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Castrellon JJ, Young JS, Dang LC, Cowan RL, Zald DH, Samanez-Larkin GR. Mesolimbic dopamine D2 receptors and neural representations of subjective value. Sci Rep 2019; 9:20229. [PMID: 31882947 PMCID: PMC6934551 DOI: 10.1038/s41598-019-56858-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 12/18/2019] [Indexed: 11/12/2022] Open
Abstract
The process by which the value of delayed rewards is discounted varies from person to person. It has been suggested that these individual differences in subjective valuation of delayed rewards are supported by mesolimbic dopamine D2-like receptors (D2Rs) in the ventral striatum. However, no study to date has documented an association between direct measures of dopamine receptors and neural representations of subjective value in humans. Here, we examined whether individual differences in D2R availability were related to neural subjective value signals during decision making. Human participants completed a monetary delay discounting task during an fMRI scan and on a separate visit completed a PET scan with the high affinity D2R tracer [18 F]fallypride. Region-of-interest analyses revealed that D2R availability in the ventral striatum was positively correlated with subjective value-related activity in the ventromedial prefrontal cortex and midbrain but not with choice behavior. Whole-brain analyses revealed a positive correlation between ventral striatum D2R availability and subjective value-related activity in the left inferior frontal gyrus and superior insula. These findings identify a link between a direct measure of mesolimbic dopamine function and subjective value representation in humans and suggest a mechanism by which individuals vary in neural representation of discounted subjective value.
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Affiliation(s)
- Jaime J Castrellon
- Department of Psychology and Neuroscience, Duke University, Durham, United States. .,Center for Cognitive Neuroscience, Duke University, Durham, United States.
| | - Jacob S Young
- Department of Neurological Surgery, University of California, San Francisco, United States
| | - Linh C Dang
- Department of Psychology, Vanderbilt University, Nashville, United States
| | - Ronald L Cowan
- Department of Psychology, Vanderbilt University, Nashville, United States.,Department of Psychiatry and Behavioral Sciences, Vanderbilt University School of Medicine, Nashville, United States.,Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, United States
| | - David H Zald
- Department of Psychology, Vanderbilt University, Nashville, United States.,Department of Psychiatry and Behavioral Sciences, Vanderbilt University School of Medicine, Nashville, United States
| | - Gregory R Samanez-Larkin
- Department of Psychology and Neuroscience, Duke University, Durham, United States.,Center for Cognitive Neuroscience, Duke University, Durham, United States
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2
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Juarez EJ, Castrellon JJ, Green MA, Crawford JL, Seaman KL, Smith CT, Dang LC, Matuskey D, Morris ED, Cowan RL, Zald DH, Samanez-Larkin GR. Reproducibility of the correlative triad among aging, dopamine receptor availability, and cognition. Psychol Aging 2019; 34:921-932. [PMID: 31589058 DOI: 10.1037/pag0000403] [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] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The evidence that dopamine function mediates the association between aging and cognition is one of the most cited findings in the cognitive neuroscience of aging. However, few and relatively small studies have directly examined these associations. Here we examined correlations among adult age, dopamine D2-like receptor (D2R) availability, and cognition in two cross-sectional studies of healthy human adults. Participants completed a short cognitive test battery and, on a separate day, a PET scan with either the high-affinity D2R tracer [18F]Fallypride (Study 1) or [11C]FLB457 (Study 2). Digit span, a measure of short-term memory maintenance and working memory, was the only cognitive test for which dopamine D2R availability partially mediated the age effect on cognition. In Study 1, age was negatively correlated with digit span. Striatal D2R availability was positively correlated with digit span controlling for age. The age effect on digit span was smaller when controlling for striatal D2R availability. Although other cognitive measures used here have individually been associated with age and D2R availability in prior studies, we found no consistent evidence for significant associations between low D2R availability and low cognitive performance on these measures. These results at best only partially supported the correlative triad of age, dopamine D2R availability, and cognition. While a wealth of other research in human and nonhuman animals demonstrates that dopamine makes critical contributions to cognition, the present studies suggest caution in interpreting PET findings as evidence that dopamine D2R loss is a primary cause of broad age-related declines in fluid cognition. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
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Affiliation(s)
| | | | | | | | | | | | - Linh C Dang
- Department of Psychology, Vanderbilt University
| | - David Matuskey
- Department of Radiology and Biomedical Imaging, Yale University
| | - Evan D Morris
- Department of Radiology and Biomedical Imaging, Yale University
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3
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Smith CT, Crawford JL, Dang LC, Seaman KL, San Juan MD, Vijay A, Katz DT, Matuskey D, Cowan RL, Morris ED, Zald DH, Samanez-Larkin GR. Partial-volume correction increases estimated dopamine D2-like receptor binding potential and reduces adult age differences. J Cereb Blood Flow Metab 2019; 39:822-833. [PMID: 29090626 PMCID: PMC6498753 DOI: 10.1177/0271678x17737693] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The relatively modest spatial resolution of positron emission tomography (PET) increases the likelihood of partial volume effects such that binding potential (BPND) may be underestimated. Given structural grey matter losses across adulthood, partial volume effects may be even more problematic in older age leading to overestimation of adult age differences. Here we examined the effects of partial volume correction (PVC) in two studies from different sites using different high-affinity D2-like radioligands (18 F-Fallypride, 11C-FLB457) and different PET camera resolutions (∼5 mm, 2.5 mm). Results across both data sets revealed that PVC increased estimated BPND and reduced, though did not eliminate, age effects on BPND. As expected, the effects of PVC were smaller in higher compared to lower resolution data. Analyses using uncorrected data that controlled for grey matter volume in each region of interest approximated PVC corrected data for some but not all regions. Overall, the findings suggest that PVC increases estimated BPND in general and reduces adult age differences especially when using lower resolution cameras. The findings suggest that the past 30 years of research on dopamine receptor availability, for which very few studies use PVC, may overestimate effects of aging on dopamine receptor availability.
