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Results for “Task demands”

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At least 631 records · Page 35Linked to original sources

PubMed2002

An fMRI study of facial emotion processing in patients with schizophrenia.

OBJECTIVE: Emotion processing deficits are notable in schizophrenia. The authors evaluated cerebral blood flow response in schizophrenia patients during facial emotion processing to test the hypothesis of diminished limbic activation related to emotional relevance of facial stimuli. METHOD: Fourteen patients with schizophrenia and 14 matched comparison subjects viewed facial displays of happiness, sadness, anger, fear, and disgust as well as neutral faces. Functional magnetic resonance imaging was used to measure blood-oxygen-level-dependent signal changes as the subjects alternated between tasks of discriminating emotional valence (positive versus negative) and age (over 30 versus under 30) of the faces with an interleaved crosshair reference condition. RESULTS: The groups did not differ in performance on either task. For both tasks, healthy participants showed activation in the fusiform gyrus, occipital lobe, and inferior frontal cortex relative to the resting baseline condition. The increase was greater in the amygdala and hippocampus during the emotional valence discrimination task than during the age discrimination task. In the patients with schizophrenia, minimal focal response was observed for all tasks relative to the resting baseline condition. Contrasting patients and comparison subjects on the emotional valence discrimination task revealed voxels in the left amygdala and bilateral hippocampus in which the comparison subjects had significantly greater activation. CONCLUSIONS: Failure to activate limbic regions during emotional valence discrimination may explain emotion processing deficits in patients with schizophrenia. While the lack of limbic recruitment did not significantly impair simple valence discrimination performance in this clinically stable group, it may impact performance of more demanding tasks.

Affect↗

PubMed2003

Computational motor control and human factors: modeling movements in real and possible environments.

An aim of human factors research is to have models that allow for the advance design of user-friendly environments. This is still a distant dream because existing models are not yet sufficiently sophisticated. Models in the domain of motor control are a case in point, but recent developments in computational motor control suggest that the gap between the current state of modeling in this area and the desired state is shrinking. To illustrate this point, we review principles of motor control research that any model of motor control must accommodate. Then we describe a model that captures many of the capacities of actors in the everyday world, including the capacity to reach for objects in different ways depending on factors such as the ease with which different joints can rotate, the required speed of movement, and whether obstacles are present. The model relies on the ideas that goal postures are internally specified before movements are generated, that tasks are defined with flexibly ordered constraint hierarchies, and that movements can be shaped according to task demands. Actual or potential applications of this research include designing and testing possible environments where motor components play a key role.

Ergonomics↗

PubMed1997

Modeling of functional trunk muscle performance: interfacing ergonomics and spine rehabilitation in response to the ADA.

The combination of increasing costs of musculoskeletal injuries and the implementation of the Americans with Disabilities Act (ADA) has created the need for a more objective functional understanding of dynamic trunk performance. In this study, trunk extensor and flexor strengths were measured as a function of angular position and velocity for 20 subjects performing maximum isometric and isokinetic exertions. Results indicate that trunk strength is significantly influenced by trunk angular position, trunk angular velocity, gender, and direction, as well as by the interaction between trunk angular position and velocity. Three-dimensional surfaces of trunk strength in response to trunk angular position and velocity were constructed for each subject per direction. Such data presentation is more accurate and gives better insight about the strength profile of an individual than does the traditional use of a single strength value. The joint strength capacity profiles may be combined with joint torque requirements from a manual material handling task, such as a lifting task, to compute the dynamic utilization ratio for the trunk muscles. This ratio can be used as a unified measure of both task demand and functional capacity to guide job assignment, return to work, and prognosis during the rehabilitation processes. Furthermore, the strength regressions developed in this study would provide dynamic strength limits that can be used as functional constraints in the computer simulation of physical activities, such as lifting. In light of the ADA, this would be of great value in predicting the consequences of task modifications and/or workstation alterations without subjecting an injured worker or an individual with a disability to unnecessary testing.

Adult↗

PubMed1988

Electrodermal lability, errors, and reaction times: an examination of the motor impulsivity hypothesis.

Two studies were designed to investigate the effects of electrodermal lability on errors and reaction times (RTs). In Study 1 (n = 56) subjects performed an RT task that in different phases either required only fast responding or additionally discrimination and selection of one of two response alternatives according to specified rules that had to be stored in memory. Results showed that labiles (above the median of resting non-specific electrodermal responses) displayed significantly faster RTs when only speed was required. There were no differences between labiles and stabiles (below the median) in RTs and error rate when discriminations and response selections had to be made. In Study 2 (n = 52) task demands were reduced. Subjects were only required to discriminate between two events and to respond by releasing or retaining one key. Labiles displayed significantly faster RTs. There was furthermore a tendency among labiles to produce fewer False-Responses, i.e. releasing the key when it should be retained. Additional joint analyses of RT and error data revealed a tendency among labiles to perform the task more efficiently. Results are discussed in terms of motor impulsivity and information-processing accounts of electrodermal lability.

