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Results for “Task Shifting”

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PubMed2006

Dependence of the cognitive set on the involvement of the ventral and dorsal visual systems in cognitive activity.

Measures of the stability of a non-verbal visual set were compared in healthy human subjects in three series of experiments: 1) controls, in which a pair of set-forming stimuli (images of circles) were presented; 2) in the context of a test with a non-verbal set, subjects were presented with an additional task consisting of recognition of pseudowords (words); and 3) as before, but the additional task consisted of identifying the position of a target stimulus in a matrix of letters. There was a significant decrease in the stability (rigidity) of the non-verbal set on introduction of the additional task consisting of identifying the spatial position of a target stimulus; conversely, there was an increase in rigidity when the task consisted of recognizing the quality of a stimulus. Coherence analysis of cortical potentials in the alpha range showed that changes in the spatial organization of cortical electrical activity were significantly different, depending on the nature of the additional task: when the additional task involved recognition of a verbal stimulus, coherence connections were strengthened in the frontal-temporal-parietal areas of the right hemisphere; presentation in the context of a visuospatial task resulted in greater changes being observed in the anterior areas of the right hemisphere. It is suggested that the successful performance of mental functions requiring relatively rapid shifts in unconscious sets on changes in situation occurs in conditions of alternation of different types of cognitive tasks when cortical processing of visual information is mediated predominantly by one of the visual systems - either the ventral ("what?") or the dorsal ("where?") and, correspondingly, with the involvement of the anterior and posterior cortical selective attention systems.

Adult↗

PubMed2006

A heart rate analysis of developmental change in feedback processing and rule shifting from childhood to early adulthood.

Over the course of development, the ability to switch between different tasks on the basis of feedback cues increases profoundly, but the role of performance monitoring remains unclear. Heart rate indexes can provide critical information about how individuals monitor feedback cues indicating that performance should be adjusted. In this study, children of three age groups (8-10, 12-14, and 16-18 years) performed a rule change task in which sorting rules needed to be detected following positive or negative feedback. The number of perseverative errors was lower for 16- to 18-year-olds than for 8- to 10-year-olds, and 12- to 14-year-olds performed at an intermediate level. Consistent with previous findings, heart rate slowed following feedback indicating a rule change, and the magnitude of slowing was similar for all age groups. Thus, 8- to 10-year-olds are already able to analyze feedback cues. In contrast, 12- to 14-year-olds and 16- to 18-year-olds, but not 8- to 10-year-olds, showed heart rate slowing following performance errors, suggesting that with age children are increasingly able to monitor their performance online. Performance monitoring may therefore be an important contributor to set-shifting ability.

Adolescent↗

PubMed2000

A mathematical programming approach for scheduling physicians in the emergency room.

Preparing a schedule for physicians in the emergency room is a complex task, which requires taking into account a large number of (often conflicting) rules, related to various aspects: limits on the number of consecutive shifts or weekly hours, special rules for night shifts and weekends, seniority rules, vacation periods, individual preferences,... In this paper, we present a mathematical programming approach to facilitate this task. The approach models the situation in a major hospital of the Montreal region (approximately 20 physicians are members of the working staff). We show that the approach can significantly reduce the time and the effort required to construct a six-month schedule. A human expert, member of the working staff, typically requires a whole dedicated week to perform this task, with the help of a spreadsheet. With our approach, a schedule can be completed in less than one day. Our approach also generates better schedules than those produced by the expert, because it can take into account simultaneously more rules than any human expert can do.

Emergency Service, Hospital↗

PubMed1977

Event-related brain potentials in selective response.

Event-related potentials were recorded during performance of a simple reaction task and two selective response tasks differing in the intensity of the non-key stimulus. Known differences in reaction between these tasks were confirmed, but there were no corresponding differences in amplitude of the slow potential shift which develops in the EEG in anticipation of the imperative signal. Since this anticipatory potential is not affected by event uncertainty, it seems to be related to motor preparation rather than to expectancy. Performance differences between simple and selective response tasks appear to depend not upon differential preparation, but upon selective processing of the imperative signal, which is reflected in the N120 component of the visual evoked response to that signal.

Brain↗

PubMed1996

Psychophysiological stress effects from the combination of night-shift work and noise.

