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Biomedical subjects

Marjan Jahanshahi

Publications and source records attributed to Marjan Jahanshahi.

At least 19 recordsLinked to original sources
PubMed2007

Quality of life in focal, segmental, and generalized dystonia.

The objective of this study was to assess quality of life (QoL) in a community-based sample of people with various forms of dystonia and to identify the factors that predict QoL in dystonia. QoL was assessed using two generic questionnaires: the Medical Outcomes Study Short-Form 36 (SF36) and the EuroQol questionnaire. A host of demographic, clinical, and psychosocial variables were measured to identify the best predictors of QoL in dystonia. A comparison of EuroQol and SF36 scores with the norms for the general UK population of similar age showed that people with dystonia had scores indicative of worse QoL on all domains, particularly those related to physical and social functioning. The impairment of QoL was seen in all age groups and was similar for men and women. Compared to the focal dystonia group, participants with generalized dystonia scored significantly worse on all QoL measures. Participants who were unemployed also scored significantly worse. There was also a trend for younger and separated/divorced participants to score worse on QoL measures. A stepwise regression analysis revealed that functional disability, body concept, and depression were important predictors of QoL in dystonia. Dystonia influences various aspects of QoL, particularly those related to physical and social functioning. The impairment of QoL was greater for participants with generalized dystonia, those who were unemployed, younger, and separated/divorced. Functional disability, body concept, and depression were the best predictors of QoL in dystonia. Efforts to improve health care for people with dystonia should not only focus on management of the movement disorder but also consider modifying functional disability and negative body concept and depression that contribute to poor QoL in this disorder.

Adult↗
PubMed2006

The striatum and probabilistic implicit sequence learning.

The distinction between implicit (unconscious) and explicit (conscious) learning is controversial. Some argue that explicit learning is dependent on the medial temporal lobes, whereas implicit learning is mediated by the basal ganglia and others propose that all learning is explicit. The purpose of the present study was to investigate the involvement of the basal ganglia in implicit learning by examining learning of a probabilistic sequence of targets, in patients with Parkinson's disease (PD) and controls. Following learning, we assessed participants' awareness of the sequence structure by asking them to generate or withhold sequence consistent responses (process dissociation procedure) and to perform a recognition test in which measures of priming and recognition were obtained concurrently. Although the PD group demonstrated evidence of probabilistic sequence learning in this study, learning was significantly attenuated compared to controls. Residual learning in the PD group was genuinely implicit in nature because (a) PD patients were not able to control the expression of their acquired knowledge, and (b) their knowledge supported subsequent priming of sequence-consistent responses but recognition ratings were at chance. In contrast, following learning controls were capable of above chance recognition indicating that their sequential knowledge was acquired in a more explicit way. The results support the view that (i) the basal ganglia contribute to probabilistic implicit sequence learning (ii) that such learning can occur implicitly without explicit knowledge in PD patients.

Aged↗
PubMed2006

STN stimulation alters pallidal-frontal coupling during response selection under competition.

To investigate the effects of bilateral subthalamic nucleus (STN) stimulation on patterns of brain activation during random number generation (RNG), a task that requires suppression of habitual counting and response selection under competition. We used H(2)(15)O positron emission tomography to investigate the changes of regional cerebral blood flow (rCBF) induced by bilateral STN stimulation during a RNG task, in six patients with Parkinson's disease. Paced RNG at 1 Hz was compared with a control counting task. Both tasks were performed off medication with deep brain stimulation on and off. Subthalamic nucleus stimulation had a negative effect on performance of fast-paced RNG, leading to reduced randomness and increased habitual counting. Subthalamic nucleus stimulation also induced a reduction of rCBF in the left dorsal frontal gyrus, inferior frontal gyrus, dorsolateral prefrontal cortex, posterior and right anterior cingulate, and an increase of rCBF in the right internal globus pallidum (GPi) during RNG. Stimulation of the STN significantly altered pallidal coupling with frontal and temporal areas compared with when the stimulators were off. In conclusion, during RNG: (i) STN stimulation activates its output neurons to the GPi; (ii) STN stimulation induces increased inhibition of a prefrontal-cingulate network. This is the first direct evidence that STN stimulation significantly alters pallidal coupling with prefrontal, cingulate, and temporal cortices during performance of a task that requires response selection under competition.

Cerebrovascular Circulation↗
PubMed2006

The substantia nigra pars compacta and temporal processing.

