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Results for “Task Shifting”

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PubMed1982

A multidimensional assessment of parent-identified behavior problem toddlers.

Sixty-eight 2- and 3-year-olds (46 parent-referred, 22 controls) participating in an identification, assessment, and follow-up study of hyperactivity and related behavior problems were evaluated on parent-report, observational, and cognitive measures. Referred youngsters were described by both parents as more active, inattentive, difficult to discipline, and aggressive with peers than were controls. Mothers of referred children also reported a more difficult infancy period. Laboratory assessments confirmed parental reports of current problems. Referred children shifted activities more during free play, were more active and inattentive during structured tasks, and made more impulsive responses on a delay task than did controls. Discriminant function analysis indicated that parental ratings of activity paired with laboratory measures of sustained attention and impulsivity correctly classified 88% of the sample. These data suggest that the core symptoms of hyperactivity can be identified in very young children, although their prognostic significance remains to be determined.

Attention↗

PubMed2002

The time course of attention shifts following perturbation of upright stance.

Recent work has revealed the specific time course of attention shifts associated with balance control in a seated model using a dual-task paradigm. This work highlighted an initial "automatic" and later "attention-demanding" phase of the evoked balance reaction. The objective of the present study was to determine if comparable influences would be observed for performance of a visuomotor tracking task when responding to perturbations of upright stability. Small-amplitude floor translations were applied in the forward or backward direction to evoke stabilizing postural reactions. Balance reactions were evoked with and without the concurrent performance of a visuomotor tracking task using the right hand. Results showed significant disruptions (pauses) in tracking that invariably occurred after onset of the earliest balance reaction measured in ankle muscles. On average, there was a delay of 345 ms between ankle-muscle activation (average onset 144 ms) and the pause in visuomotor tracking. The concurrent tracking led to modest change in later phases of the balance reaction, as measured by an increase in center-of-pressure excursions, but did not affect the earliest phase of the reaction. These results support the view that compensatory balance reactions, even those evoked by small perturbations, are characterized by an initial "automatic" phase and subsequent control that may be more dependent on cognitive resources.

Adult↗

PubMed2006

A neuro-mechanical model for interpersonal coordination.

The present study investigates the coordination between two people oscillating handheld pendulums, with a special emphasis on the influence of the mechanical properties of the effector systems involved. The first part of the study is an experiment in which eight pairs of participants are asked to coordinate the oscillation of their pendulum with the other participant's in an in-phase or antiphase fashion. Two types of pendulums, A and B, having different resonance frequencies (Freq A=0.98 Hz and Freq B=0.64 Hz), were used in different experimental combinations. Results confirm that the preferred frequencies produced by participants while manipulating each pendulum individually were close to the resonance frequencies of the pendulums. In their attempt to synchronize with one another, participants met at common frequencies that were influenced by the mechanical properties of the two pendulums involved. In agreement with previous studies, both the variability of the behavior and the shift in the intended relative phase were found to depend on the task-effector asymmetry, i.e., the difference between the mechanical properties of the effector systems involved. In the second part of the study, we propose a model to account for these results. The model consists of two cross-coupled neuro-mechanical units, each composed of a neural oscillator driving a wrist-pendulum system. Taken individually, each unit reproduced the natural tendency of the participants to freely oscillate a pendulum close to its resonance frequency. When cross-coupled through the vision of the pendulum of the other unit, the two units entrain each other and meet at a common frequency influenced by the mechanical properties of the two pendulums involved. The ability of the proposed model to address the other effects observed as a function of the different conditions of the pendulum and intended mode of coordination is discussed.

Adult↗

PubMed1996

Contingent negative variation (CNV) and determinants of the post-imperative negative variation (PINV) in schizophrenic patients and healthy controls.

