Marjan Jahanshahi - Academia.edu (original) (raw)
Papers by Marjan Jahanshahi
Journal of Neurology, Neurosurgery, and Psychiatry, Apr 1, 1988
Journal of Neurology, Neurosurgery, and Psychiatry, Oct 1, 1989
Presented at: 30th Annual General Meeting of the British-Neuropsychiatry-Association (BNPA), Royal Coll Surg, London, ENGLAND. (2017), Aug 1, 2017
NeuroRehabilitation, 2018
Computational Neuroscience Models of the Basal Ganglia, 2018
We present a cortico-basal ganglia model to study the neural mechanisms behind reaching movements... more We present a cortico-basal ganglia model to study the neural mechanisms behind reaching movements in normal and in Parkinson’s disease conditions. The model consists of the following components: a two-joint arm model (AM), a layer of motor neurons in the spinal cord (MN), the proprioceptive cortex (PC), the motor cortex (MC), the prefrontal cortex (PFC), and the basal ganglia (BG). The model thus has an outer sensory-motor cortical loop and an inner cortico-basal ganglia loop to drive learning of reaching behavior. Sensory and motor maps are formed by the PC and MC which represent the space of arm configurations. The BG sends control signals to the MC following a stochastic gradient ascent policy applied to the value function defined over the arm configuration space. The trainable connections from PFC to MC can directly activate the motor cortex, thereby producing rapid movement avoiding the slow search conducted by the BG. The model captures the two main stages of motor learning, i.e., slow movements dominated by the BG during early stages and cortically driven fast movements with smoother trajectories at later stages. The model explains PD performance in stationary and pursuit reaching tasks. The model also shows that PD symptoms like tremor and rigidity could be attributed to synchronized oscillations in STN–GPe. The model is in line with closed-loop control and with neural representations for all the nuclei which explains Parkinsonian reaching. By virtue of its ability to capture the role of cortico-basal ganglia systems in controlling a wide range of features of reaching, the proposed model can potentially serve as a benchmark to test various motor pathologies of the BG.
Behavioural Brain Research, 2020
Biological Psychiatry, 2019
Background: Deep brain stimulation (DBS) is an emerging treatment for disorders marked by perseve... more Background: Deep brain stimulation (DBS) is an emerging treatment for disorders marked by perseveration, including depression and OCD. We compared the efficacy of ventral capsule/ventral striatal (VC/VS) and anteromedial subthalamic nucleus (amSTN) DBS in the same OCD patients and tested for mechanistic differences on mood and cognitive flexibility and associated neural circuitry. Methods: Six patients with treatment-refractory OCD (5 male;YBOCS > 32) entered double-blind counterbalanced phases (12 weeks amSTN or VC/VS DBS), followed by open phases when amSTN and VC/VS were stimulated together. OCD, mood and cognitive flexibility (ID/ED) were assessed. Diffusion-weighted and intraoperative MRI scans were performed for tractography from optimally activated electrode-contacts. Baseline and 12-week were compared via two-tailed t-tests Results: Y-BOCS improved following both amSTN and VC/VS DBS (Baseline versus amSTN: p < 0.001; Baseline versus VC/ VS: p < 0.001; amSTN versus VC/VS: p ¼ 1.00). Changes in MADRS scores differed from baseline for both amSTN and VC/ VS. The amSTN effect was greater than VC/VS (Baseline versus amSTN: p ¼ 0.023; Baseline versus VC/VS: p < 0.001; amSTN versus VC/VS: p ¼ 0.001). Changes in ExtraDimensional errors were significant for amSTN but not VC/VS DBS (Baseline versus amSTN: p ¼ 0.003; Baseline versus VC/VS: p ¼ 0.157; amSTN versus VC/VS: p ¼ 0.018). Tractography streamlines from amSTN-VTAs were connected to the lateral OFC, dACC, dlPFC and medial forebrainbundle. Average streamlines from VC-VTAs were connected to the mOFC, mediodorsal thalamus, amygdala, hypothalamus and habenula. Conclusions: VC/VS and amSTN are equally effective targets for severe treatment-refractory OCD. Differential improvements in mood and cognitive flexibility and their associated connectivity suggests that DBS at these sites modulate distinct brain networks.
