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PubMed1999

Acoustic variations in adductor spasmodic dysphonia as a function of speech task.

Acoustic phonatory events were identified in 14 women diagnosed with ADSD and compared to those of 14 women age-matched (+/-2 years) with no evidence of vocal pathology/dysfunction. The three acoustic parameters examined during sustained vowel production and reading included phonatory breaks, aperiodicity, and frequency shifts. Intra- and intermeasurer correlations showed high reliability for the measures. Findings indicated that those with ADSD produced a greater frequency of aberrant acoustic events than the controls during both tasks. For the group with ADSD, the amount and type of each event also varied with utterance type. The sustained vowel sample produced by those with ADSD consisted of a greater percentage of aperiodic segments followed by phonatory breaks and frequency shifts. During reading, frequency shifts were the predominant acoustic event, followed by phonatory breaks and aperiodicity. The advantage of segmenting the acoustic waveform into these measures and the relevancy of examining intertask performances by those with ADSD is discussed.

Adult↗
PubMed1985

Discrimination shift learning and response inhibition of moderately and severely mentally retarded and non-retarded children.

Simple two-choice discrimination shift learning performances of 20 moderately and severely mentally retarded children were compared with those of 20 non-retarded ones. A learning task arranged with a pair of yellow circle and green triangle slides was used. No difference was found between mentally retarded and non-retarded children in the learning rate of initial discrimination, but the mentally retarded attained shift discrimination more slowly than the non-retarded. Also, the extinction of initial positive responses in mentally retarded children was slower than in non-retarded children. It was suggested that the difficulty of discrimination shift in severely subnormal children is due to failure to suppress a previously learned response to prior positive cues.

Adolescent↗
PubMed2001

Interactive computer aided shift scheduling.

This paper starts with a discussion of computer aided shift scheduling. After a brief review of earlier approaches, two conceptualizations of this field are introduced: First, shift scheduling as a field that ranges from extremely stable rosters at one pole to rather market-like approaches on the other pole. Unfortunately, already small alterations of a scheduling problem (e.g., the number of groups, the number of shifts) may call for rather different approaches and tools. Second, their environment shapes scheduling problems and scheduling has to be done within idiosyncratic organizational settings. This calls for the amalgamation of scheduling with other tasks (e.g., accounting) and for reflections whether better solutions might become possible by changes in the problem definition (e.g., other service levels, organizational changes). Therefore shift scheduling should be understood as a highly connected problem. Building upon these two conceptualizations, a few examples of software that ease scheduling in some areas of this field are given and future research questions are outlined.

Accounting↗
PubMed2003

Spatial interference and response control in sequence learning: the role of explicit knowledge.

In several sequence learning studies it has been suggested that response control shifts from the stimuli to some internal representation (i.e., motor program) through the learning process. The main questions addressed in this paper are whether this control shift is related to explicit knowledge and whether the formation of these internal representations depends on the stimulus attributes. In one experiment we compared the learning of a response sequence triggered by either spatial location or location symbol (left-right) by using a serial response task (SRT). Symbols were presented at either a centered or random location. The results showed that in the symbolic conditions the shift of response control correlated with the emergence of explicit knowledge. Only participants with complete explicit knowledge seemed to learn the sequence structure beyond probabilistic information (response time "RT" did not depend on the frequency of the response). Moreover, these participants were able to overcome, when needed, spatial interference (RT was the same for both spatially corresponding and non-corresponding trials). However, when spatial location was relevant, RT was always faster, especially for more frequent responses. These results suggest that the relevant stimulus dimension (location or symbol) seems to engage different sequence learning mechanisms.

Adult↗
PubMed1993

Parametric in vivo brain imaging during activation to examine pathological mechanisms of functional failure in Alzheimer disease.

