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PubMed2001

Circadian phase-shifted rats show normal acquisition but impaired long-term retention of place information in the water task.

It is thought that circadian rhythms may influence learning and memory processes. However, research supporting this view does not dissociate a mnemonic impairment from other performance deficits. Furthermore, published reports do not specify the type of memory system influenced by the circadian system. The present study assessed the effects of phase shifting on acquisition and expression of place navigation in the water maze, a task sensitive to hippocampal dysfunction. The results showed that phase-shifting circadian rhythms in rats impaired the expression of place information on a retention test but not initial acquisition or encoding of place information. These results suggest that disruption of circadian rhythms may impair consolidation of previously encoded hippocampal place information.

Animals↗
PubMed2005

Developmental coordination disorder (dyspraxia): an overview of the state of the art.

A large number of school-aged children present with motor-based performance problems that have significant negative effects on their ability to participate fully in the daily activities of home, school, and play. These children have a neurodevelopmental disorder most commonly known as developmental coordination disorder (DCD). These children are frequently brought to the attention of the family doctor and referred to health care professionals in search of answers and services. Therapists treating these children have a large number of intervention approaches at their disposal. This paper presents an overview of these approaches and a review of the available evidence. The evidence for the older, deficit-oriented approaches remains inconclusive, at best; whereas the task-oriented approaches, seem to be better supported. While more work is needed to validate the use of the task-oriented approaches, the results suggest that a shift in perspective from a deficit-oriented to a task-oriented perspective would be appropriate.

Apraxias↗
PubMed2001

TASK-1 is a highly modulated pH-sensitive 'leak' K(+) channel expressed in brainstem respiratory neurons.

Central respiratory chemoreceptors adjust respiratory drive in a homeostatic response to alterations in brain pH and/or P(CO(2)). Multiple brainstem sites are proposed as neural substrates for central chemoreception, but molecular substrates that underlie chemosensitivity in respiratory neurons have not been identified. In rat brainstem neurons expressing transcripts for TASK-1, a two-pore domain K(+) channel, we characterized K(+) currents with kinetic and voltage-dependent properties identical to cloned rat TASK-1 currents. Native currents were sensitive to acid and alkaline shifts in the same physiological pH range as TASK-1 (pK approximately 7.4), and native and cloned pH-sensitive currents were modulated similarly by neurotransmitters and inhalational anesthetics. This pH-sensitive TASK-1 channel is an attractive candidate to mediate chemoreception because it is functionally expressed in respiratory-related neurons, including airway motoneurons and putative chemoreceptor neurons of locus coeruleus (LC). Inhibition of TASK-1 channels by extracellular acidosis can depolarize and increase excitability in those cells, thereby contributing to chemoreceptor function in LC neurons and directly enhancing respiratory motoneuronal output.

Anesthetics, Inhalation↗
PubMed1989

Experimental investigation of stress-inducing properties of system response times.

System response times are regarded as a major stressor in human-computer interaction. In two earlier studies short (2s) and long (8s) response times were found to have differential effects on psychological, subjective, and performance variables, but results did not favour either response time. Therefore, in another laboratory study with 48 subjects in four independent groups working at a stimulated computer workplace, system response times of 2, 4, 6 and 8s were introduced in the same error detection task as used before, during 3 training and 5 working trials of 20 min each, and the same physiological, subjective and performance measures were obtained. There were no global effects on physiological variables, possibly due to low work load as a result of missing time pressure, but subjective and performance variables clearly favoured the longer system response times. When task periods and response time-periods were analysed separately, a shift of electrodermal activity could be observed from task- to response time-periods during the course of trials in the 8s condition. This did not appear in any other condition, which points to psychophysiological excitement that develops when system response times are too long, thus providing support for the concept of optimal system response times.

Adolescent↗
PubMed1995

Changes in the balance between motor cortical excitation and inhibition in focal, task specific dystonia.

Transcranial magnetic stimulation has been used in a double pulse paradigm to investigate the excitability of intrinsic motor cortical circuits in 15 patients with focal task specific dystonia of the right hand and a group of eight age matched controls. The left hemisphere was examined in five patients; in the remainder, both hemispheres were tested. There was no significant difference in stimulation threshold between patients and controls nor between the left and right hemispheres in the patients. There was a significant decrease in early corticocortical suppression when comparing stimulation of the left hemisphere in the patients and controls at interstimulus intervals of 1-15 ms (P < 0.01). There was no difference in the amount of suppression in the right and left hemispheres of the patients. It is concluded that in focal task specific dystonia there is shift in the balance between excitation and inhibition in local circuits of the motor cortex which leads to a net decrease in the amount of short latency suppression. These changes reflect disturbed basal ganglia input to the motor cortex. Reduced excitability of cortical inhibitory circuits may be one factor which contributes to the excessive and inappropriate muscle contraction which occurs during fine motor tasks in patients with focal dystonia.