NeuroRehabilitation, 2018
BACKGROUND: Despite their potentially significant impact, cognitive disability may be overlooked ... more BACKGROUND: Despite their potentially significant impact, cognitive disability may be overlooked in a number of progressive neurodegenerative conditions, as other difficulties dominate the clinical picture. OBJECTIVE: We examined the extent, nature and range of the research evidence relating to cognitive rehabilitation, self-management, psychotherapeutic and caregiver support interventions in Parkinsonian disorders, multiple sclerosis (MS), frontotemporal dementias (FTD), motor neuron disease and Huntington's disease. METHODS: Scoping review based on searches of MEDLINE and CINAHL up to 15 March 2016. RESULTS: We included 140 eligible papers. Over half of the studies, and almost all the randomised controlled trials, related to MS, while a number of single case studies described interventions for people with FTD. CR interventions addressed functional ability, communication and interaction, behaviour or memory. The majority of psychotherapy interventions involved cognitive behavioural therapy for depression or anxiety. Selfmanagement interventions were mainly available for people with MS. There were few reports of interventions specific to caregivers. Numerous methodological challenges were identified. CONCLUSIONS: The limited range of studies for all conditions except MS suggests a need firstly to synthesise systematically the available evidence across conditions and secondly to develop well-designed studies to provide evidence about the effectiveness of CR and other psychological interventions.
Physiology & behavior, Jan 18, 2018
In neuroscience literature, dopamine is often considered as a pleasure chemical of the brain. Dop... more In neuroscience literature, dopamine is often considered as a pleasure chemical of the brain. Dopaminergic neurons respond to rewarding stimuli which include primary rewards like opioids or food, or more abstract forms of reward like cash rewards or pictures of pretty faces. It is this reward-related aspect of dopamine, particularly its association with reward prediction error, that is highlighted by a large class of computational models of dopamine signaling. Dopamine is also a neuromodulator, controlling synaptic plasticity in several cortical and subcortical areas. But dopamine's influence is not limited to the nervous system; its effects are also found in other physiological systems, particularly the circulatory system. Importantly, dopamine agonists have been used as a drug to control blood pressure. Is there a theoretical, conceptual connection that reconciles dopamine's effects in the nervous system with those in the circulatory system? This perspective article integr...
Journal of Neurology, Neurosurgery & Psychiatry, 2017
Reviews in the Neurosciences, 2016
Postural instability (PI) is one of the most debilitating motor symptoms of Parkinson’s disease (... more Postural instability (PI) is one of the most debilitating motor symptoms of Parkinson’s disease (PD), as it is associated with an increased risk of falls and subsequent medical complications (e.g. fractures), fear of falling, decreased mobility, self-restricted physical activity, social isolation, and decreased quality of life. The pathophysiological mechanisms underlying PI in PD remain elusive. This short review provides a critical summary of the literature on PI in PD, covering the clinical features, the neural and cognitive substrates, and the effects of dopaminergic medications and deep brain stimulation. The delayed effect of dopaminergic medication combined with the success of extrastriatal deep brain stimulation suggests that PI involves neurotransmitter systems other than dopamine and brain regions extending beyond the basal ganglia, further challenging the traditional view of PD as a predominantly single-system neurodegenerative disease.
Reviews in the neurosciences, Jul 16, 2016
Parkinson's disease (PD) is characterized by a range of motor symptoms. Besides the cardinal ... more Parkinson's disease (PD) is characterized by a range of motor symptoms. Besides the cardinal symptoms (tremor, bradykinesia/akinesia, and rigidity), PD patients also show other motor deficits, including gait disturbance, speech deficits, and impaired handwriting. However, along with these key motor symptoms, PD patients also experience cognitive deficits in attention, executive function, working memory, and learning. Recent evidence suggests that these motor and cognitive deficits of PD are not completely dissociable, as aspects of cognitive dysfunction can impact motor performance in PD. In this article, we provide a review of behavioral and neural studies on the associations between motor symptoms and cognitive deficits in PD, specifically akinesia/bradykinesia, tremor, gait, handwriting, precision grip, and speech production. This review paves the way for providing a framework for understanding how treatment of cognitive dysfunction, for example cognitive rehabilitation progr...
