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Results for “Task Shifting”

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PubMed2003

[The effect of the complex rehabilitation on posture and gait in Parkinson disease].

UNLABELLED: Rehabilitation plays an important role in treatment of Parkinson's disease (PD). The influence of rehabilitation on balance and gait in PD hasn't been widely investigated. There is general agreement about positive influence of rehabilitation on postural instability and prevention of falls, but therapeutic program prevention of falls hasn't been worked out. Ambiguous results of studies indicate necessity of further investigations. MATERIAL AND METHODS: 61 patient were included (H&Y 1, 5-3) and randomly assigned to two groups with and without rehabilitation. The balance test battery included: Functional Reach Test, Balance Performance-Oriented Mobility Assessment (Tinetti), assessment on force platform of quiet standing and active standing with Rhythmic Weight Shifts Test and dynamic task (reaction time, number of hitted targets). Gait was assessed with: timed Up&Go test, 10 m walk, locomotion test and 360 degrees turn. Patients were assessed 3 times, at month intervals. Between 1 and 2 assessment, exercising group took part in 1 month complex rehabilitation, consist of the 28 therapeutic sessions. RESULTS: The group, which took part in rehabilitation significantly improved in quiet standing with closed eyes after rehabilitation in comparison with initial status. All of the rest variables significantly improved in exercising group after rehabilitation both in comparison between evaluations and in comparison with the nonexercising group. CONCLUSIONS: Rehabilitation significantly influences balance and gait of patients with PD.

Adult↗

PubMed1986

[Neuropsychologic changes in Parkinson syndrome].

In Parkinson's disease various cognitive deficits occur of which impairments of perception, memory, speech, vigilance, reaction-time, and shifting aptitude in cognitive tasks can be distinguished. Also depression is frequently observed. Personality changes are discussed originating from organic mental factors, the experience of the disease, and possible premorbid personality traits. Mental processing is probably slowed down in Parkinson's disease (bradyphrenia). However, it is not yet clarified in which cognitive categories bradyphrenia may play a role.

Amnesia↗

PubMed1986

The development of children's knowledge of temporal structure.

Adults have a rich understanding of a number of time systems, but little is known about how this knowledge develops. 3 experiments were conducted to test a model in which the first representations of the days of the week and months of the year have verbal-list properties, and these are later supplemented by image representations. In Experiments 1 and 2, fourth or fifth graders could judge forward relative order for these contents, but not until adolescence could backward order judgments be made accurately. In Experiment 3, fourth graders used a serial process to solve a categorical distance judgment task, whereas older groups shifted to a process with more rapid access to information about the position of remote items. The results are interpreted as supporting the 2-stage model and appear inconsistent with a number of alternative models.

Adolescent↗

PubMed1998

Delayed postural contraction of transversus abdominis in low back pain associated with movement of the lower limb.

The temporal parameters of the response of the trunk muscles associated with movement of the lower limb were investigated in people with and without low back pain (LBP). The weight shift component of the task was completed voluntarily prior to a stimulus to move to allow investigation of the movement component of the response. In the control subjects the onset of electromyographic (EMG) activity of all trunk muscles preceded that of the muscle responsible for limb movement, thus contributing to the feed-forward postural response. The EMG onset of transversus abdominis was delayed in the LBP subjects with movement in each direction, while the EMG onsets of rectus abdominis, erector spinae, and oblique abdominal muscles were delayed with specific movement directions. This result provides evidence of a change in the postural control of the trunk in people with LBP.

Abdominal Muscles↗

PubMed1999

Sources of position-perception error for small isolated targets.

