Naltrexone has been shown to attenuate craving and the subjective effects of methamphetamine. Alt... more Naltrexone has been shown to attenuate craving and the subjective effects of methamphetamine. Although naltrexone has modulatory effects on neural activity at dopaminergic synapses, the effect on striatal connectivity is unclear. As methamphetamine use is associated with greater resting-state functional connectivity (RSFC) in the dopaminergic system, we examined whether extended-release naltrexone (XR-NTX) can normalize striatal connectivity and whether changes in RSFC are associated with changes in craving and methamphetamine use. Thirty-seven participants in or seeking treatment for methamphetamine use disorder took part in this clinical trial at a university-based research clinic between May 2013 and March 2015 (Clinicaltrials.gov NCT01822132). Participants were randomized by a random number generator to a single four-week injection of XR-NTX or placebo. Functional magnetic resonance imaging (fMRI) and self-reported measures of craving and methamphetamine use were conducted befor...
We identified brain regions sensitive to variation in the magnitude of reward characteristics wit... more We identified brain regions sensitive to variation in the magnitude of reward characteristics with amplitude-modulated regression. The amplitude modulated predictors are significant if the hemodynamic response function scales with P, D, or M. We examined the resultant statistical maps for: Regions that responded to only one stimulus characteristic. Regions that responded to all three characteristics. Regions that differed between the subject groups.
Journal of Clinical and Experimental Neuropsychology, 2021
ABSTRACT Objective To evaluate whether cognitive performance in adults with active methamphetamin... more ABSTRACT Objective To evaluate whether cognitive performance in adults with active methamphetamine use (MA-ACT) differs from cognitive performance in adults in remission from MA use disorder (MA-REM) and adults without a history of substance use disorder (CTLs). Method MA-ACT (n = 36), MA-REM (n = 48), and CTLs (n = 62) completed the Neuropsychological Assessment Battery (NAB). Results The MA-ACT group did not perform significantly worse than CTLs on any NAB Index. The MA-REM group performed significantly (p < 0.050) worse than CTLs on the NAB Memory Index. The MA-ACT group performed significantly better than CTLs and the MA-REM group on the Executive Functions Index. Conclusions Some cognitive deficits are apparent during remission from MA use, but not during active use; this may result in clinical challenges for adults attempting to maintain recovery and continue with treatment.
Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive neuromodulation approach to ... more Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive neuromodulation approach to psychiatric treatment that is FDA approved for the management of major depressive disorder (MDD) and obsessive compulsive disorder (OCD). Standard TMS appears to exert biological effects by inducing current in the cortex more shallowly than deep TMS (dTMS); it may be that this modality of treatment differs from standard TMS. Given the potential difference in the manner in which dTMS stimulates the targeted brain regions, it is reasonable to review and summarize the various off-label and experimental applications of this variation of TMS. Deep TMS has demonstrated promise in treating mood disorders including bipolar depression and PTSD, but it is clear that more work is needed to clarify the utility of dTMS compared with rTMS. Future work may help delineate the role dTMS plays in addressing a wide spectrum of psychiatric illnesses. In addition, direct fundamental work is needed to characterize any effectiveness of dTMS in schizophrenia, anxiety, and autism spectrum disorder. Overall, neuromodulation holds promise for treating a variety of psychiatric conditions but more extensive works aimed at understanding the mechanisms and applicability are sorely needed. Continued efforts in understanding the unique application of dTMS may pave the way for future methodologies that could enhance treatment options for both mood and thought disorder.
Hepatitis C virus-infected (HCV+) adults evidence increased rates of psychiatric and cognitive di... more Hepatitis C virus-infected (HCV+) adults evidence increased rates of psychiatric and cognitive difficulties. This is the first study to use functional magnetic resonance imaging (fMRI) to examine brain activation in untreated HCV+ adults. To determine whether, relative to non-infected controls (CTLs), HCV+ adults exhibit differences in brain activation during a delay discounting task (DDT), a measure of one's tendency to choose smaller immediate rewards over larger delayed rewards-one aspect of impulsivity. Twenty adults with HCV and 26 CTLs completed an fMRI protocol during the DDT. Mixed effects regression analyses of hard versus easy trials of the DDT showed that, compared with CTLs, the HCV+ group exhibited less activation in the left lateral occipital gyrus, precuneus, and superior frontal gyrus. There were also significant interactive effects for hard-easy contrasts in the bilateral medial frontal gyrus, left insula, left precuneus, left inferior parietal lobule, and right...