Movement …, 2003
... Anette Schrag MD, PhD,; Caroline Selai PhD,; Jennifer Davis MD,; Andrew J. Lees MD, FRCP,;Mar... more ... Anette Schrag MD, PhD,; Caroline Selai PhD,; Jennifer Davis MD,; Andrew J. Lees MD, FRCP,;Marjan Jahanshahi PhD,; Niall Quinn MD, FRCP. ... The generic EQ-5D and the Parkinson&amp;#x27;s disease-specific PDQ-39 are useful instruments to assess QoL in patients with PSP. ...
We used EEG source analysis to identify which cortical areas were involved in the suppression of ... more We used EEG source analysis to identify which cortical areas were involved in the suppression of competing responses on a flanker task and compare the potential efficacy of recombinant-human erythropoietin (rHuEPO) in the performance of Parkinson’ s Disease patients.The samples were 18 medicated PD patients (9 with rHuEPO and 9 without rHuEPO) and 9 age and education-matched healthy controls (HCs) who completed the flanker task with simultaneous EEG recordings. N1, N2 and P3 event-related potential (ERP) components were identified and a low-resolution tomography (LORETA) inverse solution was employed to localize the neural generators.Reaction times and errors were increased for the incongruent flankers for PD patients compared to controls. EEG source analysis identified an effect of rHuEPO on the lingual gyri for the early N1component. N2-related sources in middle cingulate and precuneus were associated with the inhibition of automatic responses evoked by incongruent stimuli differe...
Neurocase, Aug 1, 2005
The frontal assessment battery (FAB) is a bedside test of executive function. It takes less than ... more The frontal assessment battery (FAB) is a bedside test of executive function. It takes less than 10 minutes to administer and a low score indicates executive dysfunction. To determine whether the FAB could detect the more severe subcortical dementia that is a feature of PSP and differentiate it from other bradykinetic rigid syndromes, we studied 17 patients with progressive supranuclear palsy (PSP); 11 with multiple system atrophy (MSA) and 12 with Parkinson's disease (PD). We compared FAB scores with the results of more detailed tests of executive and general cognitive function.FAB scores were significantly lower in PSP than in MSA or PD (p=0.02 and p<0.001) and were also found to be significantly lower in MSA than in PD (p=0.047). We divided the study group into those with an FAB score <15 and those with an FAB score>/=5, regardless of the clinical diagnosis. While 82% of the PSP group had FAB scores of <15, such scores were recorded in only 36% of the MSA and 8% of the PD groups. The lexical fluency and motor series subscores of the FAB discriminated 70% of the PSP, MSA and PD patients. The FAB scores correlated with tests of executive function, as well as with scores on the Mattis Dementia Rating Scale, the Mini Mental State Examination and other tests of general cognitive function. A stepwise regression analysis revealed that across the groups, among the variables that correlated with FAB scores, alternating semantic fluency accounted for 80% of FAB variance.These results suggest that the FAB is a valid and easily applicable bedside test to discriminate executive dysfunction in these three frequently confused bradykinetic rigid syndromes.
Neuropsychology (journal), Jul 1, 2020
Dopamine agonists are the main pharmacological intervention for the motor symptoms of Parkinson's... more Dopamine agonists are the main pharmacological intervention for the motor symptoms of Parkinson's disease (PD). However, dopaminergic medication has been associated with disinhibitory psychopathology in some patients. The aim of this study was to test the effect of dopaminergic medication on inhibitory control in patients with PD using the paced Random Number Generation task (RNG), which requires inhibition of pre-potent counting in series to produce a random sequence of numbers. Methods Twenty-three PD patients performed RNG on-and off-dopaminergic medication. Cognitive load was manipulated by performing RNG at faster (1Hz) and slower (0.5 Hz) rates. For RNG, two scores (CS1 and CS2) were derivedwhich are considered indices of more automatic and more controlled counting respectively. Results There were no main effects of medication on RNG performance. There was a significant main effect of cognitive load on CS1, with higher CS1 scores at the faster rate (p = <.01). A significant interaction effect between medication and rate (cognitive load) (p = .03) followed by post-hoc testing, revealed that CS2 scores were higher, on-medication, at the slower but not the faster rate. Conclusions Patients with PD displayed increased use of more controlled processing strategies onmedication at the slowest rate of RNG. Therefore, while dopaminergic medication has been associated with disinhibitory psychopathology, our results suggest that dopamine therapy may enhance some forms of inhibitory cognitive control in PD, but only there is sufficient time to engage controlled processing strategies.
