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PubMed1998

Immature oocyte retrieval combined with in-vitro oocyte maturation.

Immature oocyte retrieval combined with in-vitro oocyte maturation has a considerable potential to increase knowledge on the microenvironment and nuclear and cytoplasmic maturation, and may be an alternative or even replacement for routine in-vitro fertilization as practised today. Understanding the critical steps to accomplish this task demands ongoing research to produce a comparable microenvironment to that of the developing follicle. This will allow cytoplasmic maturation to occur, and clarify knowledge on the selection of the dominant follicle, and utilize novel aspects fertilization and embryo culture in vitro. A second aspect of the produce concerns its clinical aspects. These include a better understanding of the number of antral follicles that can be retrieved transvaginally and the nature of the endometrial window and its advancement in order to provide a window of opportunity for implantation to occur.

Adult↗

PubMed2002

Dissociations in routine behaviour across patients and everyday tasks.

We present a single case study of a patient, FK, who was severely impaired on routine, everyday tasks, such as preparing a cup of tea. We used the action coding system developed by Schwartz et al. to provide quantitative and qualitative measures of his performance in a number of experimental manipulations. In section A, we established FK's baseline performance on a range of tasks with (a) task-congruent objects only and (b) task-congruent objects and semantic distracters. In section B, we aimed to facilitate FK's performance by (a) giving him a pictorial representation of the goal, (b) giving him a set of written commands to follow, (c) giving him one command at a time, (d) demonstrating how the task should be performed and (e) dividing the task into smaller subgoals. We compared FK's performance with another patient, HG, to establish if there are qualitative differences between patients with 'action disorganization syndrome'. In section C, we aimed to hinder FK's performance by interrupting his execution of routine tasks. By comparing the factors that facilitated and impaired FK's performance in sections B and C, we hoped to isolate the key cognitive processes required to generate and control routine behaviour. In section D, we investigated how task demands impact on our ability to complete different everyday activities. The results of these experiments have important clinical implications for rehabilitation programmes for patients with action disorganization syndrome and can also help to distinguish between contemporary theoretical accounts of routine behaviour. In particular, we propose that patients who can be classified under the umbrella term of 'action disorganization syndrome' do not all have a reduction to 'non-specific cognitive resources' but can have qualitatively different impairments to a specialized action production system.

Activities of Daily Living↗

PubMed1981

Self-instruction in a perceptual motor skill.

A self-instructional strategy using an audio-visual medium for learning the rehabilitation skill of a three-point crutch gait was developed and demonstrated to be effective with normal women of various activity levels naive to task demands. Briefly discussed are theoretical considerations based upon Fitt's three stages of acquiring a perceptual-motor skill and Fleishman and Hempel's experimental demonstrations that abilities required in learning change as learning progresses. In a modified posttest-only control group experiment with 20 women, ages 36 to 60, the hypothesis that subjects could learn the cognitive aspects of a motor skill in one viewing of a 6 1/2-minute film was supported. That some transfer of learning occurred to the performance of the skill was substantiated in a second experimental-control study with 20 women, ages 35 to 54. Six criteria were used to judge filmed motor performance of the subjects. Differences in performance between the two groups appeared to be in the quality of movement and the speed with which a subject moved from one stage of learning to the next. The limitations of the two studies and applications of the findings also were discussed.

Achievement↗

PubMed1993

Motor unit recruitment and the gradation of muscle force.

The capabilities of the different types of motor units are reviewed, and their properties in a variety of muscles are discussed. Because the tension-generating capacities of motor units are so different, the order in which they are recruited will have a strong influence on the way force output of the whole muscle is graded. Activation of motor units in a random order produces a roughly linear force increase with progressive recruitment, whereas recruitment of motor units in order of increasing force produces an approximately exponential force increase as the number of active motor units increases. The latter scheme allows fine control of weak movements and rapid production of powerful movements. Motor units are shown to be well adapted to the tasks they must perform, and a "compromise" motor unit will not fulfill all the tasks demanded of it. Finally, changes in motor unit properties produced by different activity patterns and by muscle reinnervation are reviewed, and the implications for rehabilitation are discussed.

Adaptation, Physiological↗

PubMed1993

Compartmentalization of muscles and their motor nuclei: the partitioning hypothesis.