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Affiliation(s)
| | - Jennifer L Crawford
- 2 Department of Psychology, Yale University, New Haven, CT, USA.,3 Center for Cognitive Neuroscience, Duke University, Durham, NC, USA
| | - Linh C Dang
- 1 Department of Psychology, Vanderbilt University, Nashville, TN, USA
| | - Kendra L Seaman
- 2 Department of Psychology, Yale University, New Haven, CT, USA.,3 Center for Cognitive Neuroscience, Duke University, Durham, NC, USA
| | - M Danica San Juan
- 1 Department of Psychology, Vanderbilt University, Nashville, TN, USA
| | - Aishwarya Vijay
- 4 Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT, USA
| | - Daniel T Katz
- 1 Department of Psychology, Vanderbilt University, Nashville, TN, USA
| | - David Matuskey
- 4 Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT, USA.,5 Department of Psychiatry, Yale University, New Haven, CT, USA
| | - Ronald L Cowan
- 1 Department of Psychology, Vanderbilt University, Nashville, TN, USA.,6 Department of Psychiatry and Behavioral Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA.,7 Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Evan D Morris
- 4 Department of Radiology and Biomedical Imaging, Yale University, New Haven, CT, USA.,5 Department of Psychiatry, Yale University, New Haven, CT, USA.,8 Department of Biomedical Engineering, Yale University, New Haven, CT USA
| | - David H Zald
- 1 Department of Psychology, Vanderbilt University, Nashville, TN, USA.,6 Department of Psychiatry and Behavioral Sciences, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Gregory R Samanez-Larkin
- 2 Department of Psychology, Yale University, New Haven, CT, USA.,3 Center for Cognitive Neuroscience, Duke University, Durham, NC, USA.,9 Department of Psychology and Neuroscience, Duke University, Durham, NC, USA
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4
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Seaman KL, Smith CT, Juarez EJ, Dang LC, Castrellon JJ, Burgess LL, San Juan MD, Kundzicz PM, Cowan RL, Zald DH, Samanez-Larkin GR. Differential regional decline in dopamine receptor availability across adulthood: Linear and nonlinear effects of age. Hum Brain Mapp 2019; 40:3125-3138. [PMID: 30932295 DOI: 10.1002/hbm.24585] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [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: 11/15/2018] [Revised: 03/06/2019] [Accepted: 03/19/2019] [Indexed: 01/25/2023] Open
Abstract
Theories of adult brain development, based on neuropsychological test results and structural neuroimaging, suggest differential rates of age-related change in function across cortical and subcortical sub-regions. However, it remains unclear if these trends also extend to the aging dopamine system. Here we examined cross-sectional adult age differences in estimates of D2-like receptor binding potential across several cortical and subcortical brain regions using PET imaging and the radiotracer [18 F]Fallypride in two samples of healthy human adults (combined N = 132). After accounting for regional differences in overall radioligand binding, estimated percent difference in receptor binding potential by decade (linear effects) were highest in most temporal and frontal cortical regions (~6-16% per decade), moderate in parahippocampal gyrus, pregenual frontal cortex, fusiform gyrus, caudate, putamen, thalamus, and amygdala (~3-5%), and weakest in subcallosal frontal cortex, ventral striatum, pallidum, and hippocampus (~0-2%). Some regions showed linear effects of age while many showed curvilinear effects such that binding potential declined from young adulthood to middle age and then was relatively stable until old age. Overall, these data indicate that the rate and pattern of decline in D2 receptor availability is regionally heterogeneous. However, the differences across regions were challenging to organize within existing theories of brain development and did not show the same pattern of regional change that has been observed in gray matter volume, white matter integrity, or cognitive performance. This variation suggests that existing theories of adult brain development may need to be modified to better account for the spatial dynamics of dopaminergic system aging.
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Affiliation(s)
- Kendra L Seaman
- Center for the Study of Aging and Human Development, Duke University, Durham, North Carolina.,Center for Cognitive Neuroscience, Duke University, Durham, North Carolina
| | | | - Eric J Juarez
- Department of Psychology and Neuroscience, Duke University, Durham, North Carolina
| | - Linh C Dang
- Department of Psychology, Vanderbilt University, Nashville, Tennessee
| | - Jaime J Castrellon
- Department of Psychology and Neuroscience, Duke University, Durham, North Carolina
| | - Leah L Burgess
- Department of Psychology, Vanderbilt University, Nashville, Tennessee
| | - M Danica San Juan
- Department of Psychology, Vanderbilt University, Nashville, Tennessee
| | - Paul M Kundzicz
- Department of Psychology, Vanderbilt University, Nashville, Tennessee
| | - Ronald L Cowan
- Department of Psychology, Vanderbilt University, Nashville, Tennessee
| | - David H Zald
- Department of Psychology, Vanderbilt University, Nashville, Tennessee
| | - Gregory R Samanez-Larkin
- Center for Cognitive Neuroscience, Duke University, Durham, North Carolina.,Department of Psychology and Neuroscience, Duke University, Durham, North Carolina
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5
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Smith CT, Dang LC, Burgess LL, Perkins SF, Juan MDS, Smith DK, Cowan RL, Le NT, Kessler RM, Samanez-Larkin GR, Zald DH. Lack of consistent sex differences in D-amphetamine-induced dopamine release measured with [ 18F]fallypride PET. Psychopharmacology (Berl) 2019; 236:581-590. [PMID: 30350220 PMCID: PMC6401232 DOI: 10.1007/s00213-018-5083-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 10/16/2018] [Indexed: 10/28/2022]
Abstract
RATIONALE Sex differences in the dopaminergic response to psychostimulants could have implications for drug abuse risk and other psychopathology involving the dopamine system, but human data are limited and mixed. OBJECTIVES Here, we sought to investigate sex differences in dopamine release after oral D-amphetamine administration. METHODS We used [18F]fallypride positron emission tomography (PET) to measure the change in dopamine D2/3 receptor availability (%ΔBPND, an index of dopamine release) between placebo and D-amphetamine sessions in two independent datasets containing a total of 39 females (on either hormonal birth control n = 18, postmenopausal n = 10, or studied in the first 10 days of their menstrual cycle n = 11) and 37 males. RESULTS Using both a priori anatomical regions of interest based on previous findings and voxelwise analyses, we failed to consistently detect broad sex differences in D-amphetamine-induced dopamine release. Nevertheless, there was limited evidence for greater right ventral striatal dopamine release in young adult males relative to similarly aged females, but this was not consistently observed across samples. Plasma estradiol did not correlate with dopamine release and this measure did not differ in females on and off hormonal birth control. CONCLUSIONS While our finding in young adults from one dataset of greater %ΔBPND in males is partially consistent with a previously published study on sex differences in D-amphetamine-induced dopamine release, our data do not support the presence of consistent widespread sex differences in this measure of dopamine release.
