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PubMed2005

Effects of excitotoxic thalamic intralaminar nuclei lesions on attention and working memory.

In rats, lesions of the thalamic intralaminar nuclei (ILn) impair measures of working memory, but it is unclear whether alterations of attention contribute to the mnemonic deficits. The present experiment tested the effects of ILn lesions on a two-lever attention task that required discrimination of visual signals and non-signals. Rats were trained presurgically in the task and then received sham surgery or infusions of n-methyl-d-aspartate (NMDA) into the ILn to induce excitotoxic lesions. ILn lesions transiently decreased accurate detection of signals. ILn lesions also increased omissions. Compared to sham-lesioned rats, ILn-lesioned animals were not differentially affected when task demands were increased by presenting a visual distracter. Finally, a retention interval was incorporated into the task to assess whether the lesions affected acquisition of a working memory version of this behavioral paradigm. Unlike sham-lesioned animals, ILn-lesioned rats did not demonstrate a significant improvement in signal detection when a retention interval was introduced. The transient lesion-induced deficits in the attention task suggest that, in rats, the ILn may contribute to aspects of attentional processing, but through neural re-organization or activity in other regions, there is compensation for the loss of ILn functioning. The ILn appear to be necessary for maintaining performance when working memory demands are increased.

Analysis of Variance↗

PubMed2001

Distraction modulates anterior cingulate gyrus activations during the cold pressor test.

The anterior cingulate gyrus (ACG) is part of a neural network implicated in attention-demanding tasks, such as the experience of pain. However, the regions within the ACG responding to cognitive demands and to painful stimulation are not identical. Since directing attention away from a painful stimulus is known to reduce the perceived pain intensity, we hypothesized that distraction from pain would result both in decreased activation of ACG subregions responsive to painful stimulation and increased activation of ACG subregions responsive to the distraction task. BOLD fMRI has comparatively high spatial resolution and allows for better identification of ACG subregional responses than other neuroimaging techniques. Twelve subjects were tested using the cold pressor test (CPT), a verbal attention task (VAT), and a distraction task (DT) (a combination of the CPT and VAT). Analysis was performed on a voxel-by-voxel basis using a general linear model as implemented in SPM99. In addition to ACG activations common to both the CPT and VAT, we identified one CPT-specific cluster in an area corresponding to BA24'. The modulation effect of distraction on pain was assessed by contrasting (CPT-DT) and (DT-CPT). In support of our hypothesis, contrast (CPT-DT) revealed a decrease in BA24' during the DT and contrast (DT-CPT) showed increased activation in BA32/32'. These data suggest that distraction from pain and concomitant low pain ratings are reflected in distinct ACG subregional responses.

Adult↗

PubMed2004

Short-term repeatability of body sway during quiet standing in people with hemiparesis and in frail older adults.

OBJECTIVE: To investigate short-term repeatability of a posturographic quiet standing test protocol in people with hemiparesis and in frail older adults. DESIGN: Test-retest design, using 5 different quiet standing task conditions in which size and compliance of the support surface, visual influence, and cognitive demands were manipulated. Retest was performed after 15 minutes. SETTING: Rehabilitation units and day care center. PARTICIPANTS: Twenty-three people with stroke (mean age, 74.4y) and 16 frail older adults (mean age, 82.1y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Repeatability of trunk acceleration root mean square by within-subject standard deviation, coefficient of variation, and intraclass correlation coefficients (ICCs). RESULTS: The ICC(1,2) ranged from.13 to.75 for people with hemiparesis and from.73 to.92 for frail older adults when tested with their eyes open. The least demanding task condition gave the best repeatability. Standing with eyes closed resulted in very low ICC(1,2) in people with hemiparesis (.16) and in frail older adults (-.18). Interpretation of the results was similar for the other 2 reliability measures. CONCLUSIONS: A mean of 2 repeated measures gave adequate repeatability for frail older adults but not for people with stroke when they were tested with their eyes open. This study showed the importance of establishing short-term repeatability relative to each clinical population in which such tests are used.