This review article is designed to expose physical therapists to an examination of muscle organization and the implications that this organization has for therapeutic applications. The partitioning hypothesis is based on the fact that an individual muscle is arranged in a more complex array than simply fibers attaching at aponeuroses, tendons, or bones with a single muscle nerve innervation. Neuromuscular compartments, which are distinct subvolumes of a muscle, each innervated by an individual muscle nerve branch and each containing motor unit territories with a unique array of physiological attributes, are described. In addition, the organization of individual muscles into these subunits is paralleled by the organization of their parent motoneurons within the spinal cord. These notions are detailed in a review of data derived from studies performed primarily in cat and rat models. Recent data derived from morphological and anatomical study of human muscles support the existence of similar neuromuscular partitions. These data are complemented by physiological studies, the results from which suggest that partitions may have functional or task-oriented roles; that is, different portions of one muscle may be called into play depending on the task demands of the situation. The importance of these observations for reconsidering how we provide clinical applications, such as neuromuscular stimulation or kinesiological monitoring, is discussed.

Animals↗

PubMed1992

Developmental Processes in Schizophrenic Disorders: longitudinal studies of vulnerability and stress.

The Developmental Processes in Schizophrenic Disorders project is a longitudinal study of schizophrenic patients who have recently had a first episode of psychosis. The project focuses on discriminating characteristics of schizophrenic patients that are "stable vulnerability indicators," "mediating vulnerability factors," and "episode indicators" by comparing normal subjects to schizophrenic patients assessed in clinically remitted and psychotic states. A parallel project goal is to identify predictors of relapse, social and work impairment, and illness course among potential psychobiological vulnerability factors and environmental potentiating factors. Hypothesized vulnerability factors and potential environmental stressors are examined first under standardized maintenance antipsychotic medication conditions for at least 1 year. Patients showing stable remission of psychosis after 1 year of maintenance antipsychotic medication are invited to enter drug crossover and withdrawal protocols to determine the need for continuous antipsychotic medication. Vulnerability and stress factors are again assessed. A summary of results to date is presented. Deficits in early components of processing visual arrays and in sustained discrimination of successive ambiguous perceptual inputs are relatively stable across psychotic and clinically remitted states in the schizophrenic patients. Performance on a vigilance task demanding active, working memory also remains abnormal during clinical remission but covaries significantly with psychotic state and is a candidate for a mediating vulnerability factor. Autonomic activation level does not appear to be an enduring vulnerability factor, but it predicts the extent of short-term symptomatic recovery and may mediate the impact of stressors. Under conditions of standardized, injectable antipsychotic medication, independent stressful life events and highly critical attitudes toward the patient in the social environment predict relapse risk. Prospective data suggest that signs and symptoms prodromal to psychotic relapse may be present in about 60 percent of patients.

Adolescent↗

PubMed1997

Perseveration in schizophrenia.

Perseveration in schizophrenia may take a variety of forms, which can be conceptualized as varying manifestations of an underlying neurocognitive deficit. Comparative studies have demonstrated higher than normal levels of perseverative responding among schizophrenia patients on capacity-demanding tasks, including prompted discourse, reversal learning, and the generation of guessing sequences. There is little evidence that perseveration is associated with deficit signs of schizophrenia. However, perseveration appears to covary with both positive thought disorder and voluntary motor disturbance. Perseveration in schizophrenia thus appears to be a productive sign elicited by a failure to mobilize cognitive resources in situations requiring controlled information processing and the concomitant inhibition of activated but task-inappropriate responses. An information-processing model proposed by Shallice (1988) attributes perseveration to a failure of a higher level executive control system to modulate a lower level response selection system under a requirement for novel response generation. This model suggests that perseveration is the consequence of a failure of frontal specification of striatal outputs during controlled processing, resulting in the continued reselection of previously activated outputs.

Attention↗

PubMed1999

Spatial attention has different effects on the magno- and parvocellular pathways.

Attention was directed to the left or to the right of the fixation point by the lateral presentation of a target on which the subject had to perform an attention demanding task. A (task-irrelevant) grating displayed in the left visual field was the visual evoked potential (VEP) stimulus. Gratings modulated either in luminance or colour contrast at various temporal frequencies were used in order to maximise the activation of magno- or parvocellular pathways. VEPs recorded in attended and unattended conditions were compared. For luminance stimuli, both latency and amplitude of VEPs were modified by attention. For chromatic stimuli, attention affected the amplitude but not the latency of VEPs. Spatial attention uses different mechanisms when magno- or parvocellular systems are involved.

Adult↗

PubMed2000

Modulation of event-related potentials by prototypical and atypical faces.

High-density event-related potentials (HD-ERPs) were recorded while adults passively viewed colour images of faces that artificially (Experiment I) or naturally (Experiment II) differed in configuration. In Experiment I, altering features of faces to make them less typical and less attractive did not affect the amplitude of N170, but did affect the amplitude of P1 and P2. In Experiment II, the P1 and N170 were larger for unattractive and atypical faces compared with attractive and typical faces, in the absence of P2 effects. The results show for the first time that variations in facial configuration modulate ERP activity as early as P1, but that modulation of later latency components depends on the nature of the stimuli and implicit task demands.