A slowly rising cortical potential shift with negative polarity following the imperative stimulus of a forewarned reaction time task, the 'post-imperative negative variation' (PINV), is regularly observed in schizophrenic patients but not in controls. The topography of the PINV suggests that it may originate in frontal cortical regions. We used a task designed to test two putative prefrontal cortical functions: working memory and processing of ambiguity. Nineteen patients with a chronic schizophrenic disorder and 19 control subjects matched for age, sex, and education participated in two experimental sessions. The EEG was recorded from frontal, central, temporal, and parietal leads over both hemispheres using a DC amplifier. PINV amplitudes were generally larger in patients than in controls. If the result of comparing physical features of the two successively presented stimuli (warning and imperative stimulus) was ambiguous rather than clear, an augmentation of the PINV amplitudes was seen in both groups. If this comparison required high rather than low involvement of working memory functions, PINV amplitudes were augmented in schizophrenic patients only. Scalp distribution of the PINV indicated a left-hemisphere fronto-central PINV maximum in patients, and a right-hemisphere predominance in controls, which was larger following ambiguous stimulus comparisons. These results suggest that ambiguity during the comparison of physical features of successively presented stimuli may be a general factor of the PINV in schizophrenic patients and healthy controls. Augmented involvement of working memory functions, presumably subserved by the prefrontal cortex, specifically affected the fronto-centrally predominant PINV in schizophrenic patients. This result is compatible with the hypothesis of prefrontal cortical dysfunctions in schizophrenia.

Adult↗

PubMed2004

Spatial attention in individuals with pervasive developmental disorders using the gap overlap task.

The present study examined spatial attention in individuals with pervasive developmental disorders (PDD) using the gap overlap task and analyzed the express saccade, which is defined by its extremely short reaction time, as a measure of the state of attention. Participants were required to move their eyes to the target stimulus appearing on the left or right side of a fixation point. In this task, participants had to disengage their attention from the central fixation point and shift it to the peripheral target stimulus. In the gap condition, the fixation point disappeared 200 ms before the target stimulus was presented, and in the overlap condition, the fixation point remained while the target stimulus was presented. Saccade latencies were not different between the groups. However, the express saccade was more frequent in the PDD group than in the normal group in the overlap condition. We conclude that individuals with PDD have deficiencies in attentional engagement. Moreover, our study suggests that analysis of the express saccade will be useful in further examinations of attentional processes in PDD.

Adult↗

PubMed2005

Assessment of soil remediation workers' exposure to polycyclic aromatic hydrocarbons (PAH): biomonitoring of naphthols, phenanthrols, and 1-hydroxypyrene in urine.

Urinalysis of multiple polycyclic aromatic hydrocarbons (PAH) biomarkers has been applied to assess the exposure of soil remediation workers on a former creosote wood impregnation site polluted with creosote oil. The uptake of PAHs was measured in preshift, end-of-shift, evening, and next preshift specimens (n=33) of nine volunteers with diverse tasks, using sensitive HPLC-FD methods. The ranges of biomarker concentrations in urine (nmol/l) were: 1-naphthol (14-159), 2-naphthol (9-166), 1- plus 2-naphthol (35-269), 1-hydroxyphenanthrene (OHPhe) (6-56), 2- plus 3-OHPhe (6-70), 4-OHPhe (1-6), 9-OHPhe (1-7), the sum of phenanthrols (15-135), and 1-hydroxypyrene, OHP (2.2-67). Eight of nine workers had OHP levels higher than the Finnish biological limit value for non-occupationally exposed persons (3nmol/l). A linear correlation was observed between 1- and 2-naphthol (r=0.90). The biomarker OHP correlated well in urine both with the major (1-OHPhe, r=0.96; 2- plus 3-OHPhe, r=0.84) and the minor phenanthrene metabolites (4-OHPhe, r=0.77; 9-OHPhe, r=0.68), and with the sum of all phenanthrols (r=0.94), but not so well with the sum of naphthols (r=0.66, p<0.001). The smokers had 2.9-, 2.2-, and 4.8-fold higher average concentrations of naphthols, phenanthrols, and OHP, respectively, than the non-smokers. The PAH biomarker data (concentrations and diurnal excretion profiles) showed significant work-related exposure in both non-smoking and smoking subjects. The average exposure levels were clearly higher than those we have measured for instance in asphalt paving workers. The workers' exposure should be assessed by biological monitoring, because at this type of outdoor work the dermal and pulmonary uptake of PAHs are both likely. Adequate measures for preventing, particularly, dermal absorption are of crucial importance for reducing the workers' risk of exposure to carcinogens on soil remediation sites.