Aged↗

PubMed2003

Meaning of dependency on care as narrated by nurses.

This article is part of an ongoing study aimed at illuminating the meaning of dependency on care. The aim of this particular study is to illuminate the meaning of the phenomenon 'dependency on care' as narrated by nurses. Interviews with 20 nurses were conducted, tape-recorded and transcribed verbatim. A phenomenological-hermeneutic approach was used to interpret the data. The meaning of dependency on care is revealed as laborious for both patients and nurses. The nurses' text discloses that for patients, dependency on care is a miserable loss of self-determination and self-worth. Nurses appear to be moved by dependents' difficult life and want to do whatever they can for the dependent. Dependency on care is a burdensome responsibility for nurses. For nurses dependency on care is revealed as evoking feelings of guilt and insufficiency and of being constantly concerned and worried. It is to struggle to be patient and understanding, having the arduous task of putting oneself into the dependent patients' shoes in order to cope with the demanding task of balancing between helping and not helping too much. The interpretation discloses, however, that nurses distinguish between easy and trying dependency on care. The understanding indicates that when they meet 'good' patients, nurses reappraise the situation, transform it into something new and meaningful, that is dependency on care is disclosed as 'easy to take'. When coming across'difficult' patients dependency on care is disclosed as trying. It seems that within the unique nurse-patient relationship patients may participate in such a way as to facilitate or inhibit nurses in finding meaning in the immediate caregiving situation. Nurses' evaluations of what constitutes a 'good' or a 'difficult' patient, respectively, seem to play an important role in distinguishing between dependency on care that is easy and that which is trying. The result is viewed through an existential paradigm and there is also reflection about what nurses perceive as valuable qualities in patients which might influence the quality of care.

Activities of Daily Living↗

PubMed2001

Action monitoring, error detection, and the basal ganglia: an ERP study.

The error negativity (Ne or ERN) is an event-related brain potential component, which is assumed to reflect error detection. Recently it has been hypothesized that the basal ganglia are assumed to play a crucial role in error detection. In the present study we ask whether the Ne is altered in patients with Parkinson's disease (PD), who have an impaired function of the basal ganglia. We recorded the Ne in patients and in matched controls, while they performed different tasks that require a relatively high cognitive control, which is supposed to pose particular problems on PD. The Ne was in fact smaller in the patients than in the controls in all tasks. Our results suggest an impairment of error detection in PD for different types of demanding tasks. This supports the hypothesis that the basal ganglia do play an important role for error detection in action monitoring.

Aged↗

PubMed2002

The influence of explicit instructions and stimulus material on lateral frontal responses to an encoding task.

In this functional magnetic resonance imaging study, we explored the effects of both stimulus material and encoding task demands on activation in lateral prefrontal cortex (PFC). Two factors were manipulated: material type and task instructions. Subjects encoded words or abstract figures (factor 1: stimulus type) and were required to make either a meaning-based or a form-based (letter or shape) decision about each stimulus (factor 2: task instructions). Abstract figures engendered significantly higher levels of right PFC activity than did words. This effect was seen for meaning-based and form-based processing tasks and was significantly greater for the former. We did not observe a differential response of left lateral PFC to verbal and pictorial material. A double dissociation, however, was found within left PFC. A ventrolateral region (within left inferior frontal gyrus) showed the highest levels of activity when words were processed according to their meaning whereas activity in a more dorsolateral region (within left middle frontal gyrus) was greatest when words were processed according to their form (constituent letters). We have therefore observed a main effect of material type in producing lateralized activation of frontal lobes, although the strength of this effect is sensitive to the nature of the task that subjects are asked to perform. Left-side lateral PFC activity is also sensitive to task instructions but this effect was specific to verbal material. The complex patterns of frontal effect counsel against any simple dichotomy of frontal function at the level of either material or task type.

