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Results for “Task Shifting”

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At least 199 records · Page 11Linked to original sources

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↗

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↗

PubMed1987

Near vision stress: vergence adaptation and accommodative fatigue.

Changes in the visual system following prolonged near work were investigated. Fifteen young, normal subjects undertook a severe, two hour long, binocular near visual task at 20 cm without any breaks. Fusional stress was assessed by near 'phoria change. Refractive change was measured with an autorefractometer to investigate whether transient myopia occurred and its subsequent recovery. The near task caused vergence adaptation which was primarily due to the fusional stress of the task (accounting for 67% of its variance). The 'phoria change was to a lesser extent (40%) dependent on the accommodative "stress" of the task. Fatigue of the accommodative system resulted in increased accommodative innervation to maintain the same accurate response. Increased innervation can continue after the task on subsequent distance viewing, resulting in transient myopia (mean 0.29 DS). This transient myopia was found to be due to a transient regression of the far point towards the subject's tonic accommodation level. This can be accounted for by a shift of the tonic level as well as an increased bias towards the pre-task tonic level.

Accommodation, Ocular↗

PubMed1989

Lingual vibrotactile threshold shift during magnitude-estimation scaling: effects on magnitude-estimation responses and scaling behavior.

The purpose of the present study was to determine if lingual vibrotactile threshold shifts occurred during magnitude-estimation scaling of suprathreshold stimuli presented to the dorsal surface of the tongue. Possible relationships of the lingual vibrotactile threshold shifts to suprathreshold stimulus intensity, magnitude-estimation responses, and overall scaling behavior were explored. A single group of 24 subjects with an age range of 18 to 22 years participated in this study. Each subject performed two magnitude-estimation tasks. In one of the tasks, threshold of sensitivity was determined after every suprathreshold numerical response of the subject. If a threshold shift was recorded, threshold was allowed to return to the pretest baseline level before continuing to the next suprathreshold stimulus presentation. The results showed that threshold shift did occur during lingual vibrotactile magnitude-estimation scaling, and that it was related to suprathreshold stimulus intensity. The results also showed that the numerical magnitude-estimation responses of the subjects were different for the two scaling tasks. Overall scaling behavior of the subjects in the form of power-function exponents was not different for the two tasks.

Adolescent↗

PubMed1989

Vibrotactile threshold shift during magnitude-estimation scaling on the hand: effects on magnitude-estimation responses and scaling behavior.

The purpose of the present study was to determine whether threshold shifts occurred during magnitude-estimation scaling of suprathreshold stimuli presented to the thenar eminence of the right hand. Possible relationships of the vibrotactile threshold shifts to suprathreshold stimulus intensity, magnitude-estimation responses, and over-all scaling behavior were explored. A single group of 14 subjects whose ages ranged from 18 to 22 yr. participated. Each subject performed two magnitude-estimation tasks. In one of the tasks threshold of sensitivity was determined after every suprathreshold numerical response of the subject. If a threshold shift was recorded, threshold was allowed to return to pretest baseline level before continuation to the next suprathreshold stimulus presentation. Analysis showed that threshold shift did occur during vibrotactile magnitude-estimation scaling on the hand and that it was related to suprathreshold stimulus intensity. Results also showed that the subjects' numerical magnitude-estimation responses and over-all scaling behavior in the form of power function exponents were not statistically different for the two scaling tasks.

Adolescent↗

PubMedDate not supplied

[Interhemispheric EEG-asymmetry in 5--7-year-old children].

Interhemispheric asymmetry (IHA) of the theta-rhythm in the frontal, central, parietal, occipital and temporal cortical areas was studied in 5-7 years old children. The children performed visual-spatial (drawing mosaic) and verbal (reciting, associative experiment) tasks. IHA was also estimated in the state of rest, when a child doesn't move with his eyes open. It is found that in the state of rest the theta-activity is predominant in the right hemisphere in all cortical areas. During performance of visual spatial tasks this correlation does not change significantly. During verbal activity IHA values shift towards the left hemisphere. These changes are mostly pronounced in the frontal and temporal cortical areas where the left-side asymmetry of the theta-activity is revealed. In the central areas no significant IHA is recorded; in the parietal and occipital areas the theta-rhythm is predominant in the right hemisphere. The data obtained suggest a functional specialization of the hemispheres in 5-7 years old children. The left hemisphere is more active during verbal activity whereas the right one plays the leading role both during visual-spatial activity and in the organization of the rest state.

