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 1,531 records · Page 85Linked to original sources

PubMed1986

Responsibility for examining an asylum.

Parallel to the influx of asylum seekers during the 1980s, xenophobic tendencies have been witnessed in certain Western European countries. While directed at all foreigners, these tendencies sometimes have led to restrictive practices or methods which include both denying that asylum seekers qualify as refugees, so they may be sent home more easily, and shifting the responsibility for examining asylum claims to other countries. An analysis of the increasingly restrictive practices regarding the granting of asylum and the concept of a refugee is a complicated task, which requires a detailed investigation of the jurisprudence in a number of countries. This article, however, will not concentrate on an analysis of jurisprudence regarding asylum but rather on the tendency of various states to shift the responsibility for examining asylum requests to another country.

Attitude↗

PubMed2000

Shifting from the perceptual brain to the logical brain: the neural impact of cognitive inhibition training.

What happens in the human brain when the mind has to inhibit a perceptual process in order to activate a logical reasoning process? Here, we use functional imaging to show the networks of brain areas involved in a deductive logic task performed twice by the same subjects, first with a perceptual bias and then with a logical response following bias-inhibition training. The main finding is a striking shift in the cortical anatomy of reasoning from the posterior part of the brain (the ventral and dorsal pathways) to a left-prefrontal network including the middle-frontal gyrus, Broca's area, the anterior insula, and the pre-SMA. This result indicates that such brain shifting is an essential element for human access to logical thinking.

Adult↗

PubMed2001

Acute effects of alcohol on divided and covert attention in men.

RATIONALE: While several studies identified divided attention to be sensitive to alcohol effects, the impact of alcohol on covert visual attention is still not clear, despite the latter's important role in perception. OBJECTIVES: The study tests the effect of acute moderate doses of alcohol on divided and covert attention in right-handed, male volunteers. METHODS: The design of the study involved a double-blind trial with an alcohol and a placebo condition; measurements were taken before and after an oral dose of 0.6 g/kg alcohol versus placebo. In the divided-attention task, simultaneous visuo-spatial and auditory stimulation was applied. In a test of covert attention, subjects had to shift their attentional focus according to a central cue, from one location in the visual field to another. RESULTS: Under the divided-attention condition, reaction times were significantly prolonged after alcohol ingestion compared to placebo. Covert attention pre-post change was also significantly different between the alcohol and placebo groups. There is a reduction of false-cueing disturbance for left-appearing stimuli under moderate alcohol but an increase of disturbance for rightward stimuli, i.e. we found a lateralised pattern of reaction for spatial orienting. In the placebo group, no significant differences in right-left performance were obtained. CONCLUSION: The results suggest that sensory-attentional mechanisms play a key role in altered visual perceptual performance after alcohol ingestion. Furthermore, differences between the right and left visual field in the cued target-detection task indicate that alcohol exerts an influence on right-hemispheric attentional priming.

Adult↗

PubMed1994

A behavioral measure of hand preference as opposed to hand skill.

Twenty-five self-professed left-handers and 21 self-professed right-handers were given a variety of performance tests to assess handedness, along with a preference inventory and a dichotic listening test of language lateralization. The performance tests included the Annett pegboard task, that Tapley and Bryden dot-filling tasks, and two procedures, the long pegboard and long dots tasks, that were intended to assess the point in space at which a particular unimanual movement became sufficiently awkward for one to shift to the other hand. All four of these performance tests differentiated between left-handers and right-handers, although the differences between handedness groups were somewhat larger when handedness was defined in terms of the preference inventory rather than on the basis of self-report. When the difference between preferred and non-preferred hands was examined, the best predictor of hand preference was the long pegboard task. Such a finding is consistent with the view that the long pegboard provides a behavioral measure of hand preference, while the pegs and dots tasks are more closely linked to specific skills. In addition, the correlations between individual preference items and the dichotic right-ear advantage suggest that language lateralization is related to rather different handedness measures than those usually used to define handedness. This finding would suggest that handedness and language lateralization are determined by somewhat different mechanisms.

Dichotic Listening Tests↗

PubMed1998

Visuospatial attention shift and motor responses in cerebellar disorders.

