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PubMed2003

The use of visual feedback and on-line target information in catching and grasping.

Although visual feedback (i.e. seeing our hand while we move it) improves the accuracy and efficiency of grasping movements, these positive effects of visual feedback are not consistently found for catching. It was the aim of our study to compare the efficiency of the use of visual feedback in grasping and catching and to explore possible reasons why visual feedback effects have been found less consistently in catching than in grasping. The first reason might be technical. Less sensitive measurement methods have been used in catching; this might explain why some catching studies did not find visual feedback effects. This problem was avoided in our study by using the same methods for both the catching and the grasping task. The effects of visual feedback were examined under standard conditions and under conditions where subjects wore prismatic glasses. Nevertheless, visual feedback effects were obtained for grasping but not for catching movements. This confirms that the difference in the use of visual feedback is real and not due to technical differences between grasping and catching studies. The second reason relates to the different temporal demands of grasping and catching. During a catching task, subjects have less time to respond, and therefore might not have sufficient time to use visual feedback. We tested this explanation with a task that required subjects to reach for a stationary object (i.e. grasping) as quickly as they had for the moving object in the catching task. However, even in this time-constrained grasping task, significant visual feedback effects were found, suggesting that time constraints do not explain the lack of visual feedback effects in catching. In our last explanation, we suggest that possibly the mode of motor control is different for catching and grasping, more particularly while grasping allows for on-line corrections, such corrections might not be possible for catching movements. We tested this explanation with a catching task that contained perturbation trials. During those perturbation trials, the target trajectory was shifted, after the subject had already started to move. We found that subjects responded to the target shifts with an appropriate shift of their catching response. This shows that on-line corrections are possible in the case of catching movements. We conclude that neither differences in the temporal demands nor in the capacity to make on-line modifications explain why visual feedback is used less effectively in the catching than in the grasping task.

Adult↗

PubMed1994

Alzheimer patients show a sensitivity decrement over time on a tonic alertness task.

Tonic alertness was investigated in Alzheimer patients and normal elderly subjects. Sensitivity and criterion shifts were investigated across 45 min of continuous testing using a high event rate test with very low target probability. Alzheimer patients showed a significant sensitivity decrement over time that was unrelated to dementia severity. These results suggest that tonic alertness is impaired by Alzheimer's disease even in its early stages.

Aged↗

PubMed1980

Impairments in visual discrimination performance and gaze shifts in monkeys with superior colliculus lesions.

Eye movements of monkeys were recorded while they performed a visual discrimination task before and after superior colliculus (SC) lesions or control surgery. The monkeys with SC lesions were impaired in orienting their eyes toward the visual stimuli when they were presented eccentrically 15 degrees to 32 degrees from the center of the display screen, toward which their heads were directed. This impairment in shifting the gaze to eccentric stimuli may account for the concomitant deficit in discriminating between these eccentric stimuli. The eye movement deficit appears to depend on destruction of the deep as well as more superficial layers of the SC and may reflect a disturbance in visual-oculomotor coordination.

Animals↗

PubMed1994

Fatigue and the shiftworker: firefighters working on a rotating shift schedule.

Fatigue has often been viewed as a simple variable that is positively correlated with time on task in the workplace and is produced mainly by physical activity. However, shiftwork researchers have demonstrated time-of-day differences for variables including sleepiness and mood, thereby challenging this notion of fatigue. Using a within-subjects design, the present study advances this research by searching for differences in time-of-day interactions in firefighters' sleep length, sleepiness, and mood ratings as a function of shift. We examined reductions in sleep length associated with shiftwork and used sleepiness and mood scales to assess the effects of these reductions. Participants completed surveys throughout a complete cycle of their shift schedule. The study showed that firefighters working on a rotating 8-h shift schedule will sleep less and will report lower positive mood scores, higher negative mood scores, and greater sleepiness ratings on the night shift. Additionally, it was shown that over the course of a shift (two weeks), firefighters were unable to adapt to changes in their sleep schedule. Finally, the significant interactions that were observed challenge the historical, singular notion of fatigue.