Biomarkers↗

PubMedDate not supplied

Effects of training dose on amphetamine drug discrimination: dose-response functions and generalization to cocaine.

Rats were trained to discriminate one of three doses of amphetamine (AM), 0.5, 1, or 2 mg/kg, from vehicle (VEH) in a two-lever, food-reinforced, drug-discrimination task. The purpose of the study was to investigate the nature of the shift of the dose-response curve and generalization to cocaine (COC) as a function of training dose. In order to preclude potential differences among the groups in stimulus control, the three training-dose groups were required to perform the discrimination at high and equivalent levels of accuracy. The shift of the dose-response functions to the right as a function of increasing training dose was not parallel. The slope decreased as training dose increased. There was a dose-dependent increase in AM lever responding to test doses of COC that tended to be affected by training dose. The results suggest that proper evaluation of training-dose effects requires that groups be trained to equivalent levels of stimulus control.

Amphetamine↗

PubMed1998

Are human anticipatory postural adjustments affected by a modification of the initial position of the center of gravity?

During a lateral leg raising task, the position of the center of gravity (CG) in the horizontal plane shifts towards the supporting leg prior to the movement onset. The aim of this study was to explore whether the anticipatory postural adjustments were calibrated as a function of the initial horizontal location of the CG. Experiments were performed on 8 healthy subjects, with three initial positions of the CG (close to the supporting leg, between the two legs, close to the moving leg). Simultaneous kinematic, kinetic and electromyographic (EMG) data were recorded with the ELITE. system. The results show that the duration of the kinetic variables and EMG pattern are scaled as a function of the distance covered by the CG and constitute the means of modulating the CG shift. They suggest that the evaluation of the support conditions is necessary to calibrate the CG shift, this is done during the early phase of the postural adjustments.

Adult↗

PubMed2003

Semantic hyperpriming in thought-disordered patients with schizophrenia: state or trait?--a longitudinal investigation.

Enhanced semantic priming (SP) has been reported in individuals with schizophrenia who exhibit positive formal thought disorder (TD) and it has been linked to heightened automatic spreading activation in semantic networks of these patients. However, the state or trait nature of semantic hyperpriming in schizophrenia and its relation to clinical features (e.g., length of illness, symptom shifts) is not clear. To explore these issues, we administered a lexical decision task with semantically related, indirectly related or unrelated prime-target pairs to acutely ill inpatients with schizophrenia shortly after admission and again after 12-16 weeks, while most patients were already in (partial) remission (n=33). In addition, we examined 20 healthy control subjects twice (2 weeks apart). Relative to control subjects, TD patients with schizophrenia exhibited hyperpriming only in the acute psychotic state, but not during the follow-up examination, when TD and other positive symptoms had resolved. There were no associations between priming effects and length of illness or number of previous psychotic episodes. In conclusion, semantic hyperpriming in TD patients with schizophrenia appears to be clearly state-dependent and might be viewed as an episode marker of psychosis with TD.

Adult↗

PubMed1999

Visual attention deficits in Alzheimer's disease: simple versus conjoined feature search.

The authors investigated selective attention in patients with Alzheimer's disease (AD), using a well-known visual search procedure. In simple feature search, the deficit observed in AD patients represented a baseline shift in the median hit reaction time (RT). On the conjoined feature search task, the median hit RT for AD patients increased disproportionately with increasing array size, indicating an additional cognitive impairment on this task. Of particular importance, the cognitive deficit observed in conjunction search was more profound than that predicted on the basis of previous reports of global cognitive slowing in AD. There was some evidence that the performance of AD patients improved more than the performance of controls over the duration of the experimental test session. Patients also had more difficulty in detecting targets on the right side of hemispace and in more peripheral locations.

Adolescent↗

PubMed2003

Can attentional theory explain the inverse base rate effect? Comment on Kruschke (2001).