Adult↗

PubMed2000

Theta synchronization predicts efficient memory encoding of concrete and abstract nouns.

Functional and topographical differences between processing of spoken nouns which were remembered or which were forgotten were shown by means of EEG coherence analysis. Later recalled nouns were related with increased neuronal synchronization (= cooperation) between anterior and posterior brain regions regardless of presented word category (either concrete or abstract nouns). However, theta coherence exhibited topographical differences during encoding of concrete and abstract nouns whereby former were related with higher short-range (mainly intrahemispheric), later with higher long-range (mainly interhemispheric) coherence. Thus, theta synchronization possibly is a general phenomenon always occurring if task demand increases and more efficient information processing is required. Measurement of EEG coherence yields new information about the neuronal interaction of involved brain regions during memory encoding of different word classes.

Adult↗

PubMed2003

A principled method for determining the functionality of brain responses.

A challenging issue in relating brain function to perception and cognition concerns the functional interpretation of brain responses. For example, while there is agreement that the N170 component of event-related potentials is sensitive to face processing, there is considerable debate about whether its response reflects a structural encoder for faces, a feature (e.g. eye) detector, or something else. We introduce a principled approach to determine the stimulus features driving brain responses. Our analyses on two observers resolving different face categorization tasks (gender and expressive or not) reveal that the N170 responds to the eyes within a face irrespective of task demands. This suggests a new methodology to attribute function to different components of the neural system for perceiving complex stimuli.

Brain↗

PubMed1989

Glare in aviation.

The control of high-speed aircraft is a demanding task in which rapid decisions, based on visually acquired information, must frequently be made. Glare, both direct and veiling, is a prime cause of visual degradation in flight. The visual effects of glare are discussed together with means of reducing its consequences. In addition, the visual sequelae of looking at a nuclear fireball are discussed together with means of providing protection.

Aerospace Medicine↗

PubMed2004

Neural correlates of facial affect processing in children and adolescents with autism spectrum disorder.

OBJECTIVE: To examine the neural basis of impairments in interpreting facial emotions in children and adolescents with autism spectrum disorders (ASD). METHOD: Twelve children and adolescents with ASD and 12 typically developing (TD) controls matched faces by emotion and assigned a label to facial expressions while undergoing functional magnetic resonance imaging. RESULTS: Both groups engaged similar neural networks during facial emotion processing, including activity in the fusiform gyrus (FG) and prefrontal cortex. However, between-group analyses in regions of interest revealed that when matching facial expressions, the ASD group showed significantly less activity than the TD group in the FG, but reliably greater activity in the precuneus. During the labeling of facial emotions, no between-group differences were observed at the behavioral or neural level. Furthermore, activity in the amygdala was moderated by task demands in the TD group but not in the ASD group. CONCLUSIONS: These findings suggest that children and adolescents with ASD in part recruit different neural networks and rely on different strategies when processing facial emotions. High-functioning individuals with ASD may be relatively unimpaired in the cognitive assessment of basic emotions, yet still show differences in the automatic processing of facial expressions.

Adolescent↗

PubMed2000

Prolonged but delayed postischemic hypothermia: a long-term outcome study in the rat middle cerebral artery occlusion model.

Delayed but prolonged hypothermia persistently decreases cell death and functional deficits after global cerebral ischemia in rodents. Postischemic hypothermia also reduces infarction after middle cerebral artery occlusion (MCAO) in rat. Because initial neuroprotection is sometimes transient and may not subserve functional recovery, especially on demanding tasks, the authors examined whether postischemic cooling would persistently reduce infarction and forelimb reaching deficits after MCAO. Male spontaneously hypertensive rats were trained to retrieve food pellets in a staircase test that measures independent forelimb reaching ability. Later, rats underwent 90 minutes of normothermic MCAO, through a microclip, or sham operation. In some rats, prolonged cooling (33 degrees C for 24 hours and then 35 degrees C for 24 hours) began 2.5 hours after the onset of ischemia (60 minutes after the start of reperfusion; n = 17 with subsequently 1 death) or sham procedures (n = 4), whereas untreated sham (n = 4) and ischemic (n = 16 with subsequently 1 death) rats maintained normothermia. An indwelling abdominal probe continually measured core temperature, and an automated fan and water spray system was used to produce hypothermia. One month later rats were reassessed in the staircase test over five days and then killed. The contralateral limb impairment in food pellet retrieval was completely prevented by hypothermia (P = 0.0001). Hypothermia reduced an infarct volume of 67.5 mm3 after untreated ischemia to 35.8 mm3 (P < 0.0001). These findings of persistent benefit encourage the clinical assessment of hypothermia.

