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Results for “Task Shifting”

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PubMed1997

Exposure levels and determinants of inhalable dust exposure in bakeries.

The study's objectives were to measure full-shift exposure to inhalable dust in bakeries and define the determinants of full-shift exposure. Inhalable dust was measured gravimetrically. Ninety-six bakery workers, employed in seven different bakeries, participated in the study. Two side-by-side full-shift inhalable dust samples were obtained from each study participant on a single occasion. Samples were collected on 18 days selected at random. During the entire sampling period, bakers were observed and information on 14 different tasks was recorded at 15 min intervals. Other production characteristics were also recorded for each sampling day. These task and production variables were used in statistical modelling to identify significant predictors of exposure. The mean full-shift inhalable dust exposure was 8.2 mg/m3 (range: 0.1-110 mg/m3). A regression model explained 79% of the variability in exposure. The model indicated that tasks such as weighing, pouring and operating dough-brakers and reversible sheeters increased the exposure, while packing, catching and decorating decreased the exposure. Bread and bun production lines were associated with increased full-shift inhalable dust exposure, while cake production and substitution of dusting with the use of divider oil were associated with decreased exposure. Production tasks and characteristics are strong predictors of personal full-shift exposures to flour dust among bakers; these can be altered to reduce exposure levels.

Analysis of Variance↗

PubMed2003

"Phase capture" in the perception of interpolated shape: cue combination and the influence function.

This study was concerned with what stimulus information observers use to judge the shape of simple objects. We used a string of four Gabor patches to define a contour. A fifth, center patch served as a test pattern. The observers' task was to judge the location of the test pattern relative to the contour. The contour was either a straight line, or an arc with positive or negative curvature (the radius of curvature was either 2 or 6 deg). We asked whether phase shifts in the inner or outer pairs of patches distributed along the contour influence the perceived shape. That is, we measured the phase shift influence function. We found that shifting the inner patches of the string by 0.25 cycle results in almost complete phase capture (attraction) at the smallest separation (2 lambda), and the capture effect falls off rapidly with separation. A 0.25 cycle shift of the outer pair of patches has a much smaller effect, in the opposite direction (repulsion). In our experiments, the contour is defined by two cues--the cue provided by the Gabor carrier (the 'feature' cue) and that defined by the Gaussian envelope (the 'envelope' cue). Our phase shift influence function can be thought of as a cue combination task. An ideal observer would weight the cues by the inverse variance of the two cues. The variance in each of these cues predicts the main features of our results quite accurately.

Contrast Sensitivity↗

PubMedDate not supplied

A 14-h night-shift in the control room of a fire brigade.

All 29 operators in the control room of a fire brigade performed test sessions during work and leisure time at 2-h intervals on a day with a 14-h night-shift, a day off and a day with a 10-h morning shift. The test sessions consisted of a visual search choice reaction time test and two Sternberg memory search tests (1 or 5 letters had to be memorized). Furthermore, the operators recorded their oral temperature and their subjective alertness before each test session. The subject also kept a diary of work and sleep times for 14 days. The circadian rhythm of body temperature was hardly changed by a single night-shift. Parallel to the body temperature, the subjective alertness fell significantly during the night-shift reaching a minimum value at 06:00 h. The mean reaction times increased non-significantly at the end of the night-shift and the results of the two Sternberg memory search tests showed no significant trends. The sleep of the operators after the night-shift was on average reduced to 5 hs 34 min. The results of subjective rating of alertness and reaction time test are interpreted as effects of the combined influences of circadian rhythmicity, sleep loss and time on professional task. Most results support the conclusion that a 14-h night-shift without extensive breaks is not acceptable.

Adult↗

PubMed2001

Environmental enrichment enhances recovery of function but exacerbates ischemic cell death.

