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Results for “Task Shifting”

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PubMed2002

The syntagmatic-paradigmatic shift and reading development.

This study examined developmental change in the word association task as reading acquisition occurred. Syntagmatic responses follow the stimulus world in discourse, 'cold'--'outside', while paradigmatic associates are of the same form class, 'cold'--'hot'. Some 59 children were tested three times during the school year. The average age of the younger group was 5;4, and the older group, 6;2 at the October test. They were given the PPVT, the Woodcock Reading Mastery Test, and a word association task. The younger group gave an increasing number of rhyming responses and the older group gave more paradigmatic responses as the year progressed. Regression analyses with the older group attributed this to reading acquisition. The changing nature of the cognitive representation of words as reading acquisition took place was discussed.

Child↗

PubMed1991

Characteristic distribution of alpha 2 wave in electroencephalograms of schizophrenic patients during discriminative tasks: support for the hypofrontality hypothesis of schizophrenia.

In a preliminary study, we noticed that alpha 2 activity in the frontal regions was suppressed less in schizophrenic patients than in other patients during the discriminative tasks. This was confirmed with 37 schizophrenic and 16 nonschizophrenic patients under the treatment of neuroleptics, 15 nonmedicated schizophrenic patients and 32 normal controls. The EEGs in eye-closed resting and during the auditory and visual discriminative tasks were recorded. Alpha 2 power values of the frontal, central, parietal, occipital and temporal regions in every subject group were processed by cluster analysis. During the discriminative tasks, the frontal regions were the most isolated cluster in schizophrenic patients and, in the normal and medicated nonschizophrenic groups, the frontal regions were incorporated in a different cluster. The same result was obtained by different statistical analyses of F-alpha 2 power ratio. The relative abundance of alpha 2 power value shifts from the occipital to the frontal regions during the discriminative tasks in schizophrenic patients. The weakened suppression of alpha 2 waves in the frontal regions by the discriminative tasks in schizophrenic patients supports the hypofrontal hypothesis of schizophrenia.

Adolescent↗

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↗

PubMed1999

Executive function and attention deficit hyperactivity disorder: stimulant medication and better executive function performance in children.

BACKGROUND: Executive function deficits have been reported repeatedly in children with Attention Deficit Hyperactivity Disorder (ADHD). Stimulant medication has been shown to be effective in improving cognitive performance on most executive function tasks, but neuropsychological tests of executive function in this population have yielded inconsistent results. Methodological limitations may explain these inconsistencies. This study aimed to measure executive function in medicated and non-medicated children with ADHD by using a computerized battery, the Cambridge Neuropsychological Test Automated Battery (CANTAB), which is sensitive to executive function deficits in older patients with frontostriatal neurological impairments. METHODS: Executive function was assessed in 30 children with ADHD: 15 were stimulant medication naive and 15 were treated with stimulant medication. These two groups were compared to 15 age, sex and IQ matched controls. RESULTS: The unmedicated children with ADHD displayed specific cognitive impairments on executive function tasks of spatial short-term memory, spatial working memory, set-shifting ability and planning ability. Impairments were also seen on spatial recognition memory and delayed matching to sample, while pattern recognition memory remained intact. The medicated children with ADHD were not impaired on any of the above executive function tasks except for deficits in spatial recognition memory. CONCLUSIONS: ADHD is associated with deficits in executive function. Stimulant medication is associated with better executive function performance. Prospective follow-up studies are required to examine these effects.

Adolescent↗

PubMed2005

The involvement of the orbitofrontal cortex in learning under changing task contingencies.