Adult↗

PubMed1979

Are retarded children more distractible? Observational analysis of retarded and nonretarded children's classroom behavior.

Retarded children are frequently characterized as more distractible and/or more outerdirected than are nonretarded children. In this study behavior thought to reflect these processes was described and the relationship of this kind of behavior to task demands was examined. Retarded and nonretarded children were observed while they worked on academic classroom tasks; retarded children were also observed while they worked on nonacademic tasks. Results indicated that retarded children were less attentive than were nonretarded children during academic periods: They spent less time on task, more time out of their seats, and more time "looking busy" but not working. Little support was found for the notion that retarded children are more outerdirected than are nonretarded children. Retarded children responded differently in nonacademic and academic situations, suggesting that behavior reflecting attention is task-related. Results were discussed in terms of previous conceptualizations of retarded persons' attention processes. Implications for future research and for educational practice were also discussed.

Attention↗

PubMed2003

Motor function under lower and higher controlled processing demands in early and continuously treated phenylketonuria.

This study examined motor control in 61 early and continuously treated patients with phenylketonuria (PKU) and 69 control participants, aged 7 to 14 years. The pursuit task demanded concurrent planning and execution of unpredictable movements, whereas the tracking task required a highly automated circular movement that could be planned in advance. PKU patients showed significantly poorer motor control in both tasks compared with control participants. Deficits were particularly observed for younger patients (age < 11 years). Differences between control participants and PKU patients were significantly greater in the pursuit task compared with the tracking task, indicating more serious deficits when a higher level of controlled processing is required. Correlations with historical phenylalanine levels indicated a later maturation of the level of control required by the pursuit task compared with the tracking task.

Adolescent↗

PubMed1985

Perception of emotional intonation by brain-damaged adults: the influence of task processing levels.

This research examined perception of moods from the tone-of-voice of semantically neutral phrases following unilateral cerebrovascular accident. It was hypothesized that right hemisphere damage (RHD) would impair even low-level discrimination and recognition of affective prosody, while left hemisphere damage (LHD) would affect performance only as associational-cognitive task demands increased. Thirty-three male subjects, 11 each in RHD, LHD, and normal groups, were given three tasks that varied in presumed amounts of processing undertaken for successful completion. Discrimination of prosodic patterns was expected to require the fewest cognitive operations. An intermediate task involved selecting from two possibilities the label that described moods conveyed prosodically. In the third task, prosodic mood selection was made from four choices, increasing the number of comparisons necessary for accurate judgment. As hypothesized, RHD subjects were inferior to normal subjects in all tasks. LHD subjects were equivalent to normal subjects for the first two tasks, but fell to the level of the RHD group for the third task. These results indicated that the right hemisphere in men was primarily involved in the reception and recognition of emotional prosodic stimuli. Increasing cognitive demands, however, brought about a shift in emphasis from the right hemisphere to both hemispheres. An implication of these findings concerns the need to examine performance levels that invoke changes from expected patterns of hemispheric specialization to advance our knowledge of functional asymmetries.

Adult↗

PubMed2004

Sex differences in mental rotation and spatial rotation in a virtual environment.

The visuospatial ability referred to as mental rotation has been shown to produce one of the largest and most consistent sex differences, in favor of males, in the cognitive literature. The current study utilizes both a paper-and-pencil version of the mental rotations test (MRT) and a virtual environment for investigating rotational ability among 44 adult subjects. Results replicate sex differences traditionally seen on paper-and-pencil measures, while no sex effects were observed in the virtual environment. These findings are discussed in terms of task demands and motor involvement. Sex differences were also seen in the patterns of correlations between rotation tasks and other neuropsychological measures. Current results suggest men may rely more on left hemisphere processing than women when engaged in rotational tasks.

Adult↗

PubMed1992

Reasoning with conditionals containing negated constituents.