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Affiliation(s)
- Christopher T. Smith
- Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817,Corresponding Author:
| | - Linh C. Dang
- Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817
| | - Leah L. Burgess
- Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817
| | - Scott F. Perkins
- Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817
| | - M. Danica San Juan
- Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817
| | - Darcy K. Smith
- Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817
| | - Ronald L. Cowan
- Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817,Department of Psychiatry and Behavioral Sciences, Vanderbilt University Medical Center, 1601 23rd Ave South, Suite 3057, Nashville, TN, 37212,Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Medical Center North, 1161 21st Ave. South, Nashville, TN 37232 USA
| | - Nam T. Le
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Medical Center North, 1161 21st Ave. South, Nashville, TN 37232 USA
| | - Robert M. Kessler
- Department of Radiology, UAB School of Medicine, 1802 6th Ave South, Birmingham, AL 35233
| | | | - David H. Zald
- Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817,Department of Psychiatry and Behavioral Sciences, Vanderbilt University Medical Center, 1601 23rd Ave South, Suite 3057, Nashville, TN, 37212
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6
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Smith CT, San Juan MD, Dang LC, Katz DT, Perkins SF, Burgess LL, Cowan RL, Manning HC, Nickels ML, Claassen DO, Samanez-Larkin GR, Zald DH. Ventral striatal dopamine transporter availability is associated with lower trait motor impulsivity in healthy adults. Transl Psychiatry 2018; 8:269. [PMID: 30531858 PMCID: PMC6286354 DOI: 10.1038/s41398-018-0328-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 11/13/2018] [Accepted: 11/15/2018] [Indexed: 12/18/2022] Open
Abstract
Impulsivity is a transdiagnostic feature of a range of externalizing psychiatric disorders. Preclinical work links reduced ventral striatal dopamine transporter (DAT) availability with heightened impulsivity and novelty seeking. However, there is a lack of human data investigating the relationship between DAT availability, particularly in subregions of the striatum, and the personality traits of impulsivity and novelty seeking. Here we collected PET measures of DAT availability (BPND) using the tracer 18F-FE-PE2I in 47 healthy adult subjects and examined relations between BPND in striatum, including its subregions: caudate, putamen, and ventral striatum (VS), and trait impulsivity (Barratt Impulsiveness Scale: BIS-11) and novelty seeking (Tridimensional Personality Questionnaire: TPQ-NS), controlling for age and sex. DAT BPND in each striatal subregion showed nominal negative associations with total BIS-11 but not TPQ-NS. At the subscale level, VS DAT BPND was significantly associated with BIS-11 motor impulsivity (e.g., taking actions without thinking) after correction for multiple comparisons. VS DAT BPND explained 13.2% of the variance in motor impulsivity. Our data demonstrate that DAT availability in VS is negatively related to impulsivity and suggest a particular influence of DAT regulation of dopamine signaling in VS on acting without deliberation (BIS motor impulsivity). While needing replication, these data converge with models of ventral striatal functions that emphasize its role as a key interface linking motivation to action.
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Affiliation(s)
- Christopher T. Smith
- 0000 0001 2264 7217grid.152326.1Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817 USA
| | - M. Danica San Juan
- 0000 0001 2264 7217grid.152326.1Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817 USA
| | - Linh C. Dang
- 0000 0001 2264 7217grid.152326.1Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817 USA
| | - Daniel T. Katz
- 0000 0001 2264 7217grid.152326.1Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817 USA
| | - Scott F. Perkins
- 0000 0001 2264 7217grid.152326.1Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817 USA
| | - Leah L. Burgess
- 0000 0001 2264 7217grid.152326.1Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817 USA
| | - Ronald L. Cowan
- 0000 0001 2264 7217grid.152326.1Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817 USA ,0000 0004 1936 9916grid.412807.8Department of Psychiatry and Behavioral Sciences, Vanderbilt University Medical Center, 1601 23rd Avenue South, Suite 3057, Nashville, TN 37212 USA ,0000 0004 1936 9916grid.412807.8Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Medical Center North, 1161 21st Avenue South, Nashville, TN 37232 USA
| | - H. Charles Manning
- 0000 0004 1936 9916grid.412807.8Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Medical Center North, 1161 21st Avenue South, Nashville, TN 37232 USA ,0000 0001 2264 7217grid.152326.1Department of Chemistry, Vanderbilt University, 7330 Stevenson Center, Station B 351822, Nashville, TN 37235 USA ,0000 0001 2264 7217grid.152326.1Department of Biomedical Engineering, PMB 351826, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37235-1826 USA ,0000 0004 1936 9916grid.412807.8Department of Neurological Surgery, Vanderbilt University Medical Center, 1161 21st Avenue South, T4224 Medical Center North, Nashville, TN 37232-2380 USA
| | - Michael L. Nickels
- 0000 0004 1936 9916grid.412807.8Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Medical Center North, 1161 21st Avenue South, Nashville, TN 37232 USA
| | - Daniel O. Claassen
- 0000 0004 1936 9916grid.412807.8Department of Neurology, Vanderbilt University Medical Center, 1161 21st Avenue South, A-0118, Nashville, TN 37232-2551 USA
| | - Gregory R. Samanez-Larkin
- 0000 0004 1936 7961grid.26009.3dDepartment of Psychology and Neuroscience, Duke University, 417 Chapel Drive, Durham, NC 27708 USA
| | - David H. Zald
- 0000 0001 2264 7217grid.152326.1Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817 USA ,0000 0004 1936 9916grid.412807.8Department of Psychiatry and Behavioral Sciences, Vanderbilt University Medical Center, 1601 23rd Avenue South, Suite 3057, Nashville, TN 37212 USA
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7
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Seaman KL, Brooks N, Karrer TM, Castrellon JJ, Perkins SF, Dang LC, Hsu M, Zald DH, Samanez-Larkin GR. Subjective value representations during effort, probability and time discounting across adulthood. Soc Cogn Affect Neurosci 2018; 13:449-459. [PMID: 29618082 PMCID: PMC6007391 DOI: 10.1093/scan/nsy021] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 02/09/2018] [Accepted: 03/25/2018] [Indexed: 01/19/2023] Open
Abstract
Every day, humans make countless decisions that require the integration of information about potential benefits (i.e. rewards) with other decision features (i.e. effort required, probability of an outcome or time delays). Here, we examine the overlap and dissociation of behavioral preferences and neural representations of subjective value in the context of three different decision features (physical effort, probability and time delays) in a healthy adult life span sample. While undergoing functional neuroimaging, participants (N = 75) made incentive compatible choices between a smaller monetary reward with lower physical effort, higher probability, or a shorter time delay versus a larger monetary reward with higher physical effort, lower probability, or a longer time delay. Behavioral preferences were estimated from observed choices, and subjective values were computed using individual hyperbolic discount functions. We found that discount rates were uncorrelated across tasks. Despite this apparent behavioral dissociation between preferences, we found overlapping subjective value-related activity in the medial prefrontal cortex across all three tasks. We found no consistent evidence for age differences in either preferences or the neural representations of subjective value across adulthood. These results suggest that while the tolerance of decision features is behaviorally dissociable, subjective value signals share a common representation across adulthood.