The cerebellum has been implicated in higher cognitive functions including learning, memory, and attention as well as its well-known role in motor programming. Recent studies have suggested that the cerebellum plays a role in shifts of attention. We investigated the contribution of the cerebellum to visuospatial attentional ability in a trial-by-trial cueing task involving the covert orienting of spatial attention. We recorded event-related evoked potentials (ERPs) and reaction times (RTs) in patients with cerebellar degenerative disorders affecting mainly the lateral cerebellum and compared them to age-matched controls. The RT data demonstrated that both the cerebellar patients and control subjects responded to the valid cues faster than to the invalid cues for both the central and the peripheral cues. Consistent with the RT data, the ERP data showed a comparable generation of attention shift-related negativities during the cue-target interval for both the central and the peripheral cue experiments. The early negative component of the ERP to the target was also comparably modulated in both groups as a function of cue validity, suggesting efficient facilitation of sensory pathways by prior allocation of spatial attention to the cued place. Conversely, the late negative deflection preceding the imperative target stimulus and the late sustained positivity following target presentation, which reflect neural activities for response preparation and selection, were reduced in the cerebellar group. These findings suggest that the lateral cerebellum makes little contribution to visuospatial attention shift in either the voluntary or automatic modes and support a role of the lateral cerebellum in the neural system required for response preparation and selection.

Adult↗

PubMed1997

Verbal-overshadowing effect: evidence for a general shift in processing.

Two experiments investigate the nature of the verbal-overshadowing effect-the finding that recognition performance for certain stimuli is impaired if it is described verbally (Schooler & Engstler-Schooler, 1990). Impairment on a face-recognition task was found, although participants produced not a verbal description of the target but, instead, a description of another object (a car) presented in the study phase. These results support the idea that the verbal-overshadowing effect reflects a general shift in the processes involved in face recognition rather than a specific impairment for the described stimulus. Results also support the notion that the impairing effect of verbalization is unique to certain types of stimuli; verbalization impaired recognition of a face but not of a car.

Adult↗

PubMed1999

Mechanisms of recovery from aphasia: evidence from positron emission tomography studies.

OBJECTIVES: Language functions comprise a distributed neural system, largely lateralised to the left cerebral hemisphere. Late recovery from aphasia after a focal lesion, other than by behavioural strategies, has been attributed to one of two changes at a systems level: a laterality shift, with mirror region cortex in the contralateral cortex assuming the function(s) of the damaged region; or a partial lesion effect, with recovery of perilesional tissue to support impaired language functions. Functional neuroimaging with PET allows direct observations of brain functions at systems level. This study used PET to compare regional brain activations in response to a word retrieval task in normal subjects and in aphasic patients who had shown at least some recovery and were able to attempt the task. Emphasis has been placed on single subject analysis of the results as there is no reason to assume that the mechanisms of recovery are necessarily uniform among aphasic patients. METHODS: Six right handed aphasic patients, each with a left cerebral hemispheric lesion (five strokes and one glioma), were studied. Criteria for inclusion were symptomatic or formal test evidence of at least some recovery and an ability to attempt word retrieval in response to heard word cues. Each patient underwent 12 PET scans using oxygen-15 labelled water (H2(15)O) as tracer to index regional cerebral blood flow (rCBF). The task, repeated six times, required the patient to think of verbs appropriate to different lists of heard noun cues. The six scans obtained during word retrieval were contrasted with six made while the subject was "at rest". The patients' individual results were compared with those of nine right handed normal volunteers undergoing the same activation study. The data were analysed using statistical parametric mapping (SPM96, Wellcome Department of Cognitive Neurology, London, UK). RESULTS: Perception of the noun cues would be expected to result in bilateral dorsolateral temporal cortical activations, but as the rate of presentation was only four per minute the auditory perceptual activations were not evident in all people. Anterior cingulate, medial premotor (supplementary speech area) and dorsolateral frontal activations were evident in all normal subjects and patients. There were limited right dorsolateral frontal activations in three of the six patients, but a similar pattern was also found in four of the nine normal subjects. In the left inferolateral temporal cortex, activation was found for the normal subjects and five of the six patients, including two of the three subjects with lesions involving the left temporal lobe. The only patient who showed subthreshold activation in the left inferolateral temporal activation had a very high error rate when performing the verb retrieval task. CONCLUSIONS: The normal subjects showed a left lateralised inferolateral temporal activation, reflecting retrieval of words appropriate in meaning to the cue from the semantic system. Lateralisation of frontal activations to the left was only relative, with right prefrontal involvement in half of the normal subjects. Frontal activations are associated with parallel psychological processes involved in word retrieval, including task initiation, short term (working) memory for the cue and responses, and prearticulatory processes (even though no overt articulation was required). There was little evidence of a laterality shift of word retrieval functions to the right temporal lobe after a left hemispheric lesion. In particular, left inferolateral temporal activation was seen in all patients except one, and he proved to be very inefficient at the task. The results provide indirect evidence that even limited salvage of peri-infarct tissue with acute stroke treatments will have an important impact on the rehabilitation of cognitive functions.