Previous investigations examining the rat prefrontal cortex subregions in attentional-set shifting have commonly employed two-choice discriminations. To better understand how varying levels of difficulty influence the contribution of the prefrontal cortex to learning, the present studies examined the effects of orbitofrontal cortex inactivation in a two- or four-choice odor reversal learning test. Long-Evans rats were trained to dig in cups that contained distinct odors. In the two-choice odor discrimination, one odor cup was always associated with a cereal reinforcement in acquisition while the opposite odor cup was associated with a cereal reinforcement in reversal learning. In the four-choice odor discrimination, an additional two cups containing distinct odors were used that were never associated with reinforcement in acquisition or reversal learning. Bilateral infusions of the GABA-A agonist, muscimol (0.5 microg) into the orbitofrontal cortex did not impair acquisition of either the two- or four-choice discrimination task. However, muscimol infusions into the orbitofrontal cortex impaired two- and four-choice reversal learning. In the two-choice odor reversal, muscimol treatment selectively increased perseverative errors. In the four-choice odor reversal, muscimol treatment increased perseverative, regressive, as well as irrelevant errors. These findings suggest that the orbital prefrontal cortex not only enables task switching by supporting the initial inhibition of a previously relevant choice pattern, but under increasing task demands also enables the reliable execution of a new choice pattern and reduction of interference to irrelevant stimuli.

Animals↗

PubMed1995

Climatic stress in the workplace: its effect on thermoregulatory responses and muscle fatigue in female workers.

The present study was designed to determine the differences in thermoregulatory responses and the levels of muscle fatigue in the seated worker, performing a task involving a light metabolic load (typing), versus the standing worker, undertaking a task of a heavier metabolic load (lifting), in different climatic conditions (neutral and hot, humid). The results showed that environmental heat significantly influenced the cardiovascular and thermoregulatory systems in workers performing both light and heavy work tasks. In addition, environmental heat was shown to influence the magnitude of the frequency shift during the fatiguing muscle contraction in the typists rather than the lifters. These results suggest that: (1) performance of even sedentary workers performing a light manual task may be deleteriously affected by environmental heat; and (2) environmental heat may be of secondary importance to the nature of the task investigated on the level of muscle fatigue.

Journal Article↗

PubMed2005

Redirection of gaze and switching of attention during rapid stepping reactions evoked by unpredictable postural perturbation.

In many situations successful execution of a balance-recovery reaction requires visual information about the environment. In particular, reactions that involve rapid limb movements, such as stepping, must be controlled to avoid obstacles and accommodate other constraints on limb trajectory. However, it is unknown whether the central nervous system can acquire the necessary visuospatial information prior to perturbation onset or must, instead, redirect gaze at the floor during the execution of the stepping reaction. To study this we examined gaze behaviour, during rapid forward-directed stepping reactions triggered by unpredictable platform perturbation, in 12 healthy young adults. We also monitored switching of attention, as inferred from onset of significant error in performing a concurrent visuomotor tracking task. Obstacles and/or step targets were used as constraints, to increase demands for accurate foot movement. Downward gaze shifts towards the floor almost never occurred during stepping reactions when foot motion was unconstrained but did occur more frequently as the demands for accurate foot movement increased. Nonetheless, even in the most challenging condition (target plus obstacle), downward redirection of gaze occurred in less than 40% of the trials, and subjects were commonly well able to clear the obstacle and land the foot on the target without redirecting their gaze towards the floor. An apparent switching of attention, subsequent to perturbation onset, occurred frequently (>80% of trials) in all task conditions, independent of the gaze shifts. The findings indicate that visual fixation of the foot or floor was not essential for accurate control of the foot movement, nor was the apparent switching of attention that followed perturbation onset linked, in any consistent way, to overt changes in visual fixation. Spatial features of the support surface were apparently "remembered" prior to perturbation onset, thereby allowing both vision and attention to be directed to other demands during the execution of the balance reaction.

Adult↗

PubMedDate not supplied

[Classification of mental diseases. From Bertillon to CID-10: a century of international collaboration].