Animals↗

PubMed2006

Temperament and vagal tone in boys with fragile X syndrome.

Physiological hyperarousal, an elevated state of physiological arousal and poor modulation, has been postulated to be a significant source of behavior problems in children with fragile X syndrome (FXS). Temperament has been associated with behavior problems and may also reflect biological reactivity. Young boys with FXS display poorly modulated and low levels of vagal tone (Roberts, Dev Psychobiol 2001;39:107-123) and high activity, poor attention, low adaptability, poor persistence, and low intensity when compared with a reference sample of typically developing (Hatton, Dev Med Child Neurol 1991;41:625-632). In this study, we integrated physiological indices of vagal tone with temperament ratings and compared a sample of 29 young boys with FXS to 31 typically developing boys matched on chronological age and ethnicity. Boys with FXS were more active, less adaptable, and less persistent than the comparison group. Boys with FXS also showed lower baseline levels and less suppression of vagal tone in response to changing task demands. A relationship between baseline vagal tone and persistence was shown across both groups. However, group differences in temperament dimensions did not appear to be mediated or moderated by vagal tone.

Arousal↗

PubMed2006

Visual rehabilitation of children with visual impairments.

Visual rehabilitation, consisting of visual stimulation and visual training, is a common practice in the education of children with visual impairments. Ferrell and Muir have stated that scientific research into the effects of visual stimulation and training is ambiguous and that therefore stimulation and training should be abandoned. The support for this statement is reviewed by describing the scientific relevance and plausibility of the aims and presuppositions of visual stimulation and training programs as well as the results of 10 empirical intervention studies. The review results are in strong agreement with the claim of Ferrell and Muir to abandon noncontingent visual stimulation. It is hypothesized that it is possibly counterproductive for the adaptive functioning of the brain to show strong visual stimuli in artificial surroundings, which are noncontingent on the behavior of the child. Training of visual functions seems fruitful whenever skills that are ecologically valid and adapted to the individual needs and task demands of the child are trained. However, the empirical evidence is still too sparse to draw convincing conclusions. There is an urgent need for good randomized controlled trials with dependent variables that are relevant to everyday life.

Adaptation, Psychological↗

PubMed1981

Effects of lithium carbonate and haloperidol on cognition in aggressive hospitalized school-age children.

A comparison of the effects of lithium, haloperidol, and placebo on cognition is reported for a sample of hospitalized school-age children with a behavioral profile of aggressiveness and explosiveness. In this double-blind study, patients were randomly assigned to one of three treatment conditions. The cognitive battery was administered at the end of a 2-week placebo baseline period and again after 4 weeks of treatment. It included a simple reaction time (RT) task with preparatory intervals of 1, 4, and 8 seconds, the Porteus Mazes, and the Matching Familiar Figures Test. Drug effects on cognition, when found, were mild. Slower and more variable RTs were found on the RT task in the haloperidol group (mean dose, 3.1 mg/day), particularly at the 4- and 8-second preparatory intervals in comparison to placebo. This appeared to reflect decreased ability to hold a preparatory set. No other effects of haloperidol on cognitive performance were found. Lithium carbonate (mean dose, 1150 mg/day) caused a deterioration in qualitative performance on the Porteus Maze Test when compared with haloperidol but had no effect on test quotient scores or on the other cognitive measures. Results are discussed in terms of dose effects and the influences of task demands. This is part of a study critically assessing the effects of lithium and haloperidol on behavioral symptoms and other parameters.

Aggression↗

PubMedDate not supplied

Reduction of posterior hip dislocations in the lateral position using traction-countertraction: safer for the surgeon?

Closed reduction of a hip dislocation is a physically demanding task for the orthopaedic surgeon. The most commonly used methods for reduction of the hip involve vigorous axial traction on the lower extremity with the patient in the supine position, using an assistant who attempts to hold the pelvis down. The surgeon generally stands over the patient to pull up on the bent knee, which puts the surgeon at risk for a low back injury and, if done while the patient remains on a stretcher, can put the surgeon at risk for a fall from a height. Reduction in the prone position is advocated by some, but caring for the sedated patient in the prone position can be difficult and the patient's pelvis tends to roll off the edge of the stretcher, preventing the achievement of hip flexion, which is desirable in achieving reduction. We describe a traction-countertraction technique that appears to be significantly less dangerous for the surgeon. In this technique the hip is reduced with the patient remaining on the stretcher in the lateral position. In addition, fluoroscopy can be carried out during the reduction maneuver, and the images can be quite helpful in adjusting the direction of manipulative forces.

Hip Dislocation↗