Adult↗

PubMed2004

P300 investigation of phoneme change detection in dyslexic adults.

A specific impairment in phoneme awareness has been hypothesized as one of the current explanations for dyslexia. We examined attentional shifts towards phonological information as indexed by event-related potentials (ERPs) in normal readers and dyslexic adults. Participants performed a lexical decision task on spoken stimuli of which 80% started with a standard phoneme and 20% with a deviant phoneme. A P300 modulation was expected for deviants in control adults, indicating that the phonological change had been detected. A mild and right-lateralized P300 was observed for deviant stimuli in controls, but was absent in dyslexic adults. This result suggests that dyslexic adults fail to make shifts of attention to phonological cues in the same way that normal adult readers do.

Acoustic Stimulation↗

PubMed1992

Distinct syndromes of hemineglect.

Hemineglect was assessed in 34 patients with right-hemisphere stroke using a letter-cancellation task and a line bisection task. No significant correlation (r = .39) was found between scores on the two tests. Ten patients who showed neglect on the cancellation task but performed normally on line bisection had frontal or deep lesions. Eleven patients with posterior lesions deviated rightward on line bisection; several of these had minimal or no cancellation deficit. A nonmotor task involving judgment of a bisected line was also performed abnormally by six patients with line bisection shift, suggesting that such shift does not result from a motor response asymmetry. We propose that separable components of the neglect syndrome may be associated with damage to discrete areas of the nondominant hemisphere.

Adult↗

PubMed2003

Pain dynamics observed by functional magnetic resonance imaging: differential regression analysis technique.

PURPOSE: To observe the dynamic responses of the cortical areas related to the pain processing by using the differential regression analysis (DRA) technique in functional magnetic resonance imaging (fMRI) and investigation of pain mechanisms. MATERIALS AND METHODS: For pain studies, thermal stimulation was applied by immersing the index finger into a hot bath of water with a temperature of 50-52 degrees C. Motor (finger tapping) and visual (flickering light) stimulation experiments were conducted to elucidate the physiological differences between the simple sensory tasks and pain tasks. To obtain dynamic responses, T values (regression analysis) were sequentially estimated by using a series of shifted differential window functions (narrow width). RESULTS: By using the DRA technique, well-defined prompt responses were observed for both motor and visual stimuli. On the other hand, in the pain experiment, a set of sequentially varying responses was observed for the thalamus (Thal), the dorsal anterior cingulate cortex (dACC), the caudal ACC (cACC), and the rostral ACC (rACC). This time-dependent response suggests the dynamics of pain signal processing in cortical areas. CONCLUSION: The results support the hypothesis that the activated areas are similar to the previously reported pain processing areas; however, new sequential responses were observed, suggesting that the technique may reveal dynamics of pain perception and their pathway, important elements in understanding the mechanism of pain. The DRA technique can provide a new opportunity for many spatiotemporal analyses, for example, the physiologically complex and little-studied physiological phenomena, such as pain dynamics.

Cerebral Cortex↗

PubMed1993

The coordination of posture and voluntary movement in patients with hemiparesis.

