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At least 433 records · Page 24Linked to original sources
PubMed1997

Different roles of the left and right parahippocampal regions in verbal recognition: a PET study.

We examined the role of the parahippocampal regions in humans during two types of verbal recognition process, i.e. delayed matching and non-matching, by measuring regional cerebral blood flow (rCBF) using PET. The results showed differential activation of each parahippocampal region during verbal memory tasks in which the side activated shifted depending on the nature of the task employed; an increase in rCBF in the left parahippocampal gyrus was associated with retrieval strategy of non-matching, and an increase in rCBF in the right parahippocampal gyrus was associated with retrieval strategy of matching. We conclude that lateralized parahippocampal activation may depend on the type of response required.

Adolescent↗
PubMed1975

Electrophysiological orthosis for the upper extremity in hemiplegia: feasibility study.

A versatile two channel stimulator with cutaneous electrodes was designed and built to test the feasibility of multi-channel upper extremity functional electrical stimulation in hemiplegic patients. Preliminary experiments led to the choice of stimulation for hand opening (extensor carpi radialis and ulnaris, extensor digitorum communis) and elbow extension (triceps). Three channel stimulation including the deltoideus muscle was attempted successfully in one patient. Five of eight patients showed substantial improvement with the orthosis and three of these five showed some therapeutic effect over a period of two months. The stimulation was proportionally controlled by the patient by means of movement of the nonaffected shoulder. Functional tasks such as the shifting of an object between two specified areas on a desk were used for evaluation of performance. Tasks that were impossible without stimulation were easily performed with stimulation and after minimal training. The results obtained were significant for the functional rehabilitation of hemiplegic subjects. It is concluded that a more extensive clinical evaluation program including regular long term training of the subjects is justified.

Arm↗
PubMed1998

A common network of functional areas for attention and eye movements.

Functional magnetic resonance imaging (fMRI) and surface-based representations of brain activity were used to compare the functional anatomy of two tasks, one involving covert shifts of attention to peripheral visual stimuli, the other involving both attentional and saccadic shifts to the same stimuli. Overlapping regional networks in parietal, frontal, and temporal lobes were active in both tasks. This anatomical overlap is consistent with the hypothesis that attentional and oculomotor processes are tightly integrated at the neural level.

Adolescent↗
PubMed2004

Dopaminergic basis for deficits in working memory but not attentional set-shifting in Parkinson's disease.

Although Parkinson's disease is a common neurodegenerative disorder characterised by its motoric symptoms, there is an increasing recognition of accompanying impairments in cognition that have a profound impact on the quality of life of these patients. These deficits predominantly affect executive function and impairments of working memory have been frequently reported. However, the underlying neurochemical and pathological basis for these deficits are not well understood. In this study, 20 patients were tested 'on' and 'off' levodopa (L-dopa) medication on a task that allowed different aspects of working memory function such as maintenance, retrieval and manipulation to be tested within the same general paradigm as well as on an unrelated test of attentional set-shifting, which is known to be sensitive to deficits in early Parkinson's disease. Compared to healthy volunteers, PD patients were impaired at manipulation more than maintenance or retrieval of information within working memory. The patients were also impaired at the attentional set-shifting task. However, whereas L-dopa ameliorated the working memory deficit in manipulation (improving both accuracy and cognitive response time), it had no effect on the attentional set-shifting impairment. These results confirm that working memory deficits in PD are both psychologically specific and related to dopamine depletion. It is anticipated that greater understanding of these mechanisms will lead to future therapeutic improvements.

Aged↗
PubMed2004

Cooperation of the anterior cingulate cortex and dorsolateral prefrontal cortex for attention shifting.

Attention shifting in the working memory system plays an important role in goal-oriented behavior, such as reading, reasoning, and driving, because it involves several cognitive processes. This study identified brain activity leading to individual differences in attention shifting for dual-task performance by using the group comparison approach. A large-scale pilot study was initially conducted to select suitable good and poor performers. The fMRI experiment consisted of a dual-task condition and two single-task conditions. Under the dual-task condition, participants verified the status of letters while concurrently retaining arrow orientations. The behavioral results indicated that accuracy in arrow recognition was better in the good performers than in the poor performers under the dual-task condition but not under the single-task condition. Dual-task performance showed a positive correlation with mean signal change in the right anterior cingulate cortex (ACC) and right dorsolateral prefrontal cortex (DLPFC). Structural equation modeling indicated that effective connectivity between the right ACC and right DLPFC was present in the good performers but not in the poor performers, although activations of the task-dependent posterior regions were modulated by the right ACC and right DLPFC. We conclude that individual differences in attention shifting heavily depend on the functional efficiency of the cingulo-prefrontal network.