Alzheimer disease (AD) patients demonstrate reduced "resting state" regional cerebral metabolic rates for glucose (rCMRglc) and reduced regional cerebral blood flow (rCBF) in cortical association areas, early and throughout the course of disease. In this paper, we hypothesize that parametric cognitive or passive stimulation, during in vivo brain imaging, can be used to elucidate the pathological basis of these flow and metabolic abnormalities in individual AD patients. Experimental data suggest that sigmoidal relations (nonliner monotonically increasing relations reaching a horizontal asymptote) exist in the normal brain between rCBF or rCMRglc, and a function F(D,P) of task difficulty D (intensity, duration, pattern complexity) and subject performance P (reaction time, accuracy, effort, attention). Pathological mechanism I, under some conditions reversible and involving neural (including synaptic) element dropout or modification with retained capacity for full activation at high values of F(D,P), is expected early in AD and should shift the rising phase of the normal sigmoidal curve to the right. Observed rCBF responses in a face-matching task in mildly-moderately demented AD patients are consistent with mechanism I. Pathological mechanisms II and III, both irreversible and involving neural element dropout with loss of capacity for maximum activation, should alter the sigmoidal brain response at all values of F(D,P), and are expected late in disease. Our hypothesis predicts that activation paradigms with a wide range of F(D,P) values could help to distinguish among the reversible and irreversible pathological mechanisms in AD, and to evaluate drug action on these mechanisms.

Aged↗
PubMed2006

Executive functions in school-age children born very prematurely.

BACKGROUND: School-age preterm children are at risk for cognitive difficulties including Executive Dysfunction and low average IQ. AIM: The aim of this study was to determine the performance of very preterm, school-age children on three components of Executive Function (EF), two components of Executive Attention and a measure of IQ. STUDY DESIGN: Cross-sectional, independent samples comparison. METHODS: A UK sample of 40 very preterm (<32 weeks gestational age, Mean 28.43, SD 2.41) children and 41 term born control children aged between 6 and 12 years (mean ages 8 years 5 months in both groups) was assessed on IQ, EF (inhibition, working memory and set shifting) and attention (sustained and selective). Between group comparisons were made using multivariate analysis of variance and covariance. RESULTS: Multivariate analyses indicated that preterm children scored significantly lower than their term born peers across Executive Function and executive attention tasks. As expected, the preterm group achieved IQ scores at the low end of the average range. Univariate analyses indicated some difficulties with shifting and inhibition components of EF, although covariate analysis revealed that only shifting was independent of IQ. CONCLUSIONS: Preterm children showed mild executive function and executive attention difficulties in the context of average IQ scores. The findings highlight the benefit of using multivariate assessments of executive skills rather than general intellectual outcome alone, to obtain a better distinction of the specific cognitive weaknesses associated with preterm birth.

Attention↗
PubMed2005

Changes in brain activation during the acquisition of a multifrequency bimanual coordination task: from the cognitive stage to advanced levels of automaticity.

Little is known about activation changes reflecting overlearning, i.e., extensive motor training beyond asymptotic performance. Here we used functional magnetic resonance imaging to trace the neural shifts from an initial to a skilled (learning) and finally overlearned stage (automatization). Scanning occurred before training (PRE) and after 1 (MID) and 2 weeks (POST) of intensive practice on a new bimanual coordination task (>10,500 cycles). Kinematics revealed major improvements between PRE and MID sessions, whereas MID to POST session performance leveled off, indicative of learning and automatization, respectively. Imaging findings showed that activation decreased in bilateral opercular areas, bilateral ventrolateral prefrontal cortex, the right ventral premotor and supramarginal gyrus, and the anterior cingulate sulcus during the learning stage and in the supplementary motor area during the automatization stage. These changes are hypothesized to reflect decreases in attention-demanding sensory processing, as well as suppression of preferred coordination tendencies as a prelude to acquiring new coordination modes. Conversely, learning-related increases were observed in the primary motor cortex (M1), posterior cingulate zone (PCZ), putamen, and right anterior cerebellum. Importantly, both M1 and PCZ activation decreased again to initial level (PRE) during automated performance (POST). Only the putamen and anterior cerebellum remained more activated across both learning and automatization stages, supporting their crucial role in long-term motor memory formation for coordination tasks.

Adult↗
PubMed1980

Shift of attention in schizophrenics, siblings of schizophrenics, and depressed patients.

