HIV patients had CD4 count of 320 ± 50/mm3
, and a plasma viral load of 5,720 ± 3,390 copies/ml. Two HIV patients were not taking antiretroviral medications, three patients were on stable regimens of two antiretroviral medications, and five patients were taking stable potent antiretroviral regimens. The patients had minimal symptoms, with an average Karnofsky score15
of 93.0 ± 2.7, performed well on the HIV dementia scale16
(14.8 ± 0.3), and were slower on two of the reaction time tasks that required working memory (choice reaction time, 50 ms slower, p
= 0.036; one-back cued reaction time, 73 ms slower, p
= 0.047). Performance accuracy and reaction times during fMRI were similar for HIV and control subjects, and not affected by increased acoustic noise (). All HIV patients and control subjects had normal hearing and similar auditory bandwidth (HIV: mean ± SD: 6655 ± 2186 Hz; control subjects: 6667 ± 1800 Hz). The concentration of N-acetylaspartate (NAA) was lower for the HIV group in the SPF (p
= 0.02), and SP (p
= 0.003) regions (), in agreement with previous MRS studies.17
Figure 1 (A) Subjects' performance accuracy (left) and reaction times (right) during the functional magnetic resonance imaging tasks for "Quiet" and "Loud" scans. (B) Average time courses of blood oxygen level dependent (BOLD) responses across subjects in the (more ...)
For control subjects, “Loud” scans produced larger BOLD responses than “Quiet” scans in the cerebellum (CER, pcorrected < 0.0005, corrected for multiple comparisons), and the middle (MFG), medial (medFG), and lingual (LG) gyri (pcorrected < 0.029; , Upper left panel). For HIV-positive men, louder acoustic noise increased fMRI signals only in the CER and LG (pcorrected < 0.0005), but decreased fMRI signals in the superior parietal cortex (SPC; , Upper right panel, green regions). With increased noise level, HIV patients activated less compared to the effects in controls in the CER (pcorrected = 0.045), SPC (pcorrected < 0.0005), and medFG (pcorrected = 0.028) (, Bottom left panel).
Figure 2 (Top) Group analyses of differential "Loud" minus "Quiet" activation during the working memory (WM) tasks (1-back and 2-back, combined); louder scans produced increased brain activation in the lingual (LG; both groups), middle (MFG), and medial gyri (medFG) (more ...)
Across subjects in both groups, the load-responses during “Quiet” scans (2-back minus 1-back) correlated negatively with the AN-responses during the 2-back task in the medFG, SPC, and the CER (correlation factor, −0.47 >R> −0.82; p < 0.04; , bottom panel). The intercept of the regression lines with the y-axis (WM-load) was significantly higher for controls than for HIV subjects in three regions (SPC: p = 0.001, medFG: p = 0.03; CER: p = 0.04).