Faculty Bibliography

Examination of spontaneous intrinsic brain activity is drawing increasing interest, thus methods for such analyses are rapidly evolving. Here we describe a novel measure, 'network homogeneity', that allows for assessment of cohesiveness within a specified functional network, and apply it to resting-state fMRI data from adult ADHD and control participants. We examined the default mode network, a medial-wall based network characterized by high baseline activity that decreases during attention-demanding cognitive tasks. We found reduced network homogeneity within the default mode network in ADHD subjects compared to age-matched controls, particularly between the precuneus and other default mode network regions. This confirms previously published results using seed-based functional connectivity measures, and provides further evidence that altered precuneus connectivity is involved in the neuropathology of ADHD. Network homogeneity provides a potential alternative method for assessing functional connectivity of specific large-scale networks in clinical populations

Illicit drug use in urban settings is a major public health problem. A range of individual level factors are known to influence drug use and its consequences, and a number of recent studies have suggested that the neighborhood in which an individual lives may also play a role. However, studies seeking to identify neighborhood-level determinants of drug use, particularly among marginalized urban populations, need to overcome significant challenges, particularly in the area of sampling and recruitment. One key issue is defining functional neighborhoods that are relevant to local residents. Another arises from the need to sample a representative or even a diverse population when studying marginalized groups such as illicit drug users. These are common problems that raise particular challenges when both need to be addressed in the same study. For example, many sampling approaches for neighborhood-level studies have included some form of random sample of households, but this may systematically overlook marginalized populations. On the other hand, the sampling approaches commonly used in studies of hidden populations such as chain referral, snow ball, and more recently, respondent-driven sampling, typically expand beyond a geographic "neighborhood." We describe the organization and rationale for the IMPACT Studies in New York City as a case illustration on how such issues may be addressed.

BACKGROUND: Pathophysiologic models of attention-deficit/hyperactivity disorder (ADHD) have focused on frontal-striatal circuitry with alternative hypotheses relatively unexplored. On the basis of evidence that negative interactions between frontal foci involved in cognitive control and the non-goal-directed 'default-mode' network prevent attentional lapses, we hypothesized abnormalities in functional connectivity of these circuits in ADHD. METHODS: Resting-state blood oxygen level-dependent functional magnetic resonance imaging (fMRI) scans were obtained at 3.0-Tesla in 20 adults with ADHD and 20 age- and sex-matched healthy volunteers. RESULTS: Examination of healthy control subjects verified presence of an antiphasic or negative relationship between activity in dorsal anterior cingulate cortex (centered at x = 8, y = 7, z = 38) and in default-mode network components. Group analyses revealed ADHD-related compromises in this relationship, with decreases in the functional connectivity between the anterior cingulate and precuneus/posterior cingulate cortex regions (p < .0004, corrected). Secondary analyses revealed an extensive pattern of ADHD-related decreases in connectivity between precuneus and other default-mode network components, including ventromedial prefrontal cortex (p < 3 x 10(-11), corrected) and portions of posterior cingulate (p < .02, corrected). CONCLUSIONS: Together with prior unbiased anatomic evidence of posterior volumetric abnormalities, our findings suggest that the long-range connections linking dorsal anterior cingulate to posterior cingulate and precuneus should be considered as a candidate locus of dysfunction in ADHD

RATIONALE: Two previous studies have utilized diffusion tensor imaging (DTI) to examine microstructural integrity in cocaine abuse and found evidence of brain abnormalities in white matter. OBJECTIVE: Using anatomical magnetic resonance imaging (MRI), DTI, and clinical evaluation, the macrostructural and microstructural correlates of cocaine abuse were investigated. METHODS: Twenty-one men and women (mean age 42.5 and mean 18.9 years of cocaine use) and 21 age/gender-matched controls were included. Fractional anisotropy (FA) was measured in frontal white matter ROIs. Gray and white matter volumes in superior and inferior frontal regions were compared. RESULTS: DTI data revealed that cocaine users had lower FA than controls, specifically in inferior frontal white matter. FA differences were not seen in other areas. Significant volumetric differences were not seen, but both gray and white matter inferior frontal volumes trended toward smaller in the cocaine group. The data suggested that duration of use was associated with decreased gray and white matter volumes. FA and gray matter volume were correlated in cocaine users. CONCLUSIONS: Both macrostructural and microstructural abnormalities were seen in a group of cocaine abusers. Length of cocaine use was associated with severity of the brain abnormalities. Future studies of white matter tissue integrity are warranted including examination of the relationship between DTI measures and traditional volumetric measures

OBJECTIVE: Recent studies have provided variable information on the frequency and context of diversion and the use of nonprescribed and prescribed stimulant medications in adolescent and young adult populations. The purpose of this systematic review of the literature is to evaluate the extent and characteristics of stimulant misuse and diversion in attention-deficit/hyperactivity disorder (ADHD) and non-ADHD individuals. METHOD: We conducted a systematic review of the literature of available studies looking at misuse and diversion of prescription ADHD medications using misuse, diversion, stimulants, illicit use, and ADHD medications as key words for the search. RESULTS: We identified 21 studies representing 113,104 subjects. The studies reported rates of past year nonprescribed stimulant use to range from 5% to 9% in grade school- and high school-age children and 5% to 35% in college-age individuals. Lifetime rates of diversion ranged from 16% to 29% of students with stimulant prescriptions asked to give, sell, or trade their medications. Recent work suggests that whites, members of fraternities and sororities, individuals with lower grade point averages, use of immediate-release compared to extended-release preparations, and individuals who report ADHD symptoms are at highest risk for misusing and diverting stimulants. Reported reasons for use, misuse, and diversion of stimulants include to concentrate, improve alertness, 'get high,' or to experiment. CONCLUSIONS: The literature suggests that individuals both with and without ADHD misuse stimulant medications. Recent work has begun to document the context, motivation, and demographic profile of those most at risk for using, misusing, and diverting stimulants. The literature highlights the need to carefully monitor high-risk individuals for the use of nonprescribed stimulants and educate individuals with ADHD as to the pitfalls of the misuse and diversion of the stimulants

To quantify the risk of death among recent-onset (< 5 years) injection drug users, we enrolled 2089 injection drug users (IDUs) age

PMID: 18365941

ISSN: 1082-6084

CID: 1535792