Cognitive slowing in Parkinson disease is accompanied by hypofunctioning of the striatum

Blood transcriptomic signatures associated with molecular changes in the brain and clinical outcomes in Parkinson's disease

The ability to use blood to predict the outcomes of Parkinson's disease, including disease progression and cognitive and motor complications, would be of significant clinical value. We undertook bulk RNA sequencing from the caudate and putamen of postmortem Parkinson's disease (n = 35) and control (n = 40) striatum, and compared molecular profiles with clinical features and bulk RNA sequencing data obtained from antemortem peripheral blood. Cognitive and motor complications of Parkinson's disease were associated with molecular changes in the caudate (stress response) and putamen (endothelial pathways) respectively. Later and earlier-onset Parkinson's disease were molecularly distinct, and disease duration was associated with changes in caudate (oligodendrocyte development) and putamen (cellular senescence), respectively. Transcriptome patterns in the postmortem Parkinson's disease brain were also evident in antemortem peripheral blood, and correlated with clinical features of the disease. Together, these findings identify molecular signatures in Parkinson's disease patients' brain and blood of potential pathophysiologic and prognostic importance.

Cortical oscillatory dysfunction in Parkinson disease during movement activation and inhibition

Response activation and inhibition are functions fundamental to executive control that are disrupted in Parkinson disease (PD). We used magnetoencephalography to examine event related changes in oscillatory power amplitude, peak latency and frequency in cortical networks subserving these functions and identified abnormalities associated with PD. Participants (N = 18 PD, 18 control) performed a cue/target task that required initiation of an un-cued movement (activation) or inhibition of a cued movement. Reaction times were variable but similar across groups. Task related responses in gamma, alpha, and beta power were found across cortical networks including motor cortex, supplementary and pre- supplementary motor cortex, posterior parietal cortex, prefrontal cortex and anterior cingulate. PD-related changes in power and latency were noted most frequently in the beta band, however, abnormal power and delayed peak latency in the alpha band in the pre-supplementary motor area was suggestive of a compensatory mechanism. PD peak power was delayed in pre-supplementary motor area, motor cortex, and medial frontal gyrus only for activation, which is consistent with deficits in un-cued (as opposed to cued) movement initiation characteristic of PD.

Semantic fluency and processing speed are reduced in non-cognitively impaired participants with Parkinson's disease

Introduction: Parkinson's disease (PD) is associated with a range of cognitive deficits. Few studies have carefully examined the subtle impacts of PD on cognition among patients who do not meet formal criteria for MCI or dementia. The aim of the current study was thus to describe the impact of PD on cognition in those without cognitive impairment in a well-characterized cohort.Methods: Non-cognitively impaired participants (122 with PD, 122 age- and sex-matched healthy volunteers) underwent extensive cognitive testing. Linear regression analyses compared diagnostic group performance across cognitive measures. For cognitive tasks that were significantly different between groups, additional analyses examined group differences restricting the group inclusion to PD participants with mild motor symptoms or disease duration less than 10 years.Results: Processing speed and semantic verbal fluency were significantly lower in the PD group (B = -3.77, 95% CIs [-5.76 to -1.77], p < .001, and B = -2.02, 95% CIs [-3.12, -0.92], p < .001, respectively), even after excluding those with moderate to severe motor symptoms (B = -2.73, 95% CIs [-4.94 to -0.53], p = .015 and B = -2.11, 95% CIs [-3.32 to -0.91], p < .001, respectively) or longer disease duration (B = -3.89, 95% CIs [-6.14 to -1.63], p < .001 and B = -1.58, 95% CIs [-2.78 to -0.37], p = .010, respectively). Semantic verbal fluency remained significantly negatively associated with PD diagnosis after controlling for processing speed (B = -1.66, 95% CIs [-2.79 to -0.53], p = .004).Conclusions: Subtle decline in specific cognitive domains may be present among people diagnosed with PD but without evidence to support a formal cognitive diagnosis. These results suggest the importance of early awareness of the potential for diminishing aspects of cognition in PD even among those without mild cognitive impairment or dementia.

