SEARCH · PubMed Health

Results for “Task Shifting”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,171 records · Page 65Linked to original sources

PubMed1998

Interaction of hypertension and age in visual selective attention performance.

Previous research suggests that some aspects of cognitive performance decline as a joint function of age and hypertension. In this experiment, 51 unmedicated individuals with mild essential hypertension and 48 normotensive individuals, 18-78 years of age, performed a visual search task. The estimated time required to identify a display character and shift attention between display positions increased with age. This attention shift time did not differ significantly between hypertensive and normotensive participants, but regression analyses indicated some mediation of the age effect by blood pressure. For individuals less than 60 years of age, the error rate was greater for hypertensive than for normotensive participants. Although the present design could detect effects of only moderate to large size, the results suggest that effects of hypertension may be more evident in a relatively general measure of performance (mean error rate) than in the speed of shifting visual attention.

Adult↗

PubMed2005

Dissociations in perceptual learning revealed by adult age differences in adaptation to time-compressed speech.

When presented with several time-compressed sentences, young adults' performance improves with practice. Such adaptation has not been studied in older adults. To study age-related changes in perceptual learning, the authors tested young and older adults' ability to adapt to degraded speech. First, the authors showed that older adults, when equated for starting accuracy with young adults, adapted at a rate and magnitude comparable to young adults. However, unlike young adults, older adults failed to transfer this learning to a different speech rate and did not show additional benefit when practice exceeded 20 sentences. Listeners did not adapt to speech degraded by noise, indicating that adaptation to time-compressed speech was not attributable to task familiarity. Finally, both young and older adults adapted to spectrally shifted noise-vocoded speech. The authors conclude that initial perceptual learning is comparable in young and older adults but maintenance and transfer of this learning decline with age.

Adolescent↗

PubMed2006

Individual differences in executive processing predict susceptibility to interference in verbal working memory.

Recent theories have suggested that resistance to interference is a unifying principle of executive function and that individual differences in interference may be explained by executive function (M. J. Kane & R. W. Engle, 2002). Measures of executive function, memory, and perceptual speed were obtained from 121 older adults (ages 63-82). We used structural equation modeling to investigate the relationships of these constructs with interference in a working memory task. Executive function was best described as two related subcomponent processes: shifting and updating goal-relevant representations and inhibition of proactive interference. These subcomponents were distinct from verbal and visual memory and speed. Individual differences in interference susceptibility and recollection were best predicted by shifting and updating and by resistance to proactive interference, and variability in familiarity was predicted by resistance to proactive interference and speed.

Aged↗

PubMed1989

Effects of transition length on the perception of stop consonants by children and adults.

The purpose of this investigation was to determine whether children with normal linguistic skills demonstrate increasing developmental changes in their perception of place of articulation for stop consonants with short- and long-duration formant transitions. Three experimental paradigms were used with children and adults: discrimination, labeling, and selective adaptation. Two sets of synthetic CV syllables, varying along a seven-step, bilabial-to-alveolar dimension, were used as stimuli. These two synthetic continua differed in the length of the second and third formant transitions. Results showed that children's discrimination abilities gradually approximated those of adults, but did not reach adult levels even at 10 years of age. Differences were not observed in the labeling task. Further, results of the selective adaptation task indicated that only the adult subjects showed a significant boundary shift for any adapting stimuli. The absence of selective adaptation in children was interpreted as a possible reflection of their poorer auditory abilities. Thus, the pattern of speech perception development for children for place of articulation is a complex one with a strong auditory developmental component.

Adaptation, Physiological↗

PubMed2001

Low back joint loading and kinematics during standing and unsupported sitting.