The influence of night-shift work and noise on arousal and stress reactions have, to date, been investigated separately. The aim of this study was to compare their psychophysiological effects in combination. Twenty-four male student subjects continuously performed ten hours of visual display tasks per 24 h under highly controlled conditions for either five consecutive day or night shifts, followed by two days of rest. Each group worked in conditions of simulated traffic noise, at either 80 or 50 dB(A). Urinary catecholamines, electrodermal activity, heart rate, and ratings of mood and physical symptoms were recorded continuously or at specified intervals. Catecholamine excretion rates, autonomic reactions, reaction times, and ratings of subjective alertness showed changes typical for night-shift work. No main effects of noise were found, but significant interactions between the two experimental factors reflected differential actions of noise dependent on the type of shift. The results favor a multiple-arousal concept. Night-shift work primarily influences general arousal, while noise affects both general and goal-directed arousal, dependent on the presentation during day or night shift.

Adult↗

PubMed1979

Effects of exercise in the heat on body fluid distribution.

Experimental findings as to body fluid shifts during exercise appear to be greatly influenced by the mode of exercise (bicycle ergometer, treadmill, etc) and by the state of subject hydration. Endurance training has been shown to increase resting plasma (blood) volume. Also, endurance training results in modification of vascular volume dynamics during exercise, i.e. for a set task, plasma volume becomes stabilized. In the untrained individual, heat exposure exaggerates body fluid shifts during exercise. With training, stability of vascular volume is attained during heat exposure, but maximum protective responses towards exercise in heat is only gained upon heat acclimatization. Two items benefit the individual: an increase in the capacity of the sweat mechanism and an expansion of plasma volume. Benefits of training as to body fluid shifts are probably a result of metabolic changes within the active muscle mass.

Acclimatization↗

PubMed1996

Basic features of phasic activation for reaching in vertical planes.

The purpose of this study was to fully characterize the timing and intensity of the phasic portion of the electromyographic (EMG) waveform for reaching movements in vertical planes. Electromyographic activity was simultaneously recorded from nine superficial elbow and/or shoulder muscles while human subjects made rapid arm movements. Hand paths comprised 20 directions in a sagittal plane and 20 directions in a frontal plane. In order to focus on the more phasic aspects of muscle activation, estimates of postural EMG activity were subtracted from the EMG traces recorded during rapid reaches. These postural estimates were obtained from activity recorded during very slow reaches to the same targets. After subtraction of this postural activity, agonist or antagonist burst patterns were often observed in the phasic EMG traces. For nearly all muscles and all subjects, the relation between phasic EMG intensity and movement direction was a function with multiple peaks. For all muscles, the timing of phasic EMG bursts varied as a function of movement direction: the data from each muscle exhibited a gradual temporal shift of activity over a certain range of directions. This gradual temporal shift has no obvious correspondence to the mechanical requirements of the task and might represent a neuromuscular control strategy in which burst timing contributes to the specification of movement direction.

Adult↗

PubMed1985

Auditory laterality in depression: relation to circadian patterns and EEG sleep.

Unmedicated endogenous (ED) and nonendogenous depressed (ND) patients were tested in the morning and evening on a dichotic click detection task and a dichotic consonant-vowel (CV) discrimination task. The ED and ND groups showed a morning to evening shift in lateral asymmetry for detecting dichotic clicks, which was opposite in direction to that previously seen for normal subjects. In contrast, there was no morning to evening shift in asymmetry for dichotic CV discrimination. Lateral asymmetry for dichotic click detection was significantly correlated with EEG sleep characteristics (sleep latency, REM period latency, REM time) and ratings of diurnal variation on the Hamilton Depression Scale. A reversal of the normal lateral asymmetry in the morning was associated with lengthened sleep latencies and with clinical ratings of diurnal variation.

Adult↗

PubMed1995

Electrophysiologic correlates of visuo-spatial attention shift.

We investigated neurophysiologic correlates of shifting visual attention across the visual field. Event-related potentials (ERPs) were recorded in 12 normal subjects during a visual discrimination task in which target stimuli were presented at a predictable or unpredictable location in the eccentric visual field. Subjects were obliged to shift their attention from the expected site to the unpredictable site immediately after the presentation of shifted stimuli in order to detect the change of stimulus attributes. Shifted stimuli modulated the N1 component (130-200 msec), producing a larger amplitude at the posterior temporal site contralateral to the stimulus field and a smaller amplitude over the ipsilateral hemisphere. Furthermore, shifted stimuli uniquely evoked a positive ERP component with a latency of 200-300 msec, which distributed broadly over the skull maximally at the frontal and central electrode sites. Both the negative and positive components changed in amplitude as a function of shift distance and direction. These results suggest that modulations of the negative and positive deflections reflect the shift of covert visuo-spatial attention and that right hemispheric dominance does not exist at least in the early stage of shifting spatial attention.