Gender Differences and Quality of Life in Parkinson's Disease

Parkinson's disease has been found to significantly affect health-related quality of life. The gender differences of the health-related quality of life of subjects with Parkinson's disease have been observed in a number of studies. These differences have been reported in terms of the age at onset, clinical manifestations, and response to therapy. In general, women with Parkinson's disease showed more positive disease outcomes with regard to emotion processing, non-motor symptoms, and cognitive functions, although women report more Parkinson's disease-related clinical manifestations. Female gender predicted poor physical functioning and socioemotional health-related quality of life, while male gender predicted the cognitive domain of health-related quality of life. Some studies reported gender differences in the association between health-related quality of life and non-motor symptoms. Depression and fatigue were the main causes of poorer health-related quality of life in women, even in the early stages of Parkinson's disease. The aim of this review was to collect the best available evidence on gender differences in the development of Parkinson's disease symptoms and health-related quality of life.

A novel dopamine D3R agonist SK609 with norepinephrine transporter inhibition promotes improvement in cognitive task performance in rodent and non-human primate models of Parkinson's disease

Mild cognitive impairment is present in a number of neurodegenerative disorders including Parkinson's disease (PD). Mild cognitive impairment in PD (PD-MCI) often manifests as deficits in executive functioning, attention, and spatial and working memory. Clinical studies have suggested that the development of mild cognitive impairment may be an early symptom of PD and may even precede the onset of motor impairment by several years. Dysfunction in several neurotransmitter systems, including dopamine (DA), norepinephrine (NE), may be involved in PD-MCI, making it difficult to treat pharmacologically. In addition, many agents used to treat motor impairment in PD may exacerbate cognitive impairment. Thus, there is a significant unmet need to develop therapeutics that can treat both motor and cognitive impairments in PD. We have recently developed SK609, a selective, G-protein biased signaling agonist of dopamine D3 receptors. SK609 was successfully used to treat motor impairment and reduce levodopa-induced dyskinesia in a rodent model of PD. Further characterization of SK609 suggested that it is a selective norepinephrine transporter (NET) inhibitor with the ability to increase both DA and NE levels in the prefrontal cortex. Pharmacokinetic analysis of SK609 under systemic administration demonstrated 98% oral bioavailability and high brain distribution in striatum, hippocampus and prefrontal cortex. To evaluate the effects of SK609 on cognitive deficits of potential relevance to PD-MCI, we used unilateral 6-hydroxydopamine (6-OHDA) lesioned rats and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated cynomolgus macaques, with deficits in performance in a sustained attention and an object retrieval task, respectively. SK609 dose dependently improved the performance of 6-OHDA-lesioned rats, with peak performance achieved using a 4 mg/kg dose. This improvement was predominantly due to a significant reduction in the number of misses and false alarm errors, contributing to an increase in sustained attention. In MPTP-lesioned monkeys, this same dose also improved performance in an object retrieval task, significantly reducing cognitive errors (barrier reaches) and motor errors (fine motor dexterity problems). These data demonstrate that SK609 with its unique pharmacological effects on modulating both DA and NE can ameliorate cognitive impairment in PD models and may provide a therapeutic option to treat both motor and cognitive impairment in PD patients.

Protective Effects of Pituitary Adenylate Cyclase-Activating Polypeptide and Vasoactive Intestinal Peptide Against Cognitive Decline in Neurodegenerative Diseases

Cognitive impairment is one of the major symptoms in most neurodegenerative disorders such as Alzheimer’s (AD), Parkinson (PD), and Huntington diseases (HD), affecting millions of people worldwide. Unfortunately, there is no treatment to cure or prevent the progression of those diseases. Cognitive impairment has been related to neuronal cell death and/or synaptic plasticity alteration in important brain regions, such as the cerebral cortex, substantia nigra, striatum, and hippocampus. Therefore, compounds that can act to protect the neuronal loss and/or to reestablish the synaptic activity are needed to prevent cognitive decline in neurodegenerative diseases. Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are two highly related multifunctional neuropeptides widely distributed in the central nervous system (CNS). PACAP and VIP exert their action through two common receptors, VPAC1 and VPAC2, while PACAP has an additional specific receptor, PAC1. In this review article, we first presented evidence showing the therapeutic potential of PACAP and VIP to fight the cognitive decline observed in models of AD, PD, and HD. We also reviewed the main transduction pathways activated by PACAP and VIP receptors to reduce cognitive dysfunction. Furthermore, we identified the therapeutic targets of PACAP and VIP, and finally, we evaluated different novel synthetic PACAP and VIP analogs as promising pharmacological tools.

