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Dengler J, Deck BL, Stoll H, Fernandez-Nunez G, Kelkar AS, Rich RR, Erickson BA, Erani F, Faseyitan O, Hamilton RH, Medaglia JD. Enhancing cognitive control with transcranial magnetic stimulation in subject-specific frontoparietal networks. Cortex 2024; 172:141-158. [PMID: 38330778 DOI: 10.1016/j.cortex.2023.11.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 10/26/2023] [Accepted: 11/28/2023] [Indexed: 02/10/2024]
Abstract
BACKGROUND Cognitive control processes, including those involving frontoparietal networks, are highly variable between individuals, posing challenges to basic and clinical sciences. While distinct frontoparietal networks have been associated with specific cognitive control functions such as switching, inhibition, and working memory updating functions, there have been few basic tests of the role of these networks at the individual level. METHODS To examine the role of cognitive control at the individual level, we conducted a within-subject excitatory transcranial magnetic stimulation (TMS) study in 19 healthy individuals that targeted intrinsic ("resting") frontoparietal networks. Person-specific intrinsic networks were identified with resting state functional magnetic resonance imaging scans to determine TMS targets. The participants performed three cognitive control tasks: an adapted Navon figure-ground task (requiring set switching), n-back (working memory), and Stroop color-word (inhibition). OBJECTIVE Hypothesis: We predicted that stimulating a network associated with externally oriented control [the "FPCN-B" (fronto-parietal control network)] would improve performance on the set switching and working memory task relative to a network associated with attention (the Dorsal Attention Network, DAN) and cranial vertex in a full within-subjects crossover design. RESULTS We found that set switching performance was enhanced by FPCN-B stimulation along with some evidence of enhancement in the higher-demand n-back conditions. CONCLUSION Higher task demands or proactive control might be a distinguishing role of the FPCN-B, and personalized intrinsic network targeting is feasible in TMS designs.
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Affiliation(s)
- Julia Dengler
- School of Biomedical Engineering Science and Health Systems, Drexel University, Philadelphia, PA, USA
| | - Benjamin L Deck
- Department of Psychological & Brain Sciences, Drexel University, Philadelphia, PA, USA
| | - Harrison Stoll
- Department of Psychological & Brain Sciences, Drexel University, Philadelphia, PA, USA
| | | | - Apoorva S Kelkar
- Department of Psychological & Brain Sciences, Drexel University, Philadelphia, PA, USA
| | - Ryan R Rich
- Department of Psychological & Brain Sciences, Drexel University, Philadelphia, PA, USA
| | - Brian A Erickson
- Department of Psychological & Brain Sciences, Drexel University, Philadelphia, PA, USA
| | - Fareshte Erani
- Department of Psychological & Brain Sciences, Drexel University, Philadelphia, PA, USA
| | | | - Roy H Hamilton
- Department of Neurology, University of Pennsylvania, Philadelphia, PA, USA
| | - John D Medaglia
- Department of Psychological & Brain Sciences, Drexel University, Philadelphia, PA, USA; Department of Neurology, University of Pennsylvania, Philadelphia, PA, USA.
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Deck BL, Kelkar A, Erickson B, Erani F, McConathey E, Sacchetti D, Faseyitan O, Hamilton R, Medaglia JD. Individual-level functional connectivity predicts cognitive control efficiency. Neuroimage 2023; 283:120386. [PMID: 37820860 DOI: 10.1016/j.neuroimage.2023.120386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 08/30/2023] [Accepted: 09/21/2023] [Indexed: 10/13/2023] Open
Abstract
Cognitive control (CC) is essential for problem-solving in everyday life, and CC-related deficits occur alongside costly and debilitating disorders. The tri-partite model suggests that CC comprises multiple behaviors, including switching, inhibiting, and updating. Activity within the fronto-parietal control network B (FPCN-B), the dorsal attention network (DAN), the cingulo-opercular network (CON), and the lateral default-mode network (L-DMN) is related to switching and inhibiting behaviors. However, our understanding of how these brain regions interact to bring about cognitive switching and inhibiting in individuals is unclear. In the current study, subjects performed two in-scanner tasks that required switching and inhibiting. We used support vector regression (SVR) models containing individually-estimated functional connectivity between the FPCN-B, DAN, CON and L-DMN to predict switching and inhibiting behaviors. We observed that: inter-network connectivity can predict inhibiting and switching behaviors in individuals, and the L-DMN plays a role in switching and inhibiting behaviors. Therefore, individually estimated inter-network connections are markers of CC behaviors, and CC behaviors may arise due to interactions between a set of networks.