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↗

PubMed1998

The role of the Th-1 to Th-2 shift of the cytokine profiles of CD4 helper cells in the pathogenesis of autoimmune and hypercatabolic diseases.

The task of the immune system is the continuous elimination of endogenous cellular debris and the elimination, when necessary, of exogenous structures. It therefore seems useful and practical to add to the paradigms 'self' and 'not self' the term 'altered self'. The concept of stress, introduced by W. B. Cannon and H. Selye in the 1930s, covers the wide range of aggressive environmental influences which for their part result in a uniform shift of the metabolism in the direction of catabolism. This results from the activation of the neuroendocrine stress axis, hypothalamus-pituitary-adrenals, and causes an increased release of catecholamines and glucocorticoids. These latter substances limit life-threatening acute-phase reactions by endogenous inflammation mediators. The purpose of the shift of the cytokine profiles of the CD4 lymphocytes from Th-1 to Th-2 is, with the return of a raised cortisol level to normal values, to temporarily take over the anti-inflammatory functions of the cortisol. A sustained Th-2 shift is an expression of a persistent hypercortisolism in autoimmune states. The suppression of the anti-inflammatory effects of cortisol as a result of states of excessive stress leads to hypercatabolic diseases such as AIDS, sepsis and toxic shock syndrome and protein calorie malnutrition (NAIDS). In the prevention and treatment of AIDS and NAIDS, besides the elimination of the causes of stress, the prophylactic and therapeutic efforts are based mainly on the activation of the mesenchymal production of anabolic matrix components, mainly glycosaminoglycans, and the neutralization of O2 and NO radicals and inflammation mediators from macrophages by polyanions and polyphenols. In our opinion, in sepsis and toxic shock syndromes, lasting reduction of the mortality rates for these diseases is best achieved through the early administration of high intravenous doses of gammaglobulins.

Animals↗

PubMed1996

Involuntary attentional shifts due to orientation differences.

We tested the ability of orientation differences to cause involuntary shifts of visual attention and found that these attentional shifts can occur in response to an orientation "pop-out" display. Texture-like cue stimuli consisting of discrete oriented bars, with either uniform orientation or containing a noninformative orthogonally oriented bar, were presented for a variable duration. Subsequent to or partially coincident with the cue stimulus was the target display of a localization or two-interval forced-choice task, followed by a mask display. Naive subjects consistently showed greater accuracy in trials with the target at the location of the orthogonal orientation compared with trials with uniformly oriented bars, with only 100 msec between the cue and mask onsets. Discriminating these orientations required a stimulus onset asynchrony (SOA) of 50-70 msec. The attentional facilitation is transient, in most cases absent with a cue-mask SOA of 250 msec [corrected]. These results suggest that the preattentive character of some texture discrimination tasks with SOAs of only 100 msec is vitiated by the involuntary attentional shifts that are caused by orientation differences.

Adolescent↗

PubMed1997

Dyadic and tetradic nursery nurse--preschooler interaction in a numerical reproduction task.

BACKGROUND: Adult-child teaching interactions have been found to help children move to higher and more advanced levels of cognitive thinking and reasoning. AIMS: The investigation of whether nursery nurses offer more verbal and non-verbal instructions when interacting with 3-year-old than 4-year-old children, a dyad than a tetrad, girls than boys and as the difficulty of the task increases. SAMPLES: Four hundred and eighty 3- and 4-year-old preschoolers (240 boys and 240 girls) of middle class background from 25 nurseries in the area of Athens, Greece, were observed interacting with 40 nursery nurses while reproducing a numerical task. METHODS: Each nursery nurse interacted with a dyad and a tetrad of children of each age group while solving a task of numerical correspondence consisting of three, six, or nine elements. Each child was expected to reproduce in succession a model array of cubes that the nursery nurse presented to them. All sessions were videotaped. RESULTS: Nursery nurses made significantly more verbal and non-verbal instructional shifts when addressing 3-year-olds, dyads, and as the level of the task became progressively more difficult. Sex was not found to significantly affect nursery nurses' behaviour. Furthermore 4-year-olds were more successful in completing the task at all levels of difficulty. CONCLUSIONS: Nursery nurses adjust both the quality and quantity of their instructions according to the demands of the children with whom they interact. Their teaching methods in small groups are influenced by variables such as age, group size and task difficulty level.

