ABSTINENT CHRONIC CRACK-COCAINE AND CRACK-COCAINE ALCOHOL ABUSERS EVIDENCE NORMAL HIPPOCAMPAL VOLUMES ON MRI DESPITE PERSISTENT COGNITIVE IMPAIRMENTS/

We measured hippocampal volumes and cognitive functioning in crack-coc aine and crack-cocaine/alcohol-dependent subjects (abstinent approxima tely 10-12 weeks) compared to age-matched controls. Cognitive function was evaluated using the computerized MicroCog Assessment of Cognitive Functioning (which includes tests of explicit, declarative memory sub served by the hippocampus). The hippocampal volumes were quantified on T1-weighted MRIs and were expressed as a proportion of intracranial v ault volume. Both subjects and controls showed the larger right versus left hippocampal volume expected in normal anatomy, but we found no d ifferences in hippocampal volume between any of the groups. However, b oth abstinent cocaine-dependent subjects and abstinent cocaine/alcohol -dependent subjects showed persistent cognitive impairments, including deficits in explicit memory. Our results suggest that either: (1) the hippocampus is resistant to structural volume loss in young and middl e-aged cocaine or cocaine/alcohol-dependent subjects, (2) the hippocam pal volume loss suffered by young and middle-aged cocaine or cocaine/a lcohol-dependent subjects resolves after approximately 3 months of abs tinence, or (3) hippocampal atrophy is obscured by the process of glio sis. Further, the cognitive impairments persisting in these abstinent cocaine and cocaine/alcohol-dependent samples may (1) be unrelated to hippocampal function or (2) be associated with abnormal hippocampal fu nction that is not reflected in MRI measures of overall hippocampal at rophy.