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Affiliation(s)
- Benjamin L Deck
- Department of Psychological and Brain Sciences, Drexel University, 3201 Chestnut Street, Philadelphia, 19104, PA, USA
| | - Apoorva Kelkar
- Department of Psychological and Brain Sciences, Drexel University, 3201 Chestnut Street, Philadelphia, 19104, PA, USA
| | - Brian Erickson
- Department of Psychological and Brain Sciences, Drexel University, 3201 Chestnut Street, Philadelphia, 19104, PA, USA
| | - Fareshte Erani
- Department of Psychological and Brain Sciences, Drexel University, 3201 Chestnut Street, Philadelphia, 19104, PA, USA
| | - Eric McConathey
- Department of Neurology, The University of Pennsylvania: Perelman School of Medicine, 3400 Civic Center Blvd, Philadelphia, 19104, PA, USA
| | - Daniela Sacchetti
- Department of Neurology, The University of Pennsylvania: Perelman School of Medicine, 3400 Civic Center Blvd, Philadelphia, 19104, PA, USA
| | - Olufunsho Faseyitan
- Department of Neurology, The University of Pennsylvania: Perelman School of Medicine, 3400 Civic Center Blvd, Philadelphia, 19104, PA, USA
| | - Roy Hamilton
- Department of Neurology, The University of Pennsylvania: Perelman School of Medicine, 3400 Civic Center Blvd, Philadelphia, 19104, PA, USA
| | - John D Medaglia
- Department of Psychological and Brain Sciences, Drexel University, 3201 Chestnut Street, Philadelphia, 19104, PA, USA; Department of Neurology, The University of Pennsylvania: Perelman School of Medicine, 3400 Civic Center Blvd, Philadelphia, 19104, PA, USA.
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Erani F, Patel D, Deck BL, Hamilton RH, Schultheis MT, Medaglia JD. Investigating the influence of an effort-reward interaction on cognitive fatigue in individuals with multiple sclerosis. J Neuropsychol 2022. [PMID: 36208463 PMCID: PMC10082133 DOI: 10.1111/jnp.12295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 08/24/2022] [Accepted: 09/10/2022] [Indexed: 11/30/2022]
Abstract
This study examined whether an alteration in the effort-reward relationship, a theoretical framework based on cognitive neuroscience, could explain cognitive fatigue. Forty persons with MS and 40 healthy age- and education-matched cognitively healthy controls (HC) participated in a computerized switching task with orthogonal high- and low-demand (effort) and reward manipulations. We used the Visual Analog Scale of Fatigue (VAS-F) to assess subjective state fatigue before and after each condition during the task. We used mixed-effects models to estimate the association and interaction between effort and reward and their relationship to subjective fatigue and task performance. We found the high-demand condition was associated with increased VAS-F scores (p < .001), longer response times (RT) (p < .001) and lower accuracy (p < .001). The high-reward condition was associated with faster RT (p = .006) and higher accuracy (p = .03). There was no interaction effect between effort and reward on VAS-F scores or performance. Participants with MS reported higher VAS-F scores (p = .02). Across all conditions, participants with MS were slower (p < .001) and slower as a function of condition demand compared with HC (p < .001). This behavioural study did not find evidence that an effort-reward interaction is associated with cognitive fatigue. However, our findings support the role of effort in subjective cognitive fatigue and both effort and reward on task performance. In future studies, more salient reward manipulations could be necessary to identify effort-reward interactions on subjective cognitive fatigue.
