A quantitative meta-analysis of neurocognitive functioning in posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) is associated with regional alterations in brain structure and function that are hypothesized to contribute to symptoms and cognitive deficits associated with the disorder. We present here the first systematic meta-analysis of neurocognitive outcomes associated with PTSD to examine a broad range of cognitive domains and describe the profile of cognitive deficits, as well as modifying clinical factors and study characteristics. This report is based on data from 60 studies totaling 4,108 participants, including 1,779 with PTSD, 1,446 trauma-exposed comparison participants, and 895 healthy comparison participants without trauma exposure. Effect-size estimates were calculated using a mixed-effects meta-analysis for 9 cognitive domains: attention/working memory, executive functions, verbal learning, verbal memory, visual learning, visual memory, language, speed of information processing, and visuospatial abilities. Analyses revealed significant neurocognitive effects associated with PTSD, although these ranged widely in magnitude, with the largest effect sizes in verbal learning (d = -.62), speed of information processing (d = -.59), attention/working memory (d = -.50), and verbal memory (d =-.46). Effect-size estimates were significantly larger in treatment-seeking than community samples and in studies that did not exclude participants with attention-deficit/hyperactivity disorder, and effect sizes were affected by between-group IQ discrepancies and the gender composition of the PTSD groups. Our findings indicate that consideration of neuropsychological functioning in attention, verbal memory, and speed of information processing may have important implications for the effective clinical management of persons with PTSD. Results are further discussed in the context of cognitive models of PTSD and the limitations of this literature.

A quantitative meta-analysis of neurocognitive functioning in posttraumatic stress disorder

Posttraumatic stress disorder (PTSD) is associated with regional alterations in brain structure and function that are hypothesized to contribute to symptoms and cognitive deficits associated with the disorder. We present here the first systematic meta-analysis of neurocognitive outcomes associated with PTSD to examine a broad range of cognitive domains and describe the profile of cognitive deficits, as well as modifying clinical factors and study characteristics. This report is based on data from 60 studies totaling 4,108 participants, including 1,779 with PTSD, 1,446 trauma-exposed comparison participants, and 895 healthy comparison participants without trauma exposure. Effect-size estimates were calculated using a mixed-effects meta-analysis for 9 cognitive domains: attention/working memory, executive functions, verbal learning, verbal memory, visual learning, visual memory, language, speed of information processing, and visuospatial abilities. Analyses revealed significant neurocognitive effects associated with PTSD, although these ranged widely in magnitude, with the largest effect sizes in verbal learning (d = -.62), speed of information processing (d = -.59), attention/working memory (d = -.50), and verbal memory (d =-.46). Effect-size estimates were significantly larger in treatment-seeking than community samples and in studies that did not exclude participants with attention-deficit/hyperactivity disorder, and effect sizes were affected by between-group IQ discrepancies and the gender composition of the PTSD groups. Our findings indicate that consideration of neuropsychological functioning in attention, verbal memory, and speed of information processing may have important implications for the effective clinical management of persons with PTSD. Results are further discussed in the context of cognitive models of PTSD and the limitations of this literature.

Callosal white matter microstructural recovery in abstinent alcoholics: a longitudinal diffusion tensor imaging study

BACKGROUND

Previous neuroimaging studies of recently detoxified alcohol-dependent patients (RDA) have found significant loss of white matter integrity associated with the shrinkage of the frontal lobes and thinning of the corpus callosum, especially the genu. The current study hypothesized that, in addition to exhibiting the most microstructural white matter disruption in RDA, the genu will also evidence the most recovery after abstinence. This microstructural recovery will be associated with improvements in executive functioning measures.

METHODS

Fifteen RDA were examined approximately 2 weeks after abstinence and again after 1 year of abstinence and compared to 15 age- and education-matched nonalcoholic controls using diffusion tensor imaging (DTI). The effects of group, time, and their interactions on fractional anisotropy, radial diffusivity, and axial diffusivity were evaluated with repeated measures MANOVA; in addition, 2 × 2 ANOVA was used to test changes in measures of executive functioning in the 2 groups.

RESULTS

At 2 weeks of abstinence, DTI of RDA showed significantly lower fractional anisotropy and greater radial diffusivity compared to controls in the genu and body of the corpus callosum. Reexamination after 1 year showed significant time by group interaction with fractional anisotropy increasing and radial diffusivity decreasing in RDA but not controls in these 2 regions. A smaller relapsed group did not show improvements between the 2 time points. Abstinent RDA also showed improvement on Digit Span Backward, a measure of working memory, but did not benefit from practice effects on the Halstead Category Test compared to controls.

