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PubMed2005

Relationship between dual-task related gait changes and intrinsic risk factors for falls among transitional frail older adults.

BACKGROUND AND AIMS: Gait changes in dual-task conditions have been associated with an increased risk of falling in older adults, and become more important in increasingly frail older adults. We studied the relationship between commonly known intrinsic risk factors for falls and dual-task related gait changes among transitional frail older adults. METHODS: Walking time and number of steps were measured while walking alone and while walking with counting backward on a 10-m walkway in 66 transitional frail older adults (mean age 83.6+/-6.1, 84.9% women). Uni- and multiple linear regression analyses were performed to explore the relationship between dual-task related gait changes (walking time and number of steps) and age over 85 years, polymedication, psychoactive drugs, poor distance vision, abnormal mobility and cognitive impairment. RESULTS: Compared with walking alone, both walking time and number of steps increased significantly while counting backward (p<0.001). Polymedication and abnormal mobility were associated with a significant increase of walking time and number of steps (p<0.01 for unadjusted change, p<0.05 for adjusted change). CONCLUSIONS: Dual-task related gait changes were closely correlated with polymedication and impaired mobility in our sample of transitional frail older adults. These findings give some insight into the complexity of performing attention-demanding tasks while walking and accentuate the need for multi-factorial, personalized intervention strategies, to prevent decline in dual-task performance in this fall-prone population.

Accidental Falls↗

PubMed1995

Performance on motor tasks as an indication of increased behavioral asymmetry with advancing age.

Age-related asymmetrical functional decline was tested on a sample of 64 right-handed volunteers between 60 and 64 years of age who were free from neurological illnesses and physical handicaps. Increase in functional asymmetry was explored by examining performance indexes for each hand and superiority of the dominant hand on motor tasks of different complexities: the Finger Tapping Test, the Grooved Pegboard Test, and the Pin Test. Our study revealed an increase in superiority of the right hand with age on a highly demanding task (Pin Test). This finding is discussed in light of the hypothesis of a decline in callosal functioning with age and the alternative hypothesis of a greater vulnerability of the right hemisphere in the elderly.

Aged↗

PubMed2002

Transfer of sensorimotor adaptation between different movement categories.

It is well known that sensorimotor adaptation will transfer from the practiced to the unpracticed arm, which has been taken as evidence that adaptation is located in the brain before the divergence point for left and right arm control. We now explore whether adaptation will transfer between different movement categories as well. Subjects were exposed to a 60-deg visual rotation first in a tracking and then in a pointing task, or vice versa. We found a substantial transfer of adaptation between tasks, but its magnitude was larger from pointing to tracking than from tracking to pointing. This benefit of pointing persisted when the use of cognitive strategies was minimized by a concurrent, attention-demanding task, but it was lost when pointing amplitudes were very small. We conclude that adaptation is located in the brain before the divergence point for different movement categories, and that movements with a large ballistic component facilitate adaptation transfer.

Adaptation, Physiological↗

PubMed2003

Working memory and prefrontal cortex dysfunction: specificity to schizophrenia compared with major depression.

BACKGROUND: A large number of studies suggest the presence of deficits in dorsolateral prefrontal cortex function during performance of working memory tasks in individuals with schizophrenia. However, working memory deficits may also present in other psychiatric disorders, such as major depression. It is not clear whether people with major depression also demonstrate impaired prefrontal activation during performance of working memory tasks. METHODS: We used functional magnetic resonance imaging to assess the patterns of cortical activation associated with the performance of a 2-back version of the N-Back task (working memory) in 38 individuals with schizophrenia and 14 with major depression. RESULTS: We found significant group differences in the activation of dorsolateral prefrontal cortex associated with working memory performance. Consistent with prior research, participants with schizophrenia failed to show activation of right dorsolateral prefrontal cortex in response to working memory tasks demands, whereas those with major depression showed clear activation of right and left dorsolateral prefrontal cortex as well as bilateral activation of inferior and superior frontal cortex. CONCLUSIONS: During performance of working memory tasks, deficits in prefrontal activation, including dorsolateral regions, are more severe in participants with schizophrenia (most of whom were recently released outpatients) than in unmedicated outpatients with acute nonpsychotic major depression.