The longitudinal associations between cognition, mood and striatal dopaminergic binding in Parkinson's Disease

Cognitive decline and mood symptoms are common in Parkinson's disease (PD). Reductions in striatal dopaminergic binding have been associated with worse cognition and mood. We investigated whether this association persists throughout the disease progression in newly diagnosed PD. Four-year data from Parkinson's Progression Markers Initiative (PPMI) were used. Groups consisted of left and right limb dominantly affected PD patients, and controls. Longitudinal relationships between cognition, mood and striatal binding ratios were assessed by repeated measures correlations. Reduced binding was associated with general cognitive decline in controls, reduced processing speed and increased mood symptoms in PD. Anxiety was associated with striatum only in left limb dominantly affected PD. Dominantly affected limb side did not impact striatum and cognition association. There are longitudinal associations between striatum, processing speed and anxiety. Dopamine transporter availability imaging may have some prognostic value for cognition and mood in PD.

Functional correlates of cognitive slowing in Parkinson's disease

Although attentional impairments (particularly cognitive slowing) are frequent in Parkinson's disease (PD), the mechanisms underlying these phenomena have not been fully characterized. The MRI-compatible version of the Symbol Digit Modalities Test (SDMT) has been applied to healthy individuals but not previously to patients with PD. We sought to assess functional changes in brain activation patterns associated with cognitive slowing in PD. Eighteen patients with PD and 11 matched healthy controls (HCs) were enrolled. High-resolution three-dimensional T1-weighted images and blood-oxygen-level-dependent images were acquired during the SDMT. SDMT-related brain networks for the HC and PD groups were extracted from one-sample T-test maps. In each hemisphere, correlated regions were identified by selecting 120 voxels around the peak of each significant cluster (p_uncorrected<0.001). Regions of interest were then analyzed. When performing the SDMT, both groups displayed activation in the frontal, parietal and occipital regions known to be involved in attention. In the PD group, activation was lower in several parts of the cerebellum, left and right occipital cortices, and right supramarginal gyrus. In eight of these regions, fMRI activation was positively correlated with performance in the SDMT task. Our results suggest that the right supramarginal gyrus (an important interface for information integration), the cerebellum, and the left and right occipital cortices are involved in cognitive slowing in PD. A lower level of brain activation was associated with greater cognitive impairment.

A Common Function of Basal Ganglia-Cortical Circuits Subserving Speed in Both Motor and Cognitive Domains

Distinct regions of the frontal cortex connect with their basal ganglia and thalamic counterparts, constituting largely segregated basal ganglia-thalamo-cortical (BTC) circuits. However, any common role of the BTC circuits in different behavioral domains remains unclear. Indeed, whether dysfunctional motor and cognitive BTC circuits are responsible for motor slowing and cognitive slowing, respectively, in Parkinson’s disease (PD) is a matter of debate. Here, we used an effortful behavioral paradigm in which the effects of task rate on accuracy were tested in movement, imagery, and calculation tasks in humans. Using nonlinear fitting, we separated baseline accuracy (A_base) and “agility” (ability to function quickly) components of performance in healthy participants and then confirmed reduced agility and preserved A_base for the three tasks in PD. Using functional magnetic resonance imaging (fMRI) and diffusion tractography, we explored the neural substrates underlying speeded performance of the three tasks in healthy participants, suggesting the involvement of distinct BTC circuits in cognitive and motor agility. Language and motor BTC circuits were specifically active during speeded performance of the calculation and movement tasks, respectively, whereas premotor BTC circuits revealed activity for speeded performance of all tasks. Finally, PD showed reduced task rate-correlated activity in the language BTC circuits for speeded calculation, in the premotor BTC circuit for speeded imagery, and in the motor BTC circuits for speeded movement, as compared with controls. The present study casts light on the anatomo-functional organization of the BTC circuits and their parallel roles in invigorating movement and cognition through a function of dopamine.

