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Results for “Task Shifting”

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PubMed1991

A continuous-flow model for phonatory reaction time.

The purpose of this study was to validate a proposed continuous-flow model of phonatory reaction time by investigating the temporal order of selected laryngeal and neurophysiological events involved in a phonatory reaction time task. Ten normal speakers participated in a phonatory reaction time task. Laryngeal positioning movements prior to vocal fold closure (laryngeal shift) and onset of vocal fold vibration (acoustic onset) were recorded with an electroglottograph. P300 brain potentials were collected simultaneously, and they served as an index of a central process underlying reaction time. The obtained temporal ordering of laryngeal shift, P300, and acoustic onset supported a continuous-flow model of phonatory reaction time. Use of this model might yield information that is more accurate in explaining physiological function and more precise in describing temporal patterning than the serial model.

Adult↗

PubMed1992

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

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

Aged↗

PubMed1990

Asymmetries in hand movement during block design construction.

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

Adult↗

PubMed1990

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

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

Adult↗

PubMed1989

Cortical DC-potentials as electrophysiological correlates of hemispheric dominance of higher cognitive functions.

Cortical activation during cognitive processing was assessed with a new, noninvasive electrophysiological method: Cortical DC-potentials were recorded from frontal, central, temporal and parietal electrode positions on the scalps of 150 normal adult subjects while they performed cognitive tasks involving language, calculation, music and spatial vision. During the 10-s registration period, shifts in DC-potentials were analyzed with reference to a baseline 3-s preperiod. 15-30 trials were averaged. A lateralized preponderance of negativity by more than 3 microV was used as the criterion of hemispheric dominance. Language tasks caused left-sided lateralization in 76% of the right-handers (n = 80), bilaterally equal surface negativity in 15% and right-sided lateralization in 9%. During the same tasks, 22% of the left-handers (n = 45) had right-sided lateralization. Calculation tasks produced left-sided lateralization in 65% of the right-handers and left-handers. Music tasks caused more right-sided (53%) than left-sided (39%) lateralization dependent on musical training. Visuospatial processing yielded a right temporoparietal lateralization in 77%.

Adolescent↗

PubMedDate not supplied

Event-related potential correlates of non-motor anticipation.

A slow negative shift called "stimulus-preceding negativity" (SPN) has been observed preceding feedback. The aim of the present study is to investigate whether the SPN is related to perceptual or conceptual anticipation. Event-related potentials (ERPs) were recorded in an S1-S2-S3 sequence with intervals of 3 s. S1 was an auditory warning signal; the task stimulus presented at S2 consisted of two digits on which subjects (n = 8) performed an arithmetic task. They had to match their solution with a probe stimulus presented at S3. Perceptual anticipation was manipulated by varying the discriminability of S2 (intact vs. degraded). Conceptual anticipation was manipulated by varying the amount of information processing required at S2 (easy vs. difficult arithmetic). Motor preparation was varied by requiring a speeded versus a delayed response. No negativity was found before the task stimulus (S2), whereas the probe stimulus (S3) was always preceded by a negative shift. The amplitude of this negative shift was larger under the speed than under the delayed instruction. Its amplitude showed a left-hemisphere preponderance and was larger for the difficult than for the easy condition. ERPs preceding task stimuli seem to reflect functionally different processes from ERPs preceding probe and feedback stimuli. The difference is explained in terms of motivational factors that come into play with feedback and probably play a role in the anticipation of the probe stimulus.

Acoustic Stimulation↗

PubMed1992

How fast should the night shift rotate? A rejoinder.

The argument for greater use of permanent night shift does not match the three times greater use of rotating three-shift systems in Britain. Studies of industrial production show very slight differences between output on different shifts, unlike laboratory studies, suggesting that it is almost impossible to reproduce the practice, motivation, and real consequences of work in laboratory settings. People who prefer permanent night shift often prefer to avoid management, and few managements welcome this; or have important tasks to perform at home in the day-time. Some studies of adaptation have defined inversion of temperature curves poorly, and most night-workers never completely adapt. Social flexibility, which has been the main attraction of rapidly rotating shifts, can be reproduced on permanent night shifts, but then loses the possibility of adaptation.

