Bava Sunita, Frank Lawrence R, McQueeny Tim, Schweinsburg Brian C, Schweinsburg Alecia D, Tapert Susan F
Department of Psychiatry, University of California, San Diego, La Jolla, CA 92093, USA.
Psychiatry Res. 2009 Sep 30;173(3):228-37. doi: 10.1016/j.pscychresns.2009.04.005. Epub 2009 Aug 20.
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.
青少年长期使用大麻常常与大量饮酒同时存在，并与中枢神经系统改变有关，然而早期使用大麻和酒精对脑白质微结构完整性的影响尚不清楚。基于大麻素受体存在于髓鞘前体细胞中并影响神经胶质细胞加工的证据，以及过量乙醇暴露与髓鞘形成持续受损相关的证据，我们使用扩散张量成像（DTI）来表征大量使用和不使用物质的青少年的脑白质完整性。我们用DTI评估了36名使用大麻和酒精的（MJ+ALC）青少年（年龄16 - 19岁）以及36名人口统计学特征相似的不使用物质的对照者。使用基于纤维束的空间统计学方法（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.基于纤维束的空间统计学：多受试者扩散数据的体素分析。《神经影像学》31, 1487 - 1505）对扩散参数分数各向异性（FA）和平均扩散率（MD）进行全脑体素水平的组间比较。MJ+ALC组青少年在10个区域的FA显著低于对照组，包括左侧上纵束（SLF）、左侧中央后回、双侧大脑脚以及额下和颞叶白质纤维束。这些降低出现在右侧枕叶、内囊和SLF区域FA增加的背景下。MD的变化分布较少，但在右侧枕叶可见MD增加，而在MJ+ALC使用者中左侧下纵束的MD较低。研究结果表明，额顶叶神经回路可能在最常见的致幻剂——大麻和酒精的青少年使用者中受到特别影响。这个年轻群体中脑白质的破坏可能表明轴突和髓鞘成熟异常，从而导致纤维完整性受损。在其他脑区各向异性扩散增加的结果表明可能存在神经适应性过程，并且可以在未来的连通性研究中进行检验，以确定特定纤维束中的异常如何影响有效的认知加工。