Brain Stimulation, Sep 1, 2017
Background: Stopping an ongoing motor response or resolving conflict induced by conflicting stimu... more Background: Stopping an ongoing motor response or resolving conflict induced by conflicting stimuli are associated with activation of a right-lateralized network of inferior frontal gyrus (IFG), pre-supplementary motor area (pre-SMA) and subthalamic nucleus (STN). However, the roles of the right IFG and pre-SMA in stopping a movement and in conflict resolution remain unclear. We used continuous theta burst stimulation (cTBS) to examine the involvement of the right IFG and pre-SMA in inhibition and conflict resolution using the conditional stop signal task. Methods: We measured stop signal reaction time (SSRT, measure of reactive inhibition), response delay effect (RDE, measure of proactive action restraint) and conflict induced slowing (CIS, measure of conflict resolution). Results: Stimulation over the pre-SMA resulted in significantly shorter SSRTs (improved inhibition) compared to sham cTBS. This effect was not observed for CIS, RDE, or any other measures. cTBS over the right IFG had no effect on SSRT, CIS, RDE or on any other measure. Conclusions: The improvement of SSRT with cTBS over the pre-SMA suggests its critical contribution to stopping ongoing movements.
Journal of Cognitive Neuroscience, Mar 1, 2010
■ Theta burst transcranial magnetic stimulation (TBS) is considered to produce plastic changes in... more ■ Theta burst transcranial magnetic stimulation (TBS) is considered to produce plastic changes in human motor cortex. Here, we examined the inhibitory and excitatory effects of TBS on implicit sequence learning using a probabilistic serial reaction time paradigm. We investigated the involvement of several cortical regions associated with implicit sequence learning by examining probabilistic sequence learning in five age-and IQmatched groups of healthy participants following continuous inhibitory TBS over primary motor cortex (M1), or the supplementary motor area (SMA) or dorsolateral prefrontal cortex (DLPFC) or following intermittent excitatory TBS of M1, or after sham TBS. Relative to sham TBS, probabilistic sequence learning was abolished by inhibitory TBS over M1, demonstrating that this region is critical for implicit motor sequence learning. Sequence learning was not significantly affected by inhibitory TBS over the SMA, DLPFC or excitatory TBS over M1. These results demonstrate that the M1 mediates implicit sequence learning. ■
Journal of Neurology, Neurosurgery, and Psychiatry, Apr 1, 1988
Journal of Neurology, Neurosurgery, and Psychiatry, Oct 1, 1989
Presented at: 30th Annual General Meeting of the British-Neuropsychiatry-Association (BNPA), Royal Coll Surg, London, ENGLAND. (2017), Aug 1, 2017
NeuroRehabilitation, 2018
Computational Neuroscience Models of the Basal Ganglia, 2018
We present a cortico-basal ganglia model to study the neural mechanisms behind reaching movements... more We present a cortico-basal ganglia model to study the neural mechanisms behind reaching movements in normal and in Parkinson’s disease conditions. The model consists of the following components: a two-joint arm model (AM), a layer of motor neurons in the spinal cord (MN), the proprioceptive cortex (PC), the motor cortex (MC), the prefrontal cortex (PFC), and the basal ganglia (BG). The model thus has an outer sensory-motor cortical loop and an inner cortico-basal ganglia loop to drive learning of reaching behavior. Sensory and motor maps are formed by the PC and MC which represent the space of arm configurations. The BG sends control signals to the MC following a stochastic gradient ascent policy applied to the value function defined over the arm configuration space. The trainable connections from PFC to MC can directly activate the motor cortex, thereby producing rapid movement avoiding the slow search conducted by the BG. The model captures the two main stages of motor learning, i.e., slow movements dominated by the BG during early stages and cortically driven fast movements with smoother trajectories at later stages. The model explains PD performance in stationary and pursuit reaching tasks. The model also shows that PD symptoms like tremor and rigidity could be attributed to synchronized oscillations in STN–GPe. The model is in line with closed-loop control and with neural representations for all the nuclei which explains Parkinsonian reaching. By virtue of its ability to capture the role of cortico-basal ganglia systems in controlling a wide range of features of reaching, the proposed model can potentially serve as a benchmark to test various motor pathologies of the BG.