In J. K. Kruschke's (2001; see record 2001-18940-005) study, it is argued that attentional theory is the sole satisfactory explanation of the inverse base rate effect and that eliminative inference (P. Juslin, P. Wennerholm, & A. Winman, 2001; see record 2001-07828-016) plays no role in the phenomenon. In this comment, the authors demonstrate that, in contrast to the central tenets of attentional theory, (a) rapid attention shifts as implemented in ADIT decelerate learning in the inverse base-rate task and (b) the claim that the inverse base-rate effect is directly caused by an attentional asymmetry is refuted by data. It is proposed that a complete account of the inverse base-rate effect needs to integrate attention effects with inference rules that are flexibly used for both induction and elimination.

Association Learning↗

PubMed2003

The contribution of the rat prelimbic-infralimbic areas to different forms of task switching.

The experiments examined the effects of prelimbic-infralimbic inactivation in rats on the acquisition and reversal learning of different discrimination tasks: 2- or 4-choice odor discrimination in Experiments 1 and 2, the shift from 2-choice odor discrimination to 2-choice place discrimination in Experiment 3, and the shift from 2-choice place to 2-choice odor discrimination in Experiment 4. Infusions of 2% bupivacaine did not impair performance in the odor discrimination tests. Prelimbic-infralimbic inactivation did not impair acquisition but did impair the shift from an odor to a place discrimination and vice versa. Analysis of the errors revealed that the deficit was due to perseveration of the previously learned strategy. The selective deficits observed in the odor-place tests suggest that the prelimbic-infralimbic areas enable behavioral flexibility when conditions demand inhibiting the use of one type of attribute information and learning a new type of attribute information.

Animals↗

PubMed1988

Infant thresholds with enhanced attention to the signal in visual reinforcement audiometry.

Experimental data show a discrepancy between adult auditory thresholds and best estimates of infant thresholds. The source of the discrepancy has not been determined. Attentional differences between infants and adults and procedural differences to accommodate infant attentional behavior may account at least in part for the discrepancy. A standard operant procedure, Visual Reinforcement Audiometry (VRA), was modified to enhance infant attention to impending auditory signals. Results on 16 infants evaluated with conventional VRA and modified VRA revealed an average 5.5 dB improvement in threshold with the modified technique. Correction for adult performance in similar tasks indicated a 3.3 dB attentional effect between infant and adult thresholds. The shift in threshold reflects on the adequacy of VRA as a threshold procedure.

Adult↗

PubMed2006

Impact of background noise on reaction time and brain DC potential changes of VDT-based spatial attention.

Background noise is often discussed in terms of mental costs. In this study the effect of background noise on brain activity as reflected by the direct coupled (DC) potential was investigated by a within design in ten participants. During two successive blocks of 7 min each, participants performed 156 trials of a visual display terminal (VDT)-based visual-spatial attention task without noise and two blocks with a mixture of the environmental noises of barking dogs, traffic noise and irrelevant speech of 60 dBA. Brain DC potentials were recorded along the midline and analysed for change by time on task. For noise conditions, reaction time was prolonged and the DC-potential shifted towards positivity, contrary to control condition, independent of block and location. Results suggest reduced cortical resources by widespread inhibitory activation through background noise. It can be concluded that even low intensity background noise is associated with energy consumption and with impaired performance in spatial attention.

Adult↗

PubMed2005

Effects of phonological and orthographic neighbourhood density interact in visual word recognition.

The present study investigated the role of phonological and orthographic neighbourhood density in visual word recognition. Three mechanisms were identified that predict distinct facilitatory or inhibitory effects of each variable. The lexical competition account predicts overall inhibitory effects of neighbourhood density. The global activation (familiarity) account predicts overall facilitatory effects of neighbourhood density. Finally, the cross-code consistency account predicts an interaction, with inhibition of phonological neighbours in sparse orthographic regions and facilitation of phonological neighbours in dense orthographic regions. In Experiment 1 (lexical decision), a cross-over interaction was indeed found, supporting the prediction of the cross-code consistency account. In Experiment 2, this cross-over interaction was exaggerated by adding pseudohomo-phone stimuli (e.g., brane) among the nonword targets. Finally, in Experiment 3 (progressive demasking), we tried to shift the balance between inhibitory and facilitatory mechanisms by using a perceptual identification task. As predicted, the inhibitory effects of phonological neighbourhood were amplified, whereas the facilitatory effects disappeared. We conclude that the level of compatibility across co-activated orthographic and phonological representations is a major causal factor underlying this pattern of effects.