The first International Classification of Diseases (ICD) was approved during the Congress of the Statistical International Institute, in Chicago, in Paris, in 1893. It was based on a list of diseases prepared by Jacques Bertillon. Minor changes were introduced in this classification during decennial revisions made at international meetings and it remained in use until 1948, when the World Health Organization's Provisional Committee was charged with the task of producing ICD-6. ICD-6 represented a major shift from the previous internal conceptualization, particularly in what concerns the Chapter V., dealing with mental disorders. From 1955 on WHO produced with approximately a 10-year interval ICV-7, 8, and 9. Few modifications in relation to ICD-6 were introduced by these revisions, except for the introduction of a glossary of terms in the chapter on mental disorders. This glossary had a major impact towards the development of a common language in psychiatry. Based on epidemiological findings, and based also on an intensive and extensive international network of clinicians and investigators, ICD-10 was published in 1992. It represented a substantial improvement regarding the conceptualization of the classification of mental disorders, in relation to previous revisions of the ICD. Future tasks relating to ICD-10 include training of health personnel for its proper utilization, in addition to finalizing further ICD-10 versions, e.g. for research purposes and for primary health care use.

History, 19th Century↗

PubMed1997

Human stance stability improves with the repetition of the task: effect of foot position and visual condition.

The effects of repetition of quiet stance trials on body sway, recorded through a stabilometric platform, were studied in 12 normal subjects. With feet together, both with eyes open (EO) and closed (EC), a progressive shift forward of the centre of foot pressure (CFP) occurred with repetition. In addition, with EC, but not with EO, a significant progressive reduction in sway area (SA) and sway path (SP) occurred. With feet 10 cm apart, initial SA and SP values were significantly smaller than with feet together, regardless of the visual condition, but repetition of trials induced no significant effects on either position of CFP or body sway under either visual condition. Results indicate the occurrence of a learning phenomenon in this simple postural task, whereby the body shifts towards a 'safer' position with a minimum energy expenditure due to reduced corrections of sway. Forward leaning and decrease in sway are two independently-occurring processes, each possibly due to a better central integration of proprioceptive input with repetition of trials.

Adolescent↗

PubMed2006

Do parietal cortical lesions impair spatial attention or allocentric spatial perception?

It remains unclear whether monkeys with large parietal cortical lesions fail "landmark" tasks because they cannot judge the relative distances between landmark and response locations, or because they fail to attend to, or even to notice, the landmark. Monkeys with small posterior parietal (SPP), large posterior parietal (LPP), superior temporal sulcus (STS), or frontal eye field (FEF) lesions were tested on a landmark task in which the physical salience of the landmark and its location varied. Only the LPP monkeys were impaired, seemingly because they overtly failed to shift attention during each trial, responding to whichever food well they looked at first. A task based on one used with neurological patients was therefore introduced in which the monkeys had to discriminate between two white square plaques each containing a spot, where the spot on the positive stimulus was centrally placed. Solving this task requires an allocentric judgement about the relative location of each spot to the edges of the plaque. Even on the most difficult discrimination, monkeys with large parietal lobe lesions were unimpaired. The deficits previously reported on landmark tasks probably reflect a failure of spatial attention or attention to objects rather than an inability to judge allocentric spatial relationships.

Animals↗

PubMed2004

Strategy execution in cognitive skill learning: an item-level test of candidate models.

This article investigates the transition to memory-based performance that commonly occurs with practice on tasks that initially require use of a multistep algorithm. In an alphabet arithmetic task, item response times exhibited pronounced step-function decreases after moderate practice that were uniquely predicted by T. C. Rickard's (1997) component power laws model. The results challenge parallel strategy execution models as developed to date and they demonstrate that the shift to retrieval is an item-specific, as opposed to task-general, learning phenomenon. The results also call into question the entire class of smooth speed-up functions as global empirical learning laws. It is shown that overlaying of averaged item fits on averaged data can provide a sensitive test for model sufficiency. Strategy probes agreed with strategy inferences that were based on step-function speed-up patterns, supporting the validity of the probing technique.

Cognition↗

PubMed2004

Mechanisms of moving the mind's eye: planning and execution of spatial shifts of attention.

The usefulness of attentional orienting, both in the real world and in the laboratory, depends not only on the ability to attend to objects or other inputs but also on the ability to shift attention between them. Although understanding the basic characteristics of these shifts is a critical step toward understanding the brain mechanisms that produce them, the literature remains unresolved on a very basic and potentially revealing characteristic of these shifts-namely, whether attention takes longer to shift a farther distance across the visual field. We addressed this question using a series of behavioral tasks involving the voluntary orienting of attention to locations in the visual field. The findings support a model in which attentional shifts include separate "planning" and "execution" stages and in which only the planning stage requires more time for shifts of a greater distance. These results offer resolution to the longstanding debate concerning the effect of attentional shift distance on shift time and provide insight into the fundamental mechanisms of attentional shifting.