Long reaction times are associated with delayed brain activity in lewy body dementia

A significant symptom of Lewy body dementia (LBD) is slow cognitive processing or bradyphrenia. In a previous fMRI task‐based study, we found slower responses in LBD, accompanied by greater deactivation in the default mode network. In this study, we investigated the timing and magnitude of the activations and deactivations with respect to reaction time to determine whether the slower responses in LBD were associated with delayed neuronal activity. Using fMRI, we examined the magnitude and latency of activations and deactivations during an event‐related attention task in 32 patients with LBD and 23 healthy controls using predefined regions of interest. Default mode network deactivations did not significantly differ in their timing between groups or task conditions, while the task‐related activations in the parietal, occipital, frontal, and motor cortex were all significantly later in the LBD group. Repeating the analysis with reaction time as a parametric modulator of activation magnitude produced similar findings, with the reaction time modulator being significant in a number of regions including the default mode network, suggesting that the increased deactivation in LBD is partly explained by slower task completion. Our data suggest that the default mode network deactivation is initiated at the start of the task, and remains deactivated until its end, with the increased magnitude of deactivation in LBD reflecting the more prolonged cognitive processing in these patients. These data add substantially to our understanding of the neural origins of bradyphrenia, which will be essential for determining optimum therapeutic strategies for cognitive impairment in LBD. Hum Brain Mapp 39:633–643, 2018. © 2017 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Loss of phosphodiesterase 4 in Parkinson disease

Objective:

To assess in vivo the expression of phosphodiesterase 4 (PDE4) and its relevance to cognitive symptoms in patients with Parkinson disease (PD) using [11C]rolipram PET.

Methods:

We studied 12 levodopa-treated patients with PD with no concurrent diagnosis of mild cognitive impairment or dementia. Their data were compared with those from 12 healthy controls. All participants underwent neuropsychiatric and cognitive assessment using the Cambridge Neuropsychological Test Automated Battery. Parametric images of [11C]rolipram volume of distribution (VT) values were determined with the Logan plot.

Results:

Patients with PD performed worse than healthy controls in cognitive examinations assessing psychomotor speed, episodic memory, and spatial working memory and executive function. Patients with PD showed reductions in [11C]rolipram VT compared to healthy controls, in the caudate (28%), thalamus (23%), hypothalamus (32%), and cortex (16%). Within thalamic subregions, [11C]rolipram VT values in patients with PD were decreased by 12%–32%, with most marked decreases observed in prefrontal and temporal thalamic nuclei, whereas motor nuclei were less affected. Within the cortex, [11C]rolipram VT values in patients with PD were decreased by 11%–20%, with most marked decreases observed in posterior dorsolateral frontal cortex, medial frontal cortex, and supplementary motor area, whereas orbitofrontal cortex was less affected. Worse performance in spatial working memory correlated with lower [11C]rolipram VT values in posterior dorsolateral frontal cortex, medial frontal cortex, supplementary motor area, precentral gyrus, caudate, and prefrontal thalamic nuclei.

Conclusions:

Our findings demonstrate loss of PDE4 expression in the striato-thalamo-cortical circuit, which is associated with deficits of spatial working memory in patients with PD.

Depression Reduces Accuracy While Parkinsonism Slows Response Time for Processing Positive Feedback in Patients with Parkinson's Disease with Comorbid Major Depressive Disorder Tested on a Probabilistic Category-Learning Task

Major depressive disorder (MDD) is the most common non-motor manifestation of Parkinson's disease (PD) affecting 50% of patients. However, little is known about the cognitive correlates of MDD in PD. Using a computer-based cognitive task that dissociates learning from positive and negative feedback, we tested four groups of subjects: (1) patients with PD with comorbid MDD, (2) patients with PD without comorbid MDD, (3) matched patients with MDD alone (without PD), and (4) matched healthy control subjects. Furthermore, we used a mathematical model of decision-making to fit both choice and response time data, allowing us to detect and characterize differences between the groups that are not revealed by cognitive results. The groups did not differ in learning accuracy from negative feedback, but the MDD groups (PD patients with MDD and patients with MDD alone) exhibited a selective impairment in learning accuracy from positive feedback when compared to the non-MDD groups (PD patients without MDD and healthy subjects). However, response time in positive feedback trials in the PD groups (both with and without MDD) was significantly slower than the non-PD groups (MDD and healthy groups). While faster response time usually correlates with poor learning accuracy, it was paradoxical in PD groups, with PD patients with MDD having impaired learning accuracy and PD patients without MDD having intact learning accuracy. Mathematical modeling showed that both MDD groups (PD with MDD and MDD alone) were significantly slower than non-MDD groups in the rate of accumulation of information for stimuli trained by positive feedback, which can lead to lower response accuracy. Conversely, modeling revealed that both PD groups (PD with MDD and PD alone) required more evidence than other groups to make responses, thus leading to slower response times. These results suggest that PD patients with MDD exhibit cognitive profiles with mixed traits characteristic of both MDD and PD, furthering our understanding of both PD and MDD and their often-complex comorbidity. To the best of our knowledge, this is the first study to examine feedback-based learning in PD with MDD while controlling for the effects of PD and MDD.