Adult↗

PubMed1999

Similarity and categorisation: neuropsychological evidence for a dissociation in explicit categorisation tasks.

A series of experiments are reported on a patient (LEW) with difficulties in naming. Initial findings indicated severe impairments in his ability to freesort colours and facial expressions. However, LEW's performance on other tasks revealed that he was able to show implicit understanding of some of the classic hallmarks of categorical perception; for example, in experiments requiring the choice of an odd-one-out, the patient chose alternatives dictated by category rather than by perceptual distance. Thus, underlying categories appeared normal and boundaries appeared intact. Furthermore, in a two-alternative forced-choice recognition memory task, performance was worse for within-category decisions than for cross-category decisions. In a replication of the study of Kay and Kempton [Kay, P., Kempton, W., 1984. What is the Sapir-Whorf hypothesis? American Anthropologist 86, 65-78], LEW showed that his similarity judgements for colours could be based on perceptual or categorical similarity according to task demands. The consequences for issues concerned with perceptual categories and the relationship between perceptual similarity and explicit categorisation are considered; we argue for a dissociation between these kinds of judgements in the freesort tasks. LEW's inability to make explicit use of his intact (implicit) knowledge is seen as related to his language impairment.

Adult↗

PubMed2001

Medial prefrontal cortex and self-referential mental activity: relation to a default mode of brain function.

Medial prefrontal cortex (MPFC) is among those brain regions having the highest baseline metabolic activity at rest and one that exhibits decreases from this baseline across a wide variety of goal-directed behaviors in functional imaging studies. This high metabolic rate and this behavior suggest the existence of an organized mode of default brain function, elements of which may be either attenuated or enhanced. Extant data suggest that these MPFC regions may contribute to the neural instantiation of aspects of the multifaceted "self." We explore this important concept by targeting and manipulating elements of MPFC default state activity. In this functional magnetic resonance imaging (fMRI) study, subjects made two judgments, one self-referential, the other not, in response to affectively normed pictures: pleasant vs. unpleasant (an internally cued condition, ICC) and indoors vs. outdoors (an externally cued condition, ECC). The ICC was preferentially associated with activity increases along the dorsal MPFC. These increases were accompanied by decreases in both active task conditions in ventral MPFC. These results support the view that dorsal and ventral MPFC are differentially influenced by attentiondemanding tasks and explicitly self-referential tasks. The presence of self-referential mental activity appears to be associated with increases from the baseline in dorsal MPFC. Reductions in ventral MPFC occurred consistent with the fact that attention-demanding tasks attenuate emotional processing. We posit that both self-referential mental activity and emotional processing represent elements of the default state as represented by activity in MPFC. We suggest that a useful way to explore the neurobiology of the self is to explore the nature of default state activity.

Adult↗

PubMed2006

Getting in touch with Candida albicans: the cell wall of a fungal pathogen.

The cell wall of fungi is a highly complex structure consisting of a network of polysaccharides in which a plethora of different proteins are embedded. It is one of the major organelles of the cell surrounding it like an armor which protects from environmental stresses like osmotic pressure and defines the shape and physical strength of the fungal cell. It is crucial for colonization and infection since it defines the interface between host and pathogen. No similar structure is present in the host, therefore it defines a prime target for drug development. In this context, it has been shown that cell surface proteins are required for adhesion to host cells. The fact, that both pathogenic fungi, like Candida albicans as well as non-pathogenic fungi, like Saccharomyces cerevisiae, in general, have a very similar polysaccharide structure but differ significantly in their protein composition which underscores the importance of cell wall proteins for pathogenesis. However, cell wall proteomics of fungi is a highly challenging task due to the complex biochemistry of these proteins. The extensive post-translational modifications and covalent attachment to the polysaccharide backbone of a large proportion of cell wall proteins makes it a demanding task to isolate and identify them. In this article, we describe the recent approaches that have been developed to describe cell wall dynamics and to isolate and identify cell wall proteins in the pathogenic yeast C. albicans.