Prior exposure to brief 'conditioning' episodes of ischemia protects hippocampal CA1 neurons against a subsequent more severe ischemic insult. However, protected cells exhibit abnormal function and as survival times are extended this ischemic tolerance dissipates and cells begin to die. In this study, we sought to determine whether environmental enrichment could alter the above pattern of delayed cell death and functional impairment in a gerbil model of ischemic tolerance. Gerbils received either ischemic preconditioning, 5 min of ischemia without preconditioning or sham surgery. Three days after ischemia, gerbils were placed in either an enriched environment or standard laboratory housing. Open field habituation was assessed 3, 7, 10, 30 and 60 days after ischemia. Subsequently, animals were trained in two versions (win-shift and win-stay) of a T-maze task. Following behavioral testing, extracellular CA1 field potential amplitudes and CA1 cell counts were determined. Initial open field activity was significantly higher in all experimental groups compared to sham animals (P<0.001). By 60 days, enriched ischemic preconditioned and enriched ischemic gerbils were not different than shams whereas non-enriched, ischemic preconditioned and ischemic gerbils continued to have higher activity scores (P<0.05). Preconditioned and enriched ischemic animals learned the win-shift T-maze problem as quickly as shams while non-enriched ischemic gerbils were severely impaired compared with all other groups (P<0.001). Only the sham and enriched preconditioned groups readily acquired the win-stay paradigm. CA1 field potential amplitudes were lower (P<0.05) in ischemic than sham gerbils irrespective of treatment. Surprisingly, CA1 cell counts were significantly lower (P<0.01) in enriched versus non-enriched ischemic preconditioned animals. These data demonstrate that early, intensive intervention after ischemia can improve functional outcome but that this is accompanied by increased brain damage. Careful consideration needs to be given to the timing of rehabilitation after stroke and related types of brain injury.

Animals↗

PubMed2006

Inverted EEG theta lateralization in dyslexic children during phonological processing.

The phonological deficit hypothesis of dyslexia has been investigated in the present research by analysing language-related lateralization of the EEG theta band in a sample of dyslexic children. To this aim, a paradigm based on word-pair visual presentation was used in which the same words were processed in Semantic and Phonological tasks. Theta band amplitude, a cortical index that has been related to working memory processing, was analysed during four different phases of word elaboration, thus allowing to measure also the temporal dynamics of word reading/encoding in the verbal working memory. Control subjects showed a specific (and therefore efficient) task-related and time-dependent cortical activation: a peak of theta activity during word reading was found that decayed during the next inter stimulus interval. Furthermore, during word presentation in the Phonological task, theta amplitude was greater on the left hemisphere. Dyslexics evidenced an altered pattern of theta activation both in the temporal dimension and in the cortical space: their peak of activity was delayed to the first inter stimulus interval after word offset and was shifted to the right hemisphere throughout the whole epoch of Phonological task and in two phases of the Semantic task. Analysis of alpha band failed to replicate the complex pattern of lateralization found for theta band in the two groups, a result that suggests a specific functional role of theta band, which cannot be interpreted as a simple marker of cortical inhibition. Results point to a deficit, in dyslexic children, to recruit left hemisphere structures for the elaboration of the phonological component of the verbal working memory. This deficit was marked by a different, unspecific and dysfunctional hemispherical asymmetry of theta activation to language, a deficit that involved also the time course of phonological linguistic elaboration.

Acoustic Stimulation↗

PubMed2004

Prefrontal executive and cognitive functions in rodents: neural and neurochemical substrates.

The prefrontal cortex has been implicated in a variety of cognitive and executive processes, including working memory, decision-making, inhibitory response control, attentional set-shifting and the temporal integration of voluntary behaviour. This article reviews current progress in our understanding of the rodent prefrontal cortex, especially evidence for functional divergence of the anatomically distinct sub-regions of the rat prefrontal cortex. Recent findings suggest clear distinctions between the dorsal (precentral and anterior cingulate) and ventral (prelimbic, infralimbic and medial orbital) sub-divisions of the medial prefrontal cortex, and between the orbitofrontal cortex (ventral orbital, ventrolateral orbital, dorsal and ventral agranular cortices) and the adjacent medial wall of the prefrontal cortex. The dorso-medial prefrontal cortex is implicated in memory for motor responses, including response selection, and the temporal processing of information. Ventral regions of the medial prefrontal cortex are implicated in interrelated 'supervisory' attentional functions, including attention to stimulus features and task contingencies (or action-outcome rules), attentional set-shifting, and behavioural flexibility. The orbitofrontal cortex is implicated in lower-order discriminations, including reversal of stimulus-reward associations (reversal learning), and choice involving delayed reinforcement. It is anticipated that a greater understanding of the prefrontal cortex will come from using tasks that load specific cognitive and executive processes, in parallel with discovering new ways of manipulating the different sub-regions and neuromodulatory systems of the prefrontal cortex.

Acetylcholine↗

PubMed2005

Paying attention to saccadic intrusions.