Postural adjustments associated with the task of raising oneself on tiptoes were investigated in a reaction time paradigm in six normal subjects and six patients with hemiparesis due to stroke. Body and ankle position in space were measured by means of a movement analysis system (ELITE). The findings indicate that the task of going up on tiptoes is performed in two steps. First, the centre of gravity is shifted forward to a position perpendicular to the forefoot. This movement is initiated by a phasic burst of EMG activity in the tibialis anterior (TA). The activity of the quadriceps femoris (QUA) aids the forward shift and together with the biceps femoris (BF) stabilizes the knee. Following these postural adjustments, the action of going up on tip-toes is performed mainly by the gastrocnemius medialis (MG). The basic pattern of preparatory (TA, QUA, BF) and focal (MG) activity was disturbed in its temporal sequence in patients with hemiparesis. The analysis of the biomechanical data showed smaller movement velocities for leaning forward and going up on tiptoes in patients, with increased movement amplitude on the paretic side. In addition, the correlation between the start of horizontal (leaning forward) and vertical (going up on tiptoes) hip movement was lost in patients. The preserved correlation between the latency of MG activity and the onset of the vertical hip movement on the paretic side in patients and the loss of correlation on the non-paretic side indicates that the EMG activity on the healthy side is adapted to the functional requirements of the affected side.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Saccadic eye movements in normal children from 8 to 15 years of age: a developmental study of visuospatial attention.

This cross-sectional study used saccadic eye movements, as measured by infrared occulography, to assess several aspects of visuospatial attention in normal children ages 8-15 years. Saccadic latency (a global measure of the ability to shift visuospatial attention), the ability to suppress extraneous saccades during fixation, and the ability to inhibit task-provoked anticipatory saccades all improve with age. However, the pattern of development differs for different tasks; saccadic latency shortens at a linear rate across the age range 8-15 years, while the capacity to inhibit anticipatory saccades matures by 12-13 years of age, and the ability to suppress saccades matures by 10 years of age. Analyses of age-related changes in oculomotor measures of attention may provide a novel approach in the study of children with attentional difficulties.

Adolescent↗

PubMed1998

Tilt perception during dynamic linear acceleration.

Head tilt is a rotation of the head relative to gravity, as exemplified by head roll or pitch from the natural upright orientation. Tilt stimulates both the otolith organs, owing to shifts in gravitational orientation, and the semicircular canals in response to head rotation, which in turn drive a variety of behavioral and perceptual responses. Studies of tilt perception typically have not adequately isolated otolith and canal inputs or their dynamic contributions. True tilt cannot readily dissociate otolith from canal influences. Alternatively, centrifugation generates centripetal accelerations that simulate tilt, but still entails a rotatory (canal) stimulus during important periods of the stimulus profiles. We reevaluated the perception of head tilt in humans, but limited the stimulus to linear forces alone, thus isolating the influence of otolith inputs. This was accomplished by employing a centrifugation technique with a variable-radius spinning sled. This allowed us to accelerate the sled to a constant angular velocity (128 degrees/s), with the subject centered, and then apply dynamic centripetal accelerations after all rotatory perceptions were extinguished. These stimuli were presented in the subjects' naso-occipital axis by translating the subjects 50 cm eccentrically either forward or backward. Centripetal accelerations were thus induced (0.25 g), which combined with gravity to yield a dynamically shifting gravitoinertial force simulating pitch-tilt, but without actually rotating the head. A magnitude-estimation task was employed to characterize the dynamic perception of pitch-tilt. Tilt perception responded sluggishly to linear acceleration, typically reaching a peak after 10-30 s. Tilt perception also displayed an adaptation phenomenon. Adaptation was manifested as a per-stimulus decline in perceived tilt during prolonged stimulation and a reversal aftereffect upon return to zero acceleration (i.e., recentering the subject). We conclude that otolith inputs can produce tilt perception in the absence of canal stimulation, and that this perception is subject to an adaptation phenomenon and low-pass filtering of its otolith input.

Acceleration↗

PubMed2006

Differences in academic and executive function domains among children with ADHD Predominantly Inattentive and Combined Types.

Differences between the subtypes of Attention Deficit Hyperactivity Disorder (ADHD) continue to have a place in the clinical and research literature. The purpose of this study was to examine differences specific to academic and executive function deficits in a sample of 40 children, aged 9-15 years. Although there was a tendency for the Predominantly Inattentive (PI) group to evidence lower performance on calculation and written expression tasks, these differences dissipated when IQ was included as a covariate. For executive function domains of set shifting, interference, inhibition, and planning, differences emerged for interference, but only when girls were excluded from the analysis and no control for IQ was made. For parent ratings of executive function, expected differences were found on the Inhibit scale with the Combined Type (CT) group evidencing greater problems in this area; this difference remained even when girls were excluded and IQ was controlled. Implications for research and practice are presented.