Adult↗

PubMed2005

Brain bases of error-related ERPs as influenced by age and task.

Age effects in the error negativity (Ne) and error positivity (Pe) were examined in a standard letter flanker task and an age-sensitive source memory exclusion task. Older adults made more errors and produced Ne and Pe components of lower amplitude in both tasks. The Ne was insensitive to task and error rate. The Pe, however, was reduced in the source memory relative to the flanker task and was correlated with error rate in both tasks. Ne and Pe dipoles were generally localized to anterior cingulate cortex, but dipoles associated with the Pe were more frontal for flanker errors and, for young adults, more posterior for source errors. These data suggest that the Ne reflects an automatic response to error as it occurs whereas the Pe, being more sensitive to age and task demands, and more closely linked to accuracy, reflects the allocation of attention to an error that has been made.

Adult↗

PubMed2004

A glucose-caffeine 'energy drink' ameliorates subjective and performance deficits during prolonged cognitive demand.

Effects of a combination of caffeine and glucose were assessed in two double-blind, placebo-controlled, cross-over studies during extended performance of cognitively demanding tasks. In the first study, 30 participants received two drinks containing carbohydrate and caffeine (68 g/38 mg; 68 g/46 mg, respectively) and a placebo drink, in counter-balanced order, on separate days. In the second study 26 participants received a drink containing 60 g of carbohydrate and 33 mg of caffeine and a placebo drink. In both studies, participants completed a 10-min battery of tasks comprising 2-min versions of Serial 3s and Serial 7s subtraction tasks and a 5-min version of the Rapid Visual Information Processing task (RVIP), plus a rating of 'mental fatigue', once before the drink and six times in succession commencing 10 min after its consumption. In comparison to placebo, all three active drinks improved the accuracy of RVIP performance and both the drink with the higher level of caffeine in first study and the active drink in the second study resulted in lower ratings of mental fatigue. These results indicate that a combination of caffeine and glucose can ameliorate deficits in cognitive performance and subjective fatigue during extended periods of cognitive demand.

Adolescent↗

PubMed1999

The hierarchical organization of decision making in the primate prefrontal cortex.

The prefrontal cortex plays an important role in making the association between sensory information and specific behavior. For example, in a complex stimulus response situation, such as the Wisconsin card sorting test, prefrontal patients show difficulty in making appropriate decisions. To understand the neural mechanisms, we recorded prefrontal cell activity while monkeys performed a go/no-go selective attention task where the subjects made a go or no-go response depending on the color or the motion direction of compound visual stimuli (moving colored dots). Groups of cells showed differential activity for go and no-go stimuli (go/no-go activity): some showed the activity either in the color or motion attending condition, and others showed the activity both in the color and motion conditions. Cells of shorter latencies, found mainly in the prefrontal subareas receiving visual input, showed go/no-go activity only when task demands necessitated that the monkeys attended to that cell's preferred visual dimension. We also found cells with longer latencies in the motor-related periarcuate area that showed go/no-go activity regardless of the dimension attended. These results suggest that subareas in the prefrontal cortex play different roles in associating the sensory information with its behavioral meaning and are hierarchically organized to make appropriate decisions in complex tasks.

Animals↗

PubMedDate not supplied

Grammatical performance of children with language disorder on structured elicitation and narrative tasks.

The primary objective was to compare the grammatical output of children with language disorders on different tasks. Sixty-five children with language disorders, aged six to eleven, completed the syntactic formulation (elicitation) and narrative subtests from the Assessment of Comprehension and Expression 6-11 (Adams et al. 2001). Grammatical variables were computed for the narrative data and their relationship with the syntactic formulation subtest score examined. The use of ten specific constructions was compared in the two contexts. The syntactic formulation score correlated highly with narrative grammatical variables. However, for seven of the ten constructions, the elicitation task was more likely than the narrative to yield specific target structures. Structured elicitation is an efficient normative measure of grammatical production capacity. For specific structures, elicitation and narrative may give a different picture of output. Elicitation is more facilitative and may more closely reflect grammatical knowledge. Target structures were less likely to be used in the narrative, which reflects grammatical performance in a cognitively and linguistically demanding task.