CONCLUSIONS

The results suggest susceptibility of the genu and body of the corpus callosum to the effects of alcohol, and the potential for recovery of both these regions after abstinence, perhaps via mechanisms involving myelin reconstitution.

A neuropsychological investigation of multitasking in HIV infection: implications for everyday functioning

OBJECTIVE

A subset of individuals with HIV-associated neurocognitive impairment experience related deficits in "real world" functioning (i.e., independently performing instrumental activities of daily living [IADL]). While performance-based tests of everyday functioning are reasonably sensitive to HIV-associated IADL declines, questions remain regarding the extent to which these tests' highly structured nature fully captures the inherent complexities of daily life. The aim of this study was to assess the predictive and ecological validity of a novel multitasking measure in HIV infection.

METHOD

Participants included 60 individuals with HIV infection (HIV+) and 25 demographically comparable seronegative adults (HIV-). Participants were administered a comprehensive neuropsychological battery, questionnaires assessing mood and everyday functioning, and a novel standardized test of multitasking, which involved balancing the demands of four interconnected performance-based functional tasks (i.e., financial management, cooking, medication management, and telephone communication).

RESULTS

HIV+ individuals demonstrated significantly worse overall performance, fewer simultaneous task attempts, and increased errors on the multitasking test as compared to the HIV- group. Within the HIV+ sample, multitasking impairments were modestly associated with deficits on standard neuropsychological measures of executive functions, episodic memory, attention/working memory, and information processing speed, providing preliminary evidence for convergent validity. More importantly, multivariate prediction models revealed that multitasking deficits were uniquely predictive of IADL dependence beyond the effects of depression and global neurocognitive impairment, with excellent sensitivity (86%), but modest specificity (57%).

CONCLUSIONS

Taken together, these data indicate that multitasking ability may play an important role in successful everyday functioning in HIV+ individuals.

Neural correlates of verbal learning in adolescent alcohol and marijuana users

AIMS

Alcohol and marijuana are the most widely used intoxicants among adolescents, yet their potential unique and interactive influences on the developing brain are not well established. Brain regions subserving learning and memory undergo continued maturation during adolescence, and may be particularly susceptible to substance-related neurotoxic damage. In this study, we characterize brain response during verbal learning among adolescent users of alcohol and marijuana.

DESIGN

Participants performed a verbal paired associates encoding task during functional magnetic resonance imaging (fMRI) scanning.

SETTING

Adolescent subjects were recruited from local public schools and imaged at a university-based fMRI center.

PARTICIPANTS

Participants were 74 16-18-year-olds, divided into four groups: (i) 22 controls with limited alcohol and marijuana experience, (ii) 16 binge drinkers, (iii) eight marijuana users and (iv) 28 binge drinking marijuana users.

MEASUREMENTS

Diagnostic interview ensured that all teens were free from neurological or psychiatric disorders; urine toxicology and breathalyzer verified abstinence for 22-28 days before scanning; a verbal paired associates task was administered during fMRI.

FINDINGS

Groups demonstrated no differences in performance on the verbal encoding task, yet exhibited different brain response patterns. A main effect of drinking pointed to decreased inferior frontal but increased dorsal frontal and parietal fMRI response among binge drinkers (corrected P < 0.05). There was no main effect of marijuana use. Binge drinking × marijuana interactions were found in bilateral frontal regions (corrected P < 0.05), where users of either alcohol or marijuana showed greater response than non-users, but users of both substances resembled non-users.

CONCLUSIONS

Adolescent substance users demonstrated altered fMRI response relative to non-using controls, yet binge drinking appeared to be associated with more differences in activation than marijuana use. Alcohol and marijuana may have interactive effects that alter these differences, particularly in prefrontal brain regions.

The influence of recency of use on fMRI response during spatial working memory in adolescent marijuana users

Some neurocognitive recovery occurs within a month of abstinence from heavy marijuana use, yet functional magnetic resonance imaging (fMRI) has revealed altered activation among recent and abstinent adult users. We compared fMRI response during a spatial working memory (SWM) task between adolescent marijuana users with brief and sustained durations of abstinence. Participants were 13 recent users (two to seven days abstinent), 13 abstinent users (27 to 60 days abstinent), and 18 nonusing controls, all ages 15 to 18. Groups were similar on demographics, had no psychiatric or medical disorders, and user groups were similar on substance histories. Teens performed a two-back SWM task during fMRI. Recent users showed greater fMRI response in medial and left superior prefrontal cortices, as well as bilateral insula. Abstinent users had increased response in the right precentral gyrus (clusters > or = 1328 microl, p < .05). Results suggest that adolescents who recently used marijuana show increased brain activity in regions associated with working memory updating and inhibition. This study preliminarily suggests that (1) recent marijuana use may disrupt neural connections associated with SWM and result in compensatory brain response, and (2) sustained abstinence from marijuana may be associated with improvements in SWM response among adolescents.

