Impairments in memory and hippocampal function in HIV-positive vs HIV-negative women: a preliminary study.

OBJECTIVE: Neurocognitive studies of HIV typically target executive functions dependent on frontostriatal circuitry. The integrity of medial temporal systems has received considerably less attention despite high hippocampal viral load. Studies also predominately involve HIV+ men, though HIV+ women may be at increased risk for cognitive dysfunction due to the high prevalence of psychosocial/mental health problems and lower educational attainment. Our aim was to conduct a preliminary investigation of episodic memory and its neural correlates in HIV-infected and at-risk uninfected women. METHODS: Participants included 54 HIV+ and 12 HIV- women (mean age = 43 years; 86% African American) recruited from the Chicago site of the Women's Interagency HIV Study. Participants completed standardized tests of verbal and visual episodic memory, working memory, and executive function. A subset of 11 women also underwent functional MRI during a delayed verbal episodic memory task. RESULTS: HIV serostatus predicted significantly lower immediate and delayed verbal episodic memory, working memory, and visual memory. Preliminary neuroimaging findings revealed group differences in bilateral hippocampal function, with HIV+ women showing decreased activation during encoding and increased activation during delayed recognition. These alterations correlated with worse episodic verbal memory. CONCLUSIONS: Verbal episodic memory deficits are evident in HIV+ women and may be associated with hippocampal dysfunction at both encoding and retrieval.

Cortical mechanisms for acquisition and performance of bimanual motor sequences.

We used functional magnetic resonance imaging to investigate the cortical mechanisms contributing to the acquisition and performance of a complex, bimanual motor sequence. To that aim, five subjects were trained on a difficult, asymmetrical finger opposition task. Their performance rate almost doubled in the course of training and approached the performance rate in an untrained, symmetrical finger opposition task. Before training, performance of the asymmetrical sequence was associated with activity in M1, premotor cortex, supplementary motor cortex, and parietal cortex. After training, performance of the asymmetrical sequence was associated mainly with activity in M1, and little activity outside M1 remained. The latter pattern of cortical activation resembled that observed during the execution of symmetrical sequences, which was unaffected by practice with the asymmetrical sequence. The activation pattern obtained with the symmetrical bimanual sequence was indistinguishable from the combined activation measured in contralateral hemispheres during unimanual control sequences. The data indicate that cortical regions previously implicated in the acquisition of difficult unimanual motor sequences also contribute to the acquisition of asymmetrical bimanual sequences. We found no evidence for an expansion of activity in M1 after acquisition of the asymmetrical sequence (while this has been reported after acquisition of unimanual sequences). In the context of existing literature, the data suggest that the acquisition of unimanual and bimanual motor sequences may rely on similar cortical mechanisms, but that the formation of long-term, procedural memories for the two types of sequences might at least in part depend on different mechanisms.