This study investigated whether deviant types of attention, measured by reaction time, would characterize schizophrenics, depressives, and healthy siblings of the schizophrenic probands. Nineteen schizophrenics, 16 depressives, 15 healthy siblings of the schizophrenics, and 19 normals were tested on the cross-modal reaction time task. Two ways of conveying information about the impending imperative stimulus were compared to attempt to normalize schizophrenic cross-modal retardation. Deviant shift of attention was measured by cross-modal retardation, i.e., a greater than normal lengthening of reaction time to cross-modal vs. ipsimodal stimuli. Both schizophrenics and depressives showed deviant shift of attention to sound stimuli, but only schizophrenics were deviant to light stimuli. Anomalous cross-modal retardation was not normalized by the experimental manipulation. Both patient groups showed significantly slowed reaction time, suggesting deviances of general alertness. Depressed patients displayed anomalous sustained attention, indexed by significant lengthening of reaction time over trials. Siblings of schizophrenics did not differ significantly from controls on any aspect of reaction time performance. High magnitude of cross-modal retardation to sound and slow overall reaction time may be markers of psychopathological disorder rather than vulnerability. High cross-modal retardation to light may be a marker of schizophrenic disorder. Slowing of reaction time over trials is a potential marker of depressive disorder.

Adolescent↗
PubMed1984

Differential effects of prefrontal lesions and combined prefrontal and limbic lesions on subsequent learning performance in the cat.

On the basis of a previous experiment (Irle & Markowitsch, 1983) in which triple limbic lesions as opposed to double limbic lesions in the cat failed to impair the learning behavior of these animals, the effects of a lesion in a fourth brain structure, in addition to the original ones, were examined. Two groups of cats were given lesions in either the prefrontal cortex alone or in the prefrontal cortex, the anterior thalamus, the mamillary bodies, and the subiculum and subsequently tested in the acquisition of a visual reversal, a delayed alternation, and an active two-way avoidance task. Compared with control cats, cats with prefrontal lesions were strongly impaired in the acquisition of the visual reversal task and the delayed alternation task but only slightly impaired in the acquisition of the active two-way avoidance task. In contrast, animals with combined prefrontal cortical, anterior thalamic, mamillary, and subicular lesions were unimpaired in the acquisition of the visual reversal task, slightly facilitated in the acquisition of the active two-way avoidance task, but impaired in the acquisition of the delayed alternation task similarly to the animals with prefrontal lesions. The superior performance rates of the animals with fourfold lesions are considered to be due to a lesion-induced functional shift acting on intact brain structures which, prior to massive limbic lesions, remain inhibited or otherwise suppressed. The failure of the animals with fourfold lesions in the delayed alternation task indicates that the functions underlying this type of behavior cannot be compensated for or, alternatively, that a prefrontal lesion is not sufficient to disinhibit other structures involved in the same behavior.

Animals↗
PubMed1995

Trait and state anxiety before and after competitive performance.

33 subjects were tested on competitive trait and state anxiety immediately before and after a competitive motor task of short duration (average performance time of 25 seconds). It required precise coordination of correct muscular activity, timing as well as speed, and physical strength that included explosive shifts in direction of movement. Two types of performance measures were employed, (a) number of errors during the performance and (b) the time it took to complete the motor task. Analysis showed a positive relation between trait anxiety and performance errors when a linear model was applied; however, when a curvilinear model was used, a strong significant U-relationship between errors and precompetition state anxiety emerged. Further, a strong positive linear relation between poststate anxiety and number of performance errors was observed. The results indicate that making errors in performance situations is a critical factor in producing postcompetition state anxiety.

Adult↗
PubMedDate not supplied

Purse-string sutures for hyperopia following radial keratotomy.

BACKGROUND: Five years ago, we presented 19 procedures employing two intrastromal purse-string sutures to treat hyperopic shift following radial keratotomy. Thirty-four additional procedures and longer follow-up are now presented detailing the task of rehabilitating these eyes. METHODS: Fifty-three eyes of 53 radial keratotomy patients who were unhappy with their uncorrected vision and who were dissatisfied with contact lens or spectacle correction underwent double corneal intrastromal purse-string suturing and were subsequently followed for at least 1 year. There were seven eyes with primary overcorrection and 46 eyes with progressive hyperopic shift. Spherical equivalent refraction before purse-string sutures ranged from +0.50 to +6.25 D (mean, +2.60 D, SD +/- 1.26 D). Prior to purse-string suturing, uncorrected visual acuity ranged from 20/30 to 20/400 with 21 eyes (45.3%) 20/100 or worse. RESULTS: The follow-up after suturing averaged 3.6 years (range, 1 to 10 yr). All patients had follow-up of at least 1 year. The steepening in average keratometric power was 2.94 +/- 1.72 D (range, 1.06 to 6.68 D). The sherical equivalent refraction after suturing averaged -0.15 +/- 1.17 D (range, +3.75 to -2.50 D). Uncorrected visual acuity after suturing was 20/40 or better in 38 eyes (72%) and 20/50 to 20/100 in 15 eyes (28%). The number of eyes with a spherical equivalent refraction of +/- 0.50 D with 0.50 D or less refractive astigmatism was 15 (26% of eyes). There were 34 eyes (66%) with +/- 1.00 D with 1.00 D or less of refractive astigmatism, and 42 eyes (78%) with +/- 2.00 D with 2.00 D or less refractive astigmatism. Most of the spread was on the myopic side, as intended. There were no significant intraoperative or postoperative complications. Fifteen eyes gained two or more lines of best spectacle-corrected visual acuity and no eyes lost one line. CONCLUSION: Double intrastromal purse-string suturing produces steepening of the central cornea and reduces hyperopia after radial keratotomy.