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Affiliation(s)
- Kendra L Seaman
- Center for the Study of Aging and Human Development & Center for Cognitive Neuroscience, Duke University, Durham, NC 27708, USA
| | - Nickolas Brooks
- Department of Psychology, Yale University, New Haven, CT 06520, USA
| | - Teresa M Karrer
- Department of Psychology, Yale University, New Haven, CT 06520, USA
| | - Jaime J Castrellon
- Department of Psychology and Neuroscience, Duke University, Durham, NC 27708, USA
| | - Scott F Perkins
- Department of Psychology, Vanderbilt University, Nashville, TN 37240, USA
| | - Linh C Dang
- Department of Psychology, Vanderbilt University, Nashville, TN 37240, USA
| | - Ming Hsu
- Haas School of Business, University of California–Berkeley, Berkeley, CA 94720, USA
| | - David H Zald
- Department of Psychology, Vanderbilt University, Nashville, TN 37240, USA
| | - Gregory R Samanez-Larkin
- Department of Psychology and Neuroscience & Center for Cognitive Neuroscience, Duke University, Durham, NC 27708, USA
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8
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Smith CT, Dang LC, Buckholtz JW, Tetreault AM, Cowan RL, Kessler RM, Zald DH. The impact of common dopamine D2 receptor gene polymorphisms on D2/3 receptor availability: C957T as a key determinant in putamen and ventral striatum. Transl Psychiatry 2017; 7:e1091. [PMID: 28398340 PMCID: PMC5416688 DOI: 10.1038/tp.2017.45] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2016] [Revised: 12/02/2016] [Accepted: 01/17/2017] [Indexed: 12/20/2022] Open
Abstract
Dopamine function is broadly implicated in multiple neuropsychiatric conditions believed to have a genetic basis. Although a few positron emission tomography (PET) studies have investigated the impact of single-nucleotide polymorphisms (SNPs) in the dopamine D2 receptor gene (DRD2) on D2/3 receptor availability (binding potential, BPND), these studies have often been limited by small sample size. Furthermore, the most commonly studied SNP in D2/3 BPND (Taq1A) is not located in the DRD2 gene itself, suggesting that its linkage with other DRD2 SNPs may explain previous PET findings. Here, in the largest PET genetic study to date (n=84), we tested for effects of the C957T and -141C Ins/Del SNPs (located within DRD2) as well as Taq1A on BPND of the high-affinity D2 receptor tracer 18F-Fallypride. In a whole-brain voxelwise analysis, we found a positive linear effect of C957T T allele status on striatal BPND bilaterally. The multilocus genetic scores containing C957T and one or both of the other SNPs produced qualitatively similar striatal results to C957T alone. The number of C957T T alleles predicted BPND in anatomically defined putamen and ventral striatum (but not caudate) regions of interest, suggesting some regional specificity of effects in the striatum. By contrast, no significant effects arose in cortical regions. Taken together, our data support the critical role of C957T in striatal D2/3 receptor availability. This work has implications for a number of psychiatric conditions in which dopamine signaling and variation in C957T status have been implicated, including schizophrenia and substance use disorders.
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Affiliation(s)
- C T Smith
- Department of Psychology, Vanderbilt University, Nashville, TN, USA,Department of Psychology, Vanderbilt University, PMB 407817, 2301 Vanderbilt Place, Nashville, TN 37240-7817, USA. E-mail:
| | - L C Dang
- Department of Psychology, Vanderbilt University, Nashville, TN, USA
| | - J W Buckholtz
- Department of Psychology, Harvard University, Cambridge, MA, USA,Department of Psychiatry, Massachusetts General Hospital, Boston, MA, USA
| | - A M Tetreault
- Department of Psychology, Vanderbilt University, Nashville, TN, USA
| | - R L Cowan
- Department of Psychology, Vanderbilt University, Nashville, TN, USA,Department of Psychiatry, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - R M Kessler
- Department of Radiology, UAB School of Medicine, Birmingham, AL, USA
| | - D H Zald
- Department of Psychology, Vanderbilt University, Nashville, TN, USA,Department of Psychiatry, Vanderbilt University School of Medicine, Nashville, TN, USA
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9
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Dang LC, Castrellon JJ, Perkins SF, Le NT, Cowan RL, Zald DH, Samanez-Larkin GR. Reduced effects of age on dopamine D2 receptor levels in physically active adults. Neuroimage 2017; 148:123-129. [PMID: 28089678 DOI: 10.1016/j.neuroimage.2017.01.018] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [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: 10/13/2016] [Revised: 01/06/2017] [Accepted: 01/09/2017] [Indexed: 12/13/2022] Open
Abstract
Physical activity has been shown to ameliorate dopaminergic degeneration in non-human animal models. However, the effects of regular physical activity on normal age-related changes in dopamine function in humans are unknown. Here we present cross-sectional data from forty-four healthy human subjects between 23 and 80 years old, showing that typical age-related dopamine D2 receptor loss, assessed with PET [18F]fallypride, was significantly reduced in physically active adults compared to less active adults.
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Affiliation(s)
- Linh C Dang
- Department of Psychology, Vanderbilt University, 219 Wilson Hall, 111 21st Avenue South, Nashville, TN 37203, USA.
| | - Jaime J Castrellon
- Department of Psychology, Vanderbilt University, 219 Wilson Hall, 111 21st Avenue South, Nashville, TN 37203, USA
| | - Scott F Perkins
- Department of Psychology, Vanderbilt University, 219 Wilson Hall, 111 21st Avenue South, Nashville, TN 37203, USA
| | - Nam T Le
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1211 Medical Center Drive, Nashville, TN 37232, USA
| | - Ronald L Cowan
- Department of Psychiatry, Vanderbilt University School of Medicine, 1601 23rd Ave South, Nashville, TN 37212, USA; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1211 Medical Center Drive, Nashville, TN 37232, USA
| | - David H Zald
- Department of Psychology, Vanderbilt University, 219 Wilson Hall, 111 21st Avenue South, Nashville, TN 37203, USA; Department of Psychiatry, Vanderbilt University School of Medicine, 1601 23rd Ave South, Nashville, TN 37212, USA
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Dang LC, Samanez-Larkin GR, Castrellon JJ, Perkins SF, Cowan RL, Zald DH. Associations between dopamine D2 receptor availability and BMI depend on age. Neuroimage 2016; 138:176-183. [PMID: 27208860 DOI: 10.1016/j.neuroimage.2016.05.044] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [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: 03/21/2016] [Revised: 05/04/2016] [Accepted: 05/17/2016] [Indexed: 10/21/2022] Open
Abstract
OBJECTIVE The dopamine D2/3 receptor subtypes (DRD2/3) are the most widely studied neurotransmitter biomarker in research on obesity, but results to date have been inconsistent, have typically involved small samples, and have rarely accounted for subjects' ages despite the large impact of age on DRD2/3 levels. We aimed to clarify the relation between DRD2/3 availability and BMI by examining this association in a large sample of subjects with BMI spanning the continuum from underweight to extremely obese. SUBJECTS 130 healthy subjects between 18 and 81years old underwent PET with [18F]fallypride, a high affinity DRD2/3 ligand. RESULTS As expected, DRD2/3 availability declined with age. Critically, age significantly interacted with DRD2/3 availability in predicting BMI in the midbrain and striatal regions (caudate, putamen, and ventral striatum). Among subjects under 30years old, BMI was not associated with DRD2/3 availability. By contrast, among subjects over 30years old, BMI was positively associated with DRD2/3 availability in the midbrain, putamen, and ventral striatum. CONCLUSION The present results are incompatible with the prominent dopaminergic hypofunction hypothesis that proposes that a reduction in DRD2/3 availability is associated with increased BMI, and highlights the importance of age in assessing correlates of DRD2/3 function.
