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Results for “Task Shifting”

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PubMed1992

Neuropsychological aspects of dementia of motor neuron disease: a report of two cases.

We describe the neuropsychological data from two cases of dementia of motor neuron disease. In both cases, a gradually progressive presenile dementia began prior to the development of motor neuron disease involving predominantly bulbar musculature. These data, along with the neuropathologic findings available in one case, suggest that dementia of motor neuron disease differs from that of Alzheimer's disease (AD). Both patients displayed major alterations of personality and comportment. Neuropsychological test results revealed marked attention deficits, particularly on tasks requiring sustained effort and on those requiring ability to shift from one line of thinking to another. Confrontation naming, verbal fluency, insight, and judgment also showed extensive impairment. By contrast, verbal and nonverbal memory remained intact after several years of illness. This pattern is quite different from that seen in AD, where memory deficits are salient.

Aged↗

PubMed1999

Laboratory medicine: the need for a broader view the "multiple bundle" model of clinical laboratory function.

The essence of the nineties in health care, in business, in organizational management and in education, has been change. As always in a changing environment, there will be winners and losers. In the September issue of CCLM, Williamson wrote: "Poor clinical chemistry. It is a field trapped between pressures from increasing electronic automation of assays, simplified technology and reductionism of molecular genetics and the growing pressure of economic accountability and cost cutting. It may not survive" (1). Should we all be on Prozac and wait for the doomsday? Our problems are not unique. Some time ago, traditional cardiology was "trapped" between the advent of new invasive techniques on the one hand and a pressure to increase emphasis on prevention on the other. How did it end? Most of today's cardiologists are invasive cardiologists and many became leaders in cardiovascular prevention in addition to their "traditional" tasks (2). This is a classical example of a paradigm shift. The present article suggests that at least some of our problems may stem from too narrow a view of laboratory medicine that we present to decision makers who allocate funds to laboratory services.

Algorithms↗

PubMed2004

Using cross-links to study ribosomal dynamics.

After publications of 3-D models of a static ribosome and its large and small subunits, one of the next tasks is to recognize movable ribosomal elements responsible for mechanical shifts during protein synthesis. Statistic analysis of available cross-linking data allowed us to reveal three well separated groups of motions in the ribosome: I, mean magnitude of 10 A; II, most abundant, centered at 20 A and of wide dispersion, and III, sparsely populated, with large distances up to 95 A. The last group, III, comprises elements, like the L7/12-stalk and the L1- protuberance, that adopt different positions in crystallographic or electron micrographic structures, and neighboring hairpins 88 and 89, indicating mobility. We demonstrate that the cross-linking method can be applied to study ribosomal dynamics, including large-scale functional movements and, in particular, to estimate which structures participate in molecular switches.

Cross-Linking Reagents↗

PubMed1995

HOROPLAN: computer-assisted nurse scheduling using constraint-based programming.

Nurse scheduling is a difficult and time consuming task. The schedule has to determine the day to day shift assignments of each nurse for a specified period of time in a way that satisfies the given requirements as much as possible, taking into account the wishes of nurses as closely as possible. This paper presents a constraint-based, artificial intelligence approach by describing a prototype implementation developed with the Charme language and the first results of its use in the Rouen University Hospital. Horoplan implements a non-cyclical constraint-based scheduling, using some heuristics. Four levels of constraints were defined to give a maximum of flexibility: French level (e.g. number of worked hours in a year), hospital level (e.g. specific day-off), department level (e.g. specific shift) and care unit level (e.g. specific pattern for week-ends). Some constraints must always be verified and can not be overruled and some constraints can be overruled at a certain cost. Rescheduling is possible at any time specially in case of an unscheduled absence.

France↗

PubMedDate not supplied

Executive functions and updating of the contents of working memory in unipolar depression.