Animals↗

PubMedDate not supplied

[The conditioning of the N100-P200 component of the human visual evoked potential by using biofeedback].

Subjects were instructed to modify their N100-P200 component of VEP (in Cz recording) within selected time window. The aim was to increase the number of VEPs for which the amplitude of segment in question exceeded the definite threshold. The success in task performance suggests several modifications of the to-be-conditioned segment through different mechanisms. Of our 26 subjects, 14 were able to modify their VEPs according to the task demands. However, the latter subjects could be divided into 2 groups on the basis of the rate of increase in the number of correct responses under conditioning. Subjects which did not succeed in task performance could be also classed into 2 groups: one group with statistically negligible changes and the other decreasing the number of correct responses. ANOVA has shown significant distinctions in task performance for the groups with different levels of self-estimation of tiredness after experiment and different personal strategies. The success in task performance is likely to be dependent on the values of Eysenck questionnaire scales and topography of alpha activity.

Analysis of Variance↗

PubMed2001

Electrophysiological measures and dual-task performance in Tourette syndrome indicate deficient divided attention mechanisms.

Tourette syndrome has been associated with impairments of attentional functions such as distractability, even in subjects without co-morbid attention deficit hyperactivity disorder. Based on the results of earlier research we hypothesized that Tourette syndrome patients might employ altered control mechanisms of attentional processes and have concurrent difficulties in allocating their attentional resources among competing tasks. Event-related brain potentials (ERPs) were recorded in a group of Tourette syndrome patients and in a matched control group during a dual task experiment. This experiment required the simultaneous detection of visual and auditory target stimuli which were manipulated to yield two different difficulty levels each of which were varied orthogonally. The behavioural parameters confirmed the intended performance differences between difficult-to-detect targets and easy-to-detect targets. This was paralleled by lower amplitudes and longer latencies of the corresponding P3b-ERP subcomponents. Although Tourette syndrome patients were unimpaired in overall performance they showed an increased interference of visual task demands with auditory target perception. In parallel they also exhibited a reduced amplitude of the P3b component to auditory targets. The findings show that Tourette syndrome patients are not generally impaired in their dual task performance. The allocation of attentional resources to competing tasks however, is altered. We speculate that this may be related to deficient inhibitory functions.

Adolescent↗

PubMed1998

The effects of practice on the functional anatomy of task performance.

The effects of practice on the functional anatomy observed in two different tasks, a verbal and a motor task, are reviewed in this paper. In the first, people practiced a verbal production task, generating an appropriate verb in response to a visually presented noun. Both practiced and unpracticed conditions utilized common regions such as visual and motor cortex. However, there was a set of regions that was affected by practice. Practice produced a shift in activity from left frontal, anterior cingulate, and right cerebellar hemisphere to activity in Sylvian-insular cortex. Similar changes were also observed in the second task, a task in a very different domain, namely the tracing of a maze. Some areas were significantly more activated during initial unskilled performance (right premotor and parietal cortex and left cerebellar hemisphere); a different region (medial frontal cortex, "supplementary motor area") showed greater activity during skilled performance conditions. Activations were also found in regions that most likely control movement execution irrespective of skill level (e.g., primary motor cortex was related to velocity of movement). One way of interpreting these results is in a "scaffolding-storage" framework. For unskilled, effortful performance, a scaffolding set of regions is used to cope with novel task demands. Following practice, a different set of regions is used, possibly representing storage of particular associations or capabilities that allow for skilled performance. The specific regions used for scaffolding and storage appear to be task dependent.

Brain↗

PubMed2002

Perseverative behavior and adaptive control in older adults: performance monitoring, rule induction, and set shifting.