It has often been reported that, in the presence of static reference stimuli, briefly presented visual targets are perceived as being closer to the fixation point than they actually are. The first purpose of the present study was to investigate whether the same phenomenon can be demonstrated in a situation without static reference stimuli. Experiment 1, with position naming as the task, showed that such a central shift is also observed under these conditions. This finding is of importance because it completes an explanation for central near-location errors in the partial-report bar-probe task. The second purpose of the present study was to provide an explanation for these central shifts. For this explanation information about the exact size of the central shift is required. In Exps. 2, 3, and 4, with cursor setting as the task, it was attempted to assess more precisely the size of the central shifts. These experiments revealed that two different factors determine the results in cursor setting tasks; a factor "target position" and a factor "cursor position." Experiment 5 showed that it is the point of fixation, not the fixation point, that serves, at least in part, as the reference point in this type of task. All the findings together allow us to conclude that the target positions are underestimated by about 10%. From vision research it is known that saccadic eye movements, performed for bringing a target in the fovea, also show an undershoot of about 10%. It is therefore concluded that the system in charge of saccadic eye movements also provides the metric in visual space within a single eye fixation.

Fixation, Ocular↗

PubMed2005

Further evidence that mice learn a win-shift but not a win-stay contingency under water-escape motivation.

Previous research (C. Locurto, C. Emidy, & S. Hannan, 2002) indicated that mice quickly learned a water-escape task under a win-shift contingency but did not exceed chance-level performance under a win-stay contingency. We examined the robustness of this conclusion in two experiments by varying procedural and temporal aspects of that earlier experiment. Results of both experiments indicated that the preference for win-shift learning in mice under water-escape motivation could not be attributed to procedural or design features of that earlier study and were independent of the influence of intertrial interval, normally a variable that produces strong effects on learning. In neither experiment did subjects exposed to a win-stay contingency perform at above-chance levels.

Animals↗

PubMed2005

Is impaired set-shifting an endophenotype of anorexia nervosa?

OBJECTIVE: Set-shifting difficulties have been reported in subjects with anorexia nervosa and appear to persist after recovery; therefore, they may be endophenotypic traits. The goals of this study were to investigate whether set-shifting difficulties are familial by examining discordant sister-pairs in comparison with healthy unrelated women and to replicate, with a broader battery, the lack of influence of an acute illness state on neuropsychological performance. METHOD: Forty-seven pairs of sisters discordant for anorexia nervosa and 47 healthy unrelated women who were comparable in age and IQ completed neuropsychological tasks selected to assess set-shifting ability. Analyses of variance with standard errors that are robust against correlations within family clusters were used to compare the groups. Results were adjusted for obsessive-compulsive, anxiety, and depression symptoms. Subjects with acute (N=24) and fully remitted (N=23) anorexia nervosa were compared to assess state versus trait effects. RESULTS: Sisters with and without anorexia nervosa took significantly longer than unrelated healthy women to shift their cognitive set (CatBat task) and demonstrated greater perceptual rigidity (Haptic Illusion task) but did not differ significantly from each other. Women with anorexia nervosa were slower than other groups on Trail Making tasks. Women who had fully recovered from anorexia nervosa made significantly fewer errors than those with acute anorexia nervosa on the Trail Making alphabet task, but these subgroups did not differ on other measures. CONCLUSIONS: Both affected and unaffected sisters had more set-shifting difficulties than unrelated healthy women. This finding, together with the replicated finding that set-shifting difficulties persist after recovery, suggests that set-shifting difficulties are trait characteristics and may inform the search for the endophenotype in anorexia nervosa.

Adult↗

PubMed1995

The pattern of attentional deficits in Huntington's disease.

Different aspects of attention, e.g. phasic alertness, vigilance, divided attention, response flexibility, response inhibition and intermodal integration, were investigated with a computerized test-battery in a group of 20 patients with Huntington's disease and 27 healthy controls. Huntington's disease patients are not impaired in reacting to task-contingent external stimulation in the phasic alertness task, but the self-generated maintenance of attention as measured by the vigilance task, is disturbed. The simultaneous monitoring of different input-channels in the divided attention task and the ability to operate with information given to different modalities in the intermodal integration task are severely affected. The performance of Huntington's disease patients in the response flexibility task, in which internal cued shifts are required, is impaired. Huntington's disease patients are also impaired in reacting selectively to go/no-go stimuli in the response inhibition task. It is suggested that a number of 'higher' cognitive deficits described in Huntington's disease might, at least partly, be due to basic attentional disturbances.