Brain Mapping↗

PubMed1992

Cortical DC potential shifts accompanying auditory and visual short-term memory.

Negative DC potential shifts appeared over the scalp during the performance of verbal and non-verbal short-term memory tasks. Three items were successively presented (presentation of memory items) and then had to be retained in memory for 3 sec (memory retention) before being compared to a probe which was either a member (in set) or not a member (out of set) of the memory set. Verbal items (the digits "1" through "9") were tested in the auditory and visual modality and non-verbal items (musical notes) were tested in the auditory modality. Stimulus modality had a significant effect on DC potential shifts during both presentation of memory items and memory retention. There was a sustained negative shift during these periods which was larger over frontal regions with auditory than with visual material whereas the negative shift was larger over posterior temporal regions with visual than with auditory material. Out of 21 subjects who participated in the study, 9 reported the use of visual images in the auditory task, 5 used subvocal auditory rehearsal in the visual task and 7 used imagery concordant with the stimulus modality being memorized. These different strategies had a significant effect on the amplitudes and distribution of the DC potential shifts. The speed of response affected the amplitude of the DC potential shifts in the frontal regions, being larger with fast RTs than with slow RTs but only when verbal items were being processed. These results indicate that stimulus modality, modality of mental imagery, and speed of scanning of the memory store affect DC potential shifts during a 3 sec period of memory retention.

Acoustic Stimulation↗

PubMed1990

Gaze control in the cat: studies and modeling of the coupling between orienting eye and head movements in different behavioral tasks.

1. Orienting movements, consisting of coordinated eye and head displacements, direct the visual axis to the source of a sensory stimulus. A recent hypothesis suggests that the CNS may control gaze position (gaze = eye-relative-to-space = eye-relative-to-head + head-relative-to-space) by the use of a feedback circuit wherein an internally derived representation of gaze motor error drives both eye and head premotor circuits. In this paper we examine the effect of behavioral task on the individual and summed trajectories of horizontal eye- and head-orienting movements to gain more insight into how the eyes and head are coupled and controlled in different behavioral situations. 2. Cats whose heads were either restrained (head-fixed) or unrestrained (head-free) were trained to make orienting movements of any desired amplitude in a simple cat-and-mouse game we call the barrier paradigm. A rectangular opaque barrier was placed in front of the hungry animal who either oriented to a food target that was visible to one side of the barrier or oriented to a location on an edge of the barrier where it predicted the target would reappear from behind the barrier. 3. The dynamics (e.g., maximum velocity) and duration of eye- and head-orienting movements were affected by the task. Saccadic eye movements (head-fixed) elicited by the visible target attained greater velocity and had shorter durations than comparable amplitude saccades directed toward the predicted target. A similar observation has been made in human and monkey. In addition, when the head was unrestrained both the eye and head movements (and therefore gaze movements) were faster and shorter in the visible- compared with the predicted-target conditions. Nevertheless, the relative contributions of the eye and head to the overall gaze displacement remained task independent: i.e., the distance traveled by the eye and head movements was determined by the size of the gaze shift only. This relationship was maintained because the velocities of the eye and head movements covaried in the different behavioral situations. Gaze-velocity profiles also had characteristic shapes that were dependent on task. In the predicted-target condition these profiles tended to have flattened peaks, whereas when the target was visible the peaks were sharper. 4. Presentation of a visual cue (e.g., reappearance of food target) immediately before (less than 50 ms) the onset of a gaze shift to a predicted target triggered a midflight increase in first the eye- and, after approximately 20 ms, the head-movement velocity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1989

Effect of starting position on reproduction of movement: further evidence of interference between location and distance information.

Two experiments done with a short-term memory paradigm examined the influence of shifts in the starting position on the reproduction of kinesthetic location (Exp. 1) and on distance cues (Exp. 2). We assessed possible causes of the systematic pattern of undershooting and overshooting as related to the shift in the starting position. In each experiment, two groups of 10 students were given 25 trials, and each had criterion and reproduction tasks involving linear-positioning movements with a 10-sec. retention interval. Each experiment had two independent variables, the group of subjects and the shift in the starting position. The two groups differed in the possible sources of information, the distance moved (Exp. 1) or the end-location (Exp. 2), which were assumed to cause undershooting and overshooting during reproduction. Analysis showed that the information about the distance moved may produce undershooting and overshooting in reproduction of the end-location (Exp. 2). Also, the information about the end-location may produce undershooting and overshooting in reproduction of the distance moved (Exp. 2). The findings were further evidence of interference between location and distance cues in motor short-term memory.