Three experiments investigated matching bias in conditional reasoning tasks. Matching bias occurs when Ss ignore negations and match named items. Experiment 1 used an abstract and a thematic version of Evans's (1972) construction task. Results showed that matching may be due to an interaction between task demands and constructing contrast classes when interpreting negations. Experiment 2, which used Wason's (1968) selection task, introduced a manipulation to ease contrast-class construction. Confirmation plus falsification dominated over matching. Experiment 3 introduced two other manipulations to aid contrast-class construction with abstract material. Confirmation was facilitated, matching was suppressed, and falsification remained unchanged. These results suggest that matching occurs only when insufficient or ambiguous information prevents the intended interpretation of negations.

Adult↗

PubMed1981

Age-related differences in behavior across the life span of the C57BL/6J mouse.

C57Bl/6J mice, representing four divergent age groups (ranging from 3 months to 31 months) were each tested on a number of behavioral procedures, selected to sample a wide spectrum of behaviors. The evaluation demonstrated that, as with other mammalian species, not all behaviors in the mouse are affected by old age. Most severely impaired was retention of a single-trial passive avoidance task, most probably reflecting a deficit in memory ability. One tests of motor function, the most demanding tasks revealed the greatest debilitating effects of age, paralleling the effects of task difficulty previously reported in numerous learning studies. Finally, a deficit in the ability to modify preexisting habits in a T-maze learning situation was observed, corroborating reports of increased perseveration in aged humans and nonhuman primates. The similarity of these results across the life span of the C57 mouse with those previously reported for other aged mammalian species demonstrates that certain common types of behaviors seem to be impaired selectively by increased age across mammalian species and raises the possibility that common neurological etiologies may exist for these behavioral deficits.

Aging↗

PubMed1998

Language, context, and speaker effects in the identification and discrimination of English /r/ and /l/ by Japanese and Korean listeners.

Japanese and Korean listeners' identification and discrimination of English /r/ and /l/ were compared using a common set of minimal pair stimuli. The effects of speakers (two native speakers of Australian English), position of the contrast within the word (word initial, initial consonant cluster. and medial positions), and listening task (forced choice identification versus oddball discrimination) were examined, with a view to assessing the relative importance of language-specific and language-independent factors operating at the acoustic-phonetic and phonological levels of signal processing in "foreign sound" speech perception. Both prior phonological learning and the relative acoustic discriminability of the items affected subjects' performance on the identification test. Where both factors were engaged, phonological learning effects predominated over the effects of acoustic discriminability. The extent to which a speaker encoded critical acoustic cues for the /r-l/ distinction was found to affect /r-l/ identification. Dynamic spectral features known to be relevant for the /r-l/ contrast were effective in predicting (in a linear regression analysis) speaker-dependent differences in identification scores. Although the discrimination test may have been influenced by ceiling effects, the performance profiles on the identification and discrimination tests were quite different, indicating that the identification and discrimination tests imposed quite different task demands upon listeners and that phonological processing of the signal was more engaged by the former task.

Adolescent↗

PubMed1999

Differential contributions of the left and right inferior parietal lobules to number processing.

We measured cerebral activation with functional magnetic resonance imaging at 3 Tesla while eight healthy volunteers performed various number processing tasks known to be dissociable in brain-lesioned patients: naming, comparing, multiplying, or subtracting single digits. The results revealed the activation of a circuit comprising bilateral intraparietal, prefrontal, and anterior cingulate components. The extension and lateralization of this circuit was modulated by task demands. The intraparietal and prefrontal activation was more important in the right hemisphere during the comparison task and in the left hemisphere during the multiplication task and was intensely bilateral during the subtraction task. Thus, partially distinct cerebral circuits with the dorsal parietal pathway underlie distinct arithmetic operations.

Adult↗

PubMed1996

A computerized medical standards system to help place impaired employees.