Adult↗
PubMed2004

Cross-shift changes in FEV1 in relation to wood dust exposure: the implications of different exposure assessment methods.

BACKGROUND: Exposure-response analyses in occupational studies rely on the ability to distinguish workers with regard to exposures of interest. AIMS: To evaluate different estimates of current average exposure in an exposure-response analysis on dust exposure and cross-shift decline in FEV1 among woodworkers. METHODS: Personal dust samples (n = 2181) as well as data on lung function parameters were available for 1560 woodworkers from 54 furniture industries. The exposure to wood dust for each worker was calculated in eight different ways using individual measurements, group based exposure estimates, a weighted estimate of individual and group based exposure estimates, and predicted values from mixed models. Exposure-response relations on cross-shift changes in FEV1 and exposure estimates were explored. RESULTS: A positive exposure-response relation between average dust exposure and cross-shift FEV1 was shown for non-smokers only and appeared to be most pronounced among pine workers. In general, the highest slope and standard error (SE) was revealed for grouping by a combination of task and factory size, the lowest slope and SE was revealed for estimates based on individual measurements, with the weighted estimate and the predicted values in between. Grouping by quintiles of average exposure for task and factory combinations revealed low slopes and high SE, despite a high contrast. CONCLUSION: For non-smokers, average dust exposure and cross-shift FEV1 were associated in an exposure dependent manner, especially among pine workers. This study confirms the consequences of using different exposure assessment strategies studying exposure-response relations. It is possible to optimise exposure assessment combining information from individual and group based exposure estimates, for instance by applying predicted values from mixed effects models.

Cross-Sectional Studies↗
PubMed1979

Glycogen depletion in a game-simulated hockey task.

A game-simulated hockey task has been developed to closely approximate the actions in a hockey game including forward and backward skating, stops, starts, shooting and passing. As well, the test is similar to game conditions for number of shifts, activity time per shift, activity time per play and total active time on the ice. The purpose of this study was to measure the glycogen depletion during the task and to compare this with laboratory tasks and actual game conditions. The results demonstrate that the simulated tasks resembles on ice conditions during a game for heart rate and glycogen depletion. The preferential glycogen utilization by ST fibres but great depletion in FT fibres as well suggests that the task is strenuous enough to stimulate both FT and ST motor units.

Glycogen↗
PubMed1987

Tonic accommodation, cognitive demand, and ciliary muscle innervation.

An infrared optometer was used to investigate the relation between cognitive induced shifts in tonic accommodation (TA) and ciliary muscle innervation. Twenty emmetropic men volunteers took part in a double-masked protocol which involved high (a reverse counting task) and low levels of mental load and blocking of sympathetic innervation of the ciliary muscle with the nonselective beta receptor antagonist timolol maleate (0.5%). The high level of cognitive demand induced shifts in TA of up to +1 D. There was no clear reason why large differences in intersubject susceptibility to these shifts occurred. The effect of beta-antagonism on these shifts was insignificant for subjects having initial TA values less than 1.2 D. However, sympathetic antagonism induced significant increases in cognitive shifts for the remaining subjects. The inference is that cognitive induced shifts in TA are predominantly parasympathetic mediated although a sympathetic attenuation may occur at higher levels of TA.

Accommodation, Ocular↗
PubMed2006

Properties of synergies arising from a theory of optimal motor behavior.