The aim was to examine lumbar spine kinematics, spinal joint loads and trunk muscle activation patterns during a prolonged (2 h) period of sitting. This information is necessary to assist the ergonomist in designing work where posture variation is possible -- particularly between standing and various styles of sitting. Joint loads were predicted with a highly detailed anatomical biomechanical model (that incorporated 104 muscles, passive ligaments and intervertebral discs), which utilized biological signals of spine posture and muscle electromyograms (EMG) from each trial of each subject. Sitting resulted in significantly higher (p<0.001) low back compressive loads (mean +/- SD 1698 +/- 467 N) than those experienced by the lumbar spine during standing (1076 +/- 243 N). Subjects were equally divided into adopting one of two sitting strategies: a single 'static' or a 'dynamic' multiple posture approach. Within each individual, standing produced a distinctly different spine posture compared with sitting, and standing spine postures did not overlap with flexion postures adopted in sitting when spine postures were averaged across all eight subjects. A rest component (as noted in an amplitude probability distribution function from the EMG) was present for all muscles monitored in both sitting and standing tasks. The upper and lower erector spinae muscle groups exhibited a shifting to higher levels of activation during sitting. There were no clear muscle activation level differences in the individuals who adopted different sitting strategies. Standing appears to be a good rest from sitting given the reduction in passive tissue forces. However, the constant loading with little dynamic movement which characterizes both standing and sitting would provide little rest/change for muscular activation levels or low back loading.

Adult↗

PubMed1995

Control of Rapid Arm Movements When Target Position Is Altered During Saccadic Suppression.

This experiment examined whether rapid arm movements can be corrected in response to a change in target position that occurs just prior to movement onset, during saccadic suppression of displacement. Because the threshold of retinal input reaches its highest magnitude at that time, displacement of the visual target of a saccade is not perceived. Subjects (N = 6) were instructed to perform very rapid arm movements toward visual targets located 16, 20, and 24 degrees from midline (on average, movement time was 208 ms). On some trials the 20 degrees target was displaced 4 degrees either to the right or to the left during saccadic suppression. For double-step trials, arm movements did not deviate from their original trajectory. Movement endpoints and movement structure (i.e., velocity-and acceleration-time profiles) were similar whether or not target displacements occurred, showing the failure of proprioceptive signals or internal feedback loops to correct the arm trajectory. Following this movement, terminal spatially oriented movements corrected the direction of the initial movement (as compared with the single-step control trials) when the target eccentricity decreased by 4 degrees. Subjects were unaware of these spatial corrections. Therefore, spatial corrections of hand position were driven by the goal level of the task, which was updated by oculomotor corrective responses when a target shift occurred.

Journal Article↗

PubMed1998

Relation between language lateralisation and spatial ability in gay and straight women and men.

Delineating the relationship between language lateralisation and spatial ability remains an elusive goal. To explore the association of sexual orientation to the language lateralisation/spatial ability relationship, heterosexual (HT) women, HT men, lesbians, and gay men (20 per group) completed a divided-visual-field lexical-decision task to assess relative degrees of language lateralisation, as well as a Water Level Task (WLT) and two Mental Rotation (MR) Tasks designed to assess spatial ability. A significant cross-sex shift was revealed in the language lateralisation of gay men. Further, language lateralisation positively correlated with MR ability in HT men and tended to positively correlate with spatial perception in HT women. No significant associations were revealed in homosexual subjects. Different patterns of functional hemispheric asymmetry in homosexual and heterosexual individuals are discussed in relation to early neurobiological factors influencing the development of sexual orientation.

Journal Article↗

PubMed1996

Culture and meaning: expanding the metaphorical repertoire of family therapy.

This essay proposes that a family therapy founded on a contemporary, postmodern perspective demands an expanded range of metaphors for the family and the work of therapy. It describes a perspective that emphasizes a view of the family as a culture, as opposed to a system. A cultural perspective naturally addresses issues of meaning and language, narrative, politics, and practices of power-critical contemporary concerns not adequately encompassed by traditional systemic formulations. The essay explores the relationship between theory and metaphor, and contrasts the views of persons and of the family offered by the metaphors of culture and system. Case illustrations demonstrate how a cultural view effectively fashions an expanded therapeutic discourse, shifting the focus of family therapy from normative prescriptions for family "functionality" to issues of intercultural harmony. This shift in emphasis also extends to individual work, where the therapeutic task is construed as a peace-making between conflicting stories that intersect in the client's life.

Adolescent↗

PubMed1998

Understanding neural interactions in learning and memory using functional neuroimaging.