BACKGROUND: Depression is characterized by cognitive impairments, including executive dysfunctions. These executive deficits could reflect impairments of more basic executive processes, such as updating, set shifting and inhibition. While shifting and inhibition impairments are often reported, studies on depression have been somewhat obscure about specific deficits of the updating process. The main goal of that study was to assess the updating process in young in-patients with depression. METHODS: We used a verbal n-back task to assess updating process. Load and mental manipulation within working memory (WM) were incremented by using three different levels of complexity (1,2,3-back). Neuropsychological tests and an attentional task (0-back) were also administered to subjects. Twenty-two individuals meeting DSM-IV criteria for Major Unipolar Depression and 22 healthy control subjects, matched on age, verbal IQ and education, were included in the study. RESULTS: Subjects with depression showed significant deficits at the n-back task compared to control subjects. They were normal in tasks assessing the short-term maintenance in WM and attention. This suggests that depressed patients exhibit impairment in the updating process. Depressed patients also showed set shifting and inhibition deficits. Only the n-back task was correlated with the number of hospitalizations and the longitudinal course of the illness. CONCLUSIONS: Our results suggest that young depressed in-patients have widespread executive dysfunctions, including updating, shifting and inhibition processes. We also found a correlation between a longitudinal measure of depression severity and an updating task performance. We suggest that using multiple executive tasks gives the opportunity to distinguish the specific influence of various executive processes on clinical dimensions in depression.

Adult↗

PubMed2007

The role of the cerebellum in subsecond time perception: evidence from repetitive transcranial magnetic stimulation.

In three experiments, we investigated the role of the cerebellum in sub- and suprasecond time perception by using repetitive transcranial magnetic stimulation (rTMS). In Experiment 1, subjects underwent four 8-min 1-Hz rTMS sessions in a within-subject design. rTMS sites were the medial cerebellum (real and sham rTMS), left lateral cerebellum, and right lateral cerebellum. Following each rTMS session, subjects completed a subsecond temporal bisection task (stimuli in the range 400-800 msec). Compared with sham rTMS, rTMS applied over the right lateral or medial cerebellum induced a leftward shift of the psychophysical function (perceived lengthening of time). In Experiment 2, a separate sample of subjects underwent the identical rTMS procedure and completed a suprasecond bisection task (stimuli in the 1000-2000 msec range). In this experiment, rTMS to the cerebellar sites did not produce any significant changes compared with sham rTMS. Experiment 3 employed a within-subject design to replicate findings from Experiments 1 and 2. Subjects underwent four rTMS conditions (sub- and suprabisection tasks following medial cerebellar and sham rTMS). rTMS induced a significant leftward shift of psychophysical function in the subsecond bisection, but not in the suprasecond bisection. In this study, we have demonstrated that transient cerebellar stimulation can differently affect the ability to estimate time intervals below and above a duration of 1 sec. The results of this study provide direct evidence for the role of the cerebellum in processing subsecond time intervals. This study further suggests that the perception of sub- and suprasecond intervals is likely to depend upon distinct neural systems.

Adult↗

PubMed2001

Altered cortical activation with finger movement after peripheral denervation: comparison of active and passive tasks.

We wished to contrast cortical activation during hand movements in profoundly weak patients with motor neuropathy and in normal controls using a paradigm that is behaviourally matched between the two groups. Previous work has suggested that a passive movement task could be appropriate. Using functional magnetic resonance imaging (fMRI), we first characterised patterns of brain activation during active and passive index finger movements in healthy controls (n=10). Although the relative activation differences were highly variable, there was a trend for the mean number of significantly activated voxels in the primary motor cortex contralateral to the hand moved (CMC) to be lower for the passive than for the active task (40% relative decrease, P=0.09). There was a small posterior shift in the centre of mass of the CMC (mean, 8 mm, P<0.02) and of the ipsilateral sensorimotor cortex (IMC) (mean, 11 mm, P<0.05). No activation with passive movement was found in the patients with severe distal sensory neuropathy (n=2), suggesting that activation with passive movements is dependent on sensory feedback and unlikely to be due to mental imagery alone. In contrast, patients with severe pure motor neuropathies (MN, n=2) showed substantial increases in the volumes of activation compared to controls. The relative increases in numbers of voxels activated above threshold in different regions of interest for both the active (MN/controls: CMC, 2. 1; IMC, 8.1; supplementary motor area [SMA], 5.2) and passive (CMC, 2.6; IMC, 8.0; SMA, 5.1) tasks were similar. These results confirm expansion of cortical representation for finger movement in patients with motor neuropathy and demonstrate central reorganisation as a consequence of the motor nerve loss. An expanded representation for finger movement in the primary motor cortex with peripheral weakness suggests the possibility that the primary motor cortex may encode motor unit activation rather directly.