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Affiliation(s)
- Linh C Dang
- Department of Psychology, Vanderbilt University, 219 Wilson Hall, 111 21st Avenue South, Nashville, TN 37203, USA.
| | | | - Jaime J Castrellon
- Department of Psychology, Vanderbilt University, 219 Wilson Hall, 111 21st Avenue South, Nashville, TN 37203, USA
| | - Scott F Perkins
- Department of Psychology, Vanderbilt University, 219 Wilson Hall, 111 21st Avenue South, Nashville, TN 37203, USA
| | - Ronald L Cowan
- Department of Psychiatry, Vanderbilt University School of Medicine, 1601 23rd Ave South, Nashville, TN 37212, USA; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1211 Medical Center Drive, Nashville, TN 37232, USA
| | - David H Zald
- Department of Psychology, Vanderbilt University, 219 Wilson Hall, 111 21st Avenue South, Nashville, TN 37203, USA; Department of Psychiatry, Vanderbilt University School of Medicine, 1601 23rd Ave South, Nashville, TN 37212, USA
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Smith CT, Dang LC, Cowan RL, Kessler RM, Zald DH. Variability in paralimbic dopamine signaling correlates with subjective responses to d-amphetamine. Neuropharmacology 2016; 108:394-402. [PMID: 27174408 DOI: 10.1016/j.neuropharm.2016.05.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [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: 10/18/2015] [Revised: 04/26/2016] [Accepted: 05/06/2016] [Indexed: 12/14/2022]
Abstract
Subjective responses to psychostimulants vary, the basis of which is poorly understood, especially in relation to possible cortical contributions. Here, we tested for relationships between participants' positive subjective responses to oral d-amphetamine (dAMPH) versus placebo and variability in striatal and extrastriatal dopamine (DA) receptor availability and release, measured via positron emission tomography (PET) with the radiotracer (18)F-fallypride. Analyses focused on 35 healthy adult participants showing positive subjective effects to dAMPH measured via the Drug Effects Questionnaire (DEQ) Feel, Like, High, and Want More subscales (Responders), and were repeated after inclusion of 11 subjects who lacked subjective responses. Associations between peak DEQ subscale ratings and both baseline (18)F-fallypride binding potential (BPnd; an index of D2/D3 receptor availability) and the percentage change in BPnd post dAMPH (%ΔBPnd; a measure of DA release) were assessed. Baseline BPnd in ventromedial prefrontal cortex (vmPFC) predicted the peak level of High reported following dAMPH. Furthermore, %ΔBPnd in vmPFC positively correlated with DEQ Want More ratings. DEQ Want More was also positively correlated with %ΔBPnd in right ventral striatum and left insula. This work indicates that characteristics of DA functioning in vmPFC, a cortical area implicated in subjective valuation, are associated with both subjective high and incentive (wanting) responses. The observation that insula %ΔBPnd was associated with drug wanting converges with evidence suggesting its role in drug craving. These findings highlight the importance of variability in DA signaling in specific paralimbic cortical regions in dAMPH's subjective response, which may confer risk for abusing psychostimulants.
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Affiliation(s)
- Christopher T Smith
- Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817, United States.
| | - Linh C Dang
- Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817, United States
| | - Ronald L Cowan
- Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817, United States; Department of Psychiatry, Vanderbilt University School of Medicine, 1601 23rd Ave South, Suite 3057, Nashville, TN 37212, United States
| | | | - David H Zald
- Department of Psychology, PMB 407817, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37240-7817, United States; Department of Psychiatry, Vanderbilt University School of Medicine, 1601 23rd Ave South, Suite 3057, Nashville, TN 37212, United States
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12
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Smith CT, Wallace DL, Dang LC, Aarts E, Jagust WJ, D'Esposito M, Boettiger CA. Modulation of impulsivity and reward sensitivity in intertemporal choice by striatal and midbrain dopamine synthesis in healthy adults. J Neurophysiol 2016; 115:1146-56. [PMID: 26683066 PMCID: PMC4808128 DOI: 10.1152/jn.00261.2015] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [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: 03/16/2015] [Accepted: 12/15/2015] [Indexed: 01/12/2023] Open
Abstract
Converging evidence links individual differences in mesolimbic and mesocortical dopamine (DA) to variation in the tendency to choose immediate rewards ("Now") over larger, delayed rewards ("Later"), or "Now bias." However, to date, no study of healthy young adults has evaluated the relationship between Now bias and DA with positron emission tomography (PET). Sixteen healthy adults (ages 24-34 yr; 50% women) completed a delay-discounting task that quantified aspects of intertemporal reward choice, including Now bias and reward magnitude sensitivity. Participants also underwent PET scanning with 6-[(18)F]fluoro-l-m-tyrosine (FMT), a radiotracer that measures DA synthesis capacity. Lower putamen FMT signal predicted elevated Now bias, a more rapidly declining discount rate with increasing delay time, and reduced willingness to accept low-interest-rate delayed rewards. In contrast, lower FMT signal in the midbrain predicted greater sensitivity to increasing magnitude of the Later reward. These data demonstrate that intertemporal reward choice in healthy humans varies with region-specific measures of DA processing, with regionally distinct associations with sensitivity to delay and to reward magnitude.
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Affiliation(s)
- Christopher T. Smith
- 1Neurobiology Curriculum, University of North Carolina, Chapel Hill, North Carolina;
| | - Deanna L. Wallace
- 2Helen Wills Neuroscience Institute, University of California, Berkeley, California;
| | - Linh C. Dang
- 2Helen Wills Neuroscience Institute, University of California, Berkeley, California; ,3Lawrence Berkeley National Laboratory, Berkeley, California;
| | - Esther Aarts
- 2Helen Wills Neuroscience Institute, University of California, Berkeley, California; ,4Centre for Cognitive Neuroimaging, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands; and
| | - William J. Jagust
- 2Helen Wills Neuroscience Institute, University of California, Berkeley, California; ,3Lawrence Berkeley National Laboratory, Berkeley, California;
| | - Mark D'Esposito
- 2Helen Wills Neuroscience Institute, University of California, Berkeley, California;
| | - Charlotte A. Boettiger
- 1Neurobiology Curriculum, University of North Carolina, Chapel Hill, North Carolina; ,5Department of Psychology & Neuroscience, Bowles Center for Alcohol Studies, and Biomedical Research Imaging Center, University of North Carolina, Chapel Hill, North Carolina
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13
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Wallace DL, Aarts E, d'Oleire Uquillas F, Dang LC, Greer SM, Jagust WJ, D'Esposito M. Genotype status of the dopamine-related catechol-O-methyltransferase (COMT) gene corresponds with desirability of "unhealthy" foods. Appetite 2015; 92:74-80. [PMID: 25963102 DOI: 10.1016/j.appet.2015.05.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [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: 12/08/2014] [Revised: 04/07/2015] [Accepted: 05/06/2015] [Indexed: 10/23/2022]
Abstract
The role of dopamine is extensively documented in weight regulation and food intake in both animal models and humans. Yet the role of dopamine has not been well studied in individual differences for food desirability. Genotype status of the dopamine-related catechol-O-methyltransferase (COMT) gene has been shown to influence dopamine levels, with greater COMT enzymatic activity in val/val individuals corresponding to greater degradation of dopamine. Decreased dopamine has been associated with poorer cognitive control and diminished goal-directed behavior in various behavioral paradigms. Additionally, dopaminergic-rich regions such as the frontal cortex and dorsal striatum have been shown to be important for supporting food-related decision-making. However, the role of dopamine, as assessed by COMT genotype status, in food desirability has not been fully explored. Therefore, we utilized an individual's COMT genotype status (n = 61) and investigated food desirability based on self-rated "healthy" and "unhealthy" food perceptions. Here we found val/val individuals (n = 19) have greater desirability for self-rated "unhealthy" food items, but not self-rated "healthy" food items, as compared to val/met (n = 24) and met/met (n = 18) individuals (p < 0.005). Utilizing an objective health measure for the food items, we also found val/val and val/met individuals have greater desirability for objectively defined "unhealthy" food items, as compared to met/met individuals (p < 0.01). This work further substantiates the role of dopamine in food-related behaviors and more specifically in relationship to food desirability for "unhealthy" food items.