Child, Preschool↗

PubMed2001

Object discrimination learning in aged Japanese monkeys.

The authors investigated the behavioral aging effects of Japanese macaques in 3 object discrimination learning tasks: learning-set (LS) formation, go/no-go discrimination learning, and multiple discrimination reversals. Aged monkeys showed deteriorated performance in these tasks compared with younger controls. Hypothesis analysis of LS showed that aged monkeys had difficulty learning the lose-shift component of the hypothesis win-stay-lose-shift with respect to object. Deficits in go/no-go successive discrimination were clear in no-go trials only in the first 2 pairs of 5 tasks. Performance of aged monkeys was severely disturbed from a chance to criterion level in discrimination reversals. These results are attributed not only to increased tendency for perseveration but also to difficulty in associating the reward and the object in aged monkeys and may be related to the decline in the functions of the ventral frontal cortex.

Aging↗

PubMed1997

Saccade amplitude as a discriminator of flight types.

PURPOSE: Effectiveness of saccade amplitudes and dwell time lengths in determining pilots' eye scanning behaviors, and thus visual workload, during instrument- and scenery-centered simulator flight tasks was investigated. METHOD: Five male jet-aircraft pilots volunteered, and five different simulated flight tasks, including takeoff to landing, were selected for the study. RESULTS: An aerobatic flight, considered to be a scenery-centered one, showed the largest saccadic amplitude among the five flight tasks, its mean value three times that of S-shaped circular flight (SLW), considered to be instrument-centered. The shortest dwell time was for landing, its dwell time length half those of the other flights, and the longest was for SLW. The post-hoc test result revealed that this measure is only partially successful in differentiating landing from the other types of flights. The regression coefficient of the aerobatic flight was about three times that of SLW, and takeoff was almost two times SLW. CONCLUSION: Saccade amplitude was the most important factor in distinguishing between the two types of flights. Dwell time length was supportive, and shift rate of the line of slight was inconclusive in differentiating flight tasks. A scattergram drawn with amplitudes and dwell times gives us a clear understanding of the difference between the two types of flights.

Adult↗

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↗

PubMed1998

Visual responses with and without fixation: neurons in premotor cortex encode spatial locations independently of eye position.

The ventral premotor cortex (PMv) of the macaque monkey contains neurons that respond both to visual and to tactile stimuli. For almost all of these "bimodal" cells, the visual receptive field is anchored to the tactile receptive field on the head or the arms, and remains stationary when the eyes fixate different locations. This study compared the responses of bimodal PMv neurons to a visual stimulus when the monkey was required to fixate a spot of light and when no fixation was required. Even when the monkey was not fixating and the eyes were moving, the visual receptive fields remained in the same location, near the associated tactile receptive field. For many of the neurons, the response to the visual stimulus was significantly larger when the monkey was not performing the fixation task. In control tests, the presence or absence of the fixation spot itself had little or no effect on the response to the visual stimulus. These results show that even when the monkey's eye position is continuously changing, the neurons in PMv have visual receptive fields that are stable and fixed to the relevant body part. The reduction in response during fixation may reflect a shift of attention from the visual stimulus to the demands of the fixation task.

Animals↗

PubMedDate not supplied

Assessing nighttime vigilance through a three-letter cancellation task (3-LCT): effects of daytime sleep with temazepam or placebo.