We consider the properties of motor components, also known as synergies, arising from a computational theory (in the sense of Marr, 1982) of optimal motor behavior. An actor's goals were formalized as cost functions, and the optimal control signals minimizing the cost functions were calculated. Optimal synergies were derived from these optimal control signals using a variant of nonnegative matrix factorization. This was done using two different simulated two--joint arms--an arm controlled directly by torques applied at the joints and an arm in which forces were applied by muscles--and two types of motor tasks-reaching tasks and via-point tasks. Studies of the motor synergies reveal several interesting findings. First, optimal motor actions can be generated by summing a small number of scaled and time-shifted motor synergies, indicating that optimal movements can be planned in a low-dimensional space by using optimal motor synergies as motor primitives or building blocks. Second, some optimal synergies are task independent--they arise regardless of the task context-whereas other synergies are task dependent--they arise in the context of one task but not in the contexts of other tasks. Biological organisms use a combination of task--independent and task--dependent synergies. Our work suggests that this may be an efficient combination for generating optimal motor actions from motor primitives. Third, optimal motor actions can be rapidly acquired by learning new linear combinations of optimal motor synergies. This result provides further evidence that optimal motor synergies are useful motor primitives. Fourth, synergies with similar properties arise regardless if one uses an arm controlled by torques applied at the joints or an arm controlled by muscles, suggesting that synergies, when considered in "movement space," are more a reflection of task goals and constraints than of fine details of the underlying hardware.

Animals↗
PubMed2001

The integration of parallel and serial processing mechanisms in visual search: evidence from eye movement recording.

We examined timing and scanning paths of eye movements during a visual search task, in which subjects had to detect, as quickly as possible, the presence or absence of a target among distractors [Q-like element among O stimuli (QvsO) and vice-versa (OvsQ)]. According to an influential theory [Treisman, A. & Gelade, G. (1980) Cognitive Psychol, 12, 97--136; Treisman, A. & Sato, S. (1990) J. Exp. Psychol. Hum. Percept. Perform., 16, 459--478], only tasks yielding nonflat search functions (OvsQ) involve focal attention. Alternative models propose that all kinds of visual search are resolved by a biased competitive process, working in parallel across the visual field. Data show that QvsO and OvsQ tasks are characterized by quantitative rather than by qualitative differences in search strategy. No differences between the two tasks were found regarding either the percentage of saccades foveating single stimulus items or the timing of the button response with respect to the onset of the last foveation saccade within a trial. Furthermore, the number of saccades made during search predicted very accurately the time required to accomplish the task and fixation times were independent of the number of stimulus items. On the basis of our results there is no reason to postulate the occurrence of shifts of visuospatial attention, other than those associated with the executions of saccadic eye movements, which are driven by a parallel feature analysis of the visual scene, in both types of search tasks. A time-limited competitive model for attentive target identification, in which both parallel (competitive) and serial (attentive) processing mechanisms are integrated, can account for these findings, providing a unified conceptual framework for all kinds of visual search.

Adult↗
PubMed2001

Wisconsin Card Sorting revisited: distinct neural circuits participating in different stages of the task identified by event-related functional magnetic resonance imaging.

The Wisconsin Card Sorting Task (WCST) has been used to assess dysfunction of the prefrontal cortex and basal ganglia. Previous brain imaging studies have focused on identifying activity related to the set-shifting requirement of the WCST. The present study used event-related functional magnetic resonance imaging (fMRI) to study the pattern of activation during four distinct stages in the performance of this task. Eleven subjects were scanned while performing the WCST and a control task involving matching two identical cards. The results demonstrated specific involvement of different prefrontal areas during different stages of task performance. The mid-dorsolateral prefrontal cortex (area 9/46) increased activity while subjects received either positive or negative feedback, that is at the point when the current information must be related to earlier events stored in working memory. This is consistent with the proposed role of the mid-dorsolateral prefrontal cortex in the monitoring of events in working memory. By contrast, a cortical basal ganglia loop involving the mid-ventrolateral prefrontal cortex (area 47/12), caudate nucleus, and mediodorsal thalamus increased activity specifically during the reception of negative feedback, which signals the need for a mental shift to a new response set. The posterior prefrontal cortex response was less specific; increases in activity occurred during both the reception of feedback and the response period, indicating a role in the association of specific actions to stimuli. The putamen exhibited increased activity while matching after negative feedback but not while matching after positive feedback, implying greater involvement during novel than routine actions.

Adolescent↗