Fixation to a target in primary gaze is invariably interrupted by physiological conjugate saccadic intrusions (SI). These small idiosyncratic eye movements (usually <1 degrees in amplitude) take the form of an initial horizontal fast eye movement away from the desired eye position, followed after a variable duration by a return saccade or drift. As the aetiology of SI is still unclear, it was the aim of this study to investigate whether SI are related to exogenous or endogenous attentional processes. This was achieved by varying (a) the "bottom-up" target viewing conditions (target presence, servo control of the target, target background, target size) and (b) the 'top-down' attentional state (instruction change--'look' or 'hold eyes steady' and passive fixation versus active--'respond to change' fixation) in 13 subjects (the number of participants in each task varied between 7 and 11). We also manipulated the orientation of pure exogenous attention through a cue-target task, during which subjects were required to respond to a target, preceded by a non-informative cue by either pressing a button or making a saccade towards the target. SI amplitude, duration, frequency and direction were measured. SI amplitude was found to be significantly higher when the target was absent and SI frequency significantly lower during open loop conditions. Target size and background influenced SI behaviour in an idiosyncratic manner, although there was a trend for subjects to exhibit lower SI frequencies and amplitudes when a patterned background was present and larger SI amplitudes with larger target sizes. SI frequency decreased during the "hold eyes steady" passive command as well as during active fixation but SI direction was not influenced by the exogenous cue-target task. These results suggest that SI are related to endogenous rather than exogenous attention mechanisms. Our experiments lead us to propose that SI represent shifts in endogenous attention that reflect a baseline attention state present during laboratory fixation tasks and may prove to be a useful tool to explore higher cortical control of fixation.

Adult↗

PubMed1982

A signal-detection-theory measure of pitch shifts in sinusoids as a function of intensity.

Pitch shifts in sinusoids as a function of intensity result in systematic response biases and differences in performance in forced-choice frequency-discrimination tasks. Two approaches are described for converting these effects to a measure of pitch shift in Hz using standard signal-detection-theory assumptions. To illustrate these approaches, forced-choice frequency-discrimination data were obtained for three listeners at 250 and 4000 Hz, with six intensities from 40 to 90 dB SPL. The resulting pitch-shift estimates are in good agreement with adjustment data obtained from the same listeners. Collection and analysis of the forced-choice data can be greatly simplified by using an adaptive procedure. Pitch-shift estimates obtained in this way for two of the three listeners are in good agreement with the other estimates.

Adolescent↗

PubMed1987

Contingent negative variation (CNV) influenced by preceding slow potential shifts (pSPSs).

The study was undertaken to elaborate the influence of slow potential shifts preceding S1 on the CNV. Eighteen subjects participated in a forewarned reaction time task. The EEG was recorded from F3, F4, Cz, P3 and P4 referred to linked mastoids. Selected averages of EOG-corrected trials with negative, positive and no shifts greater than 8 microV - within 2 sec before S1 at the respective location - were compared. Results showed greater CNV after positive shifts compared to negative shifts (P less than 0.05) and no significant interaction with location. Slow potential shifts before S1 did not affect reaction time. Evidence of a baseline effect is discussed as a ceiling effect as well as an expression of an active regulatory mechanism responsible for a desired activation at S2. As slow potentials may also interact with task conditions, it is suggested first to control the baseline in order to obtain reliable CNV measures, and secondly to use baseline effects as a tool to get insight into brain regulatory mechanisms.

Adolescent↗

PubMed2004

Strategy shift affordance and strategy choice in young and older adults.

When skill acquisition involves a shift in strategy (such as from rule-based to retrieval-based processing), older adults typically shift later in practice than young adults do. We observed the shift from scanning-based to memory-based processing in a noun pair learning task. Young and older adults were trained in conditions in which the relationship between memory load and scanning load was manipulated by making the strategy shift more or less beneficial. Older adults in a condition with high shift affordance shifted to memory retrieval more fully and more rapidly than did older adults in conditions with lower shift affordance. Reluctance to rely on memory retrieval was related to metacognitive reports of memory confidence. The present study indicates that age differences in skill acquisition reflect qualitative age differences in strategy choice in addition to quantitative age differences in component task processes.

Adult↗

PubMed2003

Hand rim configuration: effects on physical strain and technique in unimpaired subjects?