Adult↗

PubMed2006

Strength of figure-ground activity in monkey primary visual cortex predicts saccadic reaction time in a delayed detection task.

When and where are decisions made? In the visual system a saccade, which is a fast shift of gaze toward a target in the visual scene, is the behavioral outcome of a decision. Current neurophysiological data and reaction time models show that saccadic reaction times are determined by a build-up of activity in motor-related structures, such as the frontal eye fields. These structures depend on the sensory evidence of the stimulus. Here we use a delayed figure-ground detection task to show that late modulated activity in the visual cortex (V1) predicts saccadic reaction time. This predictive activity is part of the process of figure-ground segregation and is specific for the saccade target location. These observations indicate that sensory signals are directly involved in the decision of when and where to look.

Animals↗

PubMed1990

Asymmetries in hand movement during block design construction.

Changes in patterns of hand use were examined as a function of task demand characteristics. Using blocks, right- and left-handed male and female subjects were asked to simultaneously construct two replicas of presented patterns, one with each hand. With the presentation of visual-spatial patterns, a shift toward use of the left hand from baseline was observed. This change was least evident among right-handed females. The observed shift in hand use toward the left on a visuo-constructive block design task might suggest differential involvement of the right hemisphere with changes in task demand characteristics.

Adult↗

PubMed1999

Increased blood flow in the basal ganglia when using cues to direct attention.

We used positron emission tomography (PET) in ten subjects to study the brain regions involved in voluntary shifts of attention. For six scans, subjects performed a visual target detection task in which the location of the target was indicated in advance on some proportion of trials by the appearance of an arrow cue at fixation. The informative cues were successful in speeding reaction time to the target. Blood flow in the left putamen was correlated with the proportion of informative cues provided within a scan. We discuss this finding in terms of three possible interpretations: attentional shifts, response inhibition, and motor preparation related to the use of the right hand to respond. Blood flow in cortical regions commonly associated with attention was not related to cue ratio, a finding that may reflect automatization of the processes involved in interpreting and using the cues.

Adult↗

PubMed2003

Signal detectability in digital radiography: spatial domain figures of merit.

The usefulness of Fourier-based measures of imaging performance has come into question for the evaluation of digital imaging systems. Figures of merit such as detective quantum efficiency (DQE) based on Fourier domain parameters are relevant for linear, shift-invariant systems with stationary noise. However, no digital imaging system is shift invariant, and realistic images do not satisfy the stationarity condition. Our methods for the task-based evaluation of imaging systems, based on signal detectability in the spatial domain, do not require such assumptions. We have computed the performance of ideal and quasi-ideal observers for the task of signal detection in digital radiography. Signal detectability in terms of an observer signal-to-noise-ratio (SNR) has been compared to results obtained from a Monte Carlo simulation of the digital image-acquisition process. The simulation incorporates the effects of random amplification and secondary quantum blur, integration over pixel area, and electronic noise. The observer figures of merit that have been previously shown to bracket human performance directly specify the usefulness of the images for the stated diagnostic task. In addition, the observer figures of merit give a task-dependent measure of imaging system efficiency in terms of the ratio of an output SNR2 to an input SNR2. Thus, the concept of "detective quantum efficiency" reappears in a natural way but based in the spatial domain and not dependent on shift invariance and stationarity assumptions. With respect to the optimum amount of system blur, our simulations indicate that under certain task-dependent conditions, large signals are fairly insensitive to blur in the x-ray transducer, while an optimum blur is found for small signals.

Humans↗

PubMed2005

Methods to detect response shift in quality of life data: a convergent validity study.