Adult↗

PubMed1977

A dose ratio comparison of the interaction between morphine and cyclazocine with naloxone in rhesus monkeys on the shock titration task.

Dose-response curves for morphine (0.5-20 mg/kg) were obtained in 4 rhesus monkeys performing the discrete trials shock titration task. Naloxone (5-500 microgram/kg) uniformly produced a dose dependent, parallel shift of the morphine dose-response curves to right. Plots for the 4 animals of the Log (dose ratio--1) versus --Log (naloxone) revealed that the line had a slope of -0.96. The value of the pA2 was 7.2. Similar experiments were carried out in two rhesus monkeys using cyclazocine. Naloxone (50-1000 microgram) similarly produced a rightward dose dependent, parallel shift of the cyclazocine dose response curves. Unlike the results obtained with morphine, the pA2 for naloxone obtained with cyclazocine was 6.3 and the slope of the dose ratio line was -1.6.

Animals↗

PubMed1989

Developmental trends in the understanding of perceptual adaptation.

In the first of three studies, kindergartners, third graders, and sixth graders were questioned to determine whether they comprehend five types of perceptual adaptation or contrast effects. The results indicated little consistency among kindergartners, but there were strong improvements by the third-grade level, and at the sixth-grade level almost all of the children were showing perfect performance, demonstrating comprehension of the five forms of perceptual adaptation. In the second and third studies, children and adults were placed in a situation in which adaptation to temperature and weight could occur, and they were asked to predict subsequent perceptions. Correct performance in these studies generally occurred at later ages than in Study 1 with even college students showing incorrect performance in some cases. However, the age trends shifted quite markedly depending upon the nature and structure of the task. The results were consistent with a theory stressing the relation of early formed schemas in the form of memory traces of experiences to later appearing and more abstract schemas. The results show the importance of studying older children when considering developing theories of mind.

Adaptation, Ocular↗

PubMed1991

Pentylenetetrazole can induce a conditioned place preference.

Thirty-two male Sprague-Dawley rats were randomly selected into 4 groups (n = 8/group) and conditioned in a standard place preference task. The groups differed in the dose of pentylenetetrazole (PTZ) administered prior to conditioning trials. With respect to the three treatment groups, placement into the, initially, nonpreferred side of the CPP apparatus was preceded by injections of 5.6, 10, or 17.8 mg/kg PTZ. The control group was injected with hypertonic saline (1.8% w/v) on the rats', initially, nonpreferred sides and isotonic saline (0.9% w/v) on their preferred sides, to control for any irritative effects of PTZ injections in the treatment groups. Six pairs of drug-saline conditioning trials were conducted with each subject. PTZ produced a dose-dependent increase in the amount of time spent in the drug-associated environment. Saline control subjects' preference scores did not change over the course of the study. These data suggest that PTZ is not aversive in the place learning task; more importantly, the data suggest that a dose-dependent shift in the hedonic valences associated with environmental stimuli can occur when these stimuli are repeatedly paired with PTZ administration. The data are discussed in terms of the stimulus properties of PTZ and the hypothetical "anxiety" state the drug may produce.

Animals↗

PubMed2006

More attention must be paid: the neurobiology of attentional effort.

Increases in attentional effort are defined as the motivated activation of attentional systems in response to detrimental challenges on attentional performance, such as the presentation of distractors, prolonged time-on-task, changing target stimulus characteristics and stimulus presentation parameters, circadian phase shifts, stress or sickness. Increases in attentional effort are motivated by the expected performance outcome; in the absence of such motivation, attentional performance continues to decline or may cease altogether. The beneficial effects of increased attentional effort are due in part to the activation of top-down mechanisms that act to optimize input detection and processing, thereby stabilizing or recovering attentional performance in response to challenges. Following a description of the psychological construct "attentional effort", evidence is reviewed indicating that increases in the activity of cortical cholinergic inputs represent a major component of the neuronal circuitry mediating increases in attentional effort. A neuronal model describes how error detection and reward loss, indicating declining performance, are integrated with motivational mechanisms on the basis of neuronal circuits between prefrontal/anterior cingulate and mesolimbic regions. The cortical cholinergic input system is activated by projections of mesolimbic structures to the basal forebrain cholinergic system. In prefrontal regions, increases in cholinergic activity are hypothesized to contribute to the activation of the anterior attention system and associated executive functions, particularly the top-down optimization of input processing in sensory regions. Moreover, and influenced in part by prefrontal projections to the basal forebrain, increases in cholinergic activity in sensory and other posterior cortical regions contribute directly to the modification of receptive field properties or the suppression of contextual information and, therefore, to the mediation of top-down effects. The definition of attentional effort as a cognitive incentive, and the description of a neuronal circuitry model that integrates brain systems involved in performance monitoring, the processing of incentives, activation of attention systems and modulation of input functions, suggest that 'attentional effort' represents a viable construct for cognitive neuroscience research.

