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Results for “Task Shifting”

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PubMed2004

Simple and complex movement-associated functional MRI changes in patients at presentation with clinically isolated syndromes suggestive of multiple sclerosis.

Using functional magnetic resonance imaging (fMRI), we investigated whether movement-associated functional changes of the brain are present in patients who are, most likely, at the earliest stage of multiple sclerosis (MS). Functional MRI exams were obtained from 16 patients at presentation with clinically isolated syndromes (CIS) suggestive of MS and 15 sex- and age-matched healthy volunteers during the performance of three simple and one more complex motor tasks with fully normal functioning extremities. fMRI analysis was performed using statistical parametric mapping (SPM99). Compared to healthy volunteers, CIS patients had increased activations of the contralateral primary sensorimotor cortex (SMC), secondary somatosensory cortex (SII), and inferior frontal gyrus (IFG), when performing a simple motor task with the dominant hand. The increased recruitment of the contralateral primary SMC was also found during the performance of the same motor task with the non-dominant hand and with the dominant foot. In this latter case, an anterior shift of the center of activation of this region was detected. During the performance of a complex motor task with the dominant upper and lower limbs, CIS patients had an increased recruitment of a widespread network (including the frontal lobe, the insula, the thalamus), usually considered to function in motor, sensory, and multimodal integration processing. The comparison of brain activations during the performance of simple vs. complex motor tasks showed that the movement-associated somatotopic organization of the cerebral and cerebellar cortices was retained in patients with CIS. Cortical reorganization occurs in patients at presentation with CIS highly suggestive of MS. Local synaptic reorganization, recruitment of parallel existing pathways, and reorganization of distant sites are all likely to contribute to the observed functional changes. Hum. Brain Mapping 21:106-115, 2004.

Adult↗

PubMed1990

Spatial properties of rod-cone interactions in flicker and hue detection.

Rod-cone interactions in flicker and hue detection were compared to examine the hypothesis that they are mediated by mechanisms with different spatial properties. Flicker and hue thresholds for a 1 deg test stimulus (TS) were measured as a function of background luminance and diameter. Flicker thresholds were reduced from their dark-adapted value by an 11 deg diameter background, but not by a 1 deg background. These results, in agreement with previous work, demonstrate that light adaptation of rods surrounding the TS is necessary to eliminate their effect on cone flicker thresholds. In contrast, hue thresholds were reduced from their dark-adapted value to a comparable degree by 1 and 11 deg backgrounds, indicating that light adaptation of the rods stimulated by the TS is sufficient to abolish the rod-cone hue interaction. Our results support the contention that the rod-cone flicker and hue interactions are mediated by different mechanisms. We also demonstrated that changing the detection task while keeping stimulus parameters constant is sufficient to shift between these two types of rod-cone interactions.

Adaptation, Ocular↗

PubMed1985

Need to prevent and control high-normal and high blood pressure, particularly so-called "mild" hypertension: epidemiological and clinical data.

The need to prevent and control high blood pressure (HBP), including so-called "mild" hypertension [diastolic blood pressure (DBP) 90-104 mm Hg in adults age 30+] stems from the extensive data on the increased risks due to these common blood pressure (BP) levels, including risk of catastrophic cardiovascular events (coronary, cerebrovascular, etc.), both nonfatal and fatal. Prospective population data from the national cooperative Pooling Project and the Chicago Heart Association Detection Project in Industry illustrate the extensively documented facts. They also show that only a small minority of middle-aged and older Americans have optimal low-normal BP levels, i.e., DBP less than 80 mm Hg (SBP less than 120). Thus, the problem of BP above optimal level for health over a long life span is a population-wide problem. The data also show that the great majority of excess catastrophic events attributable to elevated BP occur among people with DBP 90-104 and 80-89 mm Hg, levels very common in the population. Most people with such BP levels also have one or more other major risk factors (e.g., hypercholesterolemia, cigarette use, ECG abnormalities) and thus are at markedly increased risk, both relative and absolute. In addition to these excess risks for major illness, disability, and death, people with BP above optimal levels are more highly prone to other events, clinical and subclinical, that have adverse effects on long-term prognosis, including development of target organ damage and severe hypertension. These data lead to the following inferences about medical care and public health strategy: (a) A key task is, by safe nutritional-hygienic means, to shift the entire population distribution of BP downward, for both primary and secondary prevention of HBP. Such means include prevention and control of obesity, high sodium and alcohol intake, and sedentary habit, from early childhood on. (b) People with DBP 80-89 mm Hg need to be identified promptly, with institution of nutritional-hygienic measures to prevent development of frank hypertension and to correct other risk factors. (c) People with DBP 90-104 and higher need to be identified promptly, with institution of measures to normalize BP and control other major risk factors, by nutritional-hygienic means alone whenever possible or in combination with drug treatment for HBP when necessary to prevent organ system damage, serious illness, disability, and premature death.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1985

The roles of stimulus repetition and hemispheric activation in visual half-field asymmetries.