Altered white matter microstructure in adolescent substance users

Chronic marijuana use during adolescence is frequently comorbid with heavy alcohol consumption and associated with CNS alterations, yet the influence of early cannabis and alcohol use on microstructural white matter integrity is unclear. Building on evidence that cannabinoid receptors are present in myelin precursors and affect glial cell processing, and that excessive ethanol exposure is associated with persistently impaired myelination, we used diffusion tensor imaging (DTI) to characterize white matter integrity in heavy substance using and non-using adolescents. We evaluated 36 marijuana and alcohol-using (MJ+ALC) adolescents (ages 16-19) and 36 demographically similar non-using controls with DTI. The diffusion parameters fractional anisotropy (FA) and mean diffusivity (MD) were subjected to whole-brain voxelwise group comparisons using tract-based spatial statistics (Smith, S.M., Jenkinson, M., Johansen-Berg, H., Rueckert, D., Nichols, T.E., Mackay, C.E., Watkins, K.E., Ciccarelli, O., Cader, M.Z., Matthews, P.M., Behrens, T.E., 2006. Tract-based spatial statistics: voxelwise analysis of multi-subject diffusion data. Neuroimage 31, 1487-1505). MJ+ALC teens had significantly lower FA than controls in 10 regions, including left superior longitudinal fasciculus (SLF), left postcentral gyrus, bilateral crus cerebri, and inferior frontal and temporal white matter tracts. These diminutions occurred in the context of increased FA in right occipital, internal capsule, and SLF regions. Changes in MD were less distributed, but increased MD was evident in the right occipital lobe, whereas the left inferior longitudinal fasciculus showed lower MD in MJ+ALC users. Findings suggest that fronto-parietal circuitry may be particularly impacted in adolescent users of the most prevalent intoxicants: marijuana and alcohol. Disruptions to white matter in this young group could indicate aberrant axonal and myelin maturation with resultant compromise of fiber integrity. Findings of increased anisotropic diffusion in alternate brain regions suggest possible neuroadaptive processes and can be examined in future studies of connectivity to determine how aberrancies in specific tracts might influence efficient cognitive processing.

Altered white matter integrity in adolescent binge drinkers

BACKGROUND

White matter integrity has been found to be compromised in adult alcoholics, but it is unclear when in the course of alcohol exposure white matter abnormalities become apparent. This study assessed microstructural white matter integrity among adolescent binge drinkers with no history of an alcohol use disorder.

METHODS

We used diffusion tensor imaging to examine fractional anisotropy (FA), a measure of directional coherence of white matter tracts, among teens with (n = 14) and without (n = 14) histories of binge drinking but no history of alcohol use disorder, matched on age, gender, and education.

RESULTS

Binge drinkers had lower FA than controls in 18 white matter areas (clusters > or =27 contiguous voxels, each with p < 0.01) throughout the brain, including the corpus callosum, superior longitudinal fasciculus, corona radiata, internal and external capsules, and commissural, limbic, brainstem, and cortical projection fibers, while exhibiting no areas of higher FA. Among binge drinkers, lower FA in 6 of these regions was linked to significantly greater lifetime hangover symptoms and/or higher estimated peak blood alcohol concentrations.

CONCLUSIONS

Binge drinking adolescents demonstrated widespread reductions of FA in major white matter pathways. Although preliminary, these results could indicate that infrequent exposure to large doses of alcohol during youth may compromise white matter fiber coherence.

White matter tract injury and cognitive impairment in human immunodeficiency virus-infected individuals

Approximately half of those infected with the human immunodeficiency virus (HIV) exhibit cognitive impairment, which has been related to cerebral white matter damage. Despite the effectiveness of antiretroviral treatment, cognitive impairment remains common even in individuals with undetectable viral loads. One explanation for this may be subtherapeutic concentrations of some antiretrovirals in the central nervous system (CNS). We utilized diffusion tensor imaging and a comprehensive neuropsychological evaluation to investigate the relationship of white matter integrity to cognitive impairment and antiretroviral treatment variables. Participants included 39 HIV-infected individuals (49% with acquired immunodeficiency syndrome [AIDS]; mean CD4 = 529) and 25 seronegative subjects. Diffusion tensor imaging indices were mapped onto a common whole-brain white matter tract skeleton, allowing between-subject voxelwise comparisons. The total HIV-infected group exhibited abnormal white matter in the internal capsule, inferior longitudinal fasciculus, and optic radiation; whereas those with AIDS exhibited more widespread damage, including in the internal capsule and the corpus callosum. Cognitive impairment in the HIV-infected group was related to white matter injury in the internal capsule, corpus callosum, and superior longitudinal fasciculus. White matter injury was not found to be associated with HIV viral load or estimated CNS penetration of antiretrovirals. Diffusion tensor imaging was useful in identifying changes in white matter tracts associated with more advanced HIV infection. Relationships between diffusion alterations in specific white matter tracts and cognitive impairment support the potential utility of diffusion tensor imaging in examining the anatomical underpinnings of HIV-related cognitive impairment. The study also confirms that CNS injury is evident in persons infected with HIV despite effective antiretroviral treatment.