Adolescent↗

PubMed1985

Developmental changes in hemispheric independence.

In this research, we questioned whether children's relative inability to use the 2 cerebral hemispheres independently contributes toward their difficulty with the simultaneous execution of conflicting tasks. 2 naming tasks were simultaneously presented to either 1 visual field/hemisphere combination (unilateral) or were divided between visual fields/hemispheres (bilateral). We predicted that bilateral presentation would improve performance by insulating these conflicting tasks from mutual interference and that there would be a developmental shift in the size of the advantage for bilateral presentation. This hypothesis was confirmed in a sample of 120 children (N = 40 per group). Older children (12- and 14-year-olds) named more items when they were presented bilaterally, rather than unilaterally, when conflicting inputs were directed to different hemispheres. Younger children (10-year-olds) displayed no advantage for bilateral presentation regardless of whether conflicting tasks were projected to the same hemisphere or different hemispheres. The fact that 10-year-olds did not benefit from division of conflicting inputs between the hemispheres was interpreted as a symptom of their relative inability to use the hemispheres independently.

Adolescent↗

PubMed2002

Cerebral hemodynamic response induced by the Tower of Hanoi puzzle and the Wisconsin Card Sorting test.

Transcranial Doppler sonography (TCD) was applied in normal subjects to investigate the effect of prefrontal functions like the Tower of Hanoi (TOH) task and the Wisconsin Card Sorting test (WCST) on cerebral hemodynamics. In 20 healthy volunteers, left and right middle cerebral artery (MCA) and anterior cerebral artery (ACA) were insonated. The TOH task and the WCST were administered while cerebral blood flow velocity (CBFV) was registered. Each test was repeated once per artery pair. There was a visuomotor test to control the motor and visual stimulations. Three phases of CBFV time course were detected: an initial peak within 5 s, a following decrease within 25 s and a steady state beginning at 40 s. The TOH task, WCST and visuomotor tests had different mean CBFV during the initial peak (MCA: P<0.05; ACA: P<0.05) as well as for the decrease (ACA: P<0.01) and the steady state (MCA: P<0.01; ACA: P<0.01). The TOH showed an increased mean CBFV as compared with the WCST during the steady state (MCA: P<0.01; ACA: P<0.05). However, temporal modulation of mean CBFV during category shift of the WCST resulted in significantly increased values after category shift (MCA: P<0.001; ACA: P<0.01) as compared with CBFV before the category shift. These findings showed a different CBFV pattern during the TOH task and WCST than during the visuomotor test. In conclusion, TCD was able to assess CBFV in prefrontal functions, using a high resolution in time.

Adult↗

PubMedDate not supplied

Event-related covariances during a bimanual visuomotor task. II. Preparation and feedback.

Event-related covariance (ERC) patterns were computed from pre-stimulus and feedback intervals of a bimanual, visuomotor judgment task performed by 7 right-handed men. Late contingent negative variation (CNV) ERC patterns that preceded subsequently accurate right- or left-hand responses differed from patterns that preceded subsequently inaccurate responses. Recordings from electrodes placed at left frontal, midline antero-central, and appropriately contralateral central and parietal sites were prominent in ERC patterns of subsequently accurate performances. This suggests that a distributed cortical 'preparatory network,' composed of distinct cognitive, integrative motor, somesthetic, and motor components, is essential for accurate visuomotor performance. ERC patterns related to feedback about accurate and inaccurate responses were similar to each other in the interval immediately after feedback onset, but began to differ in an interval spanning an early P300 peak. The difference became even greater in an interval spanning a late P300 peak. For both early and late P300 peaks, ERC patterns following feedback about inaccurate performance involved more frontal sites than did those following feedback about accurate performance. Together with the stimulus- and response-locked results presented in part I, results of this study on the preparatory and feedback periods suggest that ERCs show salient features of the rapidly shifting, functional cortical networks that are responsible for simple cognitive tasks. ERCs thus provide a new perspective on information processing in the human brain in relation to behavior--a perspective that supplements conventional EEG and ERP procedures.

