Diffusion kurtosis imaging in the basal ganglia, as compared with conventional diffusion-tensor imaging, can improve the diagnosis of PD.
IMPORTANCE Currently, diagnosis of Parkinson disease is mainly based on clinical criteria characterized by motor symptoms including bradykinesia, rigidity, resting tremor, and postural instability. Reliable in vivo biomarkers to monitor disease severity and reflect the underlying dopaminergic degeneration are important for future disease-modifying therapy in Parkinson disease. OBJECTIVES To use [ 18 F]9-fluoropropyl-(+)-dihydrotetrabenazine (18 F-DTBZ; [ 18 F]AV-133) positron emission tomography (PET) to explore the characteristics of vesicular monoamine transporter type 2 imaging in patients with Parkinson disease (PD) with different severity levels as well as to investigate its capability in monitoring clinical severity. DESIGN, SETTING, AND PARTICIPANTS Regional uptakes for 18 F-DTBZ PET of different disease stages were measured. Seventeen healthy control participants and 53 patients in 3 groups of mild, moderate, and advanced stages of PD were recruited for 18 F-DTBZ PET scans from the Movement Disorders Clinic in the Chang Gung Memorial Hospital, Taiwan. MAIN OUTCOMES AND MEASURES The severity of disease in patients with PD was quantified by modified Hoehn-Yahr Scale, Unified Parkinson Disease Rating Scale total scores and subscores of posture instability and gait disturbance, tremor, akinesia, and rigidity while not taking medication. Both voxelwise-and volume of interest-based image analyses were performed. The specific uptake ratio (SUR) of each volume of interest and voxel was calculated as (target uptake − reference uptake) / reference uptake using the occipital reference region from magnetic resonance imaging-based spatially normalized 18 F-DTBZ images for each participant. Average SUR images were displayed as 2-dimensional and 3-dimensional to illustrate the image patterns in each group. The nonparametric Kruskal-Wallis test on regional SUR was used for group comparison between healthy control participants and patients with PD at different stages. Quantitative parameters were correlated with severity of disease and disease duration by Spearman correlation. Voxelwise analysis for evaluating dopaminergic neuron decline of different PD stages was performed by SPM5. RESULTS The 2-dimensional and 3-dimensional 18 F-DTBZ PET images demonstrated that the reduction of vesicular monoamine transporter type 2 availability was obviously correlated with the severity of disease in patients with PD. The mean reductions of vesicular monoamine transporter type 2 density for the caudate, putamen, and substantia nigra were 21.50%, 58.20%, and 21.10% for mild PD; 60.75%, 79.49%, and 39.87% for moderate PD; and 63.94%, 83.20%, and 44.00% for advanced PD, respectively. The SURs of bilateral striatal regions exhibited significantly exponential correlations to stage; disease duration; Unified Parkinson Disease Rating Scale motor score; posture instability and gait disturbance; and akinesia, rigidity, and tremor scores. CONCLUSIONS AND RELEVANCE In PD, 18 F-DTBZ PET is a potential imaging biomarker for measuring dopaminergic ...
A number of experiments in animals have shown that successful induction of plasticity can be abolished if an individually ineffective intervention is given shortly afterwards. Such effects are termed depotentiation/de-depression. These effects contrast with metaplasticity/homeostatic plasticity in which pretreatment of the system with one protocol modulates the response to a second plasticity-inducing protocol. Homeostatic plasticity maintains the balance of plasticity in the nervous system at a stable level whereas depotentiation/de-depression abolishes synaptic plasticity that has just occurred in order to prevent ongoing learning. In the present study, we developed novel protocols to explore the reversal of LTP-and LTD-like effects in healthy conscious humans based on the recently developed theta burst form of repetitive transcranial magnetic stimulation (TBS). The potentiation effect induced by intermittent TBS (iTBS) was completely erased by a short form of continuous TBS (cTBS150) given 1 min after iTBS, whereas the depressive effect of continuous TBS (cTBS) was successfully abolished by a short form of iTBS (iTBS150). The reversal was specific to the nature of the second protocol and was time dependent since it was less effective when the intervention was given 10 min after induction of plasticity. All these features are compatible with those of depotentiation and de-depression demonstrated in animal studies. The development of the present protocols would be helpful to study the physiology of the reversal of plasticity and learning and to probe the abnormal depotentiation/de-depression shown in animal models of neurological diseases (e.g. Parkinson's disease with dyskinesia, dystonia and Huntingon's disease).