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Affiliation(s)
- Fareshte Erani
- Department of Psychological and Brain Sciences, Drexel University, Philadelphia, Pennsylvania, USA
| | - Darshan Patel
- Department of Psychological and Brain Sciences, Drexel University, Philadelphia, Pennsylvania, USA
| | - Benjamin L Deck
- Department of Psychological and Brain Sciences, Drexel University, Philadelphia, Pennsylvania, USA
| | - Roy H Hamilton
- Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Maria T Schultheis
- Department of Psychological and Brain Sciences, Drexel University, Philadelphia, Pennsylvania, USA
| | - John D Medaglia
- Department of Psychological and Brain Sciences, Drexel University, Philadelphia, Pennsylvania, USA.,Department of Neurology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Cember ATJ, Deck BL, Kelkar A, Faseyitan O, Zimmerman JP, Erickson B, Elliott MA, Coslett HB, Hamilton RH, Reddy R, Medaglia JD. Glutamate-Weighted Magnetic Resonance Imaging (GluCEST) Detects Effects of Transcranial Magnetic Stimulation to the Motor Cortex. Neuroimage 2022; 256:119191. [PMID: 35413447 DOI: 10.1016/j.neuroimage.2022.119191] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2021] [Revised: 03/18/2022] [Accepted: 04/05/2022] [Indexed: 11/18/2022] Open
Abstract
Transcranial magnetic stimulation (TMS) is used in several FDA-approved treatments and, increasingly, to treat neurological disorders in off-label uses. However, the mechanism by which TMS causes physiological change is unclear, as are the origins of response variability in the general population. Ideally, objective in vivo biomarkers could shed light on these unknowns and eventually inform personalized interventions. Continuous theta-burst stimulation (cTBS) is a form of TMS observed to reduce motor evoked potentials (MEPs) for 60 min or longer post-stimulation, although the consistency of this effect and its mechanism continue to be under debate. Here, we use glutamate-weighted chemical exchange saturation transfer (gluCEST) magnetic resonance imaging (MRI) at ultra-high magnetic field (7T) to measure changes in glutamate concentration at the site of cTBS. We find that the gluCEST signal in the ipsilateral hemisphere of the brain generally decreases in response to cTBS, whereas consistent changes were not detected in the contralateral region of interest (ROI) or in subjects receiving sham stimulation.
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Affiliation(s)
- Abigail T J Cember
- Center for Advanced Metabolic Imaging in Precision Medicine, Department of Radiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.
| | - Benjamin L Deck
- Department of Psychological and Brain Sciences, Drexel University, Philadelphia, PA, USA
| | - Apoorva Kelkar
- Department of Psychological and Brain Sciences, Drexel University, Philadelphia, PA, USA
| | - Olu Faseyitan
- Department of Neurology, Laboratory for Cognition and Neural Stimulation, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Jared P Zimmerman
- Department of Neurology, Laboratory for Cognition and Neural Stimulation, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Brian Erickson
- Department of Psychological and Brain Sciences, Drexel University, Philadelphia, PA, USA
| | - Mark A Elliott
- Center for Advanced Metabolic Imaging in Precision Medicine, Department of Radiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - H Branch Coslett
- Department of Neurology, Laboratory for Cognition and Neural Stimulation, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Roy H Hamilton
- Department of Neurology, Laboratory for Cognition and Neural Stimulation, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Ravinder Reddy
- Center for Advanced Metabolic Imaging in Precision Medicine, Department of Radiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - John D Medaglia
- Department of Psychological and Brain Sciences, Drexel University, Philadelphia, PA, USA; Department of Neurology, Laboratory for Cognition and Neural Stimulation, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
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Purri R, Brennan L, Rick J, Xie SX, Deck BL, Chahine LM, Dahodwala N, Chen-Plotkin A, Duda JE, Morley JF, Akhtar RS, Trojanowski JQ, Siderowf A, Weintraub D. Subjective Cognitive Complaint in Parkinson's Disease Patients With Normal Cognition: Canary in the Coal Mine? Mov Disord 2020; 35:1618-1625. [PMID: 32520435 DOI: 10.1002/mds.28115] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 04/30/2020] [Accepted: 05/04/2020] [Indexed: 01/15/2023] Open
Abstract
