce it are cut off from consciousness by an amnesialike barrier. However, the results do support the notion of dissociated control, which proposes that suggestions for hypnotic analgesia directly activate pain reduction and thereby avert the need for cognitive strategies to reduce pain.

Adult↗

PubMed1994

A dual-task analysis of resource allocation in dysthymia and anhedonia.

Research has shown dysthymic individuals to be hyporesponsive at various stages of information processing, yet it is not clear whether dysthymics are deficient in the amount of available attentional resources for information processing or, instead, in the allocation of those resources. To distinguish between these possibilities, the authors compared dysthymics to anhedonic and normal control Ss during the performance of memory tasks, under conditions of varying task priority and difficulty. Although there were no performance differences, dysthymics and anhedonics exhibited a consistently smaller P300 component of the event-related potential. Furthermore, P300 results indicated that dysthymics and anhedonics responded differently from controls to variations in task demands. Thus, although evidence was obtained for group differences in both resource capacity and resource allocation strategy, the overall pattern of results is interpreted as favoring the latter.

Attention↗

PubMed2000

Perceptual organization in schizophrenia: the processing of symmetrical configurations.

The hypothesis that the perceptual organization dysfunction of patients with poor premorbid schizophrenia is due to a deficit in global visual sensory store processing was tested by assessing their ability to process symmetrical configurations that develop early and have strong prepotent structures. Two same-different judgment tasks in which performance varies as a function of the symmetrical organization and task demands were administered to participants with good and poor premorbid schizophrenia, those with mood disorders, and normal controls. Like the other groups, poor premorbid schizophrenics' latency and error response patterns closely paralled the a priori model of adequate processing. The results support their competence in perceptually processing symmetrical configurations and disconfirm the hypothesis that their input deficiencies represent a general deficiency in all forms of perceptual organization. The implications for specifying their early input dysfunction are discussed.

Adolescent↗

PubMed1988

Perceived self-efficacy in coping with cognitive stressors and opioid activation.

This experiment tested the hypothesis that perceived self-inefficacy in exercising control over cognitive stressors activates endogenous opioid systems. Subjects performed mathematical operations under conditions in which they could exercise full control over the cognitive task demands or in which the cognitive demands strained or exceeded their cognitive capabilities. Subjects with induced high perceived self-efficacy exhibited little stress, whereas those with induced low perceived self-efficacy experienced a high level of stress and autonomic arousal. Subjects were then administered either an inert saline solution or naloxone, an opiate antagonist that blocks the analgesic effects of endogenous opiates, whereupon their level of pain tolerance was measured. The self-efficacious nonstressed subjects gave no evidence of opioid activation. The self-inefficacious stressed subjects were able to withstand increasing amounts of pain stimulation under saline conditions. However, when endogenous opioid mechanisms that control pain were blocked by naloxone, the subjects were unable to bear much pain stimulation. This pattern of changes suggests that the stress-induced analgesia found under the saline condition was mediated by endogenous opioid mechanisms and counteracted by the opiate antagonist.

Cognition↗

PubMed1993

Eysenck's arousal theory of introversion-extraversion: a converging measures investigation.

Convergent electroencephalographic, performance, and psychometric measures of arousal were used to test predictions based on H. J. Eysenck's (1967) theory. Twelve introverts and 12 extraverts had their brainstem auditory evoked responses (BAERs) monitored under 3 levels of caffeine administration (0.0, 1.5, and 3.0 mg/kg) and 3 levels of task demand (resting, simple response time, and complex response time). Results revealed a decrease in the latency of Wave V of the BAER as a function of personality, with introverts evidencing significantly shorter latency of Wave V as compared with extraverts. Faster conduction time between Waves I-III and I-V were also found in introverts. Caffeine at either the 1.5 or 3.0 mg/kg level was associated with decreased latency of Wave V, compared with the placebo condition. No personality differences in subjective arousal or reaction time performance were found across any of the conditions.

Adolescent↗

PubMed1997

Ability analysis of gender relevance and sex differences in cardiovascular response to behavioral challenge.

Cardiovascular effects of gender-specific ability perceptions (ability perceptions linked to one's identity as being female or male) were examined under different task conditions. In Study I, participants were led to believe that either men (masculine task) or women (feminine task) tend to do well on a memory task and then were provided the chance to avoid noise by attaining a low or high performance standard. As expected, sex differences in systolic blood pressure response during performance depended not only on task type but also on the degree of challenge. In Study 2, high standard effects were strengthened and extended through the use of an appetitive procedure and the inclusion of conditions in which the performance standard was extreme. Findings are discussed in terms of an interactional analysis of ability percepts, task demand, and cardiovascular responsivity.

Adolescent↗

PubMed1988

Effects of speaking rate and lexical status on phonetic perception.

Among the contextual factors known to play a role in segmental perception are the rate at which the speech was produced and the lexical status of the item, that is, whether it is a meaningful word of the language. In a series of experiments on the word-initial /b/-/p/ voicing distinction, we investigated the conditions under which these factors operate during speech processing. The results indicated that under instructions of speeded responding, listeners could, on some trials, ignore some later occurring contextual information within the word that specified rate and lexical status. Importantly, however, they could not ignore speaking rate entirely. Although they could base their decision on only the early portion of the word, when doing so they treated the word as if it were physically short--that is to say, as if there were no later occurring information specifying a slower rate. This suggests that listeners always take account of rate when identifying the voicing value of a consonant, but precisely which information within the word is used to specify rate can vary with task demands.

Adult↗

PubMed1990

Effects of motor programming on the power spectral density function of finger and wrist movements.