Decreased synaptic plasticity in the medial prefrontal cortex underlies short-term memory deficits in 6-OHDA-lesioned rats

Parkinson's disease (PD) is characterized by motor dysfunction associated with dopaminergic degeneration in the dorsolateral striatum (DLS). However, motor symptoms in PD are often preceded by short-term memory deficits, which have been argued to involve deregulation of medial prefrontal cortex (mPFC). We now used a 6-hydroxydopamine (6-OHDA) rat PD model to explore if alterations of synaptic plasticity in DLS and mPFC underlie short-term memory impairments in PD prodrome. The bilateral injection of 6-OHDA (20μg/hemisphere) in the DLS caused a marked loss of dopaminergic neurons in the substantia nigra (>80%) and decreased monoamine levels in the striatum and PFC, accompanied by motor deficits evaluated after 21 days in the open field and accelerated rotarod. A lower dose of 6-OHDA (10μg/hemisphere) only induced a partial degeneration (about 60%) of dopaminergic neurons in the substantia nigra with no gross motor impairments, thus mimicking an early premotor stage of PD. Notably, 6-OHDA (10μg)-lesioned rats displayed decreased monoamine levels in the PFC as well as short-term memory deficits evaluated in the novel object discrimination and in the modified Y-maze tasks; this was accompanied by a selective decrease in the amplitude of long-term potentiation in the mPFC, but not in DLS, without changes of synaptic transmission in either brain regions. These results indicate that the short-term memory dysfunction predating the motor alterations in the 6-OHDA model of PD is associated with selective changes of information processing in PFC circuits, typified by persistent changes of synaptic plasticity.

Functions of the cortico-basal ganglia circuits for spoken language may extend beyond emotional-affective modulation in adults

We support Ackermann et al.'s proposal that the cortico-basal ganglia circuits may play essential roles in the evolution of spoken language. Here we discuss further evidence indicating that the cortico-basal ganglia circuits may contribute to various aspects of spoken language including planning, learning, and controlling of speech in adulthood.

mGlu(2) receptor-mediated modulation of conditioned avoidance behavior in rats

Inhibition of conditioned avoidance behavior in rats is generally considered predictive for antipsychotic activity in man. The present study investigated the mGlu2-mediated modulation of conditioned avoidance and compared mGlu2 agonists with available antipsychotics for their relative effects on conditioned avoidance behavior and locomotion. The mGlu2/3 orthosteric agonist 4-amino-2-thiabicyclo[3.1.0]hexane-4,6-dicarboxylic acid 2,2-dioxide (LY-404039) and mGlu2 positive allosteric modulator (PAM) 3-(cyclopropylmethyl)-7-(4-phenylpiperidin-1-yl)-8-(trifluoromethyl)[1,2,4]triazolo[4,3-a]pyridine (JNJ-42153605) inhibited avoidance and blocked escape behavior. The mGlu2/3 negative allosteric modulators (NAMs) 7-(dimethylamino)-4-(3-pyridin-3-ylphenyl)-8-(trifluoromethyl)-1,3-dihydro-2 H-1,5-benzodiazepin-2-one (JNJ-42112265) and 4-[3-(2,6-dimethylpyridin-4-yl)phenyl]-7-methyl-8-(trifluoromethyl)-1,3-dihydro-2H-1,5-benzodiazepin-2-one (RO-4491533) reversed the LY-404039-induced impairment of avoidance and escape. JNJ-42112265 also reversed the impairment of avoidance and escape induced by the mGlu2-specific PAM JNJ-42153605, suggesting that the effects on conditioned avoidance are specifically mGlu2-mediated. The mGlu2/3 antagonist (2-(2-carboxycyclopropyl)-3-(9H-xanthen-9-yl)-d-alanine (LY-341495; s.c.) reversed the LY-404039-induced escape impairment but failed to restore avoidance, suggesting interfering side effects. Like the tested antipsychotics, mGlu2/3 orthosteric and allosteric agonists inhibited avoidance behavior and locomotion at similar doses. Hence no clear-cut differences between mGlu2 modulators and currently available antipsychotics in the way they interfere with avoidance behavior in relation to inhibition of locomotion could be established.