Adult↗
PubMed1995

Conceptual perspective-taking and children's interpretation of pronouns in reported speech.

This study examines the role of cognitive development in children's use of pragmatic cues for anaphora resolution. Reported speech sentences like Minnie told Dorothy that she knew Superman are biased toward the matrix subject. This bias is claimed to depend on two conceptual shifts, first to the speaker's and then to the listener's perspective. 141 children aged 5; 0-8; 0 performed two tasks with biased and neutral sentences. In the Verbal task, they gave antecedent choices in response to a question (e.g. ...that WHO knew Superman?). In the Puppet task, which prompts the perspective shift, they made a puppet say the reported speech portion (e.g. I/you know Superman). Violations of the pragmatic constraint decreased with age and task, consistent with the perspective-shift model. Parallel function effects in neutral sentences were weaker than in previous research on conjoined sentences, but similar to recent results for adults with these materials.

Attention↗
PubMed1996

A selective role for dopamine in the nucleus accumbens of the rat in random foraging but not delayed spatial win-shift-based foraging.

The role of mesoaccumbens dopamine (DA) in radial-arm maze foraging is assessed by infusing low doses of the DA antagonist haloperidol into the nucleus accumbens (N.Acc.). Infusions of haloperidol (0, 125, 250 or 500 ng/0.5 microliter) into the N.Acc. of well-trained rats dose-dependently increase the number of re-entries to arms (errors) during the random foraging task, in which 4 arms on an 8-arm maze are baited randomly. However, in a separate group of animals, similar infusions produce no impairment when delivered prior to the test phase of the delayed spatial win-shift task, which require the animal to acquire information during a training phase, and to use that information 30 min later, during a test phase. These results suggest that DA neurotransmission in the N.Acc. is crucial for foraging behavior when there is ambiguity about the location of reward in a spatial environment, but is not needed for efficient foraging behavior when an animal has previous information as to the location of rewarding stimuli. The results are discussed with respect to of the underlying physiological interactions between limbic glutamate and mesoaccumbens DA transmission in the N.Acc.

Animals↗
PubMed1995

Evoked potential evidence for right brain activity during the recall of traumatic memories.

Auditory probe evoked potential attenuation was measured as an index of hemispheric activity in 10 subjects with a history of childhood trauma and 10 matched subjects without such history while they recalled a neutral memory and then a traumatic memory. There were prominent group differences in degree of cerebral laterality between memory tasks (P = 0.02). The trauma group had a significant left dominant asymmetry during the neutral memory (P = 0.02), which markedly shifted to the right during the unpleasant memory (P = 0.007 for degree of shift). Normal control subjects did not display a significant asymmetry during either task, nor did they show a significant shift between tasks.

Adult↗
PubMed2005

Linguistic attention control: attention shifting governed by grammaticized elements of language.

In 2 experiments, the authors investigated attention control for tasks involving the processing of grammaticized linguistic stimuli (function words) contextualized in sentence fragments. Attention control was operationalized as shift costs obtained with adult speakers of English in an alternating-runs experimental design (R. D. Rogers & S. Monsell, 1995). Experiment 1 yielded significant attention shift costs between tasks involving judgments about the meanings of grammatical function words. The authors used a 3-stage experimental design (G. Wylie & A. Allport, 2000), and the emerging pattern of results implicated task set reconfiguration and not task set inertia in these shift costs. Experiment 2 further demonstrated that shift costs were lower when the tasks involved shared attentional resources (processing the same grammatical dimension) versus unshared resources (different grammatical dimensions). The authors discuss the results from a cognitive linguistic perspective and for their implications for the view that language itself can serve a special attention-directing function.

Attention↗
PubMed2004

The scaling of postural adjustments during bimanual load-lifting in traumatic brain-injured adults.

Previous postural studies of traumatic brain injury (TBI) patients have been limited to identifying deficits in static and quasi-dynamic postural control tasks such as weight shifting. In this study, we examined whether or not patients with TBI are able to scale adequately their postural adjustments during the performance of the dynamic task of bimanual load-lifting. An age matched group of healthy adults served as controls. We used the Tetrax posturography system that calculates a stability score (ST) based on fluctuations in vertical ground reaction forces, normalized for body weight. During quiet standing, the ST scores of the TBI group were significantly higher than the control group. Forward weight shift and percentage change in the vertical ground reaction forces (lift postural adjustment (LPA) and post-lift postural adjustment (PLPA) scores) linearly increased with increasing load weight in both healthy and TBI subjects. Group differences were found in the magnitude of forward weight shift but not in the relative increase of the LPA and PLPA scores during the lifting and post-lifting phases respectively. The forward weight shift of the TBI group was lower-than-normal and asymmetrical--there was significantly less forward weight shift on the more affected than on the less affected limb. In addition, a significant amplitude coupling was found between the scaling of the weight shift of the heel and forefoot of each limb. However, no coupling was found between the weight shift amplitudes of homologous parts of both limbs in the TBI group. The results showed that scaling based on prior experience was preserved in the TBI group, though some TBI subjects demonstrated absent scaling in either the more affected or less affected heel or forefoot. The differences between the normal and TBI groups in postural adjustments are not necessarily a sign of pathology; rather they may represent a deliberate choice of the central nervous system to counteract predictable disturbances.