The paper describes a knowledge-distribution system that supports decisions on placement of impaired employees. The knowledge base consists of job profiles and medical profiles. The job profiles list tasks and the physical abilities they require. Twenty-one abilities describe the task demands. Active workers rated the exertion, frequency and importance of the physical ability required for each task. Thirty-nine work conditions were rated this way. Using identical scales, experts assessed the impact of impairments on the physical abilities of individuals and the tolerance of work conditions. The screening matches the job profile against the impairment profile. This process has been automated. The program lists tasks and work conditions that may compromise an impaired employee. This information can be used to accommodate employees, restrict duties or design a rehabilitation program. Also, the paper discusses the impact of the system on the operations of medical services within an organization.

Disability Evaluation↗

PubMed2003

Mental fatigue and the control of cognitive processes: effects on perseveration and planning.

We tested whether behavioural manifestations of mental fatigue may be linked to compromised executive control, which refers to the ability to regulate perceptual and motor processes for goal-directed behaviour. In complex tasks, compromised executive control may become manifest as decreased flexibility and sub-optimal planning. In the study we use the Wisconsin Card Sorting Test (WCST) and the Tower of London (TOL), which respectively measure flexibility (e.g., perseverative errors) and planning. A simple memory task was used as a control measure. Fatigue was induced through working for 2 h on cognitively demanding tasks. The results showed that compared to a non-fatigued group, fatigued participants displayed more perseveration on the WCST and showed prolonged planning time on the TOL. Fatigue did not affect performance on the simple memory task. These findings indicate compromised executive control under fatigue, which may explain the typical errors and sub-optimal performance that are often found in fatigued people.

Adult↗

PubMed1998

Dissociating executive mechanisms of task control following frontal lobe damage and Parkinson's disease.

Twelve patients with focal damage of the frontal cortex and 12 patients with mild, medicated, early stage Parkinson's disease switched between letter- and digit=naming tasks on every second trial of a task-switching paradigm. Compared with age- and IQ-matched control performance, patients with left-sided, but not right-sided, frontal damage exhibited markedly increased time costs associated with these predictable switches only when there was a general incidence of interference or 'crosstalk' between the tasks, and particularly so when the available task cues were relatively weak and arbitrary. The same patients also showed evidence of an increased sensitivity to the facilitatory and inhibitory effects of previous processing, when required to switch between tasks. Both groups of patients (with left- or right-sided frontal damage) exhibited slow, disorganized performance early in practice. In contrast to these frontal effects, the Parkinson's disease patients showed little indication of larger time costs of task switches but they did show progressive increases in the error costs, while age- and IQ-matched control subjects showed reductions. We propose that while both left and right frontal cortical areas are involved in the organization of cognitive and motor processes in situations involving novel task demands, only the left frontal cortex is involved in the dynamic reconfiguring between already-established task-sets, and specifically, that it is the site of an executive mechanism responsible for the modulation of exogenous task-set activity. Finally, dopaminergic transmission, along the nigrostriatal pathway, may be implicated in sustaining various cognitive and motor processes over prolonged periods, including the operation of those executive control mechanisms that accomplish reconfiguring between task-sets.

Adult↗

PubMed2004

Functional neuroanatomy of spatial orientation processing in Turner syndrome.

Turner syndrome (TS), a neurogenetic disorder characterized by the absence of one X chromosome in a phenotypic female, is frequently associated with visuospatial impairments. We investigated the neural mechanisms underlying deficits in spatial orientation processing in TS. Thirteen subjects with TS and 13 age-matched typically developing controls underwent neuropsychological assessments and were scanned using functional MRI while they performed easy and difficult versions of a judgment of line orientation (JLO) task. Controls and subjects with TS activated parietal-occipital regions involved in spatial orientation during the JLO task. However, activation was significantly less in the TS group. Control subjects responded to increased task difficulty by recruiting executive frontal areas whereas subjects with TS did not activate alternate brain regions to meet increased task demands. Subjects with TS demonstrate activation deficits in parietal-occipital and frontal areas during the JLO task. Activation, and possibly deactivation, deficits in these areas may be responsible for the visuospatial deficits observed in females with TS.

Adolescent↗