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Affiliation(s)
- Deanna L Wallace
- Helen Wills Neuroscience Institute, University of California, 132 Barker Hall, Berkeley, CA 94720-3190, USA; Department of Neurosurgery, University of California, 675 Nelson Rising Lane, San Francisco, CA, 94143, USA.
| | - Esther Aarts
- Donders Institute for Brain, Cognition and Behaviour, Radboud University, Kapittelweg 29, room 0.56, 6525 EN Nijmegen, The Netherlands
| | - Federico d'Oleire Uquillas
- Helen Wills Neuroscience Institute, University of California, 132 Barker Hall, Berkeley, CA 94720-3190, USA
| | - Linh C Dang
- Department of Psychology, Vanderbilt University, 219 Wilson Hall, 111 21st Avenue, Nashville, TN 37203, USA
| | - Stephanie M Greer
- Helen Wills Neuroscience Institute, University of California, 132 Barker Hall, Berkeley, CA 94720-3190, USA
| | - William J Jagust
- Helen Wills Neuroscience Institute, University of California, 132 Barker Hall, Berkeley, CA 94720-3190, USA
| | - Mark D'Esposito
- Helen Wills Neuroscience Institute, University of California, 132 Barker Hall, Berkeley, CA 94720-3190, USA
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14
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Dang LC, Samanez-Larkin GR, Young JS, Cowan RL, Kessler RM, Zald DH. Caudate asymmetry is related to attentional impulsivity and an objective measure of ADHD-like attentional problems in healthy adults. Brain Struct Funct 2014; 221:277-86. [PMID: 25269835 DOI: 10.1007/s00429-014-0906-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [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: 12/10/2013] [Accepted: 09/24/2014] [Indexed: 10/24/2022]
Abstract
Case-control studies comparing ADHD with typically developing individuals suggest that anatomical asymmetry of the caudate nucleus is a marker of attention deficit hyperactivity disorder (ADHD). However, there is no consensus on whether the asymmetry favors the right or left caudate nucleus in ADHD, or whether the asymmetry is increased or decreased in ADHD. The current study aimed to clarify this relationship by applying a dimensional approach to assessing ADHD symptoms that, instead of relying on clinical classification, utilizes the natural behavioral continuum of traits related to ADHD. Structural T1-weighted MRI was collected from 71 adults between 18 and 35 years and analyzed for caudate asymmetry. ADHD-like attentional symptoms were assessed with an objective measure of attentional problems, the ADHD score from the Test of Variables of Attention (TOVA). Impulsivity, a core feature in ADHD, was measured using the Barratt Impulsiveness Scale, a self-report measure that assesses attentional, non-planning, and motor features of impulsivity. We found that larger right relative to left caudate volumes correlated with both higher attentional impulsiveness and worse ADHD scores on the TOVA. Higher attentional impulsiveness also correlated with worse ADHD scores, establishing coherence between the objective measure and the self-report measure of attentional problems. These results suggest that a differential passage of information through frontal-striatal networks may produce instability leading to attentional problems. The findings also demonstrate the utility of a dimensional approach to understanding structural correlates of ADHD symptoms.
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Affiliation(s)
- Linh C Dang
- Department of Psychology, Vanderbilt University, 219 Wilson Hall, 111 21st Avenue South, Nashville, TN, 37203, USA.
| | | | - Jacob S Young
- Department of Psychology, Vanderbilt University, 219 Wilson Hall, 111 21st Avenue South, Nashville, TN, 37203, USA
| | - Ronald L Cowan
- Department of Psychiatry, Vanderbilt University School of Medicine, 1601 23rd Ave South, Nashville, TN, 37212, USA.,Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1211 Medical Center Drive, Nashville, TN, 37232, USA
| | - Robert M Kessler
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1211 Medical Center Drive, Nashville, TN, 37232, USA
| | - David H Zald
- Department of Psychology, Vanderbilt University, 219 Wilson Hall, 111 21st Avenue South, Nashville, TN, 37203, USA.,Department of Psychiatry, Vanderbilt University School of Medicine, 1601 23rd Ave South, Nashville, TN, 37212, USA
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15
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Wallace DL, Aarts E, Dang LC, Greer SM, Jagust WJ, D′Esposito M. Dorsal striatal dopamine, food preference and health perception in humans. PLoS One 2014; 9:e96319. [PMID: 24806534 PMCID: PMC4012945 DOI: 10.1371/journal.pone.0096319] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 04/06/2014] [Indexed: 12/01/2022] Open
Abstract
To date, few studies have explored the neurochemical mechanisms supporting individual differences in food preference in humans. Here we investigate how dorsal striatal dopamine, as measured by the positron emission tomography (PET) tracer [18F]fluorometatyrosine (FMT), correlates with food-related decision-making, as well as body mass index (BMI) in 16 healthy-weight to moderately obese individuals. We find that lower PET FMT dopamine synthesis binding potential correlates with higher BMI, greater preference for perceived “healthy” foods, but also greater healthiness ratings for food items. These findings further substantiate the role of dorsal striatal dopamine in food-related behaviors and shed light on the complexity of individual differences in food preference.
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Affiliation(s)
- Deanna L. Wallace
- Helen Wills Neuroscience Institute, University of California, Berkeley, California, United States of America
- * E-mail: .
| | - Esther Aarts
- Helen Wills Neuroscience Institute, University of California, Berkeley, California, United States of America
- Center for Cognitive Neuroimaging, Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, The Netherlands
| | - Linh C. Dang
- Helen Wills Neuroscience Institute, University of California, Berkeley, California, United States of America
- Department of Psychology, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Stephanie M. Greer
- Helen Wills Neuroscience Institute, University of California, Berkeley, California, United States of America
| | - William J. Jagust
- Helen Wills Neuroscience Institute, University of California, Berkeley, California, United States of America
| | - Mark D′Esposito
- Helen Wills Neuroscience Institute, University of California, Berkeley, California, United States of America
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16
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Abstract
It is often assumed that the promise of a monetary bonus improves cognitive control. We show that in fact appetitive motivation can also impair cognitive control, depending on baseline levels of dopamine-synthesis capacity in the striatum. These data not only demonstrate that appetitive motivation can have paradoxical detrimental effects for cognitive control but also provide a mechanistic account of these effects.