Hardyck, Tzeng, and Wang (1978, Brain and Language, 5, 56-71) hypothesized that ample repetition of a small number of stimuli is required in order to obtain VHF differences in tachistoscopic tasks. Four experiments, with varied levels of repetition, were conducted to test this hypothesis. Three experiments utilized the general task of object-picture naming and one utilized a word-naming task. Naming latencies constituted the dependent measure. The results demonstrate that for the object-naming paradigm repetition is required for RVF superiority to emerge. Repetition was found to be unnecessary for RVF superiority in the word-naming paradigm, with repetition actually reducing RVF superiority. Experiment I suggested the possibility that RVF superiority developed for the second half of the trials as a function of practice or hemispheric activation, regardless of repetition level. Subsequent experiments, better designed to assess this possibility, clearly refuted it. It was concluded that the effect of repetition depends on the processing requirements of the task. We propose that, for tasks which can be processed efficiently by one hemisphere, the effect of repetition will be to reduce VHF asymmetries; but tasks requiring substantial processing by both hemispheres will show shifts to RVF superiority as a function of repetition.

Adolescent↗

PubMed2005

Reviewing ambulance design for clinical efficiency and paramedic safety.

This study aimed to review the layout of the patient compartment in a UK ambulance for paramedic efficiency and safety using: (1) link analysis; (2) postural analysis. Paramedics were observed over 16 shifts (130 h) carrying out a range of clinical tasks. The most frequently occurring clinical tasks were checking blood oxygen saturation, oxygen administration, monitoring the heart and checking blood pressure. Access to the equipment and consumables to support these tasks had been designed for the attendant seat (head end of the stretcher), however, a link analysis found that paramedics preferred to sit along side the stretcher which resulted in increased reach distances. The higher frequency tasks were found to include over 40% of working postures which required corrective measures. It was concluded that future ambulance design should be based on an ergonomics analysis (including link analysis and postural analysis) of clinical activities.

Adult↗

PubMed2005

Total sleep deprivation and novelty processing: implications for frontal lobe functioning.

OBJECTIVE: Mounting evidence suggests that the frontal lobes are particularly vulnerable to total sleep deprivation (TSD). Detection of novelty involves the frontal lobes. The presentation of rare, novel stimuli elicits an event-related potential (novel P3), which maximizes over anterior regions of the scalp. We hypothesized that TSD would impair novelty detection, resulting in a smaller novel P3 over the frontal region, with a topographic shift toward posterior areas. METHODS: An auditory novelty oddball task was administered to a TSD group after 36 h of waking and again following recovery sleep, and to a control group after 12 h of waking. EEG was recorded from Fz, Cz and Pz. RESULTS: A large anterior P3 was elicited in the control group. In the TSD group, this novel P3 was smaller at Fz. A later novel positivity appeared in parietal areas. The novel P3 returned to baseline levels and the late novel P3 was difficult to observe following recovery sleep. CONCLUSIONS: TSD appears to compromise the usual automatic detection of novelty probably due to frontal deactivation. Participants may compensate by relying on posterior brain mechanisms involving active memory comparison. The late novel P3 component may also reflect a secondary effortful attempt to encode and to categorize novel stimuli. SIGNIFICANCE: This study suggests that TSD may compromise cognitive functioning in different regions of the brain. The detection of novelty, probably mediated by the frontal lobes, is particularly at risk.

Acoustic Stimulation↗

PubMed2006

DYRK1A BAC transgenic mice show altered synaptic plasticity with learning and memory defects.