Child↗

PubMed1998

Visual cognitive dysfunction in depression: an event-related potential study.

The P3(00) event-related potentials (ERPs) elicited by visual stimuli in two visual tasks were assessed in depressed patients (12 patients with major depression and 11 patients with bipolar disorder) and compared with those of 20 age-matched normal controls. At remission, the ERPs from 18 of the depressed patients were again recorded. The visual oddball (VO) paradigm presented both target and standard visual stimuli and the simple visual (SV) paradigm presented a target but no standard visual stimulus. Subjects performed the VO task significantly less accurately than the SV task, as reflected by the behavioral measures (reaction-time and task accuracy). Depressed patients of the bipolar group showed longer P3 peak latency for the VO task and no change in P3 amplitude. No significant differences were found in any other ERP component between the groups. During remission, slowing RTs and reduced P3 peak latencies were observed for both major depression and bipolar disorder groups. Thus, the P3 ERP may be an index of the contribution of the slowed central processing to psychomotor retardation in clinically homogenous samples of depressive patients performing an appropriately demanding task.

Adult↗

PubMed2002

Cultural variation in verbal versus spatial neuropsychological function across the life span.

Established culture-invariant measures are needed for cross-cultural assessment of verbal and visuospatial speed of processing and working memory across the life span. In this study, 32 younger and 32 older adults from China and from the United States were administered numerically based and spatially based measures of speed of processing and working memory. Chinese superiority on the numerically based tasks was found for younger adults. Age and increasing task demands diminished this cultural effect, as predicted by the framework proposed by D. C. Park, R. Nisbett, and T. Hedden (1999). However, the visuospatial measures of both working memory and speed of processing did not differ cross-culturally for either age group. The authors concluded that these visuospatial measures provide culture-invariant estimates of cognitive processes in East Asian and Western cultures, but that numerically based tasks show evidence of cultural and linguistic biases in performance levels.

Adult↗

PubMed1999

A biomechanical evaluation of visually impaired persons' gait and long-cane mechanics.

This study was designed to compare selected kinematic components of gait and long cane mechanics between groups of visually impaired travelers. Twenty subjects were placed in Traditional or Modified technique groups according to their long cane traveling technique. Subjects were measured during the following conditions; 1) normal walking (NW), 2) walking while anticipating a simulated drop-off (AD), 3) walking while responding to an audible task (ST) and, 4) walking while anticipating a simulated drop-off and responding to an audible task (STAD). Data were analyzed using a repeated measures analysis of variance (ANOVA) and Pearson's r correlation coefficient. Analyses revealed no differences between groups of travelers. However, significant differences were noted between trials for components of gait velocity, stride length, and hip flexion velocity. These findings may indicate a potentially dangerous alteration in the normal gait cycle of visually impaired travelers when faced with additional attention-demanding tasks while walking.

Adult↗

PubMed1993

The roles of non-temporal information processing load and temporal expectations in children's prospective time estimation.

Children in the pre-operational phase were asked to prospectively estimate the duration of a thirty-second interval. Estimated intervals were either filled by a task demanding non-temporal information processing, or were 'empty'. Children were either expecting a prize after the termination of the to-be-estimated interval, or were not expecting such a prize. Prospective time estimates were highest when a prize was expected and the to-be-estimated interval was 'empty', and lowest when a prize was not expected and the to-be-estimated interval was filled by the task. Accuracy was highest when a prize was expected and a non-temporal task required. These findings were accounted for by an attentional model of prospective time estimation. The similarity between children and adults' prospective time estimation processes was discussed.

Attention↗

PubMed2002

Perceptual-motor contributions to static and dynamic balance control in children.

The authors addressed balance control in children from the perspective of skill development and examined the relationship between specific perceptual and motor skills and static and dynamic balance performance. Fifty 11- to 13-year-old children performed a series of 1-legged balance tasks while standing on a force platform. Postural control was reflected in the maximum displacement of the center of mass in anterior-posterior and mediolateral directions. Simple visual, discrimination, and choice reaction times; sustained attention; visuomotor coordination; kinesthesis; and depth perception were also assessed in a series of perceptual and motor tests. The correlation analysis revealed that balancing under static conditions was strongly associated with the ability to perceive and process visual information, which is important for feedback-based control of balance. On the other hand, when greater task demands were imposed on the system under dynamic balancing conditions, the ability to respond to the destabilizing hip abductions-adductions in order to maintain equilibrium was associated with motor response speed, suggesting the use of a descending, feedforward control strategy. Therefore, like adults, 11- to 13-year-old children have the ability to select varying balance strategies (feedback, feedforward, or both), depending on the constraints of a particular task.