Characterization of white matter microstructure in fetal alcohol spectrum disorders

BACKGROUND

Exposure to alcohol during gestation is associated with CNS alterations, cognitive deficits, and behavior problems. This study investigated microstructural aspects of putative white matter abnormalities following prenatal alcohol exposure.

METHODS

Diffusion tensor imaging was used to assess white matter microstructure in 27 youth (age range: 8 to 18 years) with (n = 15) and without (n = 12) histories of heavy prenatal alcohol exposure. Voxelwise analyses, corrected for multiple comparisons, compared fractional anisotropy (FA) and mean diffusivity (MD) between groups, throughout the cerebrum.

RESULTS

Prenatal alcohol exposure was associated with low FA in multiple cerebral areas, including the body of the corpus callosum and white matter innervating bilateral medial frontal and occipital lobes. Fewer between-group differences in MD were observed.

CONCLUSIONS

These data provide an account of cerebral white matter microstructural integrity in fetal alcohol spectrum disorders and support extant literature showing that white matter is a target of alcohol teratogenesis. The white matter anomalies characterized in this study may relate to the neurobehavioral sequelae associated with gestational alcohol exposure, especially in areas of executive dysfunction and visual processing deficits.

Decreased white matter integrity in late-myelinating fiber pathways in Alzheimer's disease supports retrogenesis

The retrogenesis model of Alzheimer's disease (AD) posits that white matter (WM) degeneration follows a pattern that is the reverse of myelogenesis. Using diffusion tensor imaging (DTI) to test this model, we predicted greater loss of microstructural integrity in late-myelinating WM fiber pathways in AD patients than in healthy older adults, whereas differences in early-myelinating WM fiber pathways were not expected. We compared 16 AD patients and 14 demographically-matched healthy older adults with a whole-brain approach via tract-based spatial statistics (TBSS), and a region of interest (ROI) approach targeting early-myelinating (posterior limb of internal capsule, cerebral peduncles) and late-myelinating (inferior longitudinal fasciculus [ILF], superior longitudinal fasciculus [SLF]) fiber pathways. Permutation-based voxelwise analysis supported the retrogenesis model. There was significantly lower fractional anisotropy (FA) in AD patients compared to healthy older adults in late-myelinating but not early-myelinating pathways. These group differences appeared to be driven by loss of myelin integrity based on our finding of greater radial diffusion in AD than in healthy elderly. ROI analyses were generally in agreement with whole-brain findings, with significantly lower FA and increased radial diffusion in the ILF in the AD group. Consistent with the retrogenesis model, AD patients showed demonstrable changes in late-myelinating WM fiber pathways. Given greater change in the ILF than the SLF, wallerian degeneration secondary to cortical atrophy may also be a contributing mechanism. Knowledge of the pattern of WM microstructural changes in AD and its underlying mechanisms may contribute to earlier detection and intervention in at-risk groups.

Stroke risk modifies regional white matter differences in mild cognitive impairment

Forty non-demented older adults who were divided into two groups on the basis of their cognitive status (MCI: n=20; normal control: n=20) underwent diffusion tensor imaging, and estimates of fractional anisotropy (FA) and mean diffusivity (MD) were obtained for the genu and splenium of the corpus callosum. Results demonstrated the following: (1) group comparisons revealed that splenium FA was significantly lower in MCI participants than in NC participants, despite no differences in gross morphometry or hippocampal volumes; (2) in the overall sample, higher stroke risk was associated with lower white matter integrity, particularly in the genu; (3) increased stroke risk was more strongly associated with poorer splenium FA in those with MCI than in normal elderly; (4) splenium FA significantly predicted performance on verbal memory (adjusting for the effects of age, education, and whole brain volume). Findings demonstrate a relationship between increased vascular burden and white matter changes, and they support the possibility that posterior white matter pathology may contribute to the development of MCI-related cognitive changes.