Among the various phenotypes seen in Down syndrome (DS), mental retardation is the most common and most debilitating condition suffered by individuals with DS. The DYRK1A gene on human chromosome 21q22.2 encodes a subfamily of protein kinases that displays dual substrate specificities and is known to play a critical role in neurodevelopment. To study DS mental retardation, we have generated transgenic mice that contain only one copy of the complete human DYRK1A gene in a bacterial artificial chromosome. The transgenic mice showed significant impairment in hippocampal-dependent memory tasks in a Morris water maze. Interestingly, we observed shifts in both long-term potentiation and long-term depression, which suggests a role for DYRK1A in bidirectional synaptic plasticity. These mice represent the most clinically relevant DYRK1A mouse model to date and provide us a valuable tool for the in vivo study of mechanisms that underlie the learning and memory deficit in DS.

Animals↗

PubMed2004

Two hands, one brain: cognitive neuroscience of bimanual skill.

Bimanual coordination, a prototype of a complex motor skill, has recently become the subject of intensive investigation. Whereas past research focused mainly on the identification of the elementary coordination constraints that limit performance, the focus is now shifting towards overcoming these coordination constraints by means of task symbolization or perceptual transformation rules that promote the integration of the task components into a meaningful "gestalt". The study of these cognitive penetrations into action will narrow the brain-mind gap and will facilitate the development of a cognitive neuroscience perspective on bimanual movement control.

Attention↗

PubMed2002

The simon effect in schizophrenic patients with negative symptoms.

Automatic shifting of visual attention was investigated using the Simon task in schizophrenic patients with prevailing negative symptomatology. Reaction times were recorded in condition of spatial correspondence and non-correspondence between side of spatially defined responses and side of stimulus presentation. Schizophrenic patients showed asymmetries between the two hemifields attributable to a slowing down of reaction times for non-corresponding trials in the left hemifield. These results are interpreted as a deficit in the process that inhibits the automatic corresponding response, and in general as a difficulty to inhibit dependence on external stimuli, in the left hemifield/right hemisphere.

Adult↗

PubMed2002

The development of exogenous orienting: mechanisms of control.

The present study examined exogenous orienting in children ages 6 years (n=14), 10 years (n=13), 14 years (n=14), and adults (n=13). The main purpose was to identify which of the attentional operations underlying exogenous orienting (disengaging, shifting, and/or engaging) improves with age. A simple detection task was used in which single targets were correctly (80%) or incorrectly (20%) cued. The main finding was that disengaging attention alone distinguished the performance of younger children from that of older children and adults, regardless of whether attention alone (covert attention) or attention and associated sensory and motor systems (overt attention) were involved. In addition, our data, in contrast to those reported previously, raise the possibility that even the youngest children tested were able to use the predictability of the cue to enhance their performance. These and related neuroanatomical findings are taken as evidence for the development with age of more flexible control in orienting visual attention.

Adolescent↗

PubMed1997

The Wisconsin Card Sorting Test and the assessment of frontal function: a validation study with event-related potentials.

The Wisconsin Card Sorting Test (WCST) is generally regarded as the prototype of abstract reasoning task and has been routinely used to assess frontal lobe function in a variety of clinical and research contexts. However, there are growing concerns that the WCST fails to discriminate frontal patients from those with lesions in other brain regions or from normals. Event-related potentials (ERP) from frontal, fronto-temporal, temporal, parietal and occipital areas were recorded during the performance of a computerized version of the WCST in order to explore frontal versus non-frontal ERP indexes during WCST activation. The task protocol was contrived to focus on the differences between early and late trials of each WCST series. Cognitive processes underlying these two task conditions have been described as extradimensional and intradimensional shifts in attention, respectively. Differences between early and late WCST trials appeared as soon as 120 msec poststimulus and were associated with a negative field potential centred at the fronto-temporal region of the left hemisphere. Significantly larger amplitudes of the posterior P3b wave for late as compared with early WCST trials also lent support to claims of a strong involvement of working memory mechanisms during WCST performance. Results are discussed in terms of the implications for the utility of ERP measures in clinical neuropsychology.

Adult↗

PubMed2002

Working memory correlates of three symptom clusters in schizophrenia.

This study was designed to examine whether discrete working memory deficits underlie positive, negative and disorganised symptoms of schizophrenia. Symptom dimension ratings were assigned to 52 outpatients with schizophrenia (ICD-10 criteria), using items drawn from the Positive and Negative Syndrome Scale (PANSS). Linear regression and correlational analyses were conducted to examine whether symptom dimension scores were related to performance on several tests of working memory function. Severity of negative symptoms correlated with reduced production of words during a verbal fluency task, impaired ability to hold letter and number sequences on-line and manipulate them simultaneously, reduced performance during a dual task, and compromised visuospatial working memory under distraction-free conditions. Severity of disorganisation symptoms correlated with impaired visuospatial working memory under conditions of distraction, failure of inhibition during a verbal fluency task, perseverative responding on a test of set-shifting ability, and impaired ability to judge the veracity of simple declarative statements. Severity of positive symptoms was uncorrelated with performance on any of the measures examined. The present study provides evidence that the positive, negative and disorganised symptom dimensions of the PANSS constitute independent clusters, associated with unique patterns of working memory impairment.