Management of upper extremity dysfunction in people with Parkinson disease and Huntington disease: facilitating outcomes across the disease lifespan

Parkinson Disease (PD) and Huntington Disease (HD) are degenerative neurological diseases, which can result in impairments and activity limitations affecting the upper extremities from early in the disease process. The progressive nature of these diseases poses unique challenges for therapists aiming to effectively maximize physical functioning and minimize participation restrictions in these patient groups. Research is underway in both diseases to develop effective disease-modifying agents and pharmacological interventions, as well as mobility-focused rehabilitation protocols. Rehabilitation, and in particular task-specific interventions, has the potential to influence the upper extremity functional abilities of patients with these degenerative conditions. However to date, investigations of interventions specifically addressing upper extremity function have been limited in both PD, and in particular HD. In this paper, we provide an update of the known pathological features of PD and HD as they relate to upper extremity function. We further review the available literature on the use of outcome measures, and the clinical management of upper extremity function in both conditions. Due to the currently limited evidence base in both diseases, we recommend utilization of a clinical management framework specific for degenerative conditions that can serve as a guideline for disease management.

Progressive resistance exercise and Parkinson’s disease: a review of potential mechanisms. Parkinsons Dis. 2012;2012:124527. [PMID: 22191068 PMCID: PMC3236435 DOI: 10.1155/2012/124527]

This paper reviews the therapeutically beneficial effects of progressive resistance exercise (PRE) on Parkinson's disease (PD). First, this paper discusses the rationale for PRE in PD. Within the first section, the review discusses the central mechanisms that underlie bradykinesia and muscle weakness, highlights findings related to the central changes that accompany PRE in healthy individuals, and extends these findings to individuals with PD. It then illustrates the hypothesized positive effects of PRE on nigro-striatal-thalamo-cortical activation and connectivity. Second, it reviews recent findings of the use of PRE in individuals with PD. Finally, knowledge gaps of using PRE on individuals with PD are discussed along with suggestions for future research.

Gender differences in Parkinson's disease: clinical characteristics and cognition

More men than women are diagnosed with Parkinson's disease (PD), and a number of gender differences have been documented in this disorder. Examples of clinical characteristics that appear in men more often than women include rigidity and rapid eye movement behavior disorder, whereas more women than men exhibit dyskinesias and depression. Differences between men and women in cognition have not been extensively examined, though there are reports of deficits in men in aspects of cognition that contribute to activities of daily living, in verbal fluency, and in the recognition of facial emotion, and deficits in women in visuospatial cognition. Side of disease onset may interact with gender to affect cognitive abilities. One possible source of male-female differences in the clinical and cognitive characteristics of PD is the effect of estrogen on dopaminergic neurons and pathways in the brain. This effect is not yet understood, as insight into how the fluctuation of estrogen over the lifetime affects the brain is currently limited. Further attention to this area of research will be important for accurate assessment and better management of PD. Attention should also be directed to multiple covariates that may affect clinical characteristics and cognition. Knowledge about differences in the presentation of PD symptoms in men and women and about the pathophysiology underlying those differences may enhance the accuracy and effectiveness of clinical assessment and treatment of the disease.

Rostral premotor cortex as a gateway between motor and cognitive networks

This article presents a hypothesis that the rostral premotor-subcortical networks may serve as a gateway between the cognitive and motor networks. Accumulating evidence has propelled an idea that motor and cognitive behaviors considerably share neural substrates and probably computational principles regardless of the species. Here I conducted a meta-analysis of previous neuroimaging studies on motor planning and different cognitive tasks (mental calculation, visuospatial processing and cognitive control), which showed overlap of all activations in the rostral premotor cortex, with a possible rostro-caudal functional gradient. It was also suggested that the rostral premotor areas might form circuits with specific portions of the cerebellum and the basal ganglia. The rostral premotor areas may provide context-dependent connectivity and mediate information flow between the cognitive and motor networks, thereby making the two networks operating interactively or independently.