Power spectral density analysis was applied to the frequency content of the acceleration signal of pen movements in line drawing. The relative power in frequency bands between 1 and 32 Hz was measured as a function of motoric and anatomic task demands. Results showed a decrease of power at the lower frequencies (1-4 Hz) of the spectrum and an increase in the middle (9-12 Hz), with increasing motor demands. These findings evidence the inhibition of visual control and the disinhibition of physiological tremor under conditions of increased programming demands. Adductive movements displayed less power than abductive movements in the lower end of the spectrum, with a simultaneous increase at the higher frequencies. The relevance of the method for the measurement of neuromotor noise as a possible origin of delays in motor behavior is discussed.

Adult↗

PubMed1993

The locus of inhibition in the priming of static objects: object token versus location.

The inhibition witnessed in the negative priming effect has been accounted for by positing an object file containing both identity and location information. In the present study, four experiments with 31 human subjects replicate the negative priming effect and, using new dual-target conditions where subjects respond to the target first perceived on a two-target forced-choice probe trial, suggest that location alone could account for the observed inhibition. Experiment 1 establishes an RT baseline for the new dual-target condition, whereas Experiments 2 and 3 replicate previously found single-target effects under dual-target conditions. Experiment 4 allows a concurrent determination of the inhibition accruing to both the target and distractor. The results are discussed relative to the likely existence of different kinds of inhibition which reveal themselves as a function of task demands.

Adult↗

PubMed1997

Speed and sequential effects in reaching.

To investigate the impact of future task demands on reaching, participants performed repetitive sagittal-plane reaches at low and high speeds. In a control condition, they reached from a start location to a target and back. In the experimental conditions, they reached from the start to the target, then to a second target (the location of which varied between trials), then back to the first target, and finally back to the start. Contributions of the hip, shoulder, and elbow to reaches made to the first target depended on the second target's location, on movement speed, and on repetition. Participants combined sustained and transient postural adjustments to minimize effort. The results support the knowledge model of movement selection (D. A. Rosenbaum, L. D. Loukopoulos, R. G. M. Meulenbroek, J. Vaughan, & S. E. Engelbrecht, 1995) but also call for its elaboration. Variants of the model are explored through simulations of the above study.

Adult↗

PubMed1998

The psychological refractory period effect following callosotomy: uncoupling of lateralized response codes.

A callosotomy patient was tested in 2 dual-task experiments requiring successive speeded responses to lateralized stimuli. The patient showed a robust psychological refractory period (PRP) effect. Three aspects of the data indicate that, unlike for the control participants, the PRP effect for the split-brain patient should not be attributed to a response selection bottleneck. First, the patient did not show an increase in reaction time (RT) when the 2 tasks required responses from a common output system compared with when different output systems were used. Second, inconsistent stimulus-response mappings for the 2 tasks increased RTs for the control participants but had minimal effect on the performance of the split-brain patient. Third, the consistency manipulation was underadditive with stimulus onset asynchrony but was additive or overadditive for the normal participants. These results suggest that the persistent PRP effect following callosotomy should be attributed to a bottleneck associated with response initiation, a strategy adopted to comply with the task demands, or a combination of these factors.

Adult↗

PubMed1998

Texture segregation and visual search: a comparison of the effects of random variations along irrelevant dimensions.

The effects of irrelevant variations in the color and depth of elements on participants' ability to detect and discriminate elements defined by a difference in orientation were compared. Consistent with previous research, it was found that there was no effect or small effects if the targets were single elements in visual search tasks and that there were large effects for targets defined by several elements defining an area in visual segmentation tasks. It is suggested that the reason for the discrepancy between the 2 paradigms lies in the need for grouping processes in segmentation experiments. This notion was examined in 3 additional experiments that manipulated grouping processes through task demands and stimulus design. The data provide tentative support for this notion.

Adult↗

PubMed1977

Inhibition of the human eyeblink reflex: an evaluation of the sensitivity of the Wendt-Yerkes method for threshold detection.

In two experiments, human subjects showed a reduced eyewink reflex to an airpuff (S2) if it was preceded by a light flash or a noise burst (S1). The first (N=6) showed that a light inhibited the blink maximally at a 100-msec lag. In the second (N=8), thresholds for noise pips were established with the method of limits. Then the pips were presented in multiples of threshold values as S1 100 msec before S2. Sujbects pressed a button whenever they heard the sound, on S1-S2 pairs, on S1 alone, or on S2 alone trials. Eyeblinks to S2 declined in amplitude and increased in latency as S1 intensity increased. The threshold S1 (approximately 2 dB over a 50-dB background) produced reliable inhibition in 7 of 8 subjects, and a weaker S1 which never evoked a button press was sufficient to produce reliable inhibition for the group as a whole. Inhibition in any particular trial was unrelated to button pressing. The sensitivity of the reflex technique and its relative invariance to task demands suggest its usefulness as a behavioral psychophysical procedure.

Acoustic Stimulation↗

PubMed2000

The task dependence of staged versus cascaded processing: an empirical and computational study of Stroop interference in speech production.

The authors investigated the on-line relationship between overt articulation and the central processes of speech production. In 2 experiments manipulating the timing of Stroop interference in color naming, the authors found that naming behavior can shift between exhibiting a staged or cascaded mode of processing, depending on task demands: An effect of Stroop interference on naming durations arose only when there was increased pressure for speeded responding. In a simple connectionist model of information processing applied to color naming, the authors accounted for the current results by manipulating a single parameter, termed "gain," modulating the rate of information accrual within the network. Results are discussed in relation to mechanisms of strategic control and the link between cognition and action.

Adult↗