Animals↗

PubMed2006

Horizontal and vertical effects of eye-position on sound localization.

The effect of gaze direction on the localization of sound sources was investigated in the azimuthal and elevational dimension using a pointing task. In both dimensions, eccentric eye-position induced a significant shift in sound localization that was opposite to the direction of eccentricity. This finding is in accordance with the view that the azimuthal and elevational components of the auditory spatial information are processed in common neural substrates.

Acoustic Stimulation↗

PubMed2004

Temporal structure of the apparent motion perception: a magnetoencephalographic study.

Humans perceive motion when numerous small dots pattern is followed by one of the same pattern but with all the dots shifted a little in one direction. When the amount of shift exceeds a level humans no more perceive motion even though physical visual information does not change. Using this stimulus, we addressed to elucidate the temporal structure of the neural activity related to this apparent motion perception. The magnetic responses to the random-dot patterns with various amounts of shift were measured while the subjects were performing a direction discrimination task. A significant magnetic response amplitude change occurred with three distinct peaks when the response inducing apparent motion was compared with those inducing no motion without change in the response latencies. The major difference occurred at about 110, 140, 210 ms after the stimulus onset. The response origin was always within the occipitotemporal area. The results indicate that the neural activity for the perception of apparent motion can be measured by MEG that occur at least 110 ms after the stimulus onset possibly in the human MT+. Three distinct peaks in the response difference may represent the sequential multiple neural process proposed theoretically though further study is necessary to prove.

Adult↗

PubMed2001

Effect of gaze direction on sound localization in rear space.

The effect of eccentric eye position on the localization of sound in rear space was investigated, using a two-alternative forced-choice method in combination with a visual fixation task. The azimuthal position of the rear sound was perceived as shifted slightly (mean 1.2 degrees ) to the left of the subjects' median plane when fixation was 30 degrees to the right, or to the right when fixation was 30 degrees to the left. Combined with previous studies on localization in frontal space, this finding suggests that eye-position signals influence processing of binaural, but not monaural spectral, cues for directional hearing.

Acoustic Stimulation↗

PubMed1999

Dissociating beliefs about heart rates and actual heart rates in patients with cardiac pacemakers.

Performance on heartbeat counting tasks is usually interpreted in terms of cardiac sensitivity. We tested the hypothesis that heartbeat counting is influenced by beliefs about heart rates by dissociating beliefs about heart rates and actual heart rates. In a within-subjects design, heart rates of 50 patients with cardiac pacemakers were set to a low (50 bpm), medium (75 bpm), or high (110 bpm) pacing rate unknown to the patients via remote control while they performed a heartbeat tracking task. Results showed that patients' heartbeat counting did not follow the shifts in their actual heart rates adequately, although their overall performance was comparable to that of young and healthy control participants. As a result, tracking scores decreased significantly in the high pacing rate condition where beliefs about heart rates and actual heart rates were most extremely dissociated. The findings suggest that tracking scores reflect beliefs about heart rates rather than cardiac sensitivity.

Adult↗

PubMed2004

[Doctor and death].

Doctors are instilled with the need to avert and repress death. By virtue of their profession, death is considered the enemy, their mortal enemy. In modern-day hospitals in particular there is a tendency to reduce the mystery of death to a biological and technical algorithm. A critical revision of fundamental medical conduct is underway as a compensatory countercurrent to this age-old way of thinking and acting. This shift in attitudes involves a humane concept of the physician. His task is not limited to healing and reconstruction, but sometimes merely requires discriminatory restriction to palliation and accompaniment. Ever more physicians are becoming aware of the fact that they are equally responsible for the quality of dying. In coping with death, ethical imperatives are effectively juxtaposed against technical ones. Educational deficits relating to care of the terminally ill and dying have been recognized and are being rectified. This major ideational revision has led to concrete signs of turnaround which are blazing the trail toward more humane and dignified dying: palliation, adapted in accordance with modern science, is experiencing a renaissance. The essential features of a comprehensive palliative therapy are outlined. Assistance during dying (accompanying the dying, passive euthanasia) is contrasted with assistance to die (active euthanasia).

Attitude to Death↗