OBJECTIVE: Hand rim wheelchair propulsion is inefficient and physically straining. To evaluate the possibly advantageous role in this respect of three different prototype hand rim configurations (a rubber foam-coated cylindrical (II) hand rim and two profiled rubber foam-coated hand rims (wide and narrow: III, IV)), a group of 10 unimpaired subjects conducted four submaximal discontinuous wheelchair exercise tests on a computer-controlled wheelchair ergometer, thus allowing a comparison with a standard hand rim (chromium-plated round hand rim (I)). METHODS: Apart from physiological measures (oxygen uptake, heart rate (HR), ventilation, mechanical efficiency (ME)), a subjective score for the rating of each of the hand rims was determined, as well as characteristics of the force application in the propulsion phase during each test condition. Timing parameters of the push and recovery phase were determined. Each exercise test was conducted with one of the four hand rim configurations in a counter-balanced order. RESULTS: Analysis of variance with repeated measures (hand rim configuration, power output) revealed no significant effects (P>0.05) on any of the physiological parameters and force application characteristics for the main factor 'hand rim configuration'. Only the subjective score (scale 0-10) for rating of the hand rims proved significantly different between the round rubber (7.5+/-0.53) coated hand rim-receiving the highest score-versus the narrow rubber-coated flat profiled hand rim (5.5+/-1.72). DISCUSSION: In this subject group and under the selected tasks and submaximal conditions of wheelchair propulsion, the studied hand rim configurations did not introduce critical shifts in the technique of (de-)coupling and power production in the push phase. As a consequence, no systematic shifts in ME are found among the different hand rim configurations. It is suggested that the biological constraints of the task overrule the possible effects of small design variations of the different hand rim configurations within the studied subject group and under the limited test conditions. The hand rim design characteristics may however be much more critical in (1) experienced wheelchair users, (2) especially those subjects with a limited hand-arm and/or trunk function and/or (3) under much more extreme conditions of daily wheelchair ambulation (i.e. turning, stopping/starting, negotiating a slope) or during peak performance. These issues clearly require continued future research. As such, the current results can be viewed as preliminary results only.

Adult↗

PubMed1995

Recovery from work shifts: how long does it take?

Although regulations on work hours usually include a minimum weekly rest period, there is little empirical evidence concerning recovery from work. Shift-working nurses (N = 61) used a handheld computer for 28 days to complete self-ratings, cognitive-performance tasks, and a sleep diary. Many measures were worse on rest days that followed a night shift rather than a day shift and tended to be worse on first rest days compared with subsequent rest days. Alertness was lowest on the 1st rest day following a night shift. Social satisfaction was better on workdays that were preceded by 2 rather than 1 rest day. Reaction time decreased over consecutive night shifts and tended to increase over rest days following night shifts. The results are interpreted as being consistent with the combined adaptive costs of fatigue and adjustment to and from a nocturnal routine. The practical implications for scheduling rest days are considered.

Adult↗

PubMed2002

Trunk orientation induces neglect-like lateral biases in covert attention.

The purpose of this study was to resolve a paradox in the literature on the effects of body orientation on spatial attention. Neuropsychological studies have found that real or simulated trunk rotation relieves contralesional inattention in patients with unilateral neglect, suggesting that trunk orientation affects how attention is allocated to space. However in two previous studies, trunk orientation did not affect spatial attention in other populations. In this study we investigated the effects of trunk orientation on the performance of a covert attention task by neurologically intact adults. The covert attention task allowed the evaluation of the effects of trunk orientation on both the allocation of attention to space and the ability to shift that attention to new locations. As in previous research, trunk orientation did not affect participants' response times (RTs) to validly cued targets. However rotating participants' trunks to the left increased their RTs to invalidly cued targets on the right and decreased their RTs to invalidly cued targets on the left. These results indicate that trunk orientation induces directional biases in the ability to shift attention. Thus, for intact participants, trunk rotation created lateral biases in the covert attention task similar to those seen in neglect patients.

Adult↗

PubMed2000

Fragmentation of treatment and the potential for human error in neonatal intensive care.

Neonatal intensive care involves continuous monitoring of highly unstable patients in order to plan and deliver effective care and treatment. Making care and treatment decisions depends upon using information obtained in many different ways. Analysis of care and treatment tasks shows how much staff need to rely on one another for crucial information. This problem becomes more acute as personnel change shifts, yet are still obliged to maintain continuity of care. Effective sharing of information is done through the medium of shared records, shift handovers, ward rounds, and informal verbal exchanges. This article describes strategies for understanding the tasks involved in neonatal intensive care, considers issues of task fragmentation, identifies the communication systems designed to minimize the effects of this fragmentation, and reviews problems associated with those systems that give rise to the potential for human error.

Humans↗

PubMed2001

Task-specific lead exposure during residential lead hazard reduction projects.

