Smaller Regional Gray Matter Volume in Homeless African American Cocaine-Dependent Men: A Preliminary Report

Models of addiction include abnormalities in parts of the brain involving executive function/inhibitory control. Although previous studies have reported evidence of structural abnormalities in cocaine-dependent individuals, none have specifically targeted the homeless. The present preliminary study investigated brain structure in such an understudied group, homeless, crack-cocaine-dependent African American men (n = 9), comparing it to that in healthy controls (n = 8). Structural data were analyzed using voxel based morphometry (VBM) and a regions of interest (ROI) analysis. Homeless cocaine-dependent individuals had smaller gray matter volume in dorsolateral prefrontal cortex, anterior cingulate, the cerebellum, insula, and superior temporal gyrus. Most of these areas subserve executive function or inhibitory control. These results are similar to those found in most previous studies of non-homeless cocaine-dependent individuals. Reduced gray matter in executive function/inhibitory control regions of the brain in cocaine-dependent individuals may be a preexisting risk factor for the development of addiction and/or a consequence of drug abuse

Baseline Conditions and Subtractive Logic in

Abstract: Discrepancies in the patterns of cortical activation across studies may be attributable, in part, to differences in baseline tasks, and hence, reflect the limits of the subtractive logic underlying much of neuroimaging. To assess the extent of these effects, three of the most commonly used baseline conditions (rest, tone monitoring, and passive listening) were compared using phoneme discrimination as the experimentaltask.EightparticipantswerestudiedinafMRIstudywitha4.1Tsystem.Thethreebaseline conditions systematically affected the amount of activation observed in the identical phoneme task with major affects in Broca’s area, the left posterior superior temporal gyrus, and the left and right inferior parietal regions. Two central findings were: 1) adifferential effect of baseline within each region, with the rest baseline condition producing the greatest amount of activation and the passive listening condition producingtheleast,and2)systematicbaselinetaskactivationintheinferiorparietalregions.Theseresults emphasize the relativity of activation patterns observed in functional neuroimaging, and the necessity to specify the baseline processes in context to the experimental task processes. Hum. Brain Mapping 14

Phosphorus-31 MR spectroscopic imaging (MRSI) of normal and pathological human brains

The goals of this study were to evaluate 31P MR spectroscopic imaging (MRSI) for clinical studies and to survey potentially significant spatial variations of 31P metabolite signals in normal and pathological human brains. In normal brains, chemical shifts and metabolite ratios corrected for saturation were similar to previous studies using single-volume localization techniques ( n = 10; pH = 7.01 ± 0.02; PCr Pi = 2.0 ± 0.4 ; PCr ATP = 1.4 ± 0.2 ; ATP Pi = 1.6 ± 0.2 ; PCr PDE = 0.52 ± 0.06 ; PCr PME = 1.3 ± 0.2 ; [Mg 2+] free = 0.26 ± 0.02 mM.) In 17 pathological case studies, ratios of 31P metabolite signals between the pathological regions and normal-appearing (usually homologous contralateral) regions were obtained. First, in subacute and chronic infarctions ( n = 9) decreased Pi (65 ± 12%), PCr (38 ± 6%), ATP (55 ± 6%), PDE (47 ± 9%), and total 31P metabolite signals (50 ± 8%) were observed. Second, regions of decreased total 31P metabolite signals were observed in normal pressure hydrocephalus (NPH, n = 2), glioblastoma ( n = 2), temporal lobe epilepsy ( n = 2), and transient ischemic attacks (TIAs, n = 2). Third, alkalosis was detected in the NPH periventricular tissue, glioblastoma, epilepsy ipsilateral ictal foci, and chronic infarction regions; acidosis was detected in subacute infarction regions. Fourth, in TIAs with no MRI-detected infarction, regions consistent with transient neurological deficits were detected with decreased Pi, ATP, and total 31P metabolite signals. These results demonstrate an advantage of 31P MRSI over single-volume 31P MRS techniques in that metabolite information is derived simultaneously from multiple regions of brain, including those outside the primary pathological region of interest. These preliminary findings also suggest that abnormal metabolite distributions may be detected in regions that appear normal on MR images