Adult↗

PubMed2003

Effects of odors on pain perception: deciphering the roles of emotion and attention.

Emotions have been shown to alter pain perception, but the underlying mechanism is unclear since emotions also affect attention, which itself changes nociceptive transmission. We manipulated independently direction of attention and emotional state, using tasks involving heat pain and pleasant and unpleasant odors. Shifts in attention between the thermal and olfactory modalities did not alter mood or anxiety. Yet, when subjects focused attention on the pain, they perceived it as clearly more intense and somewhat more unpleasant than when they attended to the odor. In contrast, odor valence altered mood, anxiety level, and pain unpleasantness, but did not change the perception of pain intensity. Pain unpleasantness ratings correlated with mood, but not with odor valence, suggesting that emotional changes underlie the selective modulation of pain affect. These results show that emotion and attention differentially alter pain perception and thus invoke at least partially separable neural modulatory circuits.

Adolescent↗

PubMedDate not supplied

Speech disturbances and gaze behavior during public speaking in subtypes of social phobia.

Twenty-four social phobics with public speaking anxiety and 25 nonphobic individuals (controls) gave a speech in front of two people. Subjective anxiety, gaze behavior, and speech disturbances were assessed. Based on subjects' fear ratings of social situations, phobics and controls were divided into the generalized and nongeneralized subtype. Results showed that generalized phobics reported the most, and nongeneralized controls the least anxiety during public speaking. All subjects had longer and more frequent eye contact when delivering a speech than when talking with an experimenter or sitting in front of an audience. Phobics showed more filled pauses, had longer silent pauses, paused more frequently, and spent more time pausing than controls when giving a speech. Generalized phobics spent more time pausing during their speech than the other subgroups (nongeneralized controls, generalized controls, and nongeneralized phobics). These results suggest that generalized phobics tended to shift attentional resources from speech production to other cognitive tasks.

Adult↗

PubMed2003

Modulation of a brain-behavior relationship in verbal working memory by rTMS.

We investigated whether the brain-behavior relationship (BBR) between regional cerebral blood flow (rCBF) as measured by positron emission tomography (PET) and individual accuracy in verbal working memory (WM) can be modulated by repetitive transcranial magnetic stimulation (rTMS) of the left or right middle frontal gyrus (MFG). Fourteen right-handed male subjects received a 30-s rTMS train (4 Hz, 110% motor threshold) to the left or right MFG during a 2-back WM task using letters as stimuli. Simultaneously an rCBF PET tracer was injected and whole-brain functional images were acquired. A hypothesis-driven region-of-interest-analysis of the left and right MFG BBR as well as an explorative whole-brain analysis correlating the individual accuracy with rCBF was carried out. Without rTMS we found a negative BBR in the left but no significant BBR in the right MFG. This negative BBR is best explained by an increased effort of volunteers with an inferior task performance. Left-sided rTMS led to a shift of the BBR towards the superior frontal gyrus (SFG) and to a positive BBR in anterior parts of the left SFG. With rTMS of the right MFG the BBR was posterior and inferior in the left inferior frontal gyrus. Beyond the cognitive subtraction approach this correlation analysis provides information on how the prefrontal cortex is involved based on individual performance in working memory. The results are discussed along the idea of a short-term plasticity in an active neuronal network that reacts to an rTMS-induced temporary disruption of two different network modules.

Adult↗

PubMed1992

Structural comparison of apomyoglobin and metaquomyoglobin: pH titration of histidines by NMR spectroscopy.

