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Biomedical subjects

Marjan Jahanshahi

Publications and source records attributed to Marjan Jahanshahi.

14 recordsLinked to original sources
PubMed2005

Executive dysfunction in Parkinson's disease is associated with altered pallidal-frontal processing.

Executive dysfunction in Parkinson's disease is well documented, but it is still unclear whether this results from (i) prefrontal dysfunction, (ii) striatal dysfunction, or (iii) altered striatal outflow to the prefrontal cortex. To clarify this issue, we used H(2)(15)O PET to asses six nondemented and nondepressed patients with Parkinson's disease and six matched controls while they performed a task involving executive function, random number generation (RNG), and a control counting task. To assess the effect of increasing task demands, each task was performed at three rates. Both groups showed significant increase in nonrandomness of responses during RNG at faster rates, which was differentially greater for the patients at the faster rate. The controls showed significant activation of the lateral and medial prefrontal cortex and superior and medial parietal cortex during RNG relative to counting. For the same comparison, the patients did not show any activity in medial frontal structures. The controls showed significantly greater mesial frontotemporal activation during counting than RNG, whereas the patients did not show any modulation of regional cerebral blood flow (rCBF) in these areas with task. With faster rates of RNG, the controls showed rCBF increase in the right internal segment of globus pallidus (GPi) and a decrease in frontal cortex. The patients showed the opposite pattern of subcortical and frontal rCBF change with faster rates. The results suggest that executive dysfunction in Parkinson's disease is associated with a failure to modulate frontal activation with increased task demands (nature of task or rate), a deficit associated with altered rCBF in the GPi, the final basal ganglia output pathway to frontal cortex rather than any intrinsic prefrontal dysfunction.

Female↗
PubMed2004

The right dorsolateral prefrontal cortex is essential in time reproduction: an investigation with repetitive transcranial magnetic stimulation.

This study used repetitive transcranial magnetic stimulation (rTMS) to investigate the roles of the right dorsolateral prefrontal cortex (DLPFC) and supplementary motor area (SMA) in short (500 ms) and long (2 s) interval timing. The results were compared with rTMS over the leg area of motor cortex, an area not thought to be involved with time estimation. rTMS was delivered during one of two phases of a time reproduction task: at the onset of the Estimation Phase (presentation of the interval to be timed) and at the onset of the Reproduction Phase (subjects' reproduction of the timed interval). There was a significant main effect of Site (SMA vs. right DLPFC vs. leg motor area) due to the fact that rTMS over the right DLPFC caused subjects to underestimate time intervals compared with rTMS over the leg motor area. There was also a significant three-way interaction between Site, Duration and Phase (Estimation Phase vs. Reproduction Phase) that post hoc analyses showed was due to underestimation of long intervals when rTMS was given over the right DLPFC at the start of the Reproduction Phase. There was no effect of rTMS over the right DLPFC or SMA in the short interval task. This is consistent with previous studies showing that the right DLPFC is important in estimating time intervals in the seconds-range. In addition, we suggest that the selectivity of the rTMS effect for the Reproduction Phase indicates that the right DLPFC plays a particular role in memory processes.

Adult↗
PubMed2004

Learning of ambiguous versus hybrid sequences by patients with Parkinson's disease.

Implicit motor learning as indexed by the serial reaction time (SRT) task has been shown to be impaired in patients with Parkinson's disease (PD). This has only been conclusively demonstrated for sequences that require learning of second-order sequential information (ambiguous sequences). This study examines implicit learning of ambiguous sequences as well as sequences which contain first-order information (hybrid sequences) in a sample of 12 early to middle stage Parkinson's disease patients and matched controls. The study used dual-task methodology in order to prevent strategic/attentional learning of second-order information. The results showed that while ambiguous sequences were not learned by either group, both patient and control groups demonstrated learning of the hybrid sequence under dual-task conditions. This suggests that first-order associations may be learned by people with Parkinson's disease, even under attentionally demanding conditions. This may be interpreted as providing evidence for a non-attentional learning mechanism which is relatively intact in Parkinson's disease.

Aged↗
PubMed2004

Development of a measure of the impact of chronic parental illness on adolescent and adult children. The parental illness impact scale (Parkinson's disease).