When measuring changes in quality of life (QL) with a pretest-posttest design, response shift can affect results. We investigated the convergent validity of three approaches to detect response shift. (1) In the thentest approach, response shift is measured using a retrospective judgment of pretest QL-levels (thentest). (2) In the anchor-recalibration approach response shift is measured, assessing shifts in patients' individual definitions of the scale-anchors (worst and best imaginable QL) over time. (3) In the Structural Equation Modeling (SEM) approach response shift is indicated by mathematically defined changes in factor solutions and variance-covariance matrices over time. Prior to and three months after invasive surgery, 170 cancer patients completed the SF-36, the Multidimensional Fatigue Inventory (as pre-, post-, and thentest), and the anchor-recalibration task (as pre-, and posttest). Results showed agreement between the thentest and SEM approach on the absence (6 scales) and presence (2 scales) of response shift in 8 of the 9 scales. For the ninth scale both methods detected response shift, but in opposite directions. Possible explanations for this discrepancy are discussed. The anchor-recalibration task agreed with the other approaches on only the absence of response shift in 4 of the 7 scales. The convergent results of thentest and SEM support their validity, especially because they use statistically independent operationalizations of response shift. In this study, recall bias did not invalidate thentest results.

Activities of Daily Living↗

PubMed1995

Infants' pitch perception: inharmonic tonal complexes.

Two experiments assessed the effects of inharmonicity on 7- to 8-month-old infants' perception of the pitch of tonal complexes. A number of harmonic and inharmonic complexes were presented in a visually reinforced operant head turn procedure. In both experiments, infants demonstrated the ability to discriminate two harmonic complexes based on missing fundamental frequencies of 160 and 200 Hz. After learning this basic task, infants learned to discriminate inharmonic complexes, which were created by shifting the partials of the harmonic complexes upward by 30 Hz (experiment 1) or 20 Hz (experiment 2). Finally, three spectrally different inharmonic complexes represented each pitch, and infants attempted to categorize those complexes according to their pitches. In both experiments, infants successfully discriminated the pitches of the spectrally varying tonal complexes, but their performance deteriorated for the more strongly inharmonic complexes of experiment 1. These results suggest that, as for adults, the salience of pitch for inharmonic sounds decreases with increasing inharmonicity.

Female↗

PubMed2004

Early environmental experience alters baseline and ethanol-induced cognitive impulsivity: relationship to forebrain 5-HT1A receptor binding.

The relationship between impulsivity and drug abuse is poorly understood despite evidence that impulsive behaviour both predicts, and is a consequence of, drug use. Moreover, although there are clear individual differences in the propensity to addiction, this relationship has not been investigated with respect to impulsive behaviour. We tested whether early environmental experience would influence behavioural measures of impulsivity, and further, whether this experience would alter impulsive choice following ethanol intoxication. Thirty-six male, Long-Evans rats were reared in either isolated (1 rat/cage), standard (2 rats/cage), or enriched (group housed with toys) conditions. After a 3-month rearing period, animals were tested in two operant tasks measuring either motor (go/no-go) or cognitive (delay-to-reinforcement) impulsivity. Rats were then re-tested following 0, 0.3, 0.6, 0.9, and 1.2 g/kg ethanol. Forebrain 5-HT1A binding was assessed post-mortem using in vitro receptor autoradiography with the agonist [3H]8-OH-DPAT (3H-8-hydroxy-2-[di-n-propylamino]tetralin). Rearing condition did not influence baseline motor impulsivity, but isolation rearing led to decreased baseline cognitive impulsivity. Ethanol did not affect motor impulsivity, but dose-dependently increased impulsive choice in the delay-to-reinforcement task. Enriched rats were more impulsive overall, and isolation-reared rats only showed a shift in impulsive behaviour after 1.2 g/kg. Isolation rearing decreased, and enrichment rearing increased 5-HT1A binding in the frontal pole of the cortex following experience in the delay-to-reinforcement task. Isolation-reared rats also showed a significant decrease in 5-HT1A binding in the dentate gyrus of the ventral hippocampus following experience in the delay-to-reinforcement relative to the go/no-go task. These data indicate that differential rearing has a significant influence on cognitive impulsivity, and that altered serotonergic function may underlie these differences.