OBJECTIVE The objective of this study was to determine the frequency and impact of subjective cognitive complaint (SCC) in Parkinson's disease (PD) patients with normal cognition. METHODS Patients with PD with expert consensus-determined normal cognition at baseline were asked a single question regarding the presence of SCC. Baseline (N = 153) and longitudinal (up to 4 follow-up visits during a 5-year period; N = 121) between-group differences in patients with PD with (+SCC) and without (-SCC) cognitive complaint were examined, including cognitive test performance and self-rated and informant-rated functional abilities. RESULTS A total of 81 (53%) participants reported a cognitive complaint. There were no between-group differences in global cognition at baseline. Longitudinally, the +SCC group declined more than the -SCC group on global cognition (Mattis Dementia Rating Scale-2 total score, F1,431 = 5.71, P = 0.02), processing speed (Symbol Digit Modalities Test, F1,425 = 7.52, P = 0.006), and executive function (Trail Making Test Part B, F1,419 = 4.48, P = 0.04), although the results were not significant after correction for multiple testing. In addition, the +SCC group was more likely to progress to a diagnosis of cognitive impairment over time (hazard ratio = 2.61, P = 0.02). The +SCC group also demonstrated significantly lower self-reported and knowledgeable informant-reported cognition-related functional abilities at baseline, and declined more on an assessment of global functional abilities longitudinally. CONCLUSIONS Patients with PD with normal cognition, but with SCC, report poorer cognition-specific functional abilities, and are more likely to be diagnosed with cognitive impairment and experience global functional ability decline long term. These findings suggest that SCC and worse cognition-related functional abilities may be sensitive indicators of initial cognitive decline in PD. © 2020 International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Rachael Purri
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
| | - Laura Brennan
- Department of Neurology, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania, USA
| | - Jacqueline Rick
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
| | - Sharon X Xie
- Department of Biostatistics, Epidemiology, & Informatics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
| | - Benjamin L Deck
- Department of Psychology, Drexel University, Philadelphia, Pennsylvania, USA
| | - Lana M Chahine
- Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Nabila Dahodwala
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
| | - Alice Chen-Plotkin
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
| | - John E Duda
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA.,Parkinson's Disease Research, Education, and Clinical Center, Crescenz Veterans Affairs Medical Center, Philadelphia, Pennsylvania, USA
| | - James F Morley
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA.,Parkinson's Disease Research, Education, and Clinical Center, Crescenz Veterans Affairs Medical Center, Philadelphia, Pennsylvania, USA
| | - Rizwan S Akhtar
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
| | - John Q Trojanowski
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
| | - Andrew Siderowf
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
| | - Daniel Weintraub
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA.,Parkinson's Disease Research, Education, and Clinical Center, Crescenz Veterans Affairs Medical Center, Philadelphia, Pennsylvania, USA.,Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
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Deck BL, Xie SX, Choi G, Rick J, Siderowf A, Rudovsky S, Chen-Plotkin A, Duda JE, Morley JF, Dahodwala N, Trojanowski JQ, Weintraub D. Cognitive Functional Abilities in Parkinson's Disease: Agreement Between Patients and Informants. Mov Disord Clin Pract 2019; 6:440-445. [PMID: 31392244 DOI: 10.1002/mdc3.12781] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 04/19/2019] [Accepted: 04/22/2019] [Indexed: 12/20/2022] Open
Abstract
Background The Penn Parkinson's Daily Activities Questionnaire-15 (PDAQ-15) assesses cognition-related instrumental activities of daily living (IADL) in Parkinson's disease (PD). Objectives To assess the degree and predictors of disagreement between patients (PT) and knowledgeable informants (KI) on the PDAQ-15. Methods We recruited 254 PT and KI pairs (PT-KI), determined predictors of agreement, and compared scores to a performance-based functional measure (Direct Assessment of Functional Status [DAFS]; N = 61). Results PT and KI total score (intraclass correlation = 0.57) and individual item (Cohen's kappa = 0.46-0.62) agreement were moderate. Patient depression, global cognition, and caregiver burden (all P < 0.05), predicted PT-KI discrepancy. PT-KI discrepancy was highest in patients with a dementia diagnosis, followed by mild cognitive impairment and then normal cognition (all P < 0.01), with PT rating themselves relatively more functionally intact as cognition worsened. DAFS performance was more highly correlated with KI (r = 0.82; P < 0.001) than PT (r = 0.62; P < 0.001) PDAQ-15 score. Conclusions Our results support using KI as proxies when assessing cognitive IADLs in PD PTs, particularly in cases of more advanced cognitive decline.