The dopamine and cAMP regulated phosphoprotein, 32 kDa (DARPP-32) signaling pathway: a novel therapeutic target in traumatic brain injury

Traumatic brain injury (TBI) causes persistent neurologic deficits. Current therapies, predominantly focused upon cortical and hippocampal cellular survival, have limited benefit on cognitive outcomes. Striatal damage is associated with deficits in executive function, learning, and memory. Dopamine and cAMP regulated phosphoprotein 32 (DARPP-32) is expressed within striatal medium spiny neurons and regulates striatal function. We found that controlled cortical impact injury in rats produces a chronic decrease in DARPP-32 phosphorylation at threonine-34 and an increase in protein phosphatase-1 activity. There is no effect of injury on threonine-75 phosphorylation or on DARPP-32 protein. Amantadine, shown to be efficacious in treating post-TBI cognitive deficits, given daily for two weeks is able to restore the loss of DARPP-32 phosphorylation and reduce protein phosphatase-1 activity. Amantadine also decreases the phosphorylation of threonine-75 consistent with activity as a partial N-methyl-D-aspartate (NMDA) receptor antagonist and partial dopamine agonist. These data demonstrate that targeting the DARPP-32 signaling cascade represents a promising novel therapeutic approach in the treatment of persistent deficits following a TBI.

Pathologic correlates of dementia in individuals with Lewy body disease

Cognitive impairment and dementia are more common in patients with Parkinson disease (PD) than age-matched controls and appear to become more frequent as PD progresses. However, estimates of dementia in patients with PD have varied widely, likely due in part to differences in case definition, case ascertainment and methodology. First, we review investigations of usual pathologic correlates of dementia in patients with brainstem (b) Lewy Body Disease (LBD) and report our findings from the initial 266 brain autopsies from a population-based study of brain aging and incident dementia. Our results showed that 2.6% of subjects were diagnosed with PD during life but that 20% had bLBD at autopsy. Seventy percent of individuals with bLBD had high level of one or more cerebral pathologic changes significantly associated with dementia: Alzheimer's disease (AD), cerebral (c) LBD or microvascular brain injury (microVBI); these were commonly co-morbid. Next we consider proposed contributors to cognitive impairment and dementia in the approximately 30% of patients with only bLBD, including regionally selective dendritic degeneration of neostriatal medium spiny neurons. Diseases contributing to cognitive impairment and dementia in patients with bLBD are heterogeneous, providing diagnostic challenges as well as multiple opportunities for successful intervention in patients with PD.

From the cell to the clinic: a comparative review of the partial D₂/D₃receptor agonist and α2-adrenoceptor antagonist, piribedil, in the treatment of Parkinson's disease

Though L-3,4-dihydroxyphenylalanine (L-DOPA) is universally employed for alleviation of motor dysfunction in Parkinson's disease (PD), it is poorly-effective against co-morbid symptoms like cognitive impairment and depression. Further, it elicits dyskinesia, its pharmacokinetics are highly variable, and efficacy wanes upon long-term administration. Accordingly, "dopaminergic agonists" are increasingly employed both as adjuncts to L-DOPA and as monotherapy. While all recognize dopamine D(2) receptors, they display contrasting patterns of interaction with other classes of monoaminergic receptor. For example, pramipexole and ropinirole are high efficacy agonists at D(2) and D(3) receptors, while pergolide recognizes D(1), D(2) and D(3) receptors and a broad suite of serotonergic receptors. Interestingly, several antiparkinson drugs display modest efficacy at D(2) receptors. Of these, piribedil displays the unique cellular signature of: 1), signal-specific partial agonist actions at dopamine D(2)and D(3) receptors; 2), antagonist properties at α(2)-adrenoceptors and 3), minimal interaction with serotonergic receptors. Dopamine-deprived striatal D(2) receptors are supersensitive in PD, so partial agonism is sufficient for relief of motor dysfunction while limiting undesirable effects due to "over-dosage" of "normosensitive" D(2) receptors elsewhere. Further, α(2)-adrenoceptor antagonism reinforces adrenergic, dopaminergic and cholinergic transmission to favourably influence motor function, cognition, mood and the integrity of dopaminergic neurones. In reviewing the above issues, the present paper focuses on the distinctive cellular, preclinical and therapeutic profile of piribedil, comparisons to pramipexole, ropinirole and pergolide, and the core triad of symptoms that characterises PD-motor dysfunction, depressed mood and cognitive impairment. The article concludes by highlighting perspectives for clarifying the mechanisms of action of piribedil and other antiparkinson agents, and for optimizing their clinical exploitation.