Neuroimaging methods such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) provide a unique opportunity to explore activity across the entire human brain in many different behaviors. An important additional feature is the ability to examine interacting neural systems using methods that focus on the covariances of activity. Two of these methods, partial least squares and structural equation modeling, are presented with specific examples. Shifting prefrontal and limbic interactions were observed in a working memory task for faces. In an episodic memory retrieval study, the activity of right prefrontal cortex was related to either memory search or successful retrieval depending on its interactions with other brain regions. This latter observation implies that regional activity must be evaluated within the neural context in which it occurs. The general hypothesis that learning and memory are emergent properties of network interactions is discussed, emphasizing that a region can play a different role across many functions and that role is governed by its interactions with anatomically related regions.

Animals↗

PubMed2003

The case for an internal dynamics model versus equilibrium point control in human movement.

The equilibrium point hypothesis (EPH) was conceived as a means whereby the central nervous system could control limb movements by a relatively simple shift in equilibrium position without the need to explicitly compensate for task dynamics. Many recent studies have questioned this view with results that suggest the formation of an internal dynamics model of the specific task. However, supporters of the EPH have argued that these results are not incompatible with the EPH and that there is no reason to abandon it. In this study, we have tested one of the fundamental predictions of the EPH, namely, equifinality. Subjects learned to perform goal-directed wrist flexion movements while a motor provided assistance in proportion to the instantaneous velocity. It was found that the subjects stopped short of the target on the trials where the magnitude of the assistance was randomly decreased, compared to the preceding control trials (P = 0.003), i.e. equifinality was not achieved. This is contrary to the EPH, which predicts that final position should not be affected by external loads that depend purely on velocity. However, such effects are entirely consistent with predictions based on the formation of an internal dynamics model.

Adult↗

PubMed1998

Target flutter rate discrimination by bats using frequency-modulated sonar sounds: behavior and signal processing models.

This study utilized psychophysical data and acoustical measurements of sonar echoes from artificial fluttering targets to develop insights to the information used by FM bats to discriminate the wingbeat rate of flying insects. Fluttering targets were produced by rotating blades that moved towards the bat, and the animal learned to discriminate between two rates of movement, a reference rate (30 or 50 Hz) and a slower, variable rate. Threshold discrimination performance depended on the rotation rate of the reference target, with a difference value of 9 Hz for the reference rate of 30 Hz and 14 Hz for the reference rate of 50 Hz. Control experiments demonstrated that the bats used sonar echoes from the moving targets to perform the discrimination task. Acoustical measurements showed that the moving target produced a Doppler shift in the echo and a concomitant change in the arrival time of each frequency in the linear period FM sweep. The difference in delay between echoes from moving and stationary parts varied linearly with flutter rate and depended on the characteristics of the bat's sonar sounds. Simulations also showed a reduction in average echo bandwidth with increasing flutter rate, which may account for a higher delay discrimination threshold using the 50-Hz reference rate. This work suggests that Doppler-induced changes in echo delays produced by fluttering targets may contribute to the FM bat's perception of flying insect prey.

Acoustics↗

PubMed1999

The integration of nonsimultaneous frequency components into a single virtual pitch.

The integration of nonsimultaneous frequency components into a single virtual pitch was investigated by using a pitch matching task in which a mistuned 4th harmonic (mistuned component) produced pitch shifts in a harmonic series (12 equal-amplitude harmonics of a 155-Hz F0). In experiment 1, the mistuned component could either be simultaneous, stop as the target started (pre-target component), or start as the target stopped (post-target component). Pitch shifts produced by the pre-target components were significantly smaller than those obtained with simultaneous components; in the post-target condition, the size of pitch shifts did not decrease relative to the simultaneous condition. In experiment 2, a silent gap of 20, 40, 80, or 160 ms was introduced between the nonsimultaneous components and the target sound. In the pre-target condition, pitch shifts were reduced to zero for silent gaps of 80 ms or longer; by contrast, a gap of 160 ms was required to eliminate pitch shifts in the post-target condition. The third experiment tested the hypothesis that, when post-target components were presented, the processing of the pitch of the target tone started at the onset of the target, and ended at the gap duration at which pitch shifts decreased to zero. This hypothesis was confirmed by the finding that pitch shifts could not be observed when the target tone had a duration of 410 ms. Taken together, the results of these experiments show that nonsimultaneous components that occur after the onset of the target sound make a larger contribution to the virtual pitch of the target, and over a longer period, than components that precede the onset of the target sound.