Circadian Rhythm↗

PubMed1992

Visuospatial attention in dementia of the Alzheimer type.

Cue-directed shifts of spatial attention were examined for a letter-discrimination task in 15 patients with mild to moderate dementia of the Alzheimer type (DAT) and 15 healthy, age-matched controls. Spatial cues were valid, invalid or neutral in indicating probable target location and were presented either centrally at fixation or peripherally 6.7 degrees to the left or right of fixation. Stimulus-onset asynchrony (SOA) between cue and target was varied between 200 ms and 2000 ms. Reaction time (RT) benefits conferred by valid cues did not differ between the DAT group and the controls. However, RT costs incurred by invalid cues were significantly greater in the DAT group than in the control group. Group differences in RT costs plus benefits occurred at short SOAs (less than 500 ms) for peripheral cues and at long SOAs (greater than 500 ms) for central cues. Reaction time costs plus benefits were correlated with right-left asymmetry in resting levels of cerebral glucose metabolism in the superior parietal lobe for DAT patients but not for controls. The results indicate that focusing of attention to spatial location is intact in early DAT, whereas the disengagement of visuospatial attention is impaired. Automatic attention shifts elicited by peripheral cues reveal abnormalities earlier than attention shifts initiated 'effortfully' by central cues. Intact focusing and impaired disengagement of visuospatial attention may be linked to dysfunction in early DAT of cortico-cortical networks linking the posterior parietal and frontal lobes.

Aged↗

PubMed1985

Hemispheric advantages and shifts of laterality differences in visual and tactual modalities.

Laterality and practice effects were examined on two visual and two tactual-kinesthetic tasks in 32 right-handed males. There was an overall RVF superiority in accuracy of discrimination of tachistoscopically presented pairs of lines and pairs of squares of dots, and a left-hand advantage in RT in judging tactually presented lines. For the visual and tactual length tasks, these advantages were present only on the first block of trials in each half of the experiment; there were no differences in the second block in each half. These shifts in laterality are discussed in terms of development of a left-hemisphere descriptive set for length.

Adult↗

PubMedDate not supplied

Allocation of time in three academic specialties.

A survey was done to: 1) characterize the allocation and distribution of time by tenure track emergency physicians, and 2) compare the time distribution of emergency physicians to two other academic disciplines. All emergency medicine residency programs were surveyed by telephone to determine if faculty were eligible for tenure and if tenure was available, how many hours per week were spent on clinical duties, research, and administrative tasks. Similar information was compiled from cardiology and orthopedic surgery faculty at the same universities. Data from the survey revealed that a tenure track assistant professor spends 23 hours (46%) working clinical shifts in the emergency department; 11 hours (20%) doing research and 18 hours (34%) in administrative tasks. In contrast, cardiologists spend significantly more time in clinical duties (32 hours) and research (18 hours). However, cardiologists spend significantly less time in administrative duties (10 hours). Data for orthopedic surgeons show a similar pattern. Distributions within each academic discipline were also analyzed and a significant difference in research time was found between four tenure track emergency medicine programs and the other eighteen. Data from this survey may help academic emergency physicians evaluate how they are allocating their time in comparison to other busy clinical specialties.

Cardiology↗

PubMed1988

Apparent shift in visual field preference after unilateral stroke.

Patients with either a left- or a right-hemisphere stroke lesion scored higher in tasks of word-picture matching and of nonverbal shape matching when information was presented tachistoscopically (120 msec) to the visual field (VF) projecting to their undamaged hemisphere. Left-hemisphere stroke patients (n = 13) were dissociated from right-hemisphere stroke patients (n = 15) by low word recognition from memory and by low right VF but nearly normal left VF accuracy in word-picture matching or shape matching; the former appeared to rely upon processing of word meaning by the right hemisphere. In contrast, right-stroke patients had higher right than left VF scores in both tasks, and their discrimination of nonverbal shapes via the right VF was not different from that of controls (n = 15). Preferred processing by the VF projecting to the undamaged hemisphere appeared as a shift in perceptual asymmetry but may indicate, in support of a "direct access" model, that each hemisphere responds more or less efficiently to word and to nonverbal shape discriminations.

Aged↗

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↗

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↗

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↗

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↗

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↗