The authors explored the temporal mechanism of attention deficit in children with attention-deficit/hyperactivity disorder (ADHD). In rapid serial visual presentation tasks in which two targets (T-sub-1 and T-sub-2) were presented in close temporal proximity among distractors, participants tried to identify T-sub-1 and detect T-sub-2 in one (dual-task) experiment and only to detect T-sub-2 in a second control (single-task) experiment. The sensitivity of T-sub-2 detection was analyzed using signal detection theory. The attentional blink--the impairment in T-sub-2 detection following the identification of T-sub-1--was increased in magnitude and protracted in the patients. Moreover, some ADHD children appeared to have a blink largely normal in magnitude but temporally displaced toward a later time. The authors hypothesize that a slower closing of the attention gate may mediate this specific attention impairment in ADHD children.
Purpose: To determine whether progressive supranuclear palsy (PSP) is associated with specific diffusion tensor imaging (DTI) patterns of diffusivity, anisotropy, and coherence in functionally relevant brain areas. Materials and Methods:In all, 17 PSP patients and 17 controls were scanned using a 3 T magnetic resonance imaging (MRI) scanner. Patients were assessed in the offmedication condition using the Hoehn and Yahr staging and the United Parkinson's Disease Rating Scale, motor subscale (UPDRS-III). Diffusion information were analyzed in relation to disease severity and subtypes.Results: Numerous changes in diffusion properties were identified in the subcortical areas. In the midbrain, fractional anisotropy (FA) decreased and MD (mean diffusivity) increased with disease progression. UPDRS-III scores correlated positively with both FA in the caudate and MD in the pons. DTI analysis of disease subtypes demonstrated significant differences between PSP-Parkinsonism and SteeleRichardson-Olszewski syndrome in axial diffusivity values in the putamen and globus pallidus, as well as in intervoxel diffusion coherence values in the middle cerebellar peduncle.Conclusion: Our findings, cautiously interpreted, demonstrate the advantage of using a functional imaging technique to aid in the specificity of defining more precisely the pathological processes taking place in white and gray matter regions in PSP.
PET with 18 F-9-fluoropropyl-(1)-dihydrotetrabenzazine ( 18 F-DTBZ), a novel radiotracer targeting vesicular monoamine transporter type 2 (VMAT2), has been proven as a useful imaging marker to measure dopaminergic integrity. Methods: The aim of this study was to evaluate the capability of 18 F-DTBZ PET in detecting the monoaminergic degeneration in early Parkinson disease (PD) in vivo. Seventeen age-matched healthy subjects and 30 PD patients at early stage of disease (duration of disease # 5 y) with mild and unilateral motor symptoms underwent 18 F-DTBZ PET scans. The severity of disease, including Unified Parkinson Disease Rating Scale and modified Hoehn and Yahr Stage (mHY), were recorded at off-medication states. The standardized volumes of interest were applied to the spatial normalized image for quantification analysis. The specific uptake ratios (SURs) were calculated according to the formula (specific volumes-of-interest counts/occipital cortex counts) 2 1. SUR measurements were summarized for each brain region. Results: The mean duration of disease in the PD group was 3.2 6 2.1 y (range, 0.5-5 y). The mean mHY was 1.0 6 0.1 (range, 1-1.5). The SURs of bilateral caudate, anterior putamen, posterior putamen, substantia nigra, and nucleus accumbens were significantly lower in PD patients than those of healthy subjects. The reduction of SURs was most severe in the contralateral (the brain regions that are located opposite to the symptomatic side) posterior putamen (281%), followed by the ipsilateral posterior putamen (267%). Receiver-operating-characteristic curve analysis showed that the SURs of the bilateral posterior putamen and contralateral anterior putamen had a sensitivity of 100% and specificity of 100% in differentiating PD patients from healthy subjects. Conclusion: 18 F-DTBZ PET was as an excellent tool for the early diagnosis of PD. The obvious decline of 18 F-DTBZ uptake in the ipsilateral (asymptomatic) striatum suggested that 18 F-DTBZ PET might serve as an in vivo biomarker to detect the monoaminergic degeneration in the premotor phase of PD.
Evidence is accumulating that attention impairment is a core cognitive deficit in patients with schizophrenia. Here we investigate whether they are impaired in the temporal deployment of attention. Specifically, we explore how allocation of processing resources at one time point might affect the processing of a subsequent event differently in normal and schizophrenia subjects. Thirty patients and 31 age- and education-matched control subjects participated in a rapid serial visual presentation task, in which two targets (T1 and T2) were presented in rapid succession among a number of distractors. Subjects were required to identify T1 and detect T2. The sensitivity of T2 detection was analyzed with signal detection theory. The results showed that the attentional blink (the impairment in T2 detection following the identification of T1) is increased in magnitude and protracted in the patients. This observation suggests a less efficient mechanism in temporal gating of attention and in processing rapidly changing visual stimuli in schizophrenia patients.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.