Adolescent↗

PubMed2004

Effects of acute and repeated administration of a cholinesterase inhibitor on timing behaviour.

It has been hypothesised that a leftward shift in the response distribution obtained in the peak interval (PI) procedure is a characteristic of cognitive enhancement in which mental processes are speeded. Metrifonate, a cholinesterase inhibitor with reported cognitive enhancing properties in many animal models of learning and memory, was tested in the PI procedure. Acute administration of 3 and 60 mg/kg but not 1 and 30 mg/kg in fully trained rats shifted the response distribution to the right, whereas subchronic administration of 10, 30 or 50 mg/kg during task acquisition had no effect on timing behaviour. On the basis of the present data, it can be concluded that the effects of a cognition enhancer in the PI procedure cannot be predicted from the scalar expectancy theory (SET). Furthermore, SET does not appear to be an appropriate tool for analysing the acquisition of timing behaviour.

Animals↗

PubMed2005

Time-intensity trading in bilateral congenital aural atresia patients.

In an effort to examine the rules by which information of bilaterally applied bone-conducted signals arising from interaural time differences (ITD) and interaural intensity differences (IID) is combined, data were measured for continuous 500 Hz narrow band noise at 65-70 dB HL in 11 patients with bilateral congenital aural atresia. Time-intensity trading functions were obtained by shifting the sound image towards one side using ITD, and shifting back to a centered sound image by varying the IID in the same ear (auditory midline task). ITD values were varied from -600 to +600 micros at 200 micros steps, where negative values indicate delays to the right ear. The results indicate that time-intensity trading is present in patients with bilateral aural atresia. The gross response properties of time-intensity trading in response to bone-conducted signals were comparable in patients with bilateral aural atresia and normal-hearing subjects, though there was a larger inter-subject variability and higher discrimination thresholds across IIDs in the atresia group. These results suggest that the mature auditory brainstem has a potential to employ binaural cues later in life, although to a restricted degree. A binaural fitting of a bone-conducted hearing aid might optimize binaural hearing and improve sound lateralization, and we recommend now systematically bilateral fitting in aural atresia patients.

Acoustic Stimulation↗

PubMed2001

Exploration of hemispheric specialization and lexico-semantic processing in unilateral temporal lobe epilepsy with verbal fluency tasks.

Verbal production has been shown to rely on both hemispheres differentially. To determine how lateralized brain lesions affect the generation of isolated words, we evaluated three subject groups: normal controls (n=22), and patients with right (n=23), and left (n=22) non-operated temporal lobe epilepsy (TLE) using three verbal fluency tasks (letter, phonetic, semantic). LTLE patients produced fewer words than controls in the phonetic, letter, semantic conditions, whereas RTLE patients were only impaired in the semantic task. Hence, there would be a hemispheric specialization in language where phonetic processing involves mostly the left temporal lobe and semantic aspects of production involve both temporal lobes. And, in order to study disruption of semantic lexicon involved in supermarket fluency (to name things which can be bought in a supermarket), specific indicators Tröster et al., (1998) [Tröster AI, Fields JA, Testa JA, Paul RH, Blanco CR, Hames KA, Salmon DP, Beatty WW. Cortical and subcortical influences on clustering and switching in the performance of verbal fluency Tasks, Neuropsychologia 1998;36:295-304.] were exploited. Our results indicated that TLE groups made fewer category shifts than controls. Also, RTLE patients used labels more frequently and produced fewer exemplars. Results show the specificity of processing according to cue, and suggest that the semantic fluency deficits due to TLE be primarily due to an alteration of the mental lexicon.

Adult↗

PubMed2000

Amodal completion and localization.

In a three-line vernier acuity task, a central line was localized between two aligned line segments. Accuracy did not improve when the segments formed a unified amodally completed percept. In a two-line vernier acuity task, a line was localized below a target line placed next to a physically segmented flank stimulus. Shifts in mean points of subjective equality suggested that amodally completed segments influenced localization. Previous conflicting findings are explained by a representation that is available early to influence perceived alignment. However, position tuning is poor. This representation may be realized physiologically by interpolation responses between amodally completed segments.

Adult↗