Nocturnal sleepiness is a common complaint suffered by night-shift workers, especially in conditions of an abrupt shift of the wake-sleep cycle. Alertness management strategies can minimize the adverse effects of sleep loss and circadian rhythm desynchronization and promote optimal vigilance in operational settings. Within these strategies. one possibility is to use short periods of "prophylactic sleep" (before long periods of work), which can be facilitated by hypnotics. Vigilance can be evaluated by means of several tests which, sometimes, imply procedures and devices not easily employable in operational settings. In such conditions pencil and paper tests of vigilance can be very useful in the assessment of attentional performance degradation due to sleep loss and/or inversion of the sleep-wake cycle. In this study we evaluated the sensitivity of a three-Letter Cancellation Task (3-LCT) in revealing nighttime variations of vigilance in a laboratory simulation of acute night shift, after a diurnal sleep with placebo (PLC) or temazepam (TMZ). Nocturnal levels of vigilance were also assessed using the Maintenance of Wakefulness Test (MWT) and the Multiple Sleep Latency Test (MSLT). All tests were administered four times at 2-h intervals during nighttime after a daytime sleep. Results show that the 3-LCT is sensitive to variations of vigilance occurring during a laboratory simulation of acute night shift. We also found some effects of TMZ, which in the first nocturnal session caused a slowing down of visuoattentive performance. Nocturnal variations of vigilance detected through the 3-LCT were similar to those revealed by means of MSLT, while the ability to maintain wakefulness was substantially spared during the night.

Adult↗

PubMedDate not supplied

Neurobehavioral functions in operating theatre personnel: a multicenter study.

The study was conducted to evaluate neuropsychological symptoms, subjective stress and response speed functions in subjects occupationally exposed to low levels of anesthetic gases. A group of 112 operating theatre personnel exposed to anesthetic gases (nitrous oxide and isoflurane), and 135 non exposed hospital workers from 10 hospitals in Northern Italy were examined before and after the shift on the first and the last day of the working week. Three different tasks were administered: a complex reaction time test (the Stroop Color Word); a questionnaire for neuropsychological symptoms (EURO-QUEST); the block design subtest (WAIS). Biological and atmospheric indicators of exposure were measured. In the exposed group, the geometric mean of urinary nitrous oxide at the end of the shift was 7.1 micrograms/l (95th percentile 12.4, range 1.5-43) on the first and 7.8 micrograms/l (95th percentile 21.5, range 1.0-73.3) on the last day of the working week. On the same days, end of shift urinary isoflurane was 0.7 microgram/l (95th percentile 2.6, range 0-4.7) on the first day and 0.8 microgram/l (95th percentile 2.0, range 0-5.6) on the last. The exposed and control subjects were comparable for both basic intellectual abilities and subjective stress levels. No statistical differences were observed between exposed and control subjects for neuropsychological tests and symptoms. No dose-effect relationships were observed between the exposure indicators and the test results. In conclusion, no early behavioral effect on the central nervous system was detectable at the exposure levels measured. The biological exposure limits of 13 micrograms/l for nitrous oxide and 1.8 micrograms/l for isoflurane corresponding respectively to the atmospheric concentrations of 25 ppm and 0.5 ppm seem to be adequately protective for the integrity of workers' neurobehavioral functions, as measured with the tests used.

Adolescent↗

PubMedDate not supplied

E-wave and heart rate responses during anticipation of nonmotor events.

This study concentrated on three main questions: 1) can anticipatory late negative shift (expectancy wave, E-wave) be elicited in nonmotor S1-S2 paradigm, 2) is it sensitive to variation of emotional aspects of the task and 3) is there a connection between heart rate (HR) responses and E-wave. S1 was a letter row that was replaced tachistoscopically by another letter row (S2). The task of the subjects (n = 12) was to detect if the critical aspects of S2 were similar to S1. After their delayed response they received feedback of their performance. The emotional aspects of the task were varied by presenting aversive noise bursts at the end of the feedback period either always, contingently to their performance or not at all. A negative shift was present both before S2 and aversive noise (when presented). Varying the emotional aspects of the task had an effect on the amplitude of the E-wave. There was also a connection between E-wave and heart rate responses: heart rate response seemed to be a precondition for E-wave elicitation. The results support Simons's conclusion that nonmotor E-wave reflects specifically emotional anticipation.