Behavioural Brain Research, 2020
Biological Psychiatry, 2019
Background: Deep brain stimulation (DBS) is an emerging treatment for disorders marked by perseve... more Background: Deep brain stimulation (DBS) is an emerging treatment for disorders marked by perseveration, including depression and OCD. We compared the efficacy of ventral capsule/ventral striatal (VC/VS) and anteromedial subthalamic nucleus (amSTN) DBS in the same OCD patients and tested for mechanistic differences on mood and cognitive flexibility and associated neural circuitry. Methods: Six patients with treatment-refractory OCD (5 male;YBOCS > 32) entered double-blind counterbalanced phases (12 weeks amSTN or VC/VS DBS), followed by open phases when amSTN and VC/VS were stimulated together. OCD, mood and cognitive flexibility (ID/ED) were assessed. Diffusion-weighted and intraoperative MRI scans were performed for tractography from optimally activated electrode-contacts. Baseline and 12-week were compared via two-tailed t-tests Results: Y-BOCS improved following both amSTN and VC/VS DBS (Baseline versus amSTN: p < 0.001; Baseline versus VC/ VS: p < 0.001; amSTN versus VC/VS: p ¼ 1.00). Changes in MADRS scores differed from baseline for both amSTN and VC/ VS. The amSTN effect was greater than VC/VS (Baseline versus amSTN: p ¼ 0.023; Baseline versus VC/VS: p < 0.001; amSTN versus VC/VS: p ¼ 0.001). Changes in ExtraDimensional errors were significant for amSTN but not VC/VS DBS (Baseline versus amSTN: p ¼ 0.003; Baseline versus VC/VS: p ¼ 0.157; amSTN versus VC/VS: p ¼ 0.018). Tractography streamlines from amSTN-VTAs were connected to the lateral OFC, dACC, dlPFC and medial forebrainbundle. Average streamlines from VC-VTAs were connected to the mOFC, mediodorsal thalamus, amygdala, hypothalamus and habenula. Conclusions: VC/VS and amSTN are equally effective targets for severe treatment-refractory OCD. Differential improvements in mood and cognitive flexibility and their associated connectivity suggests that DBS at these sites modulate distinct brain networks.
NeuroRehabilitation, 2018
BACKGROUND: Despite their potentially significant impact, cognitive disability may be overlooked ... more BACKGROUND: Despite their potentially significant impact, cognitive disability may be overlooked in a number of progressive neurodegenerative conditions, as other difficulties dominate the clinical picture. OBJECTIVE: We examined the extent, nature and range of the research evidence relating to cognitive rehabilitation, self-management, psychotherapeutic and caregiver support interventions in Parkinsonian disorders, multiple sclerosis (MS), frontotemporal dementias (FTD), motor neuron disease and Huntington's disease. METHODS: Scoping review based on searches of MEDLINE and CINAHL up to 15 March 2016. RESULTS: We included 140 eligible papers. Over half of the studies, and almost all the randomised controlled trials, related to MS, while a number of single case studies described interventions for people with FTD. CR interventions addressed functional ability, communication and interaction, behaviour or memory. The majority of psychotherapy interventions involved cognitive behavioural therapy for depression or anxiety. Selfmanagement interventions were mainly available for people with MS. There were few reports of interventions specific to caregivers. Numerous methodological challenges were identified. CONCLUSIONS: The limited range of studies for all conditions except MS suggests a need firstly to synthesise systematically the available evidence across conditions and secondly to develop well-designed studies to provide evidence about the effectiveness of CR and other psychological interventions.
Physiology & behavior, Jan 18, 2018
In neuroscience literature, dopamine is often considered as a pleasure chemical of the brain. Dop... more In neuroscience literature, dopamine is often considered as a pleasure chemical of the brain. Dopaminergic neurons respond to rewarding stimuli which include primary rewards like opioids or food, or more abstract forms of reward like cash rewards or pictures of pretty faces. It is this reward-related aspect of dopamine, particularly its association with reward prediction error, that is highlighted by a large class of computational models of dopamine signaling. Dopamine is also a neuromodulator, controlling synaptic plasticity in several cortical and subcortical areas. But dopamine's influence is not limited to the nervous system; its effects are also found in other physiological systems, particularly the circulatory system. Importantly, dopamine agonists have been used as a drug to control blood pressure. Is there a theoretical, conceptual connection that reconciles dopamine's effects in the nervous system with those in the circulatory system? This perspective article integr...