Adult↗

PubMed2001

Attention and recognition memory in the 1st year of life: a longitudinal study of preterm and full-term infants.

Several aspects of visual attention and their implications for recognition memory were examined in a longitudinal sample of full-term and preterm (birth weight < 1,750 g) infants seen at 5, 7, and 12 months of age. At all 3 ages, full-terms had shorter look durations, faster shift rates, less off-task behavior, and higher novelty scores than preterms. Both groups followed similar developmental trajectories, with older infants having shorter looks and more shifts. Infants were consistent in attentional style across problems of the same type, across problems that used different types of stimuli (faces and patterns), and across the familiarization and test phases of this paired-comparison design; there was also modest cross-age stability. Shorter looks and higher shift rates during familiarization were related to better recognition memory, with shift rate adding to prediction independently of either peak or mean look. These findings underscore the importance of attention to infant information processing.

Attention↗

PubMed1994

Cognitive demand and transient nearwork-induced myopia.

Previous studies have suggested that nearwork-induced myopia may be related to the amount of mental effort and cognitive demand required during the course of near-vision tasks. Accordingly, we compared measurements of the far point of accommodation (FPA) obtained before and immediately after 10-min sustained near-vision tasks involving either low, moderate, or high cognitive demand. All measurements of the FPA were obtained objectively using an open-field infrared optometer. Although a significant myopic shift in the FPA was observed after all conditions, no significant difference was recorded between the three cognitive levels. The mean myopic shift in the FPA immediately after the near-vision task was 0.23 D. It is concluded that the transient, task-induced myopic shift in the FPA is related to the within-task accommodative response rather than to variations in cognitive demand during the course of the near-visual activity.

Accommodation, Ocular↗

PubMed2005

A shift of visual spatial attention is selectively associated with human EEG alpha activity.

Event-related potentials and ongoing oscillatory electroencephalogram (EEG) activity were measured while subjects performed a cued visual spatial attention task. They were instructed to shift their attention to either the left or right visual hemifield according to a cue, which could be valid or invalid. Thereafter, a peripheral target had to be evaluated. At posterior parietal brain areas early components of the event-related potential (P1 and N1) were higher when the cue had been valid compared with invalid. An anticipatory attention effect was found in EEG alpha magnitude at parieto-occipital electrode sites. Starting 200 ms before target onset alpha amplitudes were significantly stronger suppressed at sites contralateral to the attended visual hemifield than ipsilateral to it. In addition, phase coupling between prefrontal and posterior parietal electrode sites was calculated. It was found that prefrontal cortex shows stronger phase coupling with posterior sites that are contralateral to the attended hemifield than ipsilateral sites. The results suggest that a shift of attention selectively modulates excitability of the contralateral posterior parietal cortex and that this posterior modulation of alpha activity is controlled by prefrontal regions.

Adult↗

PubMed2006

Strategy shifts in classification skill acquisition: does memory retrieval dominate rule use?

In two experiments, we demonstrated two types of strategies (rule-based and memory-based) and strategy transitions within the same binary classification task. The strategy that dominated later in practice depended on the difficulty of the operative classification rule and on the salience of the cue for that rule. Accuracy increased over practice trials, and response times were faster for the dominant strategy, either rule or memory. Rule retention was superior to stimulus item retention, so that, even for participants who preferred a memory-based strategy, a rule-based strategy dominated at least temporarily after a 1-week interval. Strategy use over trials and the retention interval reflected a given task's affordance of a shift between rule- and memory-based processes.

Humans↗

PubMed1999

Discrimination, reversal, and shift learning in Huntington's disease: mechanisms of impaired response selection.