Adult↗
PubMed1994

Electroencephalographic activity associated with shifts of visuospatial attention.

The neural processes underlying shifts of visuospatial attention were studied in normal adults by non-invasive recording of brain electrical activity. Event-related evoked potentials (ERPs) were recorded during target detection tasks with targets preceded by central or peripheral directional cues in the visual field, which are hypothesized to provoke voluntary and reflexive shifts of spatial attention. Reaction time to targets varied as a function of cue type and cue-target interval, indicating that the tasks induced shifts of spatial attention across the visual field. Event-related evoked potential recordings showed that central cues elicited negative potential shifts starting 240 ms after cue onset over posterior scalp sites contralateral to the cued visual field, which spread to anterior scalp sites over time. After 500 ms post cue, negative potentials were more negative in right temporal parietal sites regardless of cue direction. Peripheral cues enhanced the N1 component (140-200 ms post cue) over the contralateral hemisphere. Following N1 enhancement, a sustained negative potential shift appeared after 460 ms post cue at posterior scalp sites contralateral to cued field and spread over the temporal and central regions. These results suggest that the neural processes underlying spatial selection are initiated in the posterior region and that other cortical activities are recruited in a serial fashion. Symmetrical early activation of each contralateral hemisphere suggest independent involvement of the hemispheres in the early stages of shifting attention toward the contralateral visual field. A predominant contribution of the right hemisphere to sustained spatial attention was demonstrated in the late stage of cue processing at the right temporal and parietal regions. Different ERP patterns generated by central and peripheral cues support the hypothesis that distinct neural systems are involved in voluntary and reflexive mechanisms of attention shift.

Adult↗
PubMed1991

Lingual vibrotactile threshold shift differences between stutterers and normal speakers during magnitude-estimation scaling.

The purpose of this study was to investigate differences in tactile sensory system function between stutterers and normal speakers. This task was accomplished by studying possible tactile threshold shifts occurring during magnitude-estimation scaling of vibratory stimuli presented to the dorsal surface of the tongue. Ten normal speaking men (M age = 19.7 yr.) and 10 stutterers (M age = 25.9 yr.) participated. Analysis suggested that stutterers and normal speakers differ in terms of the responsiveness of the sensory mechanism for the lingual tactile threshold to vibratory stimulus intensities applied at suprathreshold levels. The stutterers and normal speakers performed similarly on all aspects of the magnitude-estimation scaling tasks, but the amount of threshold shift occurring during the scaling procedures was significantly greater for the stutterers at each suprathreshold intensity level employed.

Adolescent↗
PubMed1996

Deficits in the endogenous redirection of covert visual attention in chronic schizophrenia.

In patients with schizophrenia, abnormal performance on the antisaccade task suggests that for overt attentional shifts, there is difficulty with the endogenous modes have opposite goals. We examined whether patients with schizophrenia also have difficulty with the endogenous control of exogenous orienting when endogenous and exogenous control of exogenous orienting for covert shifts of attention. Fifteen medicated patients with chronic schizophrenia and 15 matched controls performed two versions of the covert orienting of attention task (COVAT). On one COVAT, targets appeared at the cued location (TAC) on all trials. On the second COVAT, targets appeared at the contralateral location to the cue (TCC) on all trials. Reaction time (RT) for TAC and TCC trials was equal in the control group. However, for the schizophrenia group, RT for TCC trials was significantly slower than RT for TAC trials. This indicates that patients with schizophrenia were unable to inhibit the orienting of attention to peripheral cues even when they knew that targets would never appear at the same location as the cue. These results suggest that patients with chronic schizophrenia have difficulty utilizing the endogenous strategies to inhibit exogenous covert attentional shifts.

Adult↗
PubMed2004

Dimensional approaches to experimental psychopathology of schizophrenia: shift learning and report of psychotic-like experiences in college students.

Adopting a dimensional approach to experimental psychopathology, and taking into account inconsistencies in the previous literature, we examined whether reports of psychotic-like experiences in undergraduate students were associated with shift-learning deficits, akin to those seen in schizophrenia. The participants (N=72) were tested on a new compound stimulus discrimination task before and after a target shift, and were administered a multi-dimensional schizotypy inventory (O-LIFE). Performance impairment following a target shift was associated with the negative (introvertive anhedonia) and the impulsive (impulsive non-conformity) dimension of schizotypy, but not with the positive (unusual experiences), nor the disorganised (cognitive disorganisation) dimension. None of the schizotypy measures were associated with performance on discrimination learning before the target shift. The obtained results are in line with past evidence that shift learning is associated with the severity of the negative symptomatology of schizophrenia. The possibility that psychotic-like features may contribute differentially to performance deficits across successive stages of learning is considered.