Journal of Neurology, Neurosurgery & Psychiatry, 2017
Reviews in the Neurosciences, 2016
Postural instability (PI) is one of the most debilitating motor symptoms of Parkinson’s disease (... more Postural instability (PI) is one of the most debilitating motor symptoms of Parkinson’s disease (PD), as it is associated with an increased risk of falls and subsequent medical complications (e.g. fractures), fear of falling, decreased mobility, self-restricted physical activity, social isolation, and decreased quality of life. The pathophysiological mechanisms underlying PI in PD remain elusive. This short review provides a critical summary of the literature on PI in PD, covering the clinical features, the neural and cognitive substrates, and the effects of dopaminergic medications and deep brain stimulation. The delayed effect of dopaminergic medication combined with the success of extrastriatal deep brain stimulation suggests that PI involves neurotransmitter systems other than dopamine and brain regions extending beyond the basal ganglia, further challenging the traditional view of PD as a predominantly single-system neurodegenerative disease.
Reviews in the neurosciences, Jul 16, 2016
Parkinson's disease (PD) is characterized by a range of motor symptoms. Besides the cardinal ... more Parkinson's disease (PD) is characterized by a range of motor symptoms. Besides the cardinal symptoms (tremor, bradykinesia/akinesia, and rigidity), PD patients also show other motor deficits, including gait disturbance, speech deficits, and impaired handwriting. However, along with these key motor symptoms, PD patients also experience cognitive deficits in attention, executive function, working memory, and learning. Recent evidence suggests that these motor and cognitive deficits of PD are not completely dissociable, as aspects of cognitive dysfunction can impact motor performance in PD. In this article, we provide a review of behavioral and neural studies on the associations between motor symptoms and cognitive deficits in PD, specifically akinesia/bradykinesia, tremor, gait, handwriting, precision grip, and speech production. This review paves the way for providing a framework for understanding how treatment of cognitive dysfunction, for example cognitive rehabilitation progr...
Movement …, 2003
... Anette Schrag MD, PhD,; Caroline Selai PhD,; Jennifer Davis MD,; Andrew J. Lees MD, FRCP,;Mar... more ... Anette Schrag MD, PhD,; Caroline Selai PhD,; Jennifer Davis MD,; Andrew J. Lees MD, FRCP,;Marjan Jahanshahi PhD,; Niall Quinn MD, FRCP. ... The generic EQ-5D and the Parkinson&amp;#x27;s disease-specific PDQ-39 are useful instruments to assess QoL in patients with PSP. ...
We used EEG source analysis to identify which cortical areas were involved in the suppression of ... more We used EEG source analysis to identify which cortical areas were involved in the suppression of competing responses on a flanker task and compare the potential efficacy of recombinant-human erythropoietin (rHuEPO) in the performance of Parkinson’ s Disease patients.The samples were 18 medicated PD patients (9 with rHuEPO and 9 without rHuEPO) and 9 age and education-matched healthy controls (HCs) who completed the flanker task with simultaneous EEG recordings. N1, N2 and P3 event-related potential (ERP) components were identified and a low-resolution tomography (LORETA) inverse solution was employed to localize the neural generators.Reaction times and errors were increased for the incongruent flankers for PD patients compared to controls. EEG source analysis identified an effect of rHuEPO on the lingual gyri for the early N1component. N2-related sources in middle cingulate and precuneus were associated with the inhibition of automatic responses evoked by incongruent stimuli differe...
Neurocase, Aug 1, 2005
The frontal assessment battery (FAB) is a bedside test of executive function. It takes less than ... more The frontal assessment battery (FAB) is a bedside test of executive function. It takes less than 10 minutes to administer and a low score indicates executive dysfunction. To determine whether the FAB could detect the more severe subcortical dementia that is a feature of PSP and differentiate it from other bradykinetic rigid syndromes, we studied 17 patients with progressive supranuclear palsy (PSP); 11 with multiple system atrophy (MSA) and 12 with Parkinson's disease (PD). We compared FAB scores with the results of more detailed tests of executive and general cognitive function.FAB scores were significantly lower in PSP than in MSA or PD (p=0.02 and p<0.001) and were also found to be significantly lower in MSA than in PD (p=0.047). We divided the study group into those with an FAB score <15 and those with an FAB score>/=5, regardless of the clinical diagnosis. While 82% of the PSP group had FAB scores of <15, such scores were recorded in only 36% of the MSA and 8% of the PD groups. The lexical fluency and motor series subscores of the FAB discriminated 70% of the PSP, MSA and PD patients. The FAB scores correlated with tests of executive function, as well as with scores on the Mattis Dementia Rating Scale, the Mini Mental State Examination and other tests of general cognitive function. A stepwise regression analysis revealed that across the groups, among the variables that correlated with FAB scores, alternating semantic fluency accounted for 80% of FAB variance.These results suggest that the FAB is a valid and easily applicable bedside test to discriminate executive dysfunction in these three frequently confused bradykinetic rigid syndromes.