In a series of three experiments, we investigated different aspects of response selection in early-stage clinically symptomatic Huntington's disease (HD) patients in the context of discrimination learning. A series of structurally related response selection tasks involving discrimination, reversal, and shift learning were employed. In Experiment 1, the mechanisms of our previously reported [37] finding of impaired extra-dimensional shift learning were explored. The results suggested that impaired shift learning in HD is a result of perseverative responding. In Experiment 2, performance on a concurrent-pair (CP) discrimination and reversal task was examined. HD patients showed no deficits in CP discrimination learning or reversal. In Experiment 3, the performance of HD patients on a probabilistic discrimination and reversal task was examined. HD patients were impaired in the learning of a probabilistic discrimination, and also its reversal. This reversal deficit was again the result of perseverative responding. In addition, there was a strong correlation between HD patients' activities of daily living scores and reversal errors. The result are consistent with current theories of the role of the basal ganglia in cognition, and suggest specific impairments in response selection mechanisms in HD, in particular, in overcoming selection biases based on prior reinforcement.

Adult↗

PubMed1985

Basal forebrain lesions produce a dissociation of trial-dependent and trial-independent memory performance.

The behavioral effects of lesions in the basal forebrain (BF) of rats were evaluated using two tasks. The BF lesions included both the nucleus basalis magnocellularis (NBM) and the medial septal area (MSA). The first task was a Stone maze, which has 14 consecutive choice points and is a task of complex, trial-independent memory. BF lesions did not impair choice accuracy in this task. The second task was a win-shift spatial discrimination in a radial arm maze, which requires trial-dependent memory. BF lesions produced a significant decrease in choice accuracy in this task. These results demonstrate that BF lesions impair trial-dependent (working) memory but not trial-independent reference memory, and that task difficulty is not the sole factor determining whether BF lesions produce behavioral impairments.

Animals↗

PubMed1999

The role of eye height in perceiving affordances and object dimensions.

In four experiments on perceived object height and width, the effects of shifting participants' effective eye height (EEH) on affordance (intrinsic) and apparent size (extrinsic) judgments were contrasted. In Experiment 1, EEH shifts produced comparable overestimations of height in intrinsic and extrinsic tasks. A similar result was found with a more abstract extrinsic height task (Experiment 2). However, Experiment 3 revealed a dissociation between intrinsic and extrinsic tasks of perceived width. Affordance judgments were affected by EEH shifts, whereas apparent size judgments were not. Experiment 4 compared participants' performance on comparable extrinsic tasks of height and width. Height judgments were affected by EEH shifts, but width judgments were again unaffected. It is concluded that eye height may be a more natural metric for object height than for width. Moreover, this difference reflects a basic flexibility within the human visual system for selectively attuning to the most accessible sources of size information.

Eye↗

PubMed2006

Attentional modulation in the detection of irrelevant deviance: a simultaneous ERP/fMRI study.

Little is known about the neural mechanisms that control attentional modulation of deviance detection in the auditory modality. In this study, we manipulated the difficulty of a primary task to test the relation between task difficulty and the detection of infrequent, task-irrelevant deviant (D) tones (1,300 Hz) presented among repetitive standard (S) tones (1,000 Hz). Simultaneous functional magnetic resonance imaging (fMRI)/event-related potentials (ERPs) were recorded from 21 subjects performing a two-alternative forced-choice duration discrimination task (short and long tones of equal probability). The duration of the short tone was always 50 msec. The duration of the long tone was 100 msec in the easy task and 60 msec in the difficult task. As expected, response accuracy decreased and response time (RT) increased in the difficult compared with the easy task. Performance was also poorer for D than for S tones, indicating distraction by task-irrelevant frequency information on trials involving D tones. In the difficult task, an amplitude increase was observed in the difference waves for N1 and P3a, ERP components associated with increased attention to deviant sounds. The mismatch negativity (MMN) response, associated with passive deviant detection, was larger in the easy task, demonstrating the susceptibility of this component to attentional manipulations. The fMRI contrast D > S in the difficult task revealed activation on the right superior temporal gyrus (STG) and extending ventrally into the superior temporal sulcus, suggesting this region's involvement in involuntary attention shifting toward unattended, infrequent sounds. Conversely, passive deviance detection, as reflected by the MMN, was associated with more dorsal activation on the STG. These results are consistent with the view that the dorsal STG region is responsive to mismatches between the memory trace of the standard and the incoming deviant sound, whereas the ventral STG region is activated by involuntary shifts of attention to task-irrelevant auditory features.