Adult↗

PubMed1998

Trick or treat?: uneven understanding of mind and emotion and executive dysfunction in "hard-to-manage" preschoolers.

It is widely recognised that impaired social relations are characteristic of school-aged children with behavioural disorders, and predict a poor long-term outcome (Parker & Asher, 1987). However, little is known about the early antecedents of social impairment in behaviourally disturbed children. The aim of the present study was to explore three areas of potential dysfunction in younger children: theory of mind, emotion understanding, and executive function. Forty preschoolers, rated by their parents on the Strengths and Difficulties Questionnaire (Goodman, 1994) as "hard to manage" (H2M) were compared with a control group on a set of: (1) theory of mind tasks (including an emotion prediction task involving either a nice or a nasty surprise); (2) emotion understanding stories (that required affective perspective-taking skills as well as situational understanding); and (3) simple executive function tasks (adapted for preschoolers, and tapping inhibitory control, attentional set-shifting, and working memory). Small but significant group differences were found in all three cognitive domains. In particular, hard-to-manage preschoolers showed poor understanding of emotion and executive control, poor prediction or recall of a false belief, and better understanding of the belief-dependency of emotion in the context of a trick than a treat. Moreover, executive function was associated with performance on the theory of mind tasks for the hard-to-manage group alone, suggesting both direct and indirect links between executive dysfunction and disruptive behaviour.

Affect↗

PubMed1997

Electromyographic analysis of postural responses during standing leg flexion in adults with hemiparesis.

The purpose of this study was to examine muscle activation patterns during standing leg single leg flexion in adults with hemiparesis. Specifically, the electromyographic activation patterns of the flexing limb biceps femoris and gluteus medius, and the stance limb gluteus medius muscles were analyzed as a function of whether the muscles were paretic or not. Delayed activation of the affected flexing side gluteus medius, as compared with unaffected flexing side gluteus medius, resulted in it being activated simultaneous with the flexing biceps femoris rather than preceding it as was previously found in healthy subjects. This suggests a temporal change in the sequential mode of coordination of the postural and intended components of the task. In addition, the magnitude of the electromyographic integrals of both the affected and unaffected flexing side gluteus medius in the early propulsive phase of the task was significantly reduced in comparison with healthy subjects. These alterations can be attributed to spatial alterations in the sequential form of organization or to a shift to a different mode of neural control in order to perform a relatively novel task. These results suggest a potential adaptive capacity in these individuals.

Adult↗

PubMed2005

Unilateral visual cueing and asymmetric line geometry share a common attentional origin in the modulation of pseudoneglect.

Numerous factors influence the leftward bias (pseudoneglect) in perceived line midpoint of normal subjects in line bisection tasks. Cues are a potent factor; left and right cues promote shifts in perceived midpoint to the left and right, respectively. Trapezoidal lines have recently been shown to influence perceived line midpoint, displacing it toward the larger side. The present experiments test the hypothesis that the effect of line geometry, like that of unilateral cues, results from an exogenous recruitment of spatial attention. Normal right-handed subjects (N = 60) participated in two experiments employing a tachistoscopic forced-choice line bisection task. Experiment 1 crossed the effect of cue position and cue contrast, and confirmed that a significant interaction could be obtained. Experiment 2 crossed the effect of line geometry and cue position, revealing that line geometry and cue location both significantly influence perceived line midpoint, and produce a significant interaction. According to Additive Factors Logic the finding that spatial cueing interacts with line geometry suggests that both types of stimuli modulate spatial attention at a common site of processing, supporting the conclusion that the effect of line geometry itself derives from asymmetric cueing. An explanation for the interaction is offered that is based on the existence of a hypothesized compressive nonlinearity that maps attentional bias to perceptual error.

Adolescent↗