Cues↗

PubMed1991

Attentional focussing and spatial stimulus-response compatibility.

The relative functional significance of attention shifts and attentional zooming for the coding of stimulus position in spatial compatibility tasks is demonstrated by proposing and testing experimentally a tentative explanation of the absence of a Simon effect in Experiment 3 of Umiltà and Liotti (1987). It is assumed that the neutral point of the spatial frame of reference for coding spatial position is at the position where attention is focussed immediately before exposition of the stimulus pattern. If a stimulus pattern is exposed to the right or the left of this position a spatial compatibility effect can be observed when the stimulus-response pairing is incompatible. Generalizing from this, one can say that a spatial compatibility effect will be observed if the last step in attentional focussing of the stimulus attribute specifying the response is a horizontal or a vertical attention shift. If the last step in focussing is attentional zooming (change in the representational level attended to), the stimulus pattern is localized at the horizontal and the vertical positions where the last attention shift had positioned the focus. In this case the spatial code is neutral on these dimensions and so no spatial compatibility effect should result. To test this model we conducted two experiments. Experiment 1 replicated the finding of Umiltà and Liotti that there is no Simon effect in the condition with no delay between a positional cue (two small boxes on the left or right of a fixation cross) and the imperative stimulus, whereas in the condition with a delay of 500 ms a Simon effect was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

Reflections on the U.S. Preventive Services Task Force recommendations for screening for hypertension and hypercholesterolemia.

The U.S. Preventive Services Task Force recommendations for screening for hypertension and high blood cholesterol are generally consistent with preexisting national guidelines promulgated by the Joint National Committee for Detection, Evaluation, and Treatment of High Blood Pressure and the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Cholesterol in Adults. While a welcome addition to the armamentarium of the clinician, the Task Force recommendations represent only a partial solution to our current epidemic of blood-pressure- and cholesterol-related cardiovascular disease. A meaningful reduction in society's burden of cardiovascular disease can be achieved only by complementing the Task Force recommendations with community-based mass treatment strategies aimed at shifting the distribution of blood pressure and cholesterol toward a biologically more normal pattern.

Blood Pressure Determination↗

PubMed1992

Saccade programming during short duration fixations: an examination of copy typing, letter detection, and reading.

Three experiments examined saccade programming during short duration fixations between 50 ms and 150 ms. In experiment 1, subjects copy typed text, in experiment 2, subjects read and executed a letter detection task, and in experiment 3, subjects read for comprehension only. Fixation duration had no effect on the size of the departing saccade in the copy typing task; however, saccades leaving short duration fixations were larger than saccades leaving all other fixation durations in the letter detection task and smaller than saccades leaving long fixation durations in the standard reading task. Within Morrison's (1984) model, these results imply, first, that consecutive shifts of attention during a fixation can take different directions and, second, that successive shifts of attention during a fixation support different purposes. Within Fischer's (1986, in press) model, the results imply that the engagement/disengagement of attention and saccade programming do not constitute independent events.

Adult↗

PubMed1985

Lateralized rewarding brain stimulation affects forepaw preference in rats.

Rats trained to reach for food pellets into a narrow tubular feeder consistently prefer to perform this stereotype instrumental movement with either the left or right forepaw. In 16 rats with established handedness electrodes were implanted into both lateral hypothalami. The animals were rewarded by intracranial self stimulation (ICSS, 300 msec, 50 Hz, 20-60 microA) for reaching into a modified feeder for a plastic ball operandum, the movement of which between the bottom and entrance of the feeder was monitored by mechanical contacts. The rats readily continued to reach when ICSS was delivered immediately after the photoelectrically detected reach or after the displacement of the operandum. Most rats learned in a single session to modify the movement when ICSS delivery was made contingent upon holding the operandum between the bottom and entrance of the feeder for 256 or 512 msec. The efficiency of reaching (ratio of successful reaches to all reaches) decreased with increasing holding time; only a few animals were able to master a 1024 msec delay. Reaching was supported by ICSS of either lateral hypothalamus. Whereas in 8 rats the strongly expressed forepaw preference was not changed by lateralized ICSS, in 8 latently ambidextrous animals stimulation of the lateral hypothalamus ipsilateral to the preferred forepaw increased reaching with the normally non-preferred forepaw from 15% to 60%. Stimulation of the lateral hypothalamus contralateral to the preferred forepaw did not change the preference. The preference shift was equally well expressed in simple and difficult versions of the task. It is concluded that lateralization of motivational influences can be reflected in the asymmetry of the neural mechanisms processing the lateralized sensory signals and/or elaborating the lateralized motor output.

