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The locus coeruleus (LC) is the major origin of norepinephrine in the central nervous system, and is subject to age-related and neurodegenerative changes, especially in disorders such as Parkinson's disease and Alzheimer's disease. Previous studies have shown that neuromelanin (NM)-sensitive MRI can be used to visualize the LC, and it is hypothesized that magnetization transfer (MT) effects are the primary source of LC contrast. The aim of this study was to characterize the MT effects in LC imaging by applying high spatial resolution quantitative MT (qMT) imaging to create parametric maps of the macromolecular content of the LC and surrounding tissues. Healthy volunteers (n = 26; sex = 17 F/9M; age = 41.0 ± 19.1 years) underwent brain MRI on a 3.0 T scanner. qMT data were acquired using a 3D MT-prepared spoiled gradient echo sequence. A traditional NM scan consisting of a T1-weighted turbo spin echo sequence with MT preparation was also acquired. The pool-size ratio (PSR) was estimated for each voxel using a single-point qMT approach. The LC was semi-automatically segmented on the MT-weighted images. The MT-weighted images provided higher contrast-ratio between the LC and surrounding pontine tegmentum (PT) (0.215 ± 0.031) than the reference images without MT-preparation (−0.005 ± 0.026) and the traditional NM images (0.138 ± 0.044). The PSR maps showed significant differences between the LC (0.090 ± 0.009) and PT (0.188 ± 0.025). The largest difference between the PSR values in the LC and PT was observed in the central slices, which also correspond to those with the highest contrast-ratio. These results highlight the role of MT in generating NM-related contrast in the LC, and should serve as a foundation for future studies aiming to quantify pathological changes in the LC and surrounding structures in vivo.

Parkinson's disease (PD) is characterized by dysfunction in frontal cortical and striatal networks that regulate action control. We investigated the pharmacological effect of dopamine agonist replacement therapy on frontal cortical activity and motor inhibition. Using Arterial Spin Labeling MRI, we examined 26 PD patients in the off- and on-dopamine agonist medication states to assess the effect of dopamine agonists on frontal cortical regional cerebral blood flow. Motor inhibition was measured by the Simon task in both medication states. We applied the dual process activation suppression model to dissociate fast response impulses from motor inhibition of incorrect responses. General linear regression model analyses determined the medication effect on regional cerebral blood flow and motor inhibition, and the relationship between regional cerebral blood flow and motor inhibitory proficiency. We show that dopamine agonist administration increases frontal cerebral blood flow, particularly in the pre-supplementary motor area (pre-SMA) and the dorsolateral prefrontal cortex (DLPFC). Higher regional blood flow in the pre-SMA, DLPFC and motor cortex was associated with better inhibitory control, suggesting that treatments which improve frontal cortical activity could ameliorate motor inhibition deficiency in PD patients.

Background Reduced diffusion along perivascular spaces in adults with Alzheimer's-disease-related-dementias has been reported and attributed to reduced glymphatic function. Objectives To apply quantitative measures of diffusion along, and orthogonal to, perivascular spaces in a cohort of older adults with and without clinical symptoms of alpha-synuclein related neurodegeneration. Methods 181 adults with Parkinson disease (PD) or essential tremor (ET) additionally sub-classified by the presence of cognitive impairment underwent 3 T MRI. Diffusion-tensor-imaging (spatial resolution = 2x2x2 mm; b-value = 1000 s/mm2; directions = 33) measures of diffusion (mm2/s) parallel and orthogonal to perivascular spaces at the level of the medullary veins, and the ratio of these measures (ALPS-index), were calculated. Regions were identified by a board-certified neuroradiologist from T1-weighted and T2-weighted MRI. Evaluations of motor impairment and mild cognitive impairment (MCI) were interpreted by a board-certified neurologist and neuropsychologist, respectively. Multiple regression with false discovery rate correction was applied to understand how diffusion metrics related to (i) disease category (PD vs. ET), (ii) cognition (MCI status), and (iii) white matter disease severity from the Fazekas score. Results The ALPS-index was reduced in PD compared to ET participants (p = 0.037). No association between the ALPS-index and MCI status, but an inverse association between the ALPS-index and Fazekas score (p = 0.002), was observed. The ALPS-index was inversely associated with age (p = 0.007). Conclusion Diffusion aberrations near perivascular spaces are evident in patients with alpha-synuclein related neurodegenerative disorders, and are related to age and white matter disease severity.

Highlights • Photophobia is a common, disabling symptom observed in patients with Progressive Supranuclear Palsy (PSP). • We assessed the functional impacts of photophobia in PSP, and find that bright light is painful. • Symptoms limit participation in activities of daily living, reducing time spent outside the house., Objective To determine the impact of photophobia on persons with Progressive Supranuclear Palsy (pwPSP) by determining the functional impact of light sensitivity using methods established in migraine research. Methods All 60 participants (pwPSP = 15, persons with Parkinson Disease (pwPD) = 15, Older adults = 30) completed a series of questionnaires designed to assess the impact of photophobia on activities of daily living. Group comparisons were controlled for multiple comparisons using a false discovery rate of 0.05. Results Most (14/15) pwPSP participants noted that bright light hurt their eyes, and this proportion was significantly greater than pwPD (6/15; p = 0.03, corrected). PSP participants reported statistically significantly more severe light sensitivity on a subjective 0–100 scale (p = 0.003, corrected), and noted reduced time spent in both indoor and outdoor activities. Some PSP participants (n = 3) noted that they needed to wear sunglasses indoors, but most noted a reluctance to leave their house during the day due to photophobia. PwPSP indicated that they require more help from others to complete daily tasks that require them to be outside during daylight hours. Conclusions Overall, we note a significant debility due to photophobia in PSP, and this impacts outdoor more than indoor activities. The functional disability in PSP caused by photophobia appears to cause a substantive reduction in quality of life. Future studies could consider incorporating specific metrics to evaluate measurable differences with photophobia onset and worsening severity.

Objective To identify factors associated with job satisfaction and retention, we surveyed a large cohort of clinical research coordinators (CRCs). In recent years, the clinical research coordinator has changed from a semi-permanent role to one that has a high turnover rate. The CRCs are integral to clinical research and instability in this role can cause patient stress and increase the burden on clinical teams through unnecessary delegation of resources toward hiring and retraining new talent. The cultural shift toward CRCs as a temporary position may be driven by the perspective that the role positions an individual for other health care careers, but understanding what influences low retention rates are necessary. Methods A survey containing 13 multiple choice or open-ended and 32 Likert scale questions was distributed to previous and current CRCs using REDCap. The questionnaires were self-administered and completed over a 12-month period between October 11, 2017, and September 16, 2018. Results A total of 85 CRCs completed the study. From the 32 potential predictors of retention, we investigated 9 significant predictors: salary, work setting, understanding the role, level of CRC, understanding protocol development, actively engaged principal investigator (PI), having a collaborative role with PI, feeling respected by PI, and having a close relationship with PI. Adequate salary, greater respect, collaboration, and engagement from the PI were significantly associated with higher retention. Surprisingly, greater workload and lack of opportunity for professional growth were not associated with retention. Conclusion The CRCs who feel respected and engaged by the PI and are adequately compensated are more likely to have higher job satisfaction and retention.

INTRODUCTION: Dopamine medication withdrawal in Parkinson’s Disease is commonly employed in clinical practice and can be required for participation in research studies. When asked to withdraw from medications, participants often enquire as to what symptoms they should expect. OBJECTIVES: This study sought to improve the informed consent process by identifying patient-reported symptoms when withholding from dopamine treatment. We also sought to provide clinical guidance regarding the extent of these symptoms and consider participant willingness to undergo these assessments. METHODS: Participants were recruited from community-based PD programs and support groups in Nashville, Tennessee. A patient-based questionnaire determined the frequency and severity of motor and nonmotor symptoms. The questionnaire also assessed if patients would be willing to withhold from medication at a future date and for what purpose. RESULTS: A total of 31/90 participants reported withdrawing from dopaminergic medications for clinical or research purposes. Tremor, walking, and balance was the most common motor symptom that worsened during this time. Sleep dysfunction, constipation, and tremor were noted as the most severe symptoms. Of note, 10% of the participants indicated that they would not be willing to go off medications again, suggesting that to a minority of patients this can be most discomforting. When prompted for a reason that participants would be willing to come off of their medications again, “clinical” purposes were the most selected. CONCLUSIONS: Study teams should list these symptoms in the applications to their institutional review board and in the informed consent to provide guidance for participants.

Background: Heart failure with preserved ejection fraction (HFpEF) and dementia share several cardiovascular risk factors and have been independently associated with brain atrophy. However, it is unclear how HFpEF affects brain morphology in patients with preexisting dementia. Advances in bioinformatics data extraction pipelines, quantitative neuroimaging, and deep learning, have made possible the analysis of the effects of cardiovascular disease on clinical neuroimaging in large datasets. Hypothesis: We hypothesized that HFpEF in the setting of dementia would be associated with distinct brain morphology imaging changes compared to dementia in the absence of HFpEF. Methods: We used the bioinformatics tools at Vanderbilt University Medical Center to extract and analyze deidentified clinical neuroimaging from patients with a diagnosis of dementia with and without coexisting HFpEF from the electronic health record. We identified a total of 30 patients with HFpEF and dementia who had high-resolution, clinical neuroimaging as well as 301 age- and sex-matched controls. We used an automated pipeline to segment the brain into 132 distinct brain regions and estimate their volume to find structural differences associated with HFpEF. Results: We found six regions with significant atrophy associated with HFpEF: accumbens area, amygdala, posterior insula, anterior orbital gyrus, angular gyrus, and cerebellar white matter. There were no regions with atrophy inversely associated with HFpEF (Figure 1). Conclusions: Here, we show that patients with HFpEF have a distinct neuroimaging signature on patients with preexisting dementia. A possible mechanism of injury for this region and the subsequent atrophy has been linked to high aortic stiffening secondary to chronic cardiovascular disease and its risk factors, resulting in end-organ damage due to barotrauma and shear forces.

Background Parkinson's disease (PD) and essential tremor (ET) are commonly encountered movement disorders. Pathophysiologic processes that localize to the cerebellum are described in both. There are limited studies investigating cerebellar structural changes in these conditions, largely because of inherent challenges in the efficiency of segmentation. Methods We applied a novel multiatlas cerebellar segmentation method to T1-weighted images in 282 PD and 111 essential tremor patients to define 26 cerebellar lobule volumes. The severity of postural and resting tremor in both populations and gait and postural instability in PD patients were defined using subscores of the UPDRS and Washington Heights-Inwood Genetic Study motor scales. These clinical measurements were related to lobule volume size. Multiple comparisons were controlled using a false discovery rate method. Results Group differences were identified between ET and PD patients, with reductions in deep cerebellar nucleus volume in ET versus reduced lobule VI volume in PD. In ET patients, lobule VIII was negatively correlated with the severity of postural tremor. In PD patients, lobule IV was positively correlated with resting tremor and total tremor severity. We observed differences in cerebellar structure that localized to sensorimotor lobules of the cerebellum. Lobule volumes appeared to differentially relate to clinical symptoms, suggesting important clinicopathologic distinctions between these conditions. These results emphasize the role of the cerebellum in tremor symptoms and should foster future clinical and pathologic investigations of the sensorimotor lobules of the cerebellum. © 2020 International Parkinson and Movement Disorder Society.

The nigrostriatal and mesocorticolimbic dopamine networks regulate reward-driven behavior. Regional alterations to mesolimbic dopamine D2/3receptor expression are described in drug-seeking and addiction disorders. Parkinson's disease (PD) patients are frequently prescribed D2-like dopamine agonist (DAgonist) therapy for motor symptoms, yet a proportion develop clinically significant behavioral addictions characterized by impulsive and compulsive behaviors (ICBs). Until now, changes in D2/3receptor binding in both striatal and extrastriatal regions have not been concurrently quantified in this population. We identified 35 human PD patients (both male and female) receiving DAgonist therapy, with (n= 17) and without (n= 18) ICBs, matched for age, disease duration, disease severity, and dose of dopamine therapy. In the off-dopamine state, all completed PET imaging with [18F]fallypride, a high affinity D2-like receptor ligand that can measure striatal and extrastriatal D2/3nondisplaceable binding potential (BPND). Striatal differences between ICB+/ICB− patients localized to the ventral striatum and putamen, where ICB+ subjects had reduced BPND. In this group, self-reported severity of ICB symptoms positively correlated with midbrain D2/3receptor BPND. Group differences in regional D2/3BPNDrelationships were also notable: ICB+ (but not ICB−) patients expressed positive correlations between midbrain and caudate, putamen, globus pallidus, and amygdala BPNDs. These findings support the hypothesis that compulsive behaviors in PD are associated with reduced ventral and dorsal striatal D2/3expression, similar to changes in comparable behavioral disorders. The data also suggest that relatively preserved ventral midbrain dopaminergic projections throughout nigrostriatal and mesolimbic networks are characteristic of ICB+ patients, and may account for differential DAgonist therapeutic response.SIGNIFICANCE STATEMENTThe biologic determinants of compulsive reward-based behaviors have broad clinical relevance, from addiction to neurodegenerative disorders. Here, we address biomolecular distinctions in Parkinson's disease patients with impulsive compulsive behaviors (ICBs). This is the first study to image a large cohort of ICB+ patients using positron emission tomography with [18F]fallypride, allowing quantification of D2/3receptors throughout the mesocorticolimbic network. We demonstrate widespread differences in dopaminergic networks, including (1) D2-like receptor distinctions in the ventral striatum and putamen, and (2) a preservation of widespread dopaminergic projections emerging from the midbrain, which is associated with the severity of compulsive behaviors. This clearly illustrates the roles of D2/3receptors and medication effects in maladaptive behaviors, and localizes them specifically to nigrostriatal and extrastriatal regions.

A subgroup of Parkinson's disease (PD) patients treated with dopaminergic therapy develop compulsive reward-driven behaviors, which can result in life-altering morbidity. The mesocorticolimbic dopamine network guides reward-motivated behavior; however, its role in this treatment-related behavioral phenotype is incompletely understood. Here, mesocorticolimbic network function in PD patients who develop impulsive and compulsive behaviors (ICB) in response to dopamine agonists was assessed using BOLD fMRI. The tested hypothesis was that network connectivity between the ventral striatum and the limbic cortex is elevated in patients with ICB and that reward-learning proficiency reflects the extent of mesocorticolimbic network connectivity. To evaluate this hypothesis, 3.0T BOLD-fMRI was applied to measure baseline functional connectivity on and off dopamine agonist therapy in age and sex-matched PD patients with (n = 19) or without (n = 18) ICB. An incentive-based task was administered to a subset of patients (n = 20) to quantify positively or negatively reinforced learning. Whole-brain voxelwise analyses and region-of-interest-based mixed linear effects modeling were performed. Elevated ventral striatal connectivity to the anterior cingulate gyrus (P = 0.013), orbitofrontal cortex (P = 0.034), insula (P = 0.044), putamen (P = 0.014), globus pallidus (P

ObjectiveDysarthric speech of persons with Huntington disease (HD) is typically described as hyperkinetic; however, studies suggest that dysarthria can vary and resemble patterns in other neurologic conditions. To test the hypothesis that distinct motor speech subgroups can be identified within a larger cohort of patients with HD, we performed a cluster analysis on speech perceptual characteristics of patient audio recordings.MethodsAudio recordings of 48 patients with mild to moderate dysarthria due to HD were presented to 6 trained raters. Raters provided scores for various speech features (e.g., voice, articulation, prosody) of audio recordings using the classic Mayo Clinic dysarthria rating scale. Scores were submitted to an unsupervised k-means cluster analysis to determine the most salient speech features of subgroups based on motor speech patterns.ResultsFour unique subgroups emerged from the cohort of patients with HD. Subgroup 1 was characterized by an abnormally fast speaking rate among other unique speech features, whereas subgroups 2 and 3 were defined by an abnormally slow speaking rate. Salient speech features for subgroup 2 overlapped with subgroup 3; however, the severity of dysarthria differed. Subgroup 4 was characterized by mild deviations of speech features with typical speech rate. Length of CAG repeats, Unified Huntington’s Disease Rating Scale total motor score, and percent intelligibility were significantly different for pairwise comparisons of subgroups.ConclusionThis study supports the existence of distinct presentations of dysarthria in patients with HD, which may be due to divergent pathologic processes. The findings are discussed in relation to previous literature and clinical implications.

Objective Impulsive decision‐making is characterized by actions taken without considering consequences. Patients with Parkinson's disease (PD) who receive dopaminergic treatment, especially dopamine agonists, are at risk of developing impulsive–compulsive behaviors (ICBs). We assessed impulse‐related changes across a large heterogeneous PD population using the Barratt impulsivity scale (BIS‐11) by evaluating BIS‐11 first‐ and second‐order factors. Methods We assessed a total of 204 subjects: 93 healthy controls (HCs), and 68 ICB– and 43 ICB + PD patients who completed the BIS‐11. Using a general linear model and a least absolute shrinkage and selection operation regression, we compared BIS‐11 scores between the HC, ICB– PD, and ICB + PD groups. Results Patients with PD rated themselves as more impulsive than HCs in the BIS‐11 total score, second‐order attention domain, and first‐order attention and self‐control domains. ICB + patients recorded higher total scores as well as higher scores in the second‐order non‐planning domain and in self‐control and cognitive complexity than ICB– patients. Interpretation These results indicate that the patients with PD show particular problems with attentional control, whereas ICB + patients show a distinct problem in cognitive control and complexity. Additionally, it appears that all patients with PD are more impulsive than their age‐ and sex‐matched healthy peers. Increased impulsivity may be a result of the disease course, or attributed to dopaminergic medication use, but these results emphasize the importance of the cognitive components of impulsivity in patients with PD.

ObjectiveTo assess white matter integrity in patients with essential tremor (ET) and Parkinson disease (PD) with moderate to severe motor impairment.MethodsSedated participants with ET (n = 57) or PD (n = 99) underwent diffusion tensor imaging (DTI) and fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity values were computed. White matter tracts were defined using 3 well-described atlases. To determine candidate white matter regions that differ between ET and PD groups, a bootstrapping analysis was applied using the least absolute shrinkage and selection operator. Linear regression was applied to assess magnitude and direction of differences in DTI metrics between ET and PD populations in the candidate regions.ResultsFractional anisotropy values that differentiate ET from PD localize primarily to thalamic and visual-related pathways, while diffusivity differences localized to the cerebellar peduncles. Patients with ET exhibited lower fractional anisotropy values than patients with PD in the lateral geniculate body (p < 0.01), sagittal stratum (p = 0.01), forceps major (p = 0.02), pontine crossing tract (p = 0.03), and retrolenticular internal capsule (p = 0.04). Patients with ET exhibited greater radial diffusivity values than patients with PD in the superior cerebellar peduncle (p < 0.01), middle cerebellar peduncle (p = 0.05), and inferior cerebellar peduncle (p = 0.05).ConclusionsRegionally, distinctive white matter microstructural values in patients with ET localize to the cerebellar peduncles and thalamo-cortical visual pathways. These findings complement recent functional imaging studies in ET but also extend our understanding of putative physiologic features that account for distinctions between ET and PD.

A subgroup of Parkinson's disease (PD) patients treated with dopaminergic therapy develop compulsive reward-driven behaviors, which can result in life-altering morbidity. The mesocorticolimbic dopamine network guides reward-motivated behavior; however, its role in this treatment-related behavioral phenotype is incompletely understood. Here, mesocorticolimbic network function in PD patients who develop impulsive and compulsive behaviors (ICB) in response to dopamine agonists was assessed using BOLD fMRI. The tested hypothesis was that network connectivity between the ventral striatum and the limbic cortex is elevated in patients with ICB and that reward-learning proficiency reflects the extent of mesocorticolimbic network connectivity. To evaluate this hypothesis, 3.0T BOLD-fMRI was applied to measure baseline functional connectivity on and off dopamine agonist therapy in age and sex-matched PD patients with (n = 19) or without (n = 18) ICB. An incentive-based task was administered to a subset of patients (n = 20) to quantify positively or negatively reinforced learning. Whole-brain voxelwise analyses and region-of-interest-based mixed linear effects modeling were performed. Elevated ventral striatal connectivity to the anterior cingulate gyrus (P = 0.013), orbitofrontal cortex (P = 0.034), insula (P = 0.044), putamen (P = 0.014), globus pallidus (P 0.01), and thalamus (P 0.01) was observed in patients with ICB. A strong trend for elevated amygdala-to-midbrain connectivity was found in ICB patients on dopamine agonist. Ventral striatum-to-subgenual cingulate connectivity correlated with reward learning (P 0.01), but not with punishment-avoidance learning. These data indicate that PD-ICB patients have elevated network connectivity in the mesocorticolimbic network. Behaviorally, proficient reward-based learning is related to this enhanced limbic and ventral striatal connectivity. Hum Brain Mapp 39:509-521, 2018. © 2017 Wiley Periodicals, Inc.

Background: Myelodysplastic syndromes (MDS) are clonal hematologic neoplasms stratified by risk by the international prognostic scoring system (IPSS) and IPSS-revised (IPSS-R) which measure risk by morphologic dysplasia, clinical cytopenias, blast count, and cytogenetic abnormalities. (PMID: 9058730, 22740453) The IPSS/IPSS-R do not consider clinical comorbid conditions, though MDS patients with higher burden of comorbid disease have higher rates of non-leukemic death, particularly those with cardiovascular and pulmonary disease. (19324411) Despite this, there has been limited investigation into how specific comorbid conditions may help define subgroups of patients with MDS. Methods: We identified 2676 cases of MDS as defined by ICD-9 code (238.72 - 238.75) in Vanderbilt's Synthetic Derivative (SD). The SD is a de-identified electronic health record (EHR) of over 2.2 million patients with a companion biorepository of DNA (BioVU) for a subset of these patients, including all of the patients with MDS. The 2676 cases were matched by age, gender, race, burden of comorbidities in EHR, and age at last appointment in EHR with 5287 controls. ICD-9 codes for other myeloid disease (e.g., myeloproliferative neoplasms, acute myeloid leukemia) or history of hematopoietic stem cell transplant were excluded among the controls. Characterization of comorbidities, via phecode analysis, was conducted on all cases and controls. Phecodes are groups of related ICD-9 codes describing a clinical syndrome or medical problem, previously demonstrated to be useful in phenome-wide associated studies in EHRs. (28686612) A case was defined as having a phecode only if a representative ICD-9 code was present on two distinct days in the EHR. Next, a cluster analysis of the study population and their associated comorbidities, via a bipartite stochastic block model, was completed, and the study population was organized into hierarchical structure based upon the similarities in comorbidity patterns among patients. Results: ICD-9 codes from the study population made up 181 phecodes, which were found in hierarchical cluster analysis to further cluster into 54 sub-groups and 16 larger groups. MDS patients clustered throughout all groups, the majority of which contained control patients; yet some MDS cases sub-clustered into groups that included a majority of MDS cases and these were further analyzed. Notably, two groups had equivalent size and MDS status were found to have significant differences in phecode profiles. Group 1 had 795 total patients with 783 MDS cases (98.5%) and Group 2 had 769 total patients with 684 MDS cases (88.9%), as per Fig 1a. There were no significant difference in sex between the two groups. Group 1 patients were significantly younger than Group 2 patients (58.3y vs 62.9y; p = 1.36 x 10-7), yet tended have increased risk of renal, cardiovascular and thromboembolic disease than Group 2, as per Fig 1b. Additionally, a higher proportion of Group 2 patients (695/769 or 90.4%) were alive at time of data extraction than Group 1 patients (451/795 or 56.7%) (OR 4.51, p = Conclusions: By performing a phenome-wide analysis of patients with MDS in a large electronic health record (EHR), we reveal specific subgroups of MDS patients with distinct comorbidities and different survival, not affected by age or sex. This study demonstrates the ability to study comorbid conditions of MDS patients in an unbiased fashion, independent of disease specific risk factors that inform IPSS-R and which have historically been most important in stratifying risk in MDS. The role of comorbidity is instinctually clear to the adroit clinician, and this technique could provide distinct comorbid disease patterns which impute risk, or perhaps etiology in MDS. Disclosures Savona: TG Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm Therapeutics: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Selvita: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sunesis: Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees; Boehringer Ingelheim: Patents & Royalties; Celgene Corporation: Membership on an entity's Board of Directors or advisory committees.

There has been a recent increase in research on vehicular ad-hoc network VANET technology. Peer-to-peer P2P systems have also been widely used for resource sharing. This paper proposes an efficient geo-aware P2P search mechanism to enable resource discovery and sharing on VANETs. The proposed discovery and sharing schemes are based on virtual backbone architecture. The schemes limit the data-exchanging region to reduce unnecessary message transmissions. They establish coordinators to store information and manage local resource information. If more vehicles own the resources, the user has more opportunities to discover and obtain the resources. Three piece selection mechanisms, nearest-first, rarest-first and in-order, are proposed to download resource pieces from other vehicles and to improve the dissemination efficiency speed at which resources piece to networks. Experimental results demonstrate that the searching and sharing schemes are efficient and outperform other schemes in terms of satisfactory ratio and download time.