Child↗

PubMed1988

Effects of anxiety on inferential reasoning task performance.

Three experiments were conducted in which high anxiety and low anxiety subjects were required to construct inferences. In Experiment 1 there was no anxiety-related performance deficit when inferring a necessary anaphoric relation, a process argued to be automatic. Experiments 2 and 3 involved the verification of unnecessary inferences, a process argued to involve the utilization of the working memory system. In both Experiments 2 and 3 there was an anxiety-related performance deficit. The results are consistent with a working memory-oriented account of anxiety-related performance effects, as deficits were restricted to capacity-demanding tasks.

Anxiety↗

PubMed2000

Escape behavior during academic tasks: a preliminary analysis of idiosyncratic establishing operations.

The presence or absence of idiosyncratic stimuli has been demonstrated to predictably alter the occurrence of problem behavior. By specifying stimuli related to negatively reinforced behavior during academic tasks, it may be possible to identify methods of instruction that decrease the occurrence of problem behavior. The current study used a four-step procedure that involved a functional analysis, descriptive assessment, establishing operations (EO) analysis, and follow-up evaluation (a) to identify the operant function of destructive behavior and (b) to evaluate the effects of idiosyncratic features of academic task demands and related methods of instruction on the occurrence of negatively reinforced destructive behavior of 3 boys with developmental disabilities and autism in a classroom setting. The data suggest that the four-step procedure was effective in identifying methods of instruction that decreased the likelihood of destructive behavior without disrupting the maintaining contingencies for destructive behavior. Results are discussed in terms of establishing operations for negatively reinforced destructive behavior during academic tasks and related methods of instruction in classroom settings.

Child↗

PubMed2000

Benefits of interhemispheric integration on the Japanese Kana script-matching tasks.

We tested Banich's hypothesis that the benefits of bihemispheric processing were enhanced as task complexity increased, when some procedural shortcomings in the previous studies were overcome by using Japanese Kana script-matching tasks. In Exp. 1, the 20 right-handed subjects were given the Physical-Identity task (Katakana-Katakana scripts matching) and the Name-Identity task (Katakana-Hiragana scripts matching). On both tasks, a pair of Kana scripts was tachistoscopically presented in the left, right, and bilateral visual fields. Distractor stimuli were also presented with target Kana scripts on both tasks to equate the processing load between the hemispheres. Analysis showed that, while a bilateral visual-field advantage was found on the name-identity task, a unilateral visual-field advantage was found on the physical-identity task, suggesting that, as the computational complexity of the encoding stage was enhanced, the benefits of bilateral hemispheric processing increased. In Exp. 2, the 16 right-handed subjects were given the same physical-identity task as in Exp. 1, except Hiragana scripts were used as distractors instead of digits to enhance task difficulty. Analysis showed no differences in performance between the unilateral and bilateral visual fields. Taking into account these results of physical-identity tasks for both Exps. 1 and 2, enhancing task demand in the stage of ignoring distractors made the unilateral visual-field advantage obtained in Exp. 1 disappear in Exp. 2. These results supported Banich's hypothesis.

Adolescent↗

PubMed1979

[Chronic diseases of the respiratory tract (proceedings)].

On account of their increasing social-medical importance chronic diseases of the respiratory tract demand systematic measures for prevention and combat. The size of the problem is described on the basis of the results of epidemiologic investigations. Issuing from the risk degrees of the cardio-respiratory insufficiency (obstruction, hypoxaemia, pulmonary hypertension) care groups are proposed. The combat against tobacco smoking (primary prevention) and long-term treatment of the chronic obstructive bronchitis (tertiary prevention) stand in the foreground of the measures. The solution of this task demands a close cooperation with the basic medical care.

Adult↗

PubMed2003

Phonological memory and vocabulary learning in children with focal lesions.

Eleven children with early focal lesions were compared with 70 age-matched controls to assess their performance in repeating non-words, in learning new words, and in immediate serial recall, a triad of abilities that are believed to share a dependence on serial ordering mechanisms (e.g.,; ). Results for the experimental group were also compared with other assessments previously reported for the same children by. The children with brain injury showed substantial impairment relative to controls in the experimental tasks, in contrast with relatively unimpaired performance on measures of vocabulary and non-verbal intelligence. The relationships between word learning, non-word repetition, and immediate serial recall were similar to those observed in several other populations. These results support previous reports that there are persistent processing impairments following early brain injury, despite developmental plasticity. They also suggest that word learning, non-word repetition, and immediate serial recall may be relatively demanding tasks, and that their relationship is a fundamental aspect of the cognitive system.

Adolescent↗