Abstinent adolescent marijuana users show altered fMRI response during spatial working memory

Marijuana is the most widely used illicit substance among teenagers, yet little is known about the possible neural influence of heavy marijuana use during adolescence. We previously demonstrated an altered functional magnetic resonance imaging (fMRI) activity related to spatial working memory (SWM) among adolescents who were heavy users of after an average of 8 days of abstinence, but the persisting neural effects remain unclear. To characterize the potentially persisting neurocognitive effects of heavy marijuana use in adolescence, we examined fMRI response during SWM among abstinent marijuana-using teens. Participants were 15 MJ teens and 17 demographically similar non-using controls, ages 16-18. Teens underwent biweekly urine toxicology screens to ensure abstinence for 28 days before fMRI acquisition. Groups performed similarly on the SWM task, but MJ teens demonstrated lower activity in right dorsolateral prefrontal and occipital cortices, yet significantly more activation in right posterior parietal cortex. MJ teens showed abnormalities in brain response during a SWM task compared with controls, even after 1 month of abstinence. The activation pattern among MJ teens may reflect different patterns of utilization of spatial rehearsal and attention strategies, and could indicate altered neurodevelopment or persisting abnormalities associated with heavy marijuana use in adolescence.

Effects of human immunodeficiency virus and methamphetamine on cerebral metabolites measured with magnetic resonance spectroscopy

Human immunodeficiency virus (HIV) and methamphetamine (METH) use disorders are associated with cerebral dysfunction. To determine whether these effects were evident on in vivo neuroimaging, quantitative, single voxel magnetic resonance (MR) spectroscopy was used to assess frontal white matter, frontal gray matter, and basal ganglia in 40 HIV+/METH+, 66 HIV+/METH-, 48 HIV-/METH+, and 51 HIV-/METH- participants. HIV was associated with lower N-acetylaspartate (NAA) in frontal white and frontal gray matter but METH was not associated with cerebral metabolite differences in any region. Among HIV+ individuals, lower CD4 counts and higher plasma HIV viral loads were associated with lower NAA in frontal gray matter and basal ganglia. The relationship between detectable plasma HIV viral load and NAA in frontal white matter was significantly stronger in the HIV+/METH+ group, compared to HIV+/METH-. Higher detectable plasma HIV viral load was significantly associated with higher myo-inositol (MI) in frontal white and gray matter for HIV+/METH+, but not HIV+/METH-. For the HIV-/METH+ group, lifetime duration of METH use was associated with higher choline levels in frontal gray matter and higher MI levels in basal ganglia. Our findings are consistent with significant disruption of neuronal integrity in the frontal lobes of HIV-infected individuals. Although METH was not associated with cerebral metabolite levels, other findings suggested that METH use did affect the brain. For example, the relationship between detectable plasma HIV viral load and NAA levels was limited to HIV+/METH+ individuals. This evidence indicates when HIV is poorly suppressed, METH may modify the effects of the virus on neuronal integrity.

N-acetyl aspartate in autism spectrum disorders: regional effects and relationship to fMRI activation

Rapid progress in our understanding of macrostructural abnormalities in autism spectrum disorders (ASD) has occurred in recent years. However, the relationship between the integrity of neural tissue and neural function has not been previously investigated. Single-voxel proton magnetic resonance spectroscopy and functional magnetic resonance imaging of an executive functioning task was obtained in 13 high functioning adolescents and adults with ASD and 13 age-matched controls. The ASD group showed significant reductions in N-acetyl aspartate (NAA) in all brain regions combined and a specific reduction in left frontal cortex compared to controls. Regression analyses revealed a significant group interaction effect between frontal and cerebellar NAA. In addition, a significant positive semi-partial correlation between left frontal lobe NAA and frontal lobe functional activation was found in the ASD group. These findings suggest that widespread neuronal dysfunction is present in high functioning individuals with ASD. Hypothesized developmental links between frontal and cerebellar vermis neural abnormalities were supported, in that impaired neuronal functioning in the vermis was associated with impaired neuronal functioning in the frontal lobes in the ASD group. Furthermore, this study provided the first direct evidence of the relationship between abnormal functional activation in prefrontal cortex and neuronal dysfunction in ASD.

Association between dyads and correct responses on the Paced Auditory Serial Addition Task (PASAT)

The sensitivity of the Paced Auditory Serial Addition Task (PASAT) to working memory deficits may be enhanced by examining "dyads" (i.e., correct responses immediately preceded by a correct response) as a complement to the traditional total correct summary score. In a sample of 397 mostly African American (79%) healthy adults, total dyad and total correct scores were highly correlated (r = .96, p < .001); however, the magnitude of this association diminished in faster stimulus presentation trials, particularly among participants with impaired working memory abilities.