Adult↗
PubMed2004

Impairments of attention following treatment with cranial irradiation and chemotherapy in children.

Neurobehavioral impairments are frequently reported following treatment for childhood cancers, with cranial irradiation (CRT). This study investigated attention and information processing skills, predicting that these skills would be impaired due to the vulnerability of cerebral white matter in early childhood. Three treatment groups were studied: (i) CRT+chemotherapy (n = 35); (ii) chemotherapy alone (n = 19); (iii) healthy children (n = 35). All children were aged 9 to 16 years at time of assessment, with no pre-diagnosis history of neurologic, developmental, or psychiatric disorder. Children were administered a series of task measuring processing speed and sustained, selective, and shifting attention. For children treated with CRT + chemo, results identified residual deficits in processing speed for complex tasks, selective and shifting attention. In contrast, processing speed was intact for simple tasks, and there was no clear evidence of deterioration in performance over time, as might be expected in the presence of a sustained attention deficit. Children treated with chemotherapy alone demonstrated generally intact attentional skills. However, this group did record an increasing number of attentional lapses over time on tasks tapping sustained attention skills.

Adolescent↗
PubMed2002

The neuropsychology of antisocial personality disorder.

BACKGROUND: The literature on executive function in antisocial populations is unclear due to variation in diagnostic criteria and variation in the inclusion of healthy control comparison groups. Some studies suggest prototypical psychopathy is associated with specific deficits in ventromedial prefrontal (VMPFC) function rather than dorsolateral prefrontal (DLPFC). Meta-analytical studies, however, suggest that antisocial personality disorder may be associated with a broader range of executive deficits. This study assessed DLPFC and VMPFC function in antisocial personality disorder subjects and controls using the Cambridge Neuropsychological Test Automated Battery (CANTAB) and a Go/NoGo task respectively. METHODS: All subjects were screened for Axis I pathology, substance misuse and prescribed medication. The performance of 29 subjects with antisocial personality disorder DSM-IV and 20 male right-handed controls (matched for age and IQ) on the neuropsychological test battery was compared. RESULTS: Subjects with antisocial personality disorder displayed impairments on DLPFC executive function tasks of planning ability and set shifting. Impairments were also seen in VMPFC Go/NoGo tasks and in visual memory tasks. CONCLUSIONS: Antisocial personality disorder is associated with a broad range of deficits in DLPFC and VMPFC function. Future studies need to examine relationships between the interpersonal and behavioural components of antisocial personality disorder and neuropsychological function.

Adolescent↗
PubMed2007

Aging, focus switching, and task switching in a continuous calculation task: evidence toward a new working memory control process.

This study examined switching of the focus of attention in working memory in relation to global task switching in a continuous calculation task using two rules (midpoint and up-and-down) in a group of 25 younger adults and a group of 23 older adults. Age differences emerged in accuracy when participants worked on two strings simultaneously (necessitating a focus switch); focus switching did not interact with age in the response time domain. No age differences were obtained for global task switching. Ex-Gaussian decomposition showed a shift due to focus switching in all parameters, but a shift in leading edge only for task switching. The results suggest that task switching and focus switching rely on different processes, and that there is a specific age-related deficit in focus switching.

Adolescent↗
PubMed1991

Extra-dimensional versus intra-dimensional set shifting performance following frontal lobe excisions, temporal lobe excisions or amygdalo-hippocampectomy in man.

Attentional "set" shifting was assessed in a group of 20 neurosurgical patients with localized excisions of the frontal lobes, a group of 20 patients with unilateral temporal lobe lesions and a group of 11 patients who had undergone amygdalo-hippocampus removal. These three patient groups were compared with groups of both young (age-matched) and elderly normal control volunteers on a computerized test of visual discrimination learning involving both an intra- and an extra-dimensional shift. The frontal lobe group were selectively impaired in their ability to shift response set to a previously irrelevant dimension but not to shift attention to new exemplars of a previously relevant dimension. A similar pattern was observed in the elderly group of normal control volunteers. By comparison, both the temporal lobe patients and the amygdalo-hippocampectomy patients were unimpaired in their ability to perform either shift, although both groups had significantly prolonged selection latencies at the extra-dimensional shift stage of the task. These data are compared to previous findings from patients with idiopathic Parkinson's disease and are discussed in terms of a specific attentional set shifting deficit following frontal lobe damage.