Visual exploration of emotional facial expressions in Parkinson's disease

Parkinson's disease (PD) is associated with impairments in facial emotion recognition as well as visual and executive dysfunction. We investigated whether facial emotion categorization impairments in PD are attributable to visual scanning abnormalities by recording the eye movements of 16 non-demented PD and 20 healthy control (HC) participants during an emotion recognition task. We examined the influence of several factors that can affect visual scanning, including oculomotor, basic visual, and cognitive abilities (executive function). Increases in the number and duration of fixations in the top regions of surprise facial expressions were related to increases in recognition accuracy for this emotion in PD participants with left-sided motor-symptom onset. Compared to HC men, HC women spent less time fixating on fearful expressions. PD participants displayed oculomotor abnormalities (antisaccades), but these were unrelated to scanning patterns. Performance on visual measures (acuity, contrast sensitivity) correlated with scanning patterns in the PD group only. Poorer executive function was associated with longer fixation times in PD and with a greater number of fixations in HC. Our findings indicate a specific relation between facial emotion categorization impairments and scanning of facial expressions in PD. Furthermore, PD and HC participants' scanning behaviors during an emotion categorization task were driven by different perceptual processes and cognitive strategies. Our results underscore the need to consider differences in perceptual and cognitive abilities in studies of visual scanning, particularly when examining this ability in patient populations for which both vision and cognition are impaired.

Speed of processing in older adults: a cognitive overview for nursing

With advancing age, subtle declines in various cognitive abilities occur. One ability that is particularly important as people age is speed of processing. Speed of processing is suggested to impact other cognitive abilities; in fact, some studies suggest that other cognitive abilities depend on speed of processing as a foundational cognitive resource. Studies also indicate that declines in speed of processing influence everyday functioning and driving behavior. Fortunately, cognitive remediation therapy designed to improve speed of processing has been shown to accentuate speed of processing and everyday functioning in older adults. Nurses are in a unique position to listen to patient's cognitive complaints and can offer suggestions and referrals to help older adults maintain this cognitive ability. Implications for nursing research are posited.

Cognitive deficits and striato-frontal dopamine release in Parkinson's disease

Idiopathic Parkinson's disease (PD) is often accompanied by a pattern of executive deficits similar to those found in patients with frontal lobe lesions. We investigated whether such cognitive deficits are attributable to frontal lobe dysfunction as a direct consequence of impaired mesocortical dopaminergic transmission or an indirect consequence of impaired nigrostriatal dopaminergic function. For this purpose, changes in synaptic dopamine levels during task performance were monitored using a marker of dopamine D2-receptor availability (11)C-raclopride (RAC) PET. During RAC PET, seven patients with early symptomatic PD and seven age-matched healthy controls performed two types of behavioural task, a spatial working memory task (SWT) and a visuomotor control task (VMT). The SWT involves an executive process which is known to be impaired by both frontal lobe lesions and PD while the VMT is a control test for the visuomotor component of the SWT. Parametric images of RAC binding potential during performance of each task were generated, and compared between the tasks using voxel-based statistical parametric mapping as well as region of interest analysis. In controls, RAC binding was reduced in the dorsal caudate during performance of the SWT compared with the VMT, compatible with increased levels of endogenous dopamine release due to the executive process. In PD patients, this RAC binding reduction was not observed. In contrast, RAC binding in the anterior cingulate cortex within the medial prefrontal cortex was reduced by a comparable level during the SWT both in controls and PD patients. Statistical comparisons between controls and PD patients confirmed significantly attenuated dopamine release in the dorsal caudate in PD, but preserved levels of medial prefrontal dopamine release. Our data suggest that executive deficits in early patients with PD are associated with impaired nigrostriatal dopaminergic function resulting in abnormal processing in the cortico-basal ganglia circuit. In contrast, mesocortical dopaminergic transmission appears well preserved in early PD patients.