Older adults, like patients with dorsolateral frontal lobe lesions, have been shown to be progressively susceptible to errors of perseveration in the Wisconsin Card Sorting Test (WCST). This deficit may result from several types of endogenous adaptive control abilities. First, to enable behavioral modifications in response to sudden changes in task demands, one has to consider and evaluate the possible alternative categorization rules and select one for further testing (rule induction). Second, to perform the required shift appropriately, one should suppress the no-longer relevant task set and replace it by an appropriate new one (set shifting). Third, however, proper application of rule-induction and set-shifting abilities requires the ability to monitor and interpret task cues and feedback signals appropriately to guide behavior and to recognize the need to apply rule-shift operations (performance monitoring). To explore the extent to which these different endogenous adaptive control abilities are differentially sensitive to the effect of aging, young and older adults were tested in two experiments using WCST-like tasks. From the finding that older adults were not able to capitalize on explicit shift cues (either nonspecific or specific) the inference can be drawn that basic set-shifting abilities, rather than rule-induction or performance-monitoring abilities, were the primary factor responsible for the increased tendency to perseverate as adults grow into senescence.

Adaptation, Psychological↗

PubMed1994

Stimulus-driven capture and attentional set: selective search for color and visual abrupt onsets.

Recent evidence suggests that attentional capture is contingent on the attentional control setting induced by the task demands (C. L. Folk, R. Remington, & J. C. Johnston, 1992). Because the experiments on which these conclusions are based can be criticized for several reasons, the contingent capture hypothesis was tested using 2 visual search tasks in which subjects searched multielement displays in which a color singleton and onset singleton were simultaneously present. Both experiments show that the contingent capture hypothesis does not hold: Irrespective of attentional set, attention was captured by the most salient singleton. The findings suggest a stimulus-driven model of performance in which selection is basically determined by the properties of the featural singletons present in the visual field.

Adolescent↗

PubMed1987

The effects of videogame playing on the response selection processing of elderly adults.

Within an information processing framework, age-related declines in speeded responding are attributed to one or more stages of processing. It was the purpose of this experiment to demonstrate the potential reversibility of this decline in at least one processing stage, response selection. Two groups of elderly participants (57 to 83 years) were pretested on a two-choice reaction time (RT) task under two levels of spatial stimulus-response (S-R) compatibility, a task demand shown to affect response selection. Following the pretest, one group participated in 7 weeks of videogame play, whereas a second group did not. All participants were posttested on the same two-choice RT task. The results of the analysis of covariance revealed that those elderly individuals who played videogames were faster than the control participants under both levels of S-R compatibility. The effect of videogame play, however, was greater for low compatibility. These results are taken as support for a potential to improve response selection through videogame play.

Aged↗

PubMed1995

Is elevated blood pressure level associated with higher cardiovascular responsiveness in laboratory tasks and with response specificity?

Cardiovascular responsiveness and response specificity were investigated in male students, 48 with moderately elevated blood pressure (systolic blood pressure [SBP] > 140 mmHg and/or diastolic blood pressure [DBP] > 90 mmHg), 31 with mildly elevated blood pressure, and 57 with normal blood pressure. The behavioral tests and physically demanding tasks in the laboratory included mental arithmetic, free speech condition, cold pressor test, upright tilt, and ergometer exercise. Subjects with elevated blood pressure differed in baseline, task, and recovery levels of SBP, DBP, and heart rate. There were no significant effects in task-baseline differences or in residualized change scores. However, a positive initial-value dependency (LIV) in blood pressure responses was found: elevated blood pressure is associated with a larger increase under task conditions. Response scaling that employed reliability estimates and true difference scores indicated higher responsiveness in subjects with moderately elevated blood pressure and, thus, are in accordance with the positive LIV as compared with response measures based on task-baseline differences or residualized change scores. Findings from the specificity analysis indicated a higher incidence of SBP responders, that is, subjects with maximum response in SBP, among subjects with elevated blood pressure. Some of the inconsistencies in the literature with respect to blood pressure responsiveness and heart rate level in individuals with borderline hypertension may be attributed to the specific method of response scaling and to insufficient habituation to the setting and measurement.

Adult↗

PubMed2006

Integration of exogenous input into a dynamic salience map revealed by perturbing attention.