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Affiliation(s)
- Benjamin L Deck
- Departments of Neurology, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA.,Department of Psychology Drexel University Philadelphia Pennsylvania USA
| | - Sharon X Xie
- Departments of Biostatistics, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA
| | - Gyujae Choi
- Department of Radiation Oncology Baylor College of Medicine Houston Texas USA
| | - Jacqueline Rick
- Departments of Neurology, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA
| | - Andrew Siderowf
- Departments of Neurology, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA
| | - Samuel Rudovsky
- Departments of Neurology, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA
| | - Alice Chen-Plotkin
- Departments of Neurology, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA
| | - John E Duda
- Departments of Neurology, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA.,Michael J. Crescenz Veterans Affairs Medical Center, Parkinson's Disease Research Education and Clinical Center (PADRECC) Philadelphia Pennsylvania USA
| | - James F Morley
- Departments of Neurology, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA.,Michael J. Crescenz Veterans Affairs Medical Center, Parkinson's Disease Research Education and Clinical Center (PADRECC) Philadelphia Pennsylvania USA
| | - Nabila Dahodwala
- Departments of Neurology, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA
| | - John Q Trojanowski
- Departments of Pathology and Laboratory Medicine, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA
| | - Daniel Weintraub
- Departments of Neurology, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA.,Departments of Psychiatry, Perelman School of Medicine University of Pennsylvania Philadelphia Pennsylvania USA.,Michael J. Crescenz Veterans Affairs Medical Center, Parkinson's Disease Research Education and Clinical Center (PADRECC) Philadelphia Pennsylvania USA
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Deck BL, Rick J, Xie SX, Chen-Plotkin A, Duda JE, Morley JF, Chahine LM, Dahodwala N, Trojanowski JQ, Weintraub D. Statins and Cognition in Parkinson's Disease. J Parkinsons Dis 2018; 7:661-667. [PMID: 28922167 DOI: 10.3233/jpd-171113] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
BACKGROUND The relationship between statins and cognition in Parkinson's disease (PD) is poorly understood. OBJECTIVES Analyses were performed to determine associations between statin use and cross-sectional and longitudinal cognitive performance in PD. METHODS Neuropsychological tests, medication logs, and ratings of functional abilities were collected from 313 PD participants longitudinally. RESULTS At baseline, statin users (SU; N = 129) were older, more likely male, and had shorter PD duration than non-statin users (NSU; N = 184). In Cross-sectional analysis, SU performed better on global cognition, Trails B, semantic fluency, and phonemic fluency tasks. Rate of long-term global cognitive (Dementia Rating Scale-2 and MoCA) decline was significantly less in SU.
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Affiliation(s)
- Benjamin L Deck
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Jacqueline Rick
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Sharon X Xie
- Department of Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Alice Chen-Plotkin
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - John E Duda
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.,Parkinson's Disease Research, Education and Clinical Center (PADRECC), Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA, USA
| | - James F Morley
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.,Parkinson's Disease Research, Education and Clinical Center (PADRECC), Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA, USA
| | - Lana M Chahine
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Nabila Dahodwala
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - John Q Trojanowski
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Daniel Weintraub
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.,Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.,Parkinson's Disease Research, Education and Clinical Center (PADRECC), Michael J. Crescenz Veterans Affairs Medical Center, Philadelphia, PA, USA
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Abstract
Several radioisotopes of the naturally occurring uranium and thorium decay series, in addition to fallout plutonium, have unusually high concentrations in the water column of Mono Lake, a natural alkaline, saline lake. Complexing by carbonate ions appears to be responsible for the enhanced solubility of actinide elements with oxidation states of IV to VI. In contrast, fallout strontium-90 has been largely removed from the water, probably as a result of coprecipitation with calcium carbonate. The daughter/parent activity ratios of thorium, radium, and uranium isotopes suggest that thorium is removed from the water column to the sediments on time scales substantially longer than a month and that the desorption of thorium from the sediments to the water column requires less than a few years.
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Abstract
Salt used for deicing the streets near Rochester, New York, has increased the chloride concentration in Irondequoit Bay at least fivefold during the past two decades. During the winter of 1969-70 the quantity and salinity of the dense runoff that accumulated on the bottom of the bay was sufficient to prevent complete vertical mixing of the bay during the spring. Comparison with 1939 conditions indicates that the period of summer stratification has been prolonged a month by the density gradient imposed by the salt runoff.
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