Humans↗

PubMedDate not supplied

Choice-matching preference reversals in health outcome assessments.

BACKGROUND: Health outcome utility assessments generally assume procedural invariance. Preference reversals violating procedural invariance occur in economic scenarios when the assessment process shifts from a choice to a fill-in-the-blank task. PURPOSE: To determine if similar reversals occur in utility assessments. METHODS: One hundred thirty-six volunteer subjects completed 6 preference assessments of 4 personal health scenarios. Patients responded to otherwise identical tasks using either choice or fill-in-the-blank processes in a randomized crossover design. The authors determined the percentage of subjects preferring, or inferred to prefer, a given choice. RESULTS: Preference reversals occurred in all assessment scenarios. CONCLUSIONS: These preference reversals are a potential source of confusion for utility assessment and informed consent. They could be manipulated to achieve ends other than the best interest of patients. Anchoring or the prominence hypothesis may explain these findings.

Adult↗

PubMed2006

A comparative review of health-related quality-of-life measures for use in HIV/AIDS clinical trials.

With the advent of highly active antiretroviral therapy (HAART), HIV-infected patients are living longer and are concerned not only with a treatment's ability to extend their life but also with the quality of the life they are able to lead. Regulatory authorities are also paying closer attention to the use of health-related quality-of-life (HR-QOL) measures in clinical trials and to the subsequent claims that are made based on the results. This paper reviews existing HR-QOL measures reported in the HIV/AIDS literature since 1990 and identifies those most worthy of consideration for use in future clinical trials.A comprehensive review following predefined selection criteria was conducted. Generic and HIV-targeted measures were assessed for content and practicality for the clinical trial setting. The generic measures were additionally reviewed for the ability to produce preference-based index scores and for the existence of normative general population data. Three generic and six HIV-targeted measures met these selection criteria and were then assessed more fully in terms of their development (HIV-targeted measures), psychometric properties and appropriateness for use in clinical trials.It was determined that each of the selected generic measures (i.e. Medical Outcomes Study [MOS] 36-Item Short Form Survey Instrument [SF-36], EQ-5D, Health Utilities Index [HUI]) could serve as a useful adjunct to an HIV-targeted measure in a trial. The Functional Assessment of HIV Infection (FAHI) and MOS-HIV health survey were deemed the two most appropriate HIV-targeted measures. Each of the measures can be self-administered in < or = 10 minutes and there was ample evidence of their excellent psychometric properties. However, they would not be optimal in all HIV-infected subgroups (e.g. treatment naive vs advanced; adolescents vs older adults) targeted for clinical trial interventions. Although there is no one best HR-QOL measure for use in HIV/AIDS clinical trials, based on our review criteria we identified three generic and two HIV-targeted candidate measures. However, these measures have their limitations and it is clear that greater consensus needs to develop regarding more effective and efficient approaches to HR-QOL measurement in HIV/AIDS clinical trials. Along with the increasingly complex HR-QOL measurement task resulting from changes in the HIV-infected population and shifts in the HR-QOL burden associated with HIV infection and its treatment over the past 25 years, it is increasingly important that HR-QOL outcomes become viable endpoints in HIV/AIDS clinical trials.

Acquired Immunodeficiency Syndrome↗

PubMed1991

[Learning and resistance to extinction in external-self dual reinforcement as compared with those in external reinforcement].

Learning and resistance to extinction in external-self dual reinforcement (ESR) were compared with those in external reinforcement (ER). delta ESR (delta: extinction process) was also compared with the corresponding process of other two conditions; 1) discontinuation of self reinforcement after external-self dual reinforcement (delta SR), 2) discontinuation of external reinforcement following the dual reinforcement (delta ER). Undergraduates (n = 58 in Experiment I, n = 74 in Experiment II) were randomly assigned to one of the four conditions. Subjects were given association learning in Exp. I and memory task in Exp. II, respectively. Those who responded successfully were then shifted to extinction session for testing. Effects of ESR on learning were same as those of ER in the two experiments. Resistance to extinction in Exp. I was significantly higher for delta SR and delta ESR as compared with delta ER and *ER (extinction switched from external reinforcement). Resistance for delta SR in Exp. II was significantly higher than for the remaining conditions. Based on these findings, high level of the resistance for delta ESR was discussed by attributing it to the internalization of ESR.