Humans↗

PubMed2000

Plastic changes in the auditory cortex induced by intensive frequency discrimination training.

The slow auditory evoked (wave N1m) and mismatch field (MMF) elicited by sequences of pure tones of 1000 Hz and deviant tones of 1050, 1010 and 1005 Hz were measured before, during and 3 weeks after subjects were trained at frequency discrimination for 15 sessions (over 3 weeks) using an odd-ball procedure. The task of the subject was to detect deviants differing by progressively smaller frequency shifts from the standard stimulus. Frequency discrimination improved rapidly in the first week and was followed by small but constant improvements thereafter. N1m and MMF responses to the deviant stimuli increased in amplitude during training. This enhancement persisted until training was finished, but decreased 3 weeks later. The results suggest a plastic reorganization of the cortical representation for the trained frequencies.

Adult↗

PubMed2005

Neural correlates of attention and distractibility in the lateral intraparietal area.

We examined the activity of neurons in the lateral intraparietal area (LIP) during a task in which we measured attention in the monkey, using an advantage in contrast sensitivity as our definition of attention. The animals planned a memory-guided saccade but made or canceled it depending on the orientation of a briefly flashed probe stimulus. We measured the monkeys' contrast sensitivity by varying the contrast of the probe. Both subjects had better thresholds at the goal of the saccade than elsewhere. If a task-irrelevant distractor flashed elsewhere in the visual field, the attentional advantage transiently shifted to that site. The population response in LIP correlated with the allocation of attention; the attentional advantage lay at the location in the visual field whose representation in LIP had the greatest activity when the probe appeared. During a brief period in which there were two equally active regions in LIP, there was no attentional advantage at either location. This time, the crossing point, differed in the two animals, proving a strong correlation between the activity and behavior. The crossing point of each neuron depended on the relationship of three parameters: the visual response to the distractor, the saccade-related delay activity, and the rate of decay of the transient response to the distractor. Thus the time at which attention lingers on a distractor is set by the mechanism underlying these three biophysical properties. Finally, we showed that for a brief time LIP neurons showed a stronger response to signal canceling the planned saccade than to the confirmation signal.

Action Potentials↗

PubMed1997

Task-dependent representations in rat hippocampal place neurons.

It is suggested that the hippocampal formation is essential to spatial representations by flexible encoding of diverse information during navigation, which includes not only externally generated sensory information such as visual and auditory sensation but also ideothetic information concerning locomotion (i.e., internally generated information such as proprioceptive and vestibular sensation) as well as information concerning reward. In the present study, we investigated how various types of information are represented in the hippocampal formation, by recording hippocampal complex-spike cells from rats that performed three types of place learning tasks in a circular open field with the use of intracranial self-stimulation as reward. The intracranial self-stimulation reward was delivered in the following three contexts: if the rat 1) entered an experimenter-determined reward place within the open field, and this place was randomly varied in sequential trials; 2) entered two specific places, one within and one outside the place field (an area identified by change in activity of a place neuron); or 3) entered an experimenter-specified place outside the place field. Because the behavioral trails during navigation were more constant in the second task than in the first task, ideothetic information concerning locomotion was more relevant to acquiring reward in the second task than in the first task. Of 43 complex-spike cells recorded, 37 displayed place fields under the first task. Of these 37 place neurons, 34 also had significant reward correlates only inside the place field. Although reward and place correlates of the place neuron activity did not change between the first and second tasks, neuronal correlates to behavioral variables for locomotion such as movement speed, direction, and turning angle significantly increased in the second task. Furthermore, 6 of 31 place neurons tested with the third task, in which the reward place was located outside the original place field, shifted place fields. The results indicated that neuronal correlates of most place neurons flexibly increased their sensitivity to relevant information in a given context and environment, and some place neurons changed the place field per se with place reward association. These results suggest two strategies for how hippocampal neurons incorporate an incredible variety of perceptions into a unified representation of the environment: through flexible use of information and the creation of new representations.

Analysis of Variance↗