Demographically Adjusted Normative Standards for New Indices of Performance on the Paced Auditory Serial Addition Task (PASAT)

The Paced Auditory Serial Addition Task (PASAT) is a complex cognitive test sensitive to neuropsychological disorders. Its traditional Total Correct score seemingly reflects multiple cognitive abilities, including attention, working memory, and processing speed. Snyder, Aniskiewicz, and Snyder (1993) modified scoring guidelines for the PASAT to give credit only for "dyads." This method emphasizes working memory operations and has been found superior to Total Correct scores at detecting cognitive impairments in several investigations. To date, normative standards are not available for the "dyad" scoring method, thus limiting its utility in clinical and research settings. The current investigation provides demographically adjusted normative data based on a sample of 500 healthy adults of varied age, education, sex, and race (African American and Caucasian) for various indices of performance on the PASAT, including "Total Dyads" obtained across the four PASAT trials. In addition, we describe and present normative data on four other indices designed to quantify various aspects of performance on the PASAT: invalid responding, effects of varied information processing speed demands, and tendency to omit responses and to make arithmetic errors.

Brain mitochondrial injury in human immunodeficiency virus-seropositive (HIV+) individuals taking nucleoside reverse transcriptase inhibitors

Nucleoside reverse transcriptase inhibitors (NRTIs) suppress human immunodeficiency virus (HIV) replication, but are often associated with mitochondrial toxicity. Although well studied outside of the central nervous system, no investigation has examined the effects of these drugs on brain mitochondria of individuals living with HIV. The authors used proton magnetic resonance spectroscopy to evaluate NRTI-related changes in brain mitochondria. N-acetylaspartate (NAA; sensitive to alterations in mitochondrial integrity) was measured in frontal lobe white and gray matter of 18 HIV+ individuals taking didanosine and/or stavudine (two NRTIs likely to cause mitochondrial toxicity), 14 HIV+ individuals taking zidovudine and lamivudine, 16 HIV+ individuals not currently taking antiretrovirals, and 17 HIV- controls. The HIV+ groups were comparable on demographic measures, estimates of illness severity, and estimated length of HIV infection. Those taking didanosine and/or stavudine had a significant 11.4% decrease in concentrations of frontal white matter NAA compared to HIV- controls, whereas NAA levels of the other HIV+ groups were intermediate. Group differences in metabolites were not found in frontal gray matter. Lower levels of frontal white matter NAA were associated with longer periods of didanosine and/or stavudine treatment (r = -.41, P = .06). Levels of NAA were not related to length of zidovudine/lamivudine treatment (r = -.04, P = .44). Furthermore, taking more than one of stavudine, didanosine, and abacavir increased the likelihood of having reduced NAA. The results are consistent with previous studies finding HIV-related changes in neuronal integrity. However, because NRTIs can injure mitochondria, we propose that the observed reductions in NAA in individuals taking didanosine and/or stavudine may be the result of depleted brain mitochondria and/or alterations in cellular respiration. Measurement of brain metabolites sensitive to impairments in energy metabolism, including NAA, may aid in early detection of subclinical NRTI-mediated mitochondrial toxicity.

fMRI response to spatial working memory in adolescents with comorbid marijuana and alcohol use disorders

Alcohol and marijuana use are prevalent in adolescence, yet the neural impact of concomitant use remains unclear. We previously demonstrated functional magnetic resonance imaging (fMRI) response to spatial working memory (SWM) among teens with alcohol use disorders (AUD) compared to controls, and predicted that adolescents with marijuana and alcohol use disorders would show additional abnormalities. Participants were three groups of 15-17-year-olds: 19 non-abusing controls, 15 AUD teens with limited exposure to drugs, and 15 teens with comorbid marijuana and alcohol use disorders (MAUD) and minimal other drug experience. After >2 days' abstinence, participants performed a SWM task during fMRI acquisition. fMRI brain response patterns differed between groups, despite similar performance on the task. MAUD youths showed less activation in inferior frontal and temporal regions than controls, and more response in other prefrontal regions. Compared to AUD teens, MAUD youths also showed less inferior frontal and temporal activation, but more medial frontal response. Overall, MAUD youths showed different brain response abnormalities than teens with AUD alone, despite relatively short histories of substance involvement. This pattern could suggest compensation for marijuana-related attention and working memory deficits. However, relatively recent use and premorbid features may influence results, and should be examined in future studies.