Animals↗

PubMed1986

Neurogenesis and gliogenesis in the human brain.

The primary germinal neural epithelium lines the ventricular system of the brain and shows intense mitotic activity. Neuroblasts migrate from a juxtaluminal position to establish neural centres and, when this task is completed, the definitive ependymal epithelial lining of the ventricles develops, shifting the remnants of the germinal epithelium to a subendymal location. The subendymal layer continues to proliferate giving rise to glia in the postnatal brain. Premature arrest of migration of neuroblasts leads to the accumulation of heterotopic nests anywhere along the migratory path. Within such ectopia, neurons may make normal connections or they may remain undifferentiated and later become tumorigenic. The subependymal layer has long been considered the site of original of periventricular gliomas. Some migrating neuroblasts establish secondary germinal centres far removed from the ventricular system. An example of this is the external granular layer of the cerebellum which, in man, persists for the first 6 months of life. Cerebellar neuroblastomas could originate directly from this layer in the neonate, or from remnants of this layer in older individuals.

Animals↗

PubMed1987

Abnormal temporal lobe response in Alzheimer's disease during cognitive processing as measured by 11C-2-deoxy-D-glucose and PET.

Elderly controls and probable Alzheimer's disease patients underwent serial positron emission tomography (PET) studies during a baseline condition and while performing a verbal memory task. For the temporal lobes, all 7 Alzheimer patients demonstrated a relative shift in glucose metabolic rates to the right hemisphere during the memory condition relative to baseline, and 5 of 7 controls showed a shift to the left hemisphere. Baseline absolute regional metabolic rates replicate previous findings and were somewhat less useful than the memory challenge in differentiating patients from controls. These results indicate that a temporal lobe abnormality in Alzheimer's disease is related to memory performance.

Aged↗

PubMed1990

Males as helpers: the role of sons, relatives, and friends.

The informal helping networks of most frail elderly people are dominated by women. Men are also involved in helping older people, although most male caregivers are husbands. This paper examines the contributions of men other than husbands who provide assistance to a sample of community-based elderly people. Data were gathered through personal interviews with elders and their primary helpers at two points in time. Male helpers provide intermittent assistance with occasional tasks but less frequently undertake routine household chores. Some evidence indicates a shift toward female caregivers as the elder's functional capacity decreases over time.

Adult↗

PubMed1992

Expectancy and stimulus frequency: a comparative analysis in rats and humans.

We examined whether expectancy, one of several factors influencing attention, is similarly affected in rats and humans by manipulation of relative stimulus frequency. A two-choice reaction time (RT) task was developed for rats, and an analogous task was used for humans. Errors, RTs, discriminability, and response bias were measured. Both rats and humans shifted their response bias to the more frequent stimulus, with no change in overall discriminability. As stimulus probability or stimulus repetition increased, RTs and errors decreased. These results illustrate the similarity of expectancy in rats and humans. This two-choice RT task for rats can be used in future studies to examine the neuronal mechanisms of expectancy and attention.

Animals↗

PubMed1990

[Robustness of the analytic/holistic processing strategies in various cognitive tasks].

Robustness of the analytic/holistic processing strategies was examined in various cognitive tasks. The tasks in Experiment I were to classify facial patterns and verbal materials of different category structures into two categories. Stimuli were presented either with (thematization condition) or without a theme. Three types of strategies were discerned; consistently-analytic, consistently-holistic and optimal shifting. Experiment II was designed to test their performance in the Kagan type perceptual and memory identification tasks. The results from the two experiments showed that about 30% of the subjects adhered to either analytic or holistic strategy across tasks and experiments. They exhibited responses similar to the reflective and impulsive types. Approximately 40% of the subjects adjusted their strategies according to the task demands.

Acoustic Stimulation↗