Browsing by Author "Skosnik, Patrick D."

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    Neural correlates of performance monitoring in chronic cannabis users and cannabis-naïve controls
    (Sage, 2013) Fridberg, Daniel J.; Skosnik, Patrick D.; Hetrick, William P.; O’Donnell, Brian F.; Psychiatry, School of Medicine
    Chronic cannabis use is associated with residual negative effects on measures of executive functioning. However, little previous work has focused specifically on executive processes involved in performance monitoring in frequent cannabis users. The present study investigated event-related potential (ERP) correlates of performance monitoring in chronic cannabis users. The error-related negativity (ERN) and error positivity (Pe), ERPs sensitive to performance monitoring, were recorded from 30 frequent cannabis users (mean usage=5.52 days/week) and 32 cannabis-naïve control participants during a speeded stimulus discrimination task. The "oddball" P3 ERP was recorded as well. Users and controls did not differ on the amplitude or latency of the ERN; however, Pe amplitude was larger among users. Users also showed increased amplitude and reduced latency of the P3 in response to infrequent stimuli presented during the task. Among users, urinary cannabinoid metabolite levels at testing were unrelated to ERP outcomes. However, total years of cannabis use correlated negatively with P3 latency and positively with P3 amplitude, and age of first cannabis use correlated negatively with P3 amplitude. The results of this study suggest that chronic cannabis use is associated with alterations in neural activity related to the processing of motivationally-relevant stimuli (P3) and errors (Pe).
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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.