The basal ganglia and cerebellum are considered to play a role in timing, although their differential roles in timing remain unclear. It has been proposed that the timing of short milliseconds-range intervals involves the cerebellum, whereas longer seconds-range intervals engage the basal ganglia (Ivry, 1996). We tested this hypothesis using positron emission tomography to measure regional cerebral blood flow in eight right-handed males during estimation and reproduction of long and short intervals. Subjects performed three tasks: (1) reproduction of a short 500 ms interval, (2) reproduction of a long 2 s interval, and (3) a control simple reaction time (RT) task. We compared the two time reproduction tasks with the control RT task to investigate activity associated with temporal processing once additional cognitive, motor, or sensory processing was controlled. We found foci in the left substantia nigra and the left lateral premotor cortex to be significantly more activated in the time reproduction tasks than the control RT task. The left caudate nucleus and right cerebellum were more active in the short relative to the long interval, whereas greater activation of the right putamen and right cerebellum occurred in the long rather than the short interval. These results suggest that the basal ganglia and the cerebellum are engaged by reproduction of both long and short intervals but play different roles. The fundamental role of the substantia nigra in temporal processing is discussed in relation to previous animal lesion studies and evidence for the modulating influence of dopamine on temporal processing.

Acoustic Stimulation↗
PubMed2006

Longitudinal MRI in progressive supranuclear palsy and multiple system atrophy: rates and regions of atrophy.

The rate of brain atrophy and its relationship to clinical disease progression in progressive supranuclear palsy (PSP) and multiple system atrophy (MSA) is not clear. Twenty-four patients with PSP, 11 with MSA-P (Parkinsonian variant), 12 with Parkinson's disease, and 18 healthy control subjects were recruited for serial MRI scans, clinical assessments and formal neuropsychological evaluations in order to measure brain atrophy during life and its association with disease progression in PSP and MSA-P. Serial scans were registered and rates of whole brain atrophy calculated from the brain-boundary shift integral. Regional rates of atrophy were calculated in the brainstem (midbrain and pons), the cerebellum, the lateral and third ventricles as well as frontal and posterior inferior brain regions, by locally registering to a region of interest in order to derive a local boundary shift integral (BSI). 82% of recruited subjects completed serial MRI scans (17 PSP, 9 MSA-P, 9 Parkinson's disease patients and 18 healthy controls). Mean (SD) annualized rates of whole-brain atrophy were greatest in PSP: 1.2% (1.0%), three times that in controls. Mean (SD) midbrain atrophy rates in PSP, 2.2% (1.5%), were seven times greater than in healthy controls. In MSA-P, atrophy rates were greatest in the pons: 4.5% (3.2%), over 20 times that in controls and three times the rate of pontine atrophy in PSP. Atrophy rates in Parkinson's disease were not significantly different from control rates of atrophy. Variability in the atrophy rates was lower when calculated using the BSI rather than manual measurements. Worsening motor deficit was associated with midbrain atrophy in PSP, and ponto-cerebellar atrophy in MSA-P. Worsening executive dysfunction was associated with increased rates of frontal atrophy in PSP. Cerebellar atrophy rates were better discriminators of MSA-P than cross-sectional volumes. We confirm that serial MRI can be applied to measure whole brain and regional atrophy rates in PSP and MSA-P. Regional rather than whole-brain atrophy rates better discriminate PSP and MSA-P from healthy controls. Clinico-radiological associations suggest these regional atrophy rates have potential as markers of disease progression in trials of novel therapies.

Aged↗
PubMed2006

Regional brain volumes distinguish PSP, MSA-P, and PD: MRI-based clinico-radiological correlations.

Progressive supranuclear palsy (PSP) and multiple system atrophy (MSA) are neurodegenerative disorders, each with a prevalence of around 5 per 100,000. Regional brain atrophy patterns differ in the two disorders, however, and magnetic resonance imaging is sometimes helpful in distinguishing them in the later stages. We measured whole brain and regional volumes, including cerebellum, pons, midbrain, superior cerebellar peduncle (SCP), and ventricular volumes as well as frontal and posterior-inferior cerebral regions in 18 subjects with PSP, 9 with MSA-P (parkinsonian phenotype), 9 with Parkinson's disease (PD), and 18 healthy controls. Associations between these volumes, cognitive profiles, and clinical measures of disease severity and motor disability were assessed. Mean midbrain volume was 30% smaller in PSP than in PD or controls (P < 0.001) and 15% smaller than in MSA-P (P = 0.009). The mean SCP volume in PSP was 30% smaller than in MSA-P, PD, or controls (P < 0.001). Mean cerebellar volumes in MSA-P were 20% smaller than in controls and PD and 18% smaller than in PSP (P = 0.01). Mean pontine volume in MSA-P was 30% smaller than in PD or controls (P < 0.001) and 25% smaller than in PSP (P = 0.01). Motor disability was most strongly associated with midbrain volume, and more severe executive dysfunction was associated with reduced frontal volume. These distinct patterns of cortical and subcortical atrophy, when considered together rather than independently, better differentiate PSP and MSA-P from each other and also from healthy controls.

Aged↗
PubMed2006

Changes in blink reflex excitability after globus pallidus internus stimulation for dystonia.