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Affiliation(s)
- Esther Aarts
- 1Helen Wills Neuroscience Institute, University of California, Berkeley
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17
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Dang LC, O'Neil JP, Jagust WJ. Genetic effects on behavior are mediated by neurotransmitters and large-scale neural networks. Neuroimage 2012; 66:203-14. [PMID: 23142068 DOI: 10.1016/j.neuroimage.2012.10.090] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [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: 03/15/2012] [Revised: 10/01/2012] [Accepted: 10/26/2012] [Indexed: 11/17/2022] Open
Abstract
Claims of gene-behavior associations are complex and sometimes difficult to replicate because these relationships involve many downstream endogenous and environmental processes that mediate genetic effects. Knowing these mediating processes is critical to understanding the links between genes and behavior and how these factors differ between people. We identified and characterized the effects of a gene on neurochemistry and neural networks to elucidate the mechanism, at the systems level, whereby genes influence cognition. Catechol-O-methyltransferase (COMT) degrades dopamine in the prefrontal cortex (PFC) and is polymorphic with alleles differing in enzymatic activity. We found that COMT genotype determined dopamine synthesis, such that individuals with greater COMT activity synthesized more dopamine. Dopamine synthesis in the midbrain and ventral striatum affected functional connectivity in the default mode network, likely through the mesocorticolimbic pathway, in an inverted-U pattern with greater functional connectivity in medial PFC associated with intermediate levels of COMT activity and dopamine. Greater functional connectivity correlated with greater deactivation during performance of a set-shifting task that engaged the PFC. Greater deactivation was in turn associated with better performance. The integration of these results yields a model whereby COMT affects prefrontal function by a mechanism involving dopaminergic modulation of the default mode network. The model features the well-known inverted-U function between dopamine and performance and supports the hypothesis that dopamine and the default mode network shift attentional resources to influence prefrontal cognition.
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Affiliation(s)
- Linh C Dang
- Helen Wills Neuroscience Institute, University of California, Berkeley, 132 Barker Hall #3190, Berkeley, CA 94720-3190, USA; Lawrence Berkeley National Laboratory, 1 Cyclotron Road 55R0121, Berkeley, CA 94720-8119, USA.
| | - James P O'Neil
- Lawrence Berkeley National Laboratory, 1 Cyclotron Road 55R0121, Berkeley, CA 94720-8119, USA.
| | - William J Jagust
- Helen Wills Neuroscience Institute, University of California, Berkeley, 132 Barker Hall #3190, Berkeley, CA 94720-3190, USA; Lawrence Berkeley National Laboratory, 1 Cyclotron Road 55R0121, Berkeley, CA 94720-8119, USA; School of Public Health, University of California, Berkeley, USA.
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18
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Dang LC, Donde A, Madison C, O'Neil JP, Jagust WJ. Striatal dopamine influences the default mode network to affect shifting between object features. J Cogn Neurosci 2012; 24:1960-70. [PMID: 22640392 DOI: 10.1162/jocn_a_00252] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Cognitive flexibility or the ability to change behavior in response to external cues is conceptualized as two processes: one for shifting between perceptual features of objects and another for shifting between the abstract rules governing the selection of these objects. Object and rule shifts are believed to engage distinct anatomical structures and functional processes. Dopamine activity has been associated with cognitive flexibility, but patients with dopaminergic deficits are not impaired on all tasks assessing cognitive flexibility, suggesting that dopamine may have different roles in the shifting of objects and rules. The goals of this study were to identify brain regions supporting object and rule shifts and to examine the role of dopamine in modulating these two forms of cognitive flexibility. Sixteen young, healthy volunteers underwent fMRI while performing a set-shift task designed to differentiate shifting between object features from shifting between abstract task rules. Participants also underwent PET with 6-[¹⁸F]-fluoro-l-m-tyrosine (FMT), a radiotracer measuring dopamine synthesis capacity. Shifts of abstract rules were not associated with activation in any brain region, and FMT uptake did not correlate with rule shift performance. Shifting between object features deactivated the medial PFC and the posterior cingulate and activated the lateral PFC, posterior parietal areas, and the striatum. FMT signal in the striatum correlated negatively with object shift performance and deactivation in the medial PFC, a component of the default mode network, suggesting that dopamine influences object shifts via modulation of activity in the default mode network.
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Affiliation(s)
- Linh C Dang
- University of California, Berkeley, CA, USA.
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19
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Abstract
A critical step in the signal-induced activation of the transcription factor NF-kappaB is the site-specific phosphorylation of its inhibitor, IkappaB, that targets the latter for degradation by the ubiquitin-proteasome pathway. We have previously shown that mitogen-activated protein kinase/ERK kinase kinase 1 (MEKK1) can induce both this site-specific phosphorylation of IkappaB alpha at Ser-32 and Ser-36 in vivo and the activity of a high molecular weight IkappaB kinase complex in vitro. Subsequently, others have identified two proteins, IkappaB kinase alpha (IKK-alpha) and IkappaB kinase beta (IKK-beta), that are present in a tumor necrosis factor alpha-inducible, high molecular weight IkappaB kinase complex. These kinases are believed to directly phosphorylate IkappaB based on the examination of the kinase activities of IKK immunoprecipitates, but more rigorous proof of this has yet to be demonstrated. We show herein that recombinant IKK-alpha and IKK-beta can, in fact, directly phosphorylate IkappaB alpha at Ser-32 and Ser-36, as well as homologous residues in IkappaB beta in vitro, and thus are bona fide IkappaB kinases. We also show that MEKK1 can induce the activation of both IKK-alpha and IKK-beta in vivo. Finally, we show that IKK-alpha is present in the MEKK1-inducible, high molecular weight IkappaB kinase complex and treatment of this complex with MEKK1 induces phosphorylation of IKK-alpha in vitro. We conclude that IKK-alpha and IKK-beta can mediate the NF-kappaB-inducing activity of MEKK1.