Adolescent↗
PubMed2000

Neuropsychological functioning in first-episode psychosis--evidence of specific deficits.

Neuropsychological impairment is ubiquitous in schizophrenia even at the first presentation of psychotic symptoms. We sought to elucidate the nature of the neuropsychological profile at the onset of the illness by examining the neuropsychological functioning of 40 patients experiencing their first episode of psychosis and 22 matched controls. All participants completed a battery of neuropsychological tasks designed to assess attention, verbal learning/memory, non-verbal memory, spatial ability, psychomotor speed, and executive function. First-episode patients showed significant impairment on tasks of executive function, including those requiring the ability to form and initiate a strategy, to inhibit prepotent responses, and to shift cognitive set, and also on tasks of verbal fluency. Memory impairments were seen on verbal learning and delayed non-verbal memory only. Impairment on tasks of psychomotor speed suggests that there may be a significant amount of cognitive slowing even at the first onset of psychosis. We suggest that our patients may be experiencing difficulty in specific aspects of executive functions, including the ability to form and execute a strategy, and these difficulties may be mediating the deficits observed on tasks of verbal learning.

Adolescent↗
PubMed2005

Is impairment in set-shifting specific to frontal-lobe dysfunction? Evidence from patients with frontal-lobe or temporal-lobe epilepsy.

Frontal-lobe epilepsy (FLE), temporal-lobe epilepsy (TLE), and matched-control subjects were administered the Trail Making Test (TMT) of the Delis-Kaplan Executive Function System (D-KEFS; Delis et al., 2001), which assesses set-shifting on a visuomotor sequencing task. Results indicated that patients with FLE were impaired in both speed and accuracy on the switching condition relative to patients with TLE and controls. The two patient groups did not differ from controls on the four baseline conditions of the test, which assess visual scanning, motor speed, number sequencing, and letter sequencing. In addition, seizure-related variables (i.e., age of seizure onset, duration of epilepsy, and seizure frequency) failed to correlate with set-shifting performance in patients with FLE. These results suggest that patients with FLE can be reliably distinguished from those with TLE and control subjects on set-shifting as measured by the DKEFS TMT.

Adult↗
PubMed2000

Attention and selection in the growing child: views derived from developmental psychophysiology.

Our understanding of developmental changes in attentional selection in the growing child has been advanced substantially by the results of (a relatively small number of) studies undertaken from a psychophysiological perspective. The basic outcome of these studies is that, in attentional filtering as well as selective set (the two basic paradigms in attention research), the processes necessary for attentional selection are in essence available even to the young child; however, the speed and efficiency of these processes tends to increase as the child grows into an adolescent. Under optimal conditions, filtering is performed at early stages of information processing, but less optimal stimulus characteristics and task requirements may induce a shift in the locus of selection to later processing stages for young children whereas older individuals are better able to preserve their early locus of selection. When early selection is constrained, young children are substantially more sensitive to the adverse effects of response competition. In selective set, sub-optimal conditions lead not so much to a shift in locus of selection processes, but to a shift in the age at which asymptote efficiency is attained. We have proposed hierarchical regression analysis as a useful technique to examine whether age-related differences in attention effects, as observed in specific ERP components and in RT, are reflections of an age effect on a single source of attentional selection or of separate sources that each contribute uniquely to the developmental trends seen in (attention effects on) RT. Re-analyses of existing data demonstrated that (again depending on task specifics) many but not all of the different component processes involved in attentional selection contributed unique variance to the age-related changes in attention effects.

Adolescent↗
PubMed2005

Executive functioning and theory of mind in euthymic bipolar disorder.

OBJECTIVES: To examine the nature of executive deficits in euthymic patients with bipolar disorder (BD). METHODS: Fifteen euthymic BD patients and 13 controls were administered a battery of executive tasks including verbal fluency, Stroop, Theory of Mind (ToM) tests and selected subtests from the Cambridge Neuropsychological Test Automated Battery (CANTAB). Self-report and clinician ratings of mood and social and occupational functioning were also obtained. RESULTS: There were no significant differences between BD patients and controls on the primary measures of the following executive tasks: verbal fluency, attentional set-shifting, problem solving or planning. On secondary measures of speed, BD patients were slower to complete the first trial of the Stroop task (p = 0.001). Patients with BD committed more errors across all secondary measures. Patients performed poorly when compared with controls on tests of verbal ToM (p = 0.02), and although they performed non-verbal ToM tasks at a level comparable to controls (p = 0.60), they were slower to initiate a response (p = 0.006). ToM was not significantly correlated with any measure of social and occupational functioning; however it correlated with the achievement scores of the CANTAB Stockings of Cambridge task (Pearson's r = 0.68, p < 0.01). CONCLUSIONS: Deficits found in euthymic bipolar patients suggest fronto-subcortical pathway dysfunction. This is consistent with other neuropsychological and neuroimaging research that points to a trait deficit in BD. Further investigation is necessary perhaps using more real-world tests.