Neurocognitive performance of methamphetamine users discordant for history of marijuana exposure

Abuse of the stimulant drug methamphetamine is associated with neural injury and neuropsychological (NP) deficits, while the residual effects of marijuana use remain uncertain. We sought to determine if methamphetamine dependent persons who also met criteria for marijuana abuse or dependence evidenced different NP performance than those with dependence for methamphetamine alone. We examined three groups that did not differ significantly on important demographic factors: (1) subjects with a history of methamphetamine dependence and history of marijuana abuse/dependence (METH+/MJ+, n=27); (2) methamphetamine dependent subjects without history of marijuana abuse/dependence (METH+/MJ-, n=26); (3) a control group with minimal or no drug use (n=41). A comprehensive NP battery was administered and performance was quantified for five cognitive ability areas. The METH+/MJ- group generally demonstrated the greatest NP impairment, with statistically significant differences observed between the METH+/MJ- and control group in learning, retention/retrieval, and a summary score of global NP performance. The METH+/MJ+ group did not differ significantly from the control or METH+/MJ- group on any NP ability. However, there was a significant linear trend in the global NP score suggesting that the METH+/MJ+ performed intermediate to the control and METH+/MJ- groups. Based on these findings, we cannot conclude that there is a protective effect of marijuana use in methamphetamine users; however, marijuana use clearly did not appear to exacerbate methamphetamine neurotoxicity. Further investigations are needed to determine if the emerging literature, suggesting that certain cannabinoids might have neuroprotective actions, is generalizable to community-dwelling substance abusers.

Effects of alcoholism and gender on brain metabolism

OBJECTIVE

Proton magnetic resonance spectroscopy was used to evaluate gender influences on alcohol-associated changes in brain metabolism.

METHOD

Concentrations of N-acetylaspartate, choline-containing compounds, myo-inositol, and creatine plus phosphocreatine in frontal lobe gray matter and white matter were estimated in eight women and 17 men who were recently detoxified from long-term alcoholism. Twelve women and 13 men with no history of alcoholism were used as a comparison group.

RESULTS

In male and female alcoholics, frontal lobe white matter concentrations of N-acetylaspartate were significantly lower (-8.8%) than those seen in nonalcoholic comparison subjects. In the frontal lobe gray matter region, a significant alcoholism status-by-gender interaction and follow-up analyses revealed that female alcoholics had significantly lower N-acetylaspartate concentrations (-10.73%) relative to female comparison subjects, while male alcoholics and male comparison subjects had similar levels of this metabolite (<1% difference).

CONCLUSIONS

Lower concentrations of white matter N-acetylaspartate, which may indicate neuronal loss or dysfunction, is equally severe in men and women with comparable alcohol abuse histories. However, female alcoholics exhibited significantly less N-acetylaspartate in frontal gray matter relative to female nonalcoholic comparison subjects, which could mean that female alcoholics are more susceptible to gray matter injury than their male counterparts. However, this finding could also be explained by higher-than-expected levels of N-acetylaspartate in the healthy female comparison group.

Chemical pathology in brain white matter of recently detoxified alcoholics: a 1H magnetic resonance spectroscopy investigation of alcohol-associated frontal lobe injury

BACKGROUND

Investigations have suggested that frontal lobe abnormalities are a prominent feature of the alcoholic brain, indicated by impaired neuropsychological performance on tests of frontal lobe function and by reduced frontal lobe volume in neuroimaging and neuropathological examinations. White matter compartment volume loss may underlie observed brain shrinkage and cognitive deficits associated with the frontal lobes, although the nature of this change has not been well-characterized.

METHOD

To investigate the susceptibility of frontal lobe white matter to alcohol-associated metabolic change and to understand the nature of alcohol-related white matter injury, 1H magnetic resonance spectroscopy (MRS) was used to measure concentrations of metabolites in frontal white matter (FWM) and parietal white matter (PWM) of recently detoxified alcoholics (RDA) and nonalcoholic controls (CON). Concentrations of N-acetylaspartate (NAA), choline-containing compounds (Cho), myo-inositol (Ins), and creatine plus phosphocreatine (Cr) were measured in 37 RDA (mean age, 40.4 years; mean length of abstinence, 27.9 days) and 15 CON (mean age, 38.0 years).

RESULTS

Analysis of variance (ANOVA) revealed a group by region of interest interaction for concentrations of NAA. Simple effects analysis revealed a significant 14.7% reduction in FWM NAA, while NAA levels in PWM were similar in RDA and CON. In addition, RDA had an 11.8% increase (averaged across both regions of interest) in brain white matter Ins relative to CON. Reductions in FWM NAA were associated with a longer drinking history in the RDA group, but this result was not found when both age and drinking history were used to predict the level of FWM NAA.