Although chronic illness is likely to affect the well-being of patients' children, no assessment tools are currently available to measure this impact of parental illness. We therefore developed such an instrument based on interviews with children of patients with Parkinson's disease (PD). This questionnaire and other measures of psychological well-being were completed by 89 children, aged 12-48, years of patients with PD. Factor analysis revealed six domains with 38 questions. These six domains of the 'Parental Illness Impact Scale (Parkinson's disease)' or PIIS (PD) had satisfactory internal consistency and validity. Its six sub-scales correlated significantly and differentially with corresponding measures, including the Quality of Life in Epilepsy Inventory for Adolescents (QOLIE-AD-48; r = -0.2 to 0.85), the Beck Depression Inventory (r = -0.07 to -0.40) or Birleson Depression Self-Rating Scale (r = 0.04 to -0.62), and the Rosenberg Self-Esteem Scale (r = -0.01 to 0.33) as well as age (r = -0.37 to 0.28) and parent's disease duration (r = -0.31 to 0.34). The PIIS is the first instrument to assess the impact of parental illness on children. Its psychometric properties should be tested further in larger samples, including children of patients with other chronic disorders such as multiple sclerosis or chronic heart disease.

Adolescent↗
PubMed2004

Impact of Parkinson's disease on patients' adolescent and adult children.

We assessed the impact of Parkinson's disease (PD) on the well-being of patients' adolescent and adult children. Eighty-nine participants aged 12-48 completed a number of questionnaires on quality of life (QoL) and psychosocial variables. One fifth of the participants were mildly to moderately depressed, and children below the age of 18 years scored similarly to children with epilepsy in the domains of Attitude, School behaviour, and Social support on a QoL instrument for children with epilepsy. The impact of parental PD increased with disease duration. Younger children perceived a higher burden of daily help and impact on their social interactions than older children, while older participants reported greater impairment of family functioning. More than 50% felt that they did not have sufficient information about PD and half of all participants felt that more information would reduce their feelings of uncertainty and insecurity. PD has a marked effect on the well-being of the adult and adolescent children of patients. The difficulties of children of parents with PD should receive greater attention.

Adolescent↗
PubMed2004

The basal ganglia: anatomy, physiology, and pharmacology.

The basal ganglia are perceived as important nodes in cortico-subcortical networks involved in the transfer, convergence, and processing of information in motor, cognitive, and limbic domains. How this integration might occur remains a matter of some debate, particularly given the consistent finding in anatomic and physiologic studies of functional segregation in cortico-subcortical loops. More recent theories, however, have raised the notion that modality-specific information might be integrated not spatially, but rather temporally, by coincident processing in discrete neuronal populations. Basal ganglia neurotransmitters, given their diverse roles in motor performance, learning, working memory, and reward-related activity are also likely to play an important role in the integration of cerebral activity. Further work will elucidate this to a greater extent, but for now, it is clear that the basal ganglia form an important nexus in the binding of cognitive, limbic, and motor information into thought and action.

Acetylcholine↗
PubMed2003

Plasticity of motor cortex excitability induced by rehabilitation therapy for writing.

The mechanisms of rehabilitation-induced plasticity in the motor system after stroke are not defined. The authors studied seven patients with residual poststroke agraphia, aphasia, and right hemiparesis. After a 40-minute rehabilitation therapy that promoted use of the paretic hand for writing, the authors observed a task-specific increase in recruitment of ipsilateral corticospinal pathways. Rehabilitation aimed to increase the use of the paretic hand may induce recruitment of previously silent ipsilateral corticospinal pathways even in poorly recovered poststroke patients.

Adult↗
PubMed2003

Pallidotomy and incidental sequence learning in Parkinson's disease.

Converging evidence from animal research and human brain imaging studies, points to an important role of cortical-striatal motor circuitry in the incidental learning of serial order information. To date, attempts to address this role through the study of patients with striatal disorder have proved inconclusive. The present study examined the impact of a therapeutic lesion of the globus pallidus in patients with Parkinson's disease. The lesion, which blocks a primary output of the putamen to the motor cortices, eliminated incidental learning relative both to controls and unoperated patients. The finding offers support for models proposing that context detection within the striatum is a central process in serial order learning. An unexpected effect of the lesion was to significantly reduce the response time to random stimuli relative to an ordered series, the opposite of the normal pattern. It is speculated that this may reflect an unconscious alerting response to novelty, a process suggested to involve the ventral striatum and its cortical targets. Research on Parkinson's disease patients undergoing functional basal ganglia surgery may shed further light on the mechanisms and neuronal substrate of serial order learning in humans.

Aged↗
PubMed2003

Young- versus older-onset Parkinson's disease: impact of disease and psychosocial consequences.