Although it is widely accepted that exogenous and voluntary factors jointly determine the locus of attention, the rules governing the integration of these factors are poorly understood. We investigated neural responses in the lateral intraparietal area (LIP) to transient, distracting visual perturbations presented during task performance. Monkeys performed a covert search task in which they discriminated the orientation of a target embedded among distractors, and brief visual perturbations were presented at various moments and locations during task performance. LIP neurons responded to perturbations consisting of the appearance of new objects, as well as to abrupt changes in the color, luminance, or position of existing objects. The LIP response correlated with the bottom-up behavioral effects of different perturbation types. In addition, neurons showed two types of top-down modulations. One modulation was a context-specific multiplicative gain that affected perturbation, target, and distractor activity in a spatially nonspecific manner. Gain was higher in blocks of trials in which perturbations directly marked target location than in blocks in which they invariably appeared opposite the target, thus encoding a behavioral context defined by the statistical contingency between target and perturbation location. A second modulation reflected local competitive interactions with search-related activity, resulting in the converse effect: weaker perturbation-evoked responses if perturbations appeared at the location of the target than if they appeared opposite the target. Thus, LIP encodes an abstract dimension of salience, which is shaped by local and global top-down mechanisms. These interacting mechanisms regulate responsiveness to external input as a function of behavioral context and momentary task demands.

Animals↗

PubMed1981

[Subjective and objective effects of music use during mental effort].

The subjective and objective effects of music consumption during intellectual work were assessed by a special questionnaire and the concentration paper-pencil-test (Brickencamp). Three different styles of music (pop-music, classical music and folk-music) were presented in a standardized way. It appeared that pop-music was experienced to be less conscious, less irritable and more pleasant than classical music. Although there was a subjective preference for pop- and folk-music an adequate increase of the concentration-test-scores could not be ascertained. On the contrary a significant discrepancy was found between subjective recorded music-effect and objective measured task-performance. Under the condition of classical music which was least preferred there was a significant greater variance of false responses than under the condition of no music. Nevertheless the total output of the discrimination-task was relatively the highest during classical music. The results are interpreted primarily as an enhanced psycho-physiological activation and a different selective concentration on music-presentation and task-demands. In accordance with empirical findings on psychological and physiological effects of music the results of this study reinforce the statement that also i mental activities music per se does not principally increase or lower the task output.

Achievement↗

PubMed1979

The effects of EMG feedback training during problem solving: a case study.

The present case study investigated the effects of competing task demands on biofeedback training to reduce frontalis muscle tension. Baseline levels of frontalis muscle tension were recorded for relaxation and problem solving. The subject was trained to decrease muscle tension with biofeedback for the problem-solving task alone. The results indicated that EMG training during problem-solving was successfully accomplished. Frontalis muscle tension during relaxation baseline did not change as a result of reductions in muscle tension during problem-solving feedback training. This suggests that the decrease of muscle tension cannot be attributed to reductions in overall muscle tension levels. Instead, training was specific to the problem-solving feedback phases. Additionally, it was found that accuracy in problem-solving did not decline as a result of simultaneous feedback training. Thus EMG biofeedback training can be accomplished and exercised without disruption of ongoing mental activity.

Adult↗

PubMed1996

[Functional magnetic resonance tomography during the activation of working memory].

AIMS: Functional magnetic resonance imaging was used in conjunction with a letter detection task for the study of working memory in 16 normal subjects. Because of movement artifacts, data from only 9 subjects were analysed. METHODS: In the activation task, subjects responded by pressing a button whenever any presented letter was the same as the second last in the sequence. In the control condition, the subjects had to respond to a fixed letter. Hence, the activation condition and the control condition differed only subjectively, i.e., regarding the task demand, whereas the stimuli and the type and frequency of response were identical. RESULTS: The activation condition produced significant activation in the dorsolateral prefrontal cortex (Brodmann's areas 10, 46, and 9). CONCLUSIONS: In contrast to experimental tasks previously used rather extensively to study the prefrontal cortex, the present paradigm is characterized by its simplicity, interpretability, and its ties to known neurophysiology of the frontal cortex.

Adult↗