Proton NMR spectroscopy was applied to myoglobin in the ferric, water-liganded form (metMbH2O) and the apo form (apoMb) to probe the structure and stability of the latter. Proteins from sperm whale and horse skeletal muscles were studied to simplify the spectral assignment task. Nuclear Overhauser effects and the response of chemical shifts to variations of pH were used as indicators of residual native holoprotein structure in the apoprotein. The investigation was focused in the histidine side chains and their environment. In metMbH2O, the resonances of all imidazole rings not interacting with the heme were assigned by applying standard two-dimensional methods. These assignments were found to differ from those reported elsewhere [Carver, J. A., & Bradbury, J. H. (1984) Biochemistry 23, 4890-4905] except for His-12, -113, and -116. Only one histidine (His-36) has a pK(a) higher than 7, two (His-48 and His-113) have a pK(a) lower than 5.5, and two (His-24 and His-82) appear not to titrate between pH 5.5 and pH 10. In the apoproteins, the signals of His-113 and His-116, as well as those of His-24, -36, -48, and -119 previously assigned in the horse globin [Cocco, M. J.. & Lecomte, J. T. J. (1990) Biochemistry 29, 11067-11072], could be followed between pH 5 and pH 10. A comparison to the holoprotein data indicated that heme removal has limited effect on the pK(a) and the surroundings of these residues. Five additional histidines which occur in the two helices and connecting loops forming the heme binding site were identified in the horse apoprotein. Four of these were found to have pK(a) values lower than that expected of an exposed residue. The NOE and titration data were proposed to reflect the fact that several holoprotein structural elements, in particular outside the heme binding site, are maintained in the apoprotein. In the heme binding region of the apoprotein structure, the low pK(a)'s suggest local environments which are resistant to protonation.

Amino Acid Sequence↗

PubMed2006

A sensitizing regimen of amphetamine impairs visual attention in the 5-choice serial reaction time test: reversal by a D1 receptor agonist injected into the medial prefrontal cortex.

Exposure to repeated, intermittent, escalating doses of amphetamine in rats disrupts information processing in several tasks. Some of these deficits, notably impaired attentional set shifting, may reflect altered prefrontal cortex function. This study examined the effects of repeated treatment with amphetamine on performance in the 5-choice serial reaction time test. This test measures sustained visual attention, a behavior that is known to require the prefrontal cortex. Rats were trained to respond to a brief light stimulus presented randomly in one of five spatial locations, with 100 trials per session. Once performance had stabilized rats were treated with escalating doses of amphetamine (three injections per week for 5 weeks at 1-5 mg/kg per week); testing was continued on nondrug days, and for several weeks of withdrawal. During the amphetamine-treatment and withdrawal phases accuracy of responding was unaffected, but errors of omission increased. Lengthening the stimulus duration abolished this effect. Reducing the stimulus duration also reduced response accuracy and this effect was more marked in amphetamine-treated rats. Both reduced accuracy, and increased omissions, seen in amphetamine-treated rats were reversed by injecting the D1 receptor agonist SKF38393 into the medial prefrontal cortex. This treatment also prevented the decline in accuracy in control animals that resulted from reducing the stimulus duration. These results, indicating that exposure to amphetamine induces a long-lasting deficit in visual attention, add to a growing list of deficits suggesting that amphetamine-sensitized state may model the cognitive deficit state in schizophrenia. The reversal of these deficits by a D1 receptor agonist provides further evidence that prefrontal D1 dopamine receptors are involved in cognition, and may be a potential target for treatment of impaired cognition in schizophrenia.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed2002

New approaches for assessment of occupational exposure to metals using on-site measurements.

Traditional assessment of occupational exposure to metals typically involves static or personal aerosol sampling on a membrane filter followed by a laboratory determination of the metal content on the filter sample. These techniques give results with high accuracy and low detection limits. However, they all have a drawback in that, since the samples have to be analysed in a laboratory, the results will usually be obtained days or weeks after the sampling took place. Today there is available a new generation of portable electronic micro-balances and instruments for metal analysis based on X-ray fluorescence. These instruments will make on-site measurements of metal exposure possible, which opens the way for new approaches for assessment of occupational exposure to metals. In combination with high-flow pumps, short-term sampling is possible, which allows monitoring of the exposure variation during a work shift as well as the exposure during individual work tasks of short duration. Screening measurements and emission measurements are other examples of monitoring that are facilitated using on-site determinations. Measure control monitoring can effectively be performed using on-site measurements and is an effective tool in the assessment of workplace improvements. On-site determinations can also form an effective and pedagogic tool showing workers how to perform specific tasks and demonstrating the effectiveness of different measures intended to improve their work environment. Other examples are the assessment of skin exposure using aerosol deposition on pads and screening of contamination using bulk samples.

Electronics↗