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Affiliation(s)
- F S Lee
- Department of Molecular and Cellular Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA 02138, USA
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20
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Dang LC, Melandri FD, Stein RL. Kinetic and mechanistic studies on the hydrolysis of ubiquitin C-terminal 7-amido-4-methylcoumarin by deubiquitinating enzymes. Biochemistry 1998; 37:1868-79. [PMID: 9485312 DOI: 10.1021/bi9723360] [Citation(s) in RCA: 196] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Deubiquitinating enzymes constitute a family of cysteine hydrolases that specifically cleave ubiquitin-derived substrates of general structure Ub-X, where X can be any number of leaving groups ranging from small thiols and amines to Ub and other proteins (Ub, ubiquitin). We have developed a general assay for deubiquitinating enzymes based on the substrate ubiquitin C-terminal 7-amido-4-methylcoumarin (Ub-AMC). Ub-AMC is efficiently hydrolyzed with liberation of highly fluorescent AMC by two rabbit reticulocyte deubiquitinating enzymes: isopeptidase T (IPaseT), a member of the gene family of ubiquitin-specific processing enzymes, and UCH-L3, a member of the family of ubiquitin C-terminal hydrolases. We used this new assay to probe kinetic and mechanistic aspects of catalysis by IPaseT and UCH-L3. Results from four series of experiments are discussed: (1) For UCH-L3, we determined steady-state kinetic parameters that suggest a diffusion-limited reaction of UCH-L3 with Ub-AMC. To probe this, we determined the viscosity dependence of kc/Km, as well as kc. We found complex viscosity dependencies and interpreted these in the context of a model in which association and acylation are viscosity-dependent but deacylation is viscosity-independent. (2) The kinetics of inhibition of UCH-L3 by ubiquitin C-terminal aldehyde (Ub-H) were determined and reveal a Ki that is less than 10(-14) M. Several mechanisms are considered to account for the extreme inhibition. (3) The IPaseT-catalyzed hydrolysis of Ub-AMC is modulated by Ub with activation at low [Ub] and inhibition at high [Ub]. (4) Finally, we compare kc/Km values for deubiquitinating enzyme-catalyzed hydrolysis of Ub-AMC and Z-Leu-Arg-Gly-Gly-AMC. For IPaseT, the ratio of rate constants is 10(4), while for UCH-L3 this ratio is > 10(7). These results suggest the following: (i) Deubiquitinating enzymes are able to utilize the free energy that is released from remote interactions with Ub-containing substrates for stabilization of catalytic transition states, and (ii) UCHs are more efficient at utilizing the energy from these interactions, presumably because they do not possess a binding domain for a Ub "leaving group".
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Affiliation(s)
- L C Dang
- ProScript, Inc., Cambridge, Massachusetts 02139, USA
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21
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Dang LC, Talanian RV, Banach D, Hackett MC, Gilmore JL, Hays SJ, Mankovich JA, Brady KD. Preparation of an autolysis-resistant interleukin-1 beta converting enzyme mutant. Biochemistry 1996; 35:14910-6. [PMID: 8942655 DOI: 10.1021/bi9617771] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We describe the expression, purification, and characterization of human interleukin-1 beta converting enzyme (ICE) containing an affinity tag and modified to resist autoproteolysis. The point mutation Asp381 to Glu was added to eliminate the major site of autolytic degradation while maintaining catalytic activity, and an N-terminal polyhistidine tag was added in place of the ICE pro-region to facilitate purification. N-His (D381E) ICE was expressed in Escherichia coli and purified by nickel-chelating Sepharose and size-exclusion chromatography (SEC). The enzyme was stabilized greater than 80-fold against autolytic degradation relative to wild-type N-His ICE. SDS-PAGE analysis with silver-staining revealed no impurities, and 85% of the protein was catalytically active as determined by titration with a novel titrant, PD 163594 (3-[2-(2-benzyloxycarbonylamino-3-methylbutyrylamino)prop ionylamino]-4- oxo-5-(2-oxo-2H-chromen-7-yloxypentanoic acid). An oxidized adduct of ICE with glutathione, formed by disulfide rearrangement with oxidized glutathione to inhibit and stabilize the enzyme during purification, was rapidly reduced upon exposure to 5 mM DTT. One mole of glutathione was released per mole of active enzyme. Of the nine cysteines in ICE, eight were present in their reduced form in the glutathione adduct. N-His (D381E) ICE cleaved Ac-YVAD-Amc with the Michaelis-Menten parameters K(M) = 14 microM and Kcat = 0.7 s-1, values essentially identical to those reported for enzyme from natural sources.
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Affiliation(s)
- L C Dang
- BASF Bioresearch Corporation, Worcester, Massachusetts 01605, USA
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Talanian RV, Dang LC, Ferenz CR, Hackett MC, Mankovich JA, Welch JP, Wong WW, Brady KD. Stability and oligomeric equilibria of refolded interleukin-1beta converting enzyme. J Biol Chem 1996; 271:21853-8. [PMID: 8702986 DOI: 10.1074/jbc.271.36.21853] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
We report the preparation and characterization of interleukin-1beta converting enzyme (ICE) refolded from its p20 and p10 protein fragments. Refolded ICE heterodimer (p20p10) was catalytically active but unstable, and in size exclusion chromatography eluted at an apparent molecular mass of 30 kDa. The mechanisms of the observed instability were pH-dependent dissociation at low enzyme concentrations, and autolytic degradation of the p10 subunit at high concentrations. Binding and subsequent removal of a high affinity peptidic inhibitor increased the apparent molecular mass to 43 kDa (by size exclusion chromatography), and significantly increased its stability and specific activity. Chemical cross-linking and SDS-polyacrylamide gel electrophoresis analysis of the 43-kDa size exclusion chromatography conformer revealed a 60-kDa species, which was absent in the 30-kDa conformer, suggesting that inhibitor binding caused formation of a (p20p10)2 homodimer. The observation of a reversible equilibrium between ICE (p20p10) and (p20p10)2 suggests that analogous associations, possibly between ICE and ICE homologs, can occur in vivo, resulting in novel oligomeric protease species.
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Affiliation(s)
- R V Talanian
- BASF Bioresearch Corporation, Worcester, Massachusetts 01605, USA
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Walker NP, Talanian RV, Brady KD, Dang LC, Bump NJ, Ferenz CR, Franklin S, Ghayur T, Hackett MC, Hammill LD. Crystal structure of the cysteine protease interleukin-1 beta-converting enzyme: a (p20/p10)2 homodimer. Cell 1994; 78:343-52. [PMID: 8044845 DOI: 10.1016/0092-8674(94)90303-4] [Citation(s) in RCA: 421] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Interleukin-1 beta-converting enzyme (ICE) proteolytically cleaves pro-IL-1 beta to its mature, active form. The crystal structure at 2.5 A resolution of a recombinant human ICE-tetrapeptide chloromethylketone complex reveals that the holoenzyme is a homodimer of catalytic domains, each of which contains a p20 and a p10 subunit. The spatial separation of the C-terminus of p20 and the N-terminus of p10 in each domain suggests two alternative pathways of assembly and activation in vivo. ICE is homologous to the C. elegans cell death gene product, CED-3, and these may represent a novel class of cytoplasmic cysteine proteases that are important in programmed cell death (apoptosis). Conservation among members of the ICE/CED-3 family of the amino acids that form the active site region of ICE supports the hypothesis that they share functional similarities.
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Affiliation(s)
- N P Walker
- BASF Aktiengesellschaft, Main Laboratory, Ludwigshafen, Federal Republic of Germany
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