Acoustic Stimulation↗

PubMed2005

Neuropsychological functioning in stimulant-naive boys with hyperkinetic disorder.

BACKGROUND: Although children with hyperkinetic disorder and/or attention deficit hyperactivity disorder (ADHD) show disordered executive neuropsychological functioning, the nature of these changes remains controversial. Additionally, impairments in non-executive neuropsychological functioning have been relatively unexplored. Here, the authors describe the neuropsychological functioning of a sample of stimulant drug-naive boys with hyperkinetic disorder on a battery of neuropsychological tasks sensitive to impairments of both executive and non-executive functions. METHOD: Seventy-five stimulant drug-naive boys meeting diagnostic criteria for ICD-10 hyperkinetic disorder were compared with 70 healthy developing controls matched for age but not IQ on computerized tests of neuropsychological functioning from the Cambridge Neuropsychological Test Automated Battery (CANTAB) and a Go/No-Go inhibition task. RESULTS: Boys with hyperkinetic disorder exhibited impairments on tasks with a prominent executive component--working memory, planning, strategy formation, attentional set-shifting and on a reaction time task. However, they were also impaired on tasks without prominent executive components--pattern and spatial recognition, spatial span, delayed matching to sample and paired associates learning. Contrary to predictions, no impairment was observed on the Go/No-Go inhibition task. CONCLUSIONS: Medication-naive boys with hyperkinetic disorder displayed a broad range of neuropsychological impairments. Deficits were demonstrated on tasks with and without prominent executive components. Impairments were not confined to tasks dependent upon frontostriatal functioning, cannot wholly be explained by deficits in inhibitory control, nor can they be attributed to intelligence or previous exposure to stimulant medication.

Adolescent↗

PubMed2003

Clockwise and counterclockwise rotating shifts: effects on vigilance and performance.

INTRODUCTION: Arguments against counterclockwise shift schedules, such as those used in air traffic control, are prevalent in the literature; however, few studies have examined direction of rotation in rapidly rotating schedules. The present study directly compared clockwise (CW) and counterclockwise (CCW) rapidly rotating shiftwork schedules on measures of complex and vigilance task performance. METHODS: Participants (n = 28) worked day shifts for the first week of the study (0800-1600 h), followed by 2 wk of either a CW (n = 14) or CCW (n = 14) shiftwork schedule. Participants completed three 1.5-h sessions on the Multiple Task Performance Battery (MTPB) on each shift. Each session contained active- and passive-task components. In addition, participants completed a 0.5-h Bakan Vigilance Test at the beginning and end of each shift. RESULTS: A three-way, rotation condition by shift by session interaction (F (8,19) = 3.0, p < 0.05) for the active task composite scores and a rotation condition by shift interaction (F (4,23) = 6.2, p < 0.05) for the Bakan Vigilance Task indicated that effects of rotation condition were modulated by shift type, such that on particular shifts, performance in the CCW rotation was actually better than in the CW rotation. DISCUSSION: These data do not support the hypothesis that a CW rotation will result in better outcomes on complex or vigilance task performance. The results of this study indicate that two problem areas in both CW and CCW rapidly rotating shift schedules are early morning and midnight shifts.

Aviation↗