The effect of Parkinson's disease (PD) on young patients' lives is likely to differ from that in older patients. For this study, 75 patients with onset of PD before the age of 50 and 66 patients with later onset completed a booklet of questionnaires on demographic and clinical variables, quality of life, and psychosocial factors. Apart from a higher rate of treatment-related dyskinesias in the younger onset group, the two groups did not differ in self-reported disease severity or disability. A higher percentage of young-onset patients was unemployed due to disability or had retired early. Quality of life as measured on the PDQ-39 was significantly worse in young-onset patients than in older-onset patients. Young-onset patients also had worse scores on the stigma and marital satisfaction scales, and were depressed more frequently. Differences between the two groups in their most commonly employed coping strategies and in terms of their satisfaction with emotional support did not reach significance. We conclude that young-onset patients more frequently experience loss of employment, disruption of family life, greater perceived stigmatization, and depression than do older-onset patients with PD. In addition to more severe treatment-related motor complications, social and psychosocial factors may contribute to greater impairment of quality of life in young patients with PD.

Activities of Daily Living↗
PubMed2003

Health-related quality of life in patients with progressive supranuclear palsy.

We assessed health-related quality of life (QoL) of patients with progressive supranuclear palsy (PSP), identified the most important QoL issues in patients with this disorder, and assessed the usefulness of existing QoL measures in patients with PSP. Twenty-seven patients in all stages of PSP and their carers underwent a semistructured in-depth interview on the impact of PSP and a neurological examination. They were also asked to complete existing measures of QoL and depression. An item-pool of issues relevant to QoL of patients with PSP was created from the patient and carer interviews. Carers and patients largely agreed on issues relevant for patients' QoL but more carers than patients considered symptoms of frontal lobe dysfunction as problematic for the patients. There was no association of QoL with age and gender, as assessed in interviews and on two QoL instruments. QoL deteriorated with increasing disease duration and severity and greater cognitive impairment and was associated with worse depression scores. While the generic SF-36 was not found to be useful to assess QoL in PSP, feasibility and validity for the PDQ-39 and the EQ-5D were acceptable in this study. However, additional issues relevant to patients with PSP that were not addressed in these instruments included visual disturbances, dysarthria, dysphagia, muddled thinking, confusion, and apathy. The generic EQ-5D and the Parkinson's disease-specific PDQ-39 are useful instruments to assess QoL in patients with PSP. However, they lack questions on important aspects of QoL in PSP that were reported by patients and carers in semistructured interviews. The item pool created in these interviews provides the basis for the development of disease-specific QoL instruments for patients with PSP.

Aged↗
PubMed2003

Cognitive executive function in dystonia.

Dystonia is a movement disorder considered to result from basal ganglia dysfunction. The aim of this study was to investigate the functional significance of frontal hyperactivity demonstrated in dystonia in imaging studies by examining executive function and working memory, in which the prefrontal cortex is known to be involved. We assessed 10 patients with idiopathic dystonia and 12 age- and IQ-matched normal controls. All subjects completed tests of first letter, category, and alternating category word fluency, the Wisconsin Card Sorting Test, the Stroop Colour Word Naming Test, the Missing Digit Test of working memory, a test of random number generation, a test requiring generation of self-ordered random number sequences, the Paced Serial Addition Test, a test of conditional associative learning, and finger tapping and peg insertion under unimanual, bimanual, and dual task conditions. The patients with dystonia did not differ significantly from controls on any measures of executive function or working memory used other than category word fluency and the extent of decline in tapping with one hand under dual task conditions when simultaneously inserting pegs with the other hand. For this small sample, the results suggest that unlike other movement disorders associated with fronto-striatal dysfunction such as Parkinson's disease or Huntington's disease, dystonia was not associated with deficits on the tests of executive function or working memory used. A more detailed investigation of cognitive function in a larger sample of patients is required.

Cognition Disorders↗
PubMed2003

[Brain imaging and mobility in Parkinson's disease].

Numerous abnormalities of motor function have been identified in Parkinson's disease and functional imaging methods have given us a better understanding of underlying mechanisms. An underactivity of some frontal areas, in particular the supplementary motor area and the dorsolateral-prefrontal cortex, has been found in several studies. The activity of these areas increases when motor function improves following administration of dopaminergic drugs or functional neurosurgery. The dysfunction of the basal ganglia-thalamo-cortical loops in Parkinson's disease and in particular the excess of inhibition of the thalamo-cortical pathway by the internal pallidum is likely to be involved in the abnormal activity of the cortical areas. An excess of activation has been demonstrated in other areas and is probably compensatory.

Basal Ganglia↗