Neuropsychology (journal), Jul 1, 2020
Dopamine agonists are the main pharmacological intervention for the motor symptoms of Parkinson's... more Dopamine agonists are the main pharmacological intervention for the motor symptoms of Parkinson's disease (PD). However, dopaminergic medication has been associated with disinhibitory psychopathology in some patients. The aim of this study was to test the effect of dopaminergic medication on inhibitory control in patients with PD using the paced Random Number Generation task (RNG), which requires inhibition of pre-potent counting in series to produce a random sequence of numbers. Methods Twenty-three PD patients performed RNG on-and off-dopaminergic medication. Cognitive load was manipulated by performing RNG at faster (1Hz) and slower (0.5 Hz) rates. For RNG, two scores (CS1 and CS2) were derivedwhich are considered indices of more automatic and more controlled counting respectively. Results There were no main effects of medication on RNG performance. There was a significant main effect of cognitive load on CS1, with higher CS1 scores at the faster rate (p = <.01). A significant interaction effect between medication and rate (cognitive load) (p = .03) followed by post-hoc testing, revealed that CS2 scores were higher, on-medication, at the slower but not the faster rate. Conclusions Patients with PD displayed increased use of more controlled processing strategies onmedication at the slowest rate of RNG. Therefore, while dopaminergic medication has been associated with disinhibitory psychopathology, our results suggest that dopamine therapy may enhance some forms of inhibitory cognitive control in PD, but only there is sufficient time to engage controlled processing strategies.
Brain Stimulation, Sep 1, 2017
Background: Stopping an ongoing motor response or resolving conflict induced by conflicting stimu... more Background: Stopping an ongoing motor response or resolving conflict induced by conflicting stimuli are associated with activation of a right-lateralized network of inferior frontal gyrus (IFG), pre-supplementary motor area (pre-SMA) and subthalamic nucleus (STN). However, the roles of the right IFG and pre-SMA in stopping a movement and in conflict resolution remain unclear. We used continuous theta burst stimulation (cTBS) to examine the involvement of the right IFG and pre-SMA in inhibition and conflict resolution using the conditional stop signal task. Methods: We measured stop signal reaction time (SSRT, measure of reactive inhibition), response delay effect (RDE, measure of proactive action restraint) and conflict induced slowing (CIS, measure of conflict resolution). Results: Stimulation over the pre-SMA resulted in significantly shorter SSRTs (improved inhibition) compared to sham cTBS. This effect was not observed for CIS, RDE, or any other measures. cTBS over the right IFG had no effect on SSRT, CIS, RDE or on any other measure. Conclusions: The improvement of SSRT with cTBS over the pre-SMA suggests its critical contribution to stopping ongoing movements.
Journal of Cognitive Neuroscience, Mar 1, 2010
■ Theta burst transcranial magnetic stimulation (TBS) is considered to produce plastic changes in... more ■ Theta burst transcranial magnetic stimulation (TBS) is considered to produce plastic changes in human motor cortex. Here, we examined the inhibitory and excitatory effects of TBS on implicit sequence learning using a probabilistic serial reaction time paradigm. We investigated the involvement of several cortical regions associated with implicit sequence learning by examining probabilistic sequence learning in five age-and IQmatched groups of healthy participants following continuous inhibitory TBS over primary motor cortex (M1), or the supplementary motor area (SMA) or dorsolateral prefrontal cortex (DLPFC) or following intermittent excitatory TBS of M1, or after sham TBS. Relative to sham TBS, probabilistic sequence learning was abolished by inhibitory TBS over M1, demonstrating that this region is critical for implicit motor sequence learning. Sequence learning was not significantly affected by inhibitory TBS over the SMA, DLPFC or excitatory TBS over M1. These results demonstrate that the M1 mediates implicit sequence learning. ■