This article describes a study of worker airborne lead exposure during residential lead hazard reduction projects. The study was performed to characterize short-term, task-specific exposures and to test an airborne lead exposure prediction equation that could assist residential lead abatement contractors in selecting engineering controls and personal protection prior to bidding on a project. A total of 224 personal air samples were collected from 16 workers employed by three contractors at 11 San Francisco Bay-area homes. Exposures ranged from <1.0 microg/m3 to 146.0 microg/m3. Although exposures were low overall (geometric mean = 4.2 microg/m3), there was considerable variability (geometric standard deviation = 4.3 microg/m3). The task-specific approach to exposure assessment used in this study was effective in revealing short-term, high exposures that would be missed during full shift sampling. The highest exposures occurred during paint scraping, demolition, and chemical stripping. Task-specific sampling was also effective in identifying tasks with low exposure potential, such as wet sanding, component removal, and clean-up. Since exposures were not significantly correlated with paint lead content or task area size, two of the variables of the prediction equation, the equation does not appear to be an effective means of predicting airborne lead exposures. Additionally, other factors such as water usage and contractor type had a significant effect on exposure levels. By controlling for these factors, exposures were significantly correlated with the third variable of the prediction equation, the proportion of paint removed from task areas. This study also demonstrates the importance of contractor specific exposure assessments, as there were significant differences in exposures between contractors, even with similar work methods and water use frequency.

Air Pollutants, Occupational↗

PubMed2002

[Effects on eyestrain of outward stimuli for accommodation].

PURPOSE: We investigated experimentally the effect on eyestrain of outward-shift stimuli for accommodation. METHODS: Six female students fixed optical outward-shift stimuli for accommodation during 2 min immediately after 15 min of a sustained task on a 3-D display. Before and after the trial, their ocular functions were measured and their subjective symptoms were assessed. The outward-shift stimuli were applied by moving the targets of scenery images from far to near and near to far repetitively at around both eyes' far point position. As a control, stationary targets at the position of 0 D were used instead of moving targets. The same experiment was repeated twice for each subject. RESULTS: In the first experiment, there were significant changes in the accommodative contraction time, the accommodation lag, and the myopic shift, and the subjective symptoms of "eyestrain" and "eye dryness" in the control group, but in the stimulus group there were only increases of the complaint of "eyestrain". In the second experiment, the changed items were the contraction time and the complaints of "eyestrain" and "eye dryness" in both groups. The outward-shift stimuli caused a tendency in the far point to shift outward in the first experiment, and there was a statistically significant inward shift in the second experiment. CONCLUSION: From these results, it is suggested that the outward-shift stimuli for accommodation are effective in relieving eyestrain following the deterioration of ocular functions except when the far point is shifted inward.

Accommodation, Ocular↗

PubMed2001

Dermal exposure: how to get information.

Risk assessment of chemical substances at the workplace requires information about intrinsic hazards and workers' exposure. At many workplaces health risks from both inhalative and dermal exposure to hazardous substances may occur. Exposure assessment therefore must include both modes of exposure. Very often, qualitative and quantitative information about dermal exposure is lacking. Measurement methods are of questionable quality when applied to monitoring dermal exposure at workplaces and the results are difficult to interpret. A questionnaire was designed for the description of dermal exposure situations taking into account the different factors influencing dermal exposure. In conjunction with an air monitoring survey in German car repair shops the questionnaire was applied by a hygienist. The hands of car mechanics are the most exposed parts of their bodies. The typical duration of tasks (and dermal exposure) was from either 5-10 minutes or up to about 1 hour. This corresponds to typical jobs in car repair shops like inspection and repair, respectively. In some cases other parts of the body are also exposed, for example, the face and forearms. Parts of the body may be covered by wetted or greasy clothes. Only in a few cases do mechanics clean their hands immediately after finishing a task. Normally, hands are cleaned at the end of a shift. The questionnaire was further developed for general application making use of multiple choice entries together with an explanatory manual. The questionnaire is still under development to be applied for a qualitative survey of dermal exposure as part of the European project RISKOFDERM.

Automobiles↗

PubMed1990

Patterns of task-related slow brain potentials in dyslexia.

Six dyslexic youths who met the Hughes and Denckla criteria of "dyslexia pure" and 10 normal control subjects were investigated with DC recordings of task-related cortical negativity using 10 leads over the right and left hemispheres. Potentials were recorded during the following tasks: reading, orthographic error detection, letter series, word assembly, word fluency, finding of antonyms, and viewing of Necker cubes. Both groups exhibited greater right hemisphere negativity during the Necker cube task. Whereas controls revealed greater left hemisphere negativity during linguistic tasks, the reverse was found with dyslexics. The right shift was pronounced with the reading, orthographic error detection, and antonym conditions. Differences between the two groups were also found for the pattern of cortical distribution. We conclude that dyslexia is associated with changes in the lateral distribution of cortical activity during certain types of language processing.

Adolescent↗