A pathophysiological feature of dystonia is reduced inhibition at various levels of the nervous system, which may be detected in clinically unaffected body parts. Chronic deep brain stimulation (DBS) of the globus pallidus internus (GPi) has emerged as an effective treatment for primary torsion dystonia (PTD), although its mechanism of action and impact on inhibitory abnormalities in dystonia are unknown. We sought to understand the effect of GPi DBS on brainstem excitability in patients with PTD. We measured the blink reflex from orbicularis oculi in response to paired electrical stimulation of the supraorbital nerve at interstimulus intervals of 500 and 1,000 milliseconds in 10 patients with PTD before and at intervals of 1, 3, and 6 months after bilateral GPi DBS and in 10 healthy subjects. Patients were clinically evaluated using the Burke-Fahn-Marsden dystonia rating scale. We found R2 inhibition was significantly decreased in PTD patients compared with control subjects and progressively increased after GPi DBS, which correlated with clinical improvement in dystonia. We conclude that GPi DBS for PTD results in functional reorganization of the nervous system, which includes a long-term increase in brainstem inhibition.

Adult↗
PubMed2006

Holmes tremor: Application of modern neuroimaging techniques.

Holmes tremor has a characteristic rest, intention, and postural component. The syndrome arises as a consequence of a lesion in the upper brainstem and cerebral peduncles, which, it is postulated, interrupts the cerebello-rubrothalamic pathway. Ataxia, ophthalmoplegia, and bradykinesia are associated features. We present a case of Holmes tremor secondary to a midbrain cavernoma. Modern neuroimaging techniques in this case confirm that a combination of damage to the cerebello-rubrothalamic pathway and the nigrostriatal pathway is required for the full Holmes tremor syndrome to occur.

Adult↗
PubMed2006

Random number generation as an index of controlled processing.

Random number generation (RNG) is a functionally complex process that is highly controlled and therefore dependent on Baddeley's central executive. This study addresses this issue by investigating whether key predictions from this framework are compatible with empirical data. In Experiment 1, the effect of increasing task demands by increasing the rate of the paced generation was comprehensively examined. As expected, faster rates affected performance negatively because central resources were increasingly depleted. Next, the effects of participants' exposure were manipulated in Experiment 2 by providing increasing amounts of practice on the task. There was no improvement over 10 practice trials, suggesting that the high level of strategic control required by the task was constant and not amenable to any automatization gain with repeated exposure. Together, the results demonstrate that RNG performance is a highly controlled and demanding process sensitive to additional demands on central resources (Experiment 1) and is unaffected by repeated performance or practice (Experiment 2). These features render the easily administered RNG task an ideal and robust index of executive function that is highly suitable for repeated clinical use.

Adult↗
PubMed2006

The validity of the hospital anxiety and depression scale and the geriatric depression scale in Parkinson's disease.

We assessed the concurrent validity of the Hospital Anxiety and Depression Scale (HADS) and the Geriatric Depression Scale (GDS) against the Hamilton Rating Scale for Depression (Ham-D) in patients with Parkinson's disease (PD). Forty-six non-demented PD patients were assessed by a neurologist on the Ham-D. Patients also completed four mood rating scales: the HADS, the GDS, the VAS and the Face Scale. For the HADS and the GDS, Receiver Operating Characteristics (ROC) curves were obtained and the positive and negative predictive values (PPV, NPV) were calculated for different cut-off scores. Maximum discrimination between depressed and non-depressed PD patients was reached at a cut-off score of 10/11 for both the HADS and the GDS. At the same cut-off score of 10/11 for both the HADS and the GDS, the high sensitivity and NPV make these scales appropriate screening instruments for depression in PD. A high specificity and PPV, which is necessary for a diagnostic test, was reached at a cut-off score of 12/13 for the GDS and at a cut-off score of 11/12 for the HADS. The results indicate the validity of using the HADS and the GDS to screen for depressive symptoms and to diagnose depressive illness in PD.

Aged↗
PubMed2005

Caregiver-burden in parkinson's disease is closely associated with psychiatric symptoms, falls, and disability.

The majority of care of patients with Parkinson's disease (PD) is provided by informal caregivers; their caregiving not only offers physical and emotional support for patients but also plays a large economic role and prevents early nursing home placement. In order to support caregivers in this role, it is necessary to understand the extent of caregiver-burden and factors associated with increased caregiver-burden and distress. We therefore conducted a postal survey in 123 caregivers of patients with PD to assess caregiver-burden and factors associated with it. The majority of caregivers were female (66%). Over 40% of caregivers indicated that their health had suffered as a result of caregiving, almost half had increased depression scores, and two-thirds reported that their social life had suffered. After adjustment of disease duration, there was no difference in caregiver-burden between younger and older caregivers, or between male and female caregivers. Caregiver-burden increased with increasing disability and symptoms of PD, particularly with mental health problems such as depression, hallucinations, or confusion, and with falls. Caregiver-burden scores also correlated significantly with the patients' depression and quality of life scores, and with caregivers' own satisfaction with their marital and sexual relationship. We conclude that more attention should be paid to caregivers' emotional and physical health, particularly in advancing PD with psychiatric complications and falls. These findings also demonstrate that caregiver and patient quality of life are closely linked and emphasize the importance of including caregiver-burden among the problems associated with PD in order to improve patient and caregiver lives.

Accidental Falls↗
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↗