Acoustic Stimulation↗

PubMed2006

The perception of musical phrase structure: a cross-cultural ERP study.

Electroencephalography (EEG) was used in a cross-cultural music study investigating phrase boundary perception. Chinese and German musicians performed a cultural categorization task under Chinese and Western music listening conditions. Western music was the major subject for both groups of musicians, while Chinese music was familiar to Chinese subjects only. By manipulating the presence of pauses between two phrases in the biphrasal melodies, EEG correlates for the perception of phrase boundaries were found in both groups under both music listening conditions. Between 450 and 600 ms, the music CPS (closure positive shift), which had been found in earlier studies with a false tone detection task, was replicated for the more global categorization task and for all combinations of subject group and musical style. At short latencies (100 and 450 ms post phrase boundary offset), EEG correlates varied as a function of musical styles and subject group. Both bottom-up (style properties of the music) and top-down (acculturation of the subjects) information interacted during this early processing stage.

Acoustic Stimulation↗

PubMed2005

Prefrontal serotonin depletion affects reversal learning but not attentional set shifting.

Recently, we have shown that serotonin (5-HT) depletion from the prefrontal cortex (PFC) of the marmoset monkey impairs performance on a serial discrimination reversal (SDR) task, resulting in perseverative responding to the previously correct stimulus (Clarke et al., 2004). This pattern of impairment is just one example of inflexible responding seen after damage to the PFC, with performance on the SDR task being dependent on the integrity of the orbitofrontal cortex. However, the contribution of 5-HT to other forms of flexible responding, such as attentional set shifting, an ability dependent on lateral PFC (Dias et al., 1996a), is unknown. The present study addresses this issue by examining the effects of 5,7-dihydroxytryptamine-induced PFC 5-HT depletions on the ability to shift attention between two perceptual dimensions of a compound visual stimulus (extradimensional shift). Monkeys with selective PFC 5-HT lesions, despite being impaired in their ability to reverse a stimulus-reward association, were unimpaired in their ability to make an extradimensional shift when compared with sham-operated controls. These findings suggest that 5-HT is critical for flexible responding at the level of changing stimulus-reward contingencies but is not essential for the higher-order shifting of attentional set. Thus, psychological functions dependent on different loci within the PFC are differentially sensitive to serotonergic modulation, a finding of relevance to our understanding of cognitive inflexibility apparent in disorders such as obsessive-compulsive disorder and schizophrenia.

5,7-Dihydroxytryptamine↗

PubMed2002

Task switching deficits associated with Parkinson's disease reflect depleted attentional resources.

Using a Stroop task switching paradigm, Brown and Marsden [Brain 111 (1988) 323; Brain 114 (1991) 215] proposed that set shifting deficits in Parkinson's disease (PD) reflect limited attentional resources rather than deficits in internal control, as was previously supposed. In the present study, we tested this claim using a more recently developed Stroop task switching paradigm for which the internal control and attentional resources accounts made contrasting predictions. A PD group (N=30) was compared with an age-matched control group (N=34) on vocal response time (RT) for color naming and word reading in response to neutral and incongruent Stroop stimuli. Participants carried out four blocks of task repetition trials, and eight blocks of task switching trials. The results revealed that a deficit due to PD was absent for two conditions necessitating internal control, but was present in the condition which placed the highest demand on attentional resources. This selective deficit is congruent with Brown and Marsden's conclusions that depleted attentional resources, not an impairment in internal control per se, is the basis of the set shifting deficits associated with PD.

Aged↗