CONCLUSIONS

Alcohol-associated reductions in FWM NAA may be the result of neuronal loss or dysfunction in the metabolism of NAA. While alcohol-induced oxidative stress may cause global brain impairments in the metabolism and subsequent reduction of NAA, the frontal lobes are particularly rich in excitatory amino acid pathways, and axonal damage or destruction secondary to glutamate-mediated excitotoxicity during alcohol withdrawal may cause frontal lobe-specific reductions in NAA. Elevations in brain white matter Ins may reflect astrocyte proliferation as well as an osmotic response to cell shrinkage.

Regional cerebral blood flow in cocaine- versus methamphetamine-dependent patients with a history of alcoholism

Although abuse of cocaine or methamphetamine usually takes place in the context of heavy drinking, there is little information on the effects of such substance use comorbidity on brain perfusion. We explored similarities and differences in the effects of these two drugs in combination with alcohol on brain function using SPECT. Global and regional cerebral blood flow (CBF) were examined in 7 abstinent cocaine-dependent alcoholics (CDA; mean age = 39.2 yr, S.D. = 9.2 yr), 7 abstinent methamphetamine-dependent alcoholics (MDA; mean age = 36.8 yr, S.D. = 5.0 yr), and 7 non-alcoholic/non-stimulant abusing controls (NAC; mean age = 37.3 yr, S.D. = 9.6 yr). MDA had significantly lower global CBF than CDA who, in turn, were significantly lower than NAC. In addition, CDA had abnormal perfusion in the superior posterior frontal region compared to NAC; while MDA did not display specific regional deficits. Therefore, it appears that cocaine alters the relationship between global and regional CBF in alcoholics, while methamphetamine does not.

Elevated myo-inositol in gray matter of recently detoxified but not long-term abstinent alcoholics: a preliminary MR spectroscopy study

BACKGROUND

Individuals in short-term abstinence from chronic alcohol consumption commonly have neuropsychological impairments with parallel abnormalities in brain structure. Stable, long-term sobriety often results in improvements in both brain structure and function, although the mechanisms underlying these changes are currently not well understood.

METHODS

To investigate further the neurobiological underpinnings of alcohol-associated brain abnormalities in short-term and long-term abstinence from alcohol, proton magnetic resonance spectroscopy (echo time, 35 msec; repetition time, 1.5 sec) was used to assay metabolites in the anterior centrum semiovale, anterior cingulate gyrus, and right thalamus of two groups of non-Korsakoff alcoholic men, at different stages of abstinence, compared with a control group of alcohol-nonabusing men. Absolute concentrations of N-acetylaspartate, choline, myo-inositol, and creatine were measured in four recently detoxified alcoholics (mean age, 48.7 years; median abstinence, 41.5 days), five long-term abstinent alcoholics (mean age, 45.1 years; median abstinence, 1.7 years), and five nonalcoholic controls (mean age, 45.0 years).

RESULTS

Although there were no between-group differences in concentrations of N-acetylaspartate, choline, or creatine, recently detoxified alcoholics had significantly higher myo-inositol in the thalamus, compared with controls and long-term abstinent alcoholics, and significantly higher myo-inositol in the anterior cingulate gyrus, compared with the controls.

CONCLUSIONS

Elevations in myo-inositol in recently detoxified alcoholics are compatible with an acute alcohol cytotoxicity model. myo-Inositol is elevated in hyperosmolar states such as hypernatremia, renal failure, and diabetes; alcohol-induced hyperosmolarity may trigger accumulation of myo-inositol to stabilize the intracellular environment. Increases in myo-inositol may also reflect proliferation or activation of glia. The reduction of myo-inositol to control group levels in long-term abstinent alcoholics may reflect osmolar stability in abstinent alcoholics and/or a reduction in glial cell activation.

MR spectroscopy in HIV and stimulant dependence HNRC Group. HIV Neurobehavioral Research Center

HIV infection and abuse of central nervous system (CNS) stimulants are both associated with brain damage and dysfunction. CNS stimulant overdose can lead to microinfarction, hemorrhagic lesions, and vasculitis (Bostwick, 1981; Cahill et al., 1981), and may impact frontostriatal systems. Investigations of HIV-infected (HIV+) individuals have demonstrated deficits in attention, speed of information processing, motor functioning, executive functioning, and learning efficiency. These deficits are consistent with frontostriatal involvement (Heaton et al., 1995; Martin, 1994). Given the rise in AIDS cases attributable to drug use at a time when the number of AIDS cases due to sexual transmission is stable or declining, it is critical to determine if drug use, especially CNS stimulants, potentiates HIV-related neuronal injury.