Alterations in the hemodynamic response function in cognitively impaired HIV/AIDS subjects.

Functional magnetic resonance imaging (fMRI) has revealed much about altered CNS function in HIV/AIDS. In this study, we compared the blood oxygen level dependent hemodynamic response function (BOLD HRF) signal in HIV/AIDS and control subjects as a necessary pre-condition for fMRI studies of higher level cognitive function. Using event-related fMRI, subjects performed a simple sensory-motor activity allowing the measurement of the BOLD HRF in the precentral gyrus. There were no significant differences in the HRF when viewed as a function of age, hemisphere, or HIV serostatus. However, significant results were found after dividing the subjects by NIMH impairment classifications. There were 16 control subjects, 19 Normal/Asymptomatic Neuropsychological Impairment (ANI), and 11 Minor Neurocognitive Disorder (MNCD)/HIV-Associated Dementia (HAD) subjects. The HRF of MNCD/HAD subjects did not return to baseline after 16s, suggesting subtle alterations in neuronal function, which may affect event-related fMRI studies.