Naltrexone has been shown to attenuate craving and the subjective effects of methamphetamine. Alt... more Naltrexone has been shown to attenuate craving and the subjective effects of methamphetamine. Although naltrexone has modulatory effects on neural activity at dopaminergic synapses, the effect on striatal connectivity is unclear. As methamphetamine use is associated with greater resting-state functional connectivity (RSFC) in the dopaminergic system, we examined whether extended-release naltrexone (XR-NTX) can normalize striatal connectivity and whether changes in RSFC are associated with changes in craving and methamphetamine use. Thirty-seven participants in or seeking treatment for methamphetamine use disorder took part in this clinical trial at a university-based research clinic between May 2013 and March 2015 (Clinicaltrials.gov NCT01822132). Participants were randomized by a random number generator to a single four-week injection of XR-NTX or placebo. Functional magnetic resonance imaging (fMRI) and self-reported measures of craving and methamphetamine use were conducted befor...
We identified brain regions sensitive to variation in the magnitude of reward characteristics wit... more We identified brain regions sensitive to variation in the magnitude of reward characteristics with amplitude-modulated regression. The amplitude modulated predictors are significant if the hemodynamic response function scales with P, D, or M. We examined the resultant statistical maps for: Regions that responded to only one stimulus characteristic. Regions that responded to all three characteristics. Regions that differed between the subject groups.
Journal of Clinical and Experimental Neuropsychology, 2021
ABSTRACT Objective To evaluate whether cognitive performance in adults with active methamphetamin... more ABSTRACT Objective To evaluate whether cognitive performance in adults with active methamphetamine use (MA-ACT) differs from cognitive performance in adults in remission from MA use disorder (MA-REM) and adults without a history of substance use disorder (CTLs). Method MA-ACT (n = 36), MA-REM (n = 48), and CTLs (n = 62) completed the Neuropsychological Assessment Battery (NAB). Results The MA-ACT group did not perform significantly worse than CTLs on any NAB Index. The MA-REM group performed significantly (p < 0.050) worse than CTLs on the NAB Memory Index. The MA-ACT group performed significantly better than CTLs and the MA-REM group on the Executive Functions Index. Conclusions Some cognitive deficits are apparent during remission from MA use, but not during active use; this may result in clinical challenges for adults attempting to maintain recovery and continue with treatment.
Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive neuromodulation approach to ... more Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive neuromodulation approach to psychiatric treatment that is FDA approved for the management of major depressive disorder (MDD) and obsessive compulsive disorder (OCD). Standard TMS appears to exert biological effects by inducing current in the cortex more shallowly than deep TMS (dTMS); it may be that this modality of treatment differs from standard TMS. Given the potential difference in the manner in which dTMS stimulates the targeted brain regions, it is reasonable to review and summarize the various off-label and experimental applications of this variation of TMS. Deep TMS has demonstrated promise in treating mood disorders including bipolar depression and PTSD, but it is clear that more work is needed to clarify the utility of dTMS compared with rTMS. Future work may help delineate the role dTMS plays in addressing a wide spectrum of psychiatric illnesses. In addition, direct fundamental work is needed to characterize any effectiveness of dTMS in schizophrenia, anxiety, and autism spectrum disorder. Overall, neuromodulation holds promise for treating a variety of psychiatric conditions but more extensive works aimed at understanding the mechanisms and applicability are sorely needed. Continued efforts in understanding the unique application of dTMS may pave the way for future methodologies that could enhance treatment options for both mood and thought disorder.
Hepatitis C virus-infected (HCV+) adults evidence increased rates of psychiatric and cognitive di... more Hepatitis C virus-infected (HCV+) adults evidence increased rates of psychiatric and cognitive difficulties. This is the first study to use functional magnetic resonance imaging (fMRI) to examine brain activation in untreated HCV+ adults. To determine whether, relative to non-infected controls (CTLs), HCV+ adults exhibit differences in brain activation during a delay discounting task (DDT), a measure of one's tendency to choose smaller immediate rewards over larger delayed rewards-one aspect of impulsivity. Twenty adults with HCV and 26 CTLs completed an fMRI protocol during the DDT. Mixed effects regression analyses of hard versus easy trials of the DDT showed that, compared with CTLs, the HCV+ group exhibited less activation in the left lateral occipital gyrus, precuneus, and superior frontal gyrus. There were also significant interactive effects for hard-easy contrasts in the bilateral medial frontal gyrus, left insula, left precuneus, left inferior parietal lobule, and right...
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Papers by Laura Dennis