Adult↗

PubMed1999

A comparison of phonemic, semantic, and alternating word fluency in Parkinson's disease.

Word fluency in 45 medicated non-demented Parkinson's disease (PD) patients and 45 normal control subjects was studied with a Phonemic Word Fluency (PWF) task using the letters F, A, and S, a Semantic Word Fluency (SWF) task using the categories animals, boys' names, and states, and an Alternating Word Fluency (AWF) task requiring the person to alternate between colors and occupations, animals and states, and words beginning with C and P. The number of words generated did not differ for trials with F, A, S, or states, but PD patients generated significantly fewer animal names and boys' names. PD patients also generated significantly fewer words on each of the three AWF trials. The PD patients scored 21% lower than the normal control group on the total AWF score, but only 10% lower for the PWF and SWF scores. The greater impairment on the AWF task which requires the use of internal attentional control to rapidly shift mental set can be considered a type of executive functioning deficit. This is consistent with the growing literature suggesting frontal systems dysfunction in PD and with the view that dopaminergic treatment only incompletely restores functioning in the frontostriatal system.

Journal Article↗

PubMed2004

Functional magnetic resonance imaging of working memory among multiple sclerosis patients.

BACKGROUND AND PURPOSE: Verbal working memory (VWM) deficits have been a well-replicated finding among patients with multiple sclerosis (MS). Functional magnetic resonance imaging (FMRI) studies have described a VWM system in healthy samples; however, functional neuroimaging of this system among MS patients is just beginning to appear. METHODS: Fifteen MS patients and 15 sex-, age-, education-, and IQ-matched healthy control (HC) participants completed a 2-Back VWM task as whole-brain FMRI was conducted. RESULTS: Each group exhibited increased brain activity compared to the O-Back control task in regions associated with the 2-Back in previous neuroimaging studies. These included Broca's area, supplementary motor area (SMA), premotor cortices (PMC), and dorsolateral prefrontal cortices (DLPFC). MS patients exhibited greater cortical activity than did HC participants in left primary motor and somatosensory cortices, PMC, DLPFC, anterior cingulate, and bilateral SMA. MS patients exhibited relatively less activation in Broca's area, bilateral cerebellum, and other regions not typically associated with the 2-Back (e.g., right fusiform gyrus, left lingual gyrus, right hippocampus). Performance accuracy and reaction time did not differ between groups. CONCLUSIONS: Normal performance of a challenging VWM task among high-functioning MS patients is associated with a shift toward greater activity in regions related to sensorimotor functions and anterior attentional/executive components of the VWM system. Posterior memory storage systems appeared unaffected, while portions of the visual processing and subvocal rehearsal systems were less active. Although a shift in neural activity was noted relative to HC participants, deviation from regions normally involved in VWM function was not observed in this patient sample.

Adult↗

PubMed1990

[Effort--a form of self-imposed stress].

Effort is analyzed as a top-down process which is a feature of autonomous work procedures. A rise in effort may affect different aspects of efficiency in performance: (a) Increment in speed, (b) increment in accuracy, (c) shifts in difficulty level, (d) focus on central aspects of the task. A "law of diminishing returns" is postulated which calls for a balanced utilization of all options. In an experiment, subjects worked in a simulated office environment. The main independent variables were high-effort vs. low-effort instructions, and assignment vs. free choice of tasks. The subjects were also grouped according to their scores in an intelligence and an anxiety test. The results confirm the general expectation that a rise in effort may affect performance in terms of speed, accuracy, choice of difficulty level, and focus. However, the result vary considerably with experimental conditions and personality variables. Apparently, effort imposes a mental and emotional load which is best coped with by the low anxious and high intelligent.

Arousal↗