Adult↗
PubMed1988

Compression and lateral shift of mental coordinate systems in a line bisection task.

Subjects (N = 18) were required to imagine how far lines of three different lengths which were presented to them previously would extend to the left or to the right of a vertical mark. They were asked to indicate the midpoint of the imagined line length. The frequency of deviations to the left or to the right of the geometrical midpoint of the line which had to be visualized was dependent on the length of the line and on the direction towards which the subjects imagined the line to extend. Whereas a compression of imagined half space compared to geometric half space was observed both for the left and right side, imagined half space on the right side of the visual field was shifted in addition more towards the periphery. It is suggested that the latter result is related to properties of left hemisphere functioning which could explain the occurrence of a typical symptom of unilateral neglect after a right hemisphere lesion.

Adult↗
PubMed2002

Microsaccades as an overt measure of covert attention shifts.

Microsaccades, or tiny eye movements that take place during periods of fixation, have long been thought to be random artifacts of the oculomotor system. Here we demonstrate a possible link between microsaccades and covert attention shifts. We designed two psychophysical tasks involving spatial cues that had identical sensory stimuli but differing patterns of attentional benefits and costs. We found that microsaccades, rather than being randomly distributed, had directions that were directly correlated with the directions of covert attention shifts in the two tasks. Our results suggest that microsaccades occur because of subliminal activation of the oculomotor system by covert attention.

Adolescent↗
PubMed1999

Visuomotor mental rotation of saccade direction.

This investigation studied the latencies of saccadic eye movements that were directed away from a target by a variable angular distance, which was given by instruction. Such a movement presumably requires an intentional, visuomotor mental rotation of the saccade vector, resulting in prolonged reaction times. From a study on the control of directed hand movements, it has been hypothesized that all visuomotor and visual mental rotation tasks share a common processing stage. We tested this hypothesis with a saccade task in which subjects shifted their gaze either towards (0 degrees, pro-saccade), or 30, 60, 90, 120, 150, or 180 degrees(anti-saccade) away from a randomly cued position on an imaginary clock face. With four different cueing conditions, latencies increased monotonically with required gaze shift from 0-150 degrees, thus exhibiting a mental rotation latency pattern. However, we also found anti-saccades faster than 150 degrees gaze shift and slower rotation speeds with peripheral cues than with central cues. Together with the overall shallower latency increase compared with previous findings with mental rotation tasks, these results cast doubt on the notion of a common, central processing mechanism for the different types of tasks.

Cues↗
PubMed2006

Biological monitoring for trimethylbenzene exposure: a human volunteer study and a practical example in the workplace.

This paper presents data from both a human volunteer study looking at exposure to 1,3,5-trimethylbenzene (TMB) and an occupational hygiene study of a printing firm using screen wash containing technical grade TMB. The biomarkers measured were TMB in blood and breath, and urinary dimethylbenzoic acids (DMBAs). The volunteer (N = 4) study showed that TMB was rapidly absorbed into the bloodstream reaching a mean level of 0.85 micromol l(-1) during a 4 h exposure to 25 p.p.m. TMB. There was little decline 1 h post-exposure possibly indicating storage of TMB in adipose tissue. Breath TMB levels peaked within an hour of exposure commencing and averaged 137 nmol l(-1) during exposure. Elimination of TMB in breath was biphasic with an initial half-life of 60 min. Peak excretion of urinary DMBA occurred 4-8 h after the end of exposure and averaged 40 mmol mol(-1) creatinine. Elimination of DMBA in urine was biphasic with half-lives of 13 and 60 h indicating that accumulation of body burden throughout the working week is likely if exposure is repeated. The occupational hygiene study demonstrated an excellent correlation between personal air TMB levels and post-shift urinary DMBA levels (r = 0.997) collected on the third working day. The regression equation from this study indicates that 8 h exposure to 25 p.p.m. TMB would result in a urinary DMBA level of 206 mmol mol(-1) creatinine. All workers showed pre-shift levels of DMBA from exposure to TMB on previous days. Both urinary DMBA and breath TMB levels can be used as biomarkers of TMB exposure. Urine samples should be taken post-shift towards the end of the working week as significant body burden accumulation throughout the working week can be expected. Breath sampling is more suited to task or single-shift monitoring.

9,10-Dimethyl-1,2-benzanthracene↗