Adult↗
PubMed2000

Immediate and delayed after-effects of long lasting mentally demanding work.

This study investigates the hypothesis that long lasting mental work demands are reflected in after-effects on attention demanding post-test probe tasks. Sixteen subjects were engaged in 2 simulated workdays consisting of mentally demanding tasks. On the difficult day the afternoon consisted of highly demanding information processing tasks; on the easy day the demands during the afternoon were low. The mornings of both days were equally demanding. At the start (pre-test) and the end (post-test) of both days, after 5 min (immediate post-test) as well as after approximately 2 h of recuperation (delayed post-test), a probe task was carried out. A memory-search task (varied mapping) is used as probe task. After-effects were expected in terms of a shift in the ratio between performance and effort on the post-test probe tasks compared with the pre-test probe task. Performance measures were reaction time and errors; effort was indicated by heart rate variability in the 0.07-0. 14 Hz band, referred to as 0.1 Hz component. Dayload manipulation appeared to be effective because of the load-related differences between the urinary excretion rates of adrenaline during both afternoons. Compared with the pre-test, only the number of errors was significantly increased in the post-test, carried out immediately at the end of the difficult afternoon. However, compared with the easy day, in the delayed post-test probe task after the difficult day, subjects tended to shorten reaction times, made significantly more errors, and invested significantly less effort. Moreover, at that time they felt more fatigued and deactivated as indicated by the results of the 'Scale of Experienced Load' (SEB) (fatigue) and 'Groninger Adjective Checklist' (GACL) (mood) questionnaires. The observed shift towards low-effort, more 'risky' task strategies in the post-tests fits well with Hockey's (1993) fatigue after-effects degradation pattern expected after periods of high workload. The repeated measurement of the relation of performance, effort and feelings reveals the dynamics of the pattern of fatigue after-effects over the (recovery) time.

Adult↗
PubMed1990

Frontal lobe function in progressive supranuclear palsy.

Performance on tasks evaluating "executive and attentional" processes presumably subserved by prefrontal cortex were compared in patients with progressive supranuclear palsy and with age- and education-matched control subjects. The results indicated that patients with progressive supranuclear palsy were particularly impaired when a task required sequential movements, conceptual shifting, monitoring the frequency with which stimuli are presented, or rapid retrieval of verbal knowledge. These deficits could not simply be accounted for by slowed information processing or by a deficit in representational knowledge. Conceivably, "weak activation" of frontal lobe representational knowledge characterized by an observed attentional deficit results in the neuropsychological impairments noted in patients with progressive supranuclear palsy. The oral administration of physostigmine, under double-blind placebo-controlled conditions, did not facilitate executive or attentional performance as evaluated by our tasks.

Affect↗
PubMed1989

Sequential analyses of therapist-client interaction during change events: a task-focused approach.

In this article, we describe a task-focused approach that uses sequential analyses as deductive techniques for studying therapist-client interactions in the context of clinical microtheories of change events. The methodology is demonstrated in a study of a class of change events in client-centered therapy referred to as the resolution of problematic reactions. Logit-loglinear analysis and binomial z scores were used to test the effects of therapist behavior, assessed by therapist vocal quality and by the therapist task-relevant system, on client process assessed by client vocal quality and by the Experiencing Scale. The results indicated (a) that therapist productive voice facilitated a shift from poor to productive client voice and a shift from low to intermediate experiencing and (b) that therapist task-specific interventions directed toward resolution facilitated shifts to high experiencing. This task-focused approach to sequential analyses has the potential to yield clinically and theoretically relevant findings.

Adaptation, Psychological↗
PubMed2006

Go with the flow: How to master a nonlinear multiple-cue judgment task.

The authors examined the cognitive processes that participants use in linear and nonlinear multiple-cue judgment tasks, hypothesizing that people are unable to use explicit cue abstraction in a nonlinear task, instead turning to exemplar memory. Experiment 1 confirmed that people are unable to use cue abstraction in nonlinear tasks but failed to confirm the hypothesized, spontaneous shift to exemplar memory. Instead, the participants appeared to be trapped in persistent and futile attempts to abstract the cue-criterion relations. Only after being instructed to rely on exemplar memory in Experiment 2 did they master the nonlinear task. The results suggest that adaptive shifts of representation need not occur spontaneously and that analytical thought may sometimes harm performance in nonlinear tasks.

Adult↗