The human immunodeficiency virus reduces network capacity: Acoustic noise effect

Abstract

Increased acoustic noise (AN) during working memory (WM) leads to increased brain activation in healthy individuals, and may have greater impact in human immunodeficiency virus (HIV) patients. Compared to controls, HIV subjects showed reduced AN-activation and lower neuronal marker Nacetylaspartate in prefrontal and parietal cortices. Competing use of the WM network between AN and cognitive load showed lower dynamic range of the hemodynamic responses in prefrontal and parietal cortices in HIV patients. These findings suggest reduced reserve capacity of the WM network in HIV patients and additional stress (e.g. AN) might exhaust the impaired network for more demanding tasks.

Adaptive working memory training improved brain function in human immunodeficiency virus–seropositive patients

“…At baseline, HIV participants showed a reorganized neural network compared to SN participants even on the relatively simple 1‐back task, with greater activation in the medial and lateral frontal regions, but lesser activation in brainstem and bilateral cingulate gyri, which are consistent with previous studies of WM and sustained attention tasks in HIV participants 20, 22, 23, 41. Similarly, on the 2‐back task, the greater activation in bilateral medial frontal regions and the right precentral gyrus is also consistent with greater usage of the reserve attention network, or increased attentional modulation for this more‐difficult task in HIV patients 21, 24…”

“…On fMRI, both groups showed typical robust activation patterns during the 1‐back and 2‐back WM tasks20, