Browsing by Author "Vollmer, Jennifer M."

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    A magnetic resonance imaging-safe method for the study of human eyeblink conditioning
    (Elsevier, 2013) Kent, Jerillyn S.; Bailey, D. Michael; Vollmer, Jennifer M.; Newman, Sharlene D.; Bolbecker, Amanda R.; O’Donnell, Brian F.; Hetrick, William P.; Psychiatry, School of Medicine
    Eyeblink conditioning (EBC) is a widely used translational probe of cerebellar function in both humans and non-human animals. Decades of animal research have identified the cerebellum as critical for EBC. While there is evidence for the involvement of the cerebellum in human EBC, the neural circuitry of EBC in healthy humans has yet to be fully elucidated. The purpose of this study was to design and validate a highly customisable system for EBC stimulus presentation and response recording using infrared (IR) reflectance suitable for use in magnetic resonance imaging (MRI) environments; in this way, the neural activity of EBC could be investigated using fMRI in humans. Four participants underwent delay EBC and simultaneous fMRI. The results indicate (1) a high signal-to-noise ratio in the IR reflectance data that effectively quantifies the eyeblink morphology and timing and (2) evidence of conditioning in the fMRI environment. The quality of the data, the feasibility of conducting EBC experiments in the fMRI environment, and the customisability of the current system to fit a variety of EBC experimental design parameters are discussed.
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    Striatal D2/D3 Receptor Availability is Inversely Correlated with Cannabis Consumption in Chronic Marijuana Users
    (Elsevier, 2013) Albrecht, Daniel S.; Skosnik, Patrick D.; Vollmer, Jennifer M.; Brumbaugh, Margaret S.; Perry, Kevin M.; Mock, Bruce H.; Zheng, Qi-Huang; Federici, Lauren A.; Patton, Elizabeth A.; Herring, Christine M.; Yoder, Karmen K.; Radiology and Imaging Sciences, School of Medicine
    Background: Although the incidence of cannabis abuse/dependence in Americans is rising, the neurobiology of cannabis addiction is not well understood. Imaging studies have demonstrated deficits in striatal D(2)/D(3) receptor availability in several substance-dependent populations. However, this has not been studied in currently using chronic cannabis users. Objective: The purpose of this study was to compare striatal D(2)/D(3) receptor availability between currently using chronic cannabis users and healthy controls. Methods: Eighteen right-handed males age 18-34 were studied. Ten subjects were chronic cannabis users; eight were demographically matched controls. Subjects underwent a [(11)C]raclopride (RAC) PET scan. Striatal RAC binding potential (BP(ND)) was calculated on a voxel-wise basis. Prior to scanning, urine samples were obtained from cannabis users for quantification of urine Δ-9-tetrahydrocannabinol (THC) and THC metabolites (11-nor-Δ-9-THC-9-carboxylic acid; THC-COOH and 11-hydroxy-THC;OH-THC). Results: There were no differences in D(2)/D(3) receptor availability between cannabis users and controls. Voxel-wise analyses revealed that RAC BP(ND) values were negatively associated with both urine levels of cannabis metabolites and self-report of recent cannabis consumption. Conclusions: In this sample, current cannabis use was not associated with deficits in striatal D(2)/D(3) receptor availability. There was an inverse relationship between chronic cannabis use and striatal RAC BP(ND). Additional studies are needed to identify the neurochemical consequences of chronic cannabis use on the dopamine system.
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    URINE THC METABOLITE LEVELS CORRELATE WITH STRIATAL D2/D3 RECEPTOR AVAILABILITY
    (Office of the Vice Chancellor for Research, 2012-04-13) Albrecht, Daniel S.; Skosnik, Patrick D.; Vollmer, Jennifer M.; Brumbaugh, Margaret S.; Perry, Kevin M.; Zheng, Qi-Huang; Federici, Lauren A.; Patton, Elizabeth A.; Herring, Christine M.; Yoder, Karmen K.
    Rationale: Although the incidence of cannabis abuse/dependence in Americans is rising, the neurobiology of cannabis addiction is not well understood. Previous PET and SPECT studies have demonstrated deficits in striatal D2/D3 receptor availability in several substance-dependent populations. However, this has not been studied in chronic cannabis users. Objective: The purpose of this study was to compare striatal D2/D3 receptor availability between currently-using chronic cannabis users and healthy controls. Methods: Eighteen right-handed males, 18-34 years of age, were studied. Ten subjects were chronic cannabis users; eight were demographically matched controls. Subjects underwent a [11C]raclopride (RAC) PET scan. On the scan day, urine samples were obtained from cannabis users for quantification of urine Δ-9-tetrahydrocannabinol (THC; the active compound in cannabis smoke) and THC metabolites (11-nor-Δ-9-THC-9-carboxylic acid and 11-hydroxy-THC). Striatal RAC binding potential (BPND) was used as an index of D2/D3 receptor availability; this parameter was estimated at each image voxel for every subject. SPM5 software was used to test for differences in BPND between groups and, in cannabis subjects, for associations between BPND and markers of cannabis use. Results: There were no differences in D2/D3 receptor availability between cannabis users and controls. Smokers of either cannabis and/or tobacco had 10.2% lower BPND values than nonsmokers in the bilateral putamen (“any-smokers”: 2.66 ± 0.2; nonsmokers: 2.97 ± 0.2). In cannabis users, RAC BPND values were negatively associated with both urine levels of cannabis metabolites and self-report of recent cannabis consumption. Conclusions: There is an inverse relationship between chronic cannabis use and striatal RAC BPND. This may be caused by inhibition of monoamine oxidase (MAO) by the pyrolyzation of cannabis, which could lead to increased endogenous dopamine levels (and hence, lower BPND in heavier users). Additional studies are needed to identify the neurochemical consequences of chronic cannabis use on the dopamine system.