Age Factors↗

PubMed1990

Cortisol reactivity and cognitive performance in a continuous mental task paradigm.

The after-effects of fatigue or stress on the performance of cognitive tests have been particularly difficult to demonstrate. In this study we examined whether salivary cortisol, used as an index of stress evoked by the continuous performance of mental tasks, reflected individual differences in cognitive performance. In a within-subject experiment in which 24 subjects were exposed to 4 hours of continuous mental activity and to a control session, significantly higher cortisol levels were found during the continuous task session. Cognitive performance was assessed before and after each session. The relevant test parameters involved aspects of verbal memory, concept shifting and divided attention. When subjects were divided into two groups based on the magnitude of individual cortisol responses to the continuous tasks, it was found that the subgroup with higher cortisol responses decreased in attention compared with their attention after the control session. In contrast, the performance of the subgroup with no or lower cortisol responses did not differ between the two sessions. There was no evidence of similar effects on verbal memory or concept shifting.

Adult↗

PubMed2004

Anticipatory balance control is affected by loadless training experiences.

The main purpose of this study was to identify whether a lot of sports training had any effect on the balance control associated with a leg movement. The nature of the training experience was also an important concern and we chose subject who had undergone specific training experience in absence of equilibrium constraints. To this end a comparison between control (untrained) subjects, triathletes and swimmers was designed to establish whether a general training in sports (triathletes) or a specific loadless training (swimmers), leads to differences in the balance control. A leg movement is preceded by a shift of the center of mass (CM) towards the supporting side to maintain equilibrium and forward to create the condition for progression. To provide an acceleration of the CM sideward and forward, an initial displacement of the center of pressure (CP) towards the moving limb and in posterior direction was performed. Interestingly, the lateral pressure onto the ground was greater increased in swimmers in both leg raising and obstacle avoidance tasks compared to the control group and/or triathletes whereas the backward CP shift in all group was the same. The initial control of the CM shift is very different in swimmers compared to triathletes and controls. The increased lateral pressure onto the ground in swimmers may be a result of a prolonged training in water. This suggests that prolonged training in the absence of equilibrium constraints has more of an effect on balance control than a prolonged general training. In addition, the lack of differences in the backward CP shift suggests that M/L and A/P controls support two functional goals: equilibrium maintenance and movement initiation.

Awareness↗

PubMed1995

Superior parietal cortex activation during spatial attention shifts and visual feature conjunction.

Positron emission tomography was used to measure changes in the regional cerebral blood flow of normal people while they searched visual displays for targets defined by color, by motion, or by a conjunction of color and motion. A region in the superior parietal cortex was activated only during the conjunction task, at a location that had previously been shown to be engaged by successive shifts of spatial attention. Correspondingly, the time needed to detect a conjunction target increased with the number of items in the display, which is consistent with the use of a mechanism that successively analyzes each item in the visual field.

Attention↗

PubMed1999

Selective visual-spatial attention alters induced gamma band responses in the human EEG.

OBJECTIVES: The present study was designed to investigate the attentional modulation of gamma band responses in a visual spatial attention task using a 128-channel-EEG-montage. METHODS: Colored rectangles were presented on a screen. After 500 ms an arrow indicated whether subjects had to shift their attention to the left or right half of the screen to detect target stimuli. During the task, either the attended half of the screen rotated horizontally while the unattended part remained motionless, or vice versa. RESULTS: When subjects attended the rotating stimulus, we found significantly higher power in a specific gamma band from 35-51 Hz on parieto-occipital electrode sites contralateral to the stimulation side. In addition, after the onset of the arrow which indicated what side subjects should direct their attention to, the 35-51 Hz response shifted from a broad posterior distribution to an increase of power at parieto-occipital sites contralateral to the to-be-attended side. Furthermore, the rotating stimulus elicited higher gamma band power as compared to the standing stimulus at electrode locations, which may be related to the activity of underlying cortical structures specialized for motion processing. CONCLUSIONS: The present results replicate important parts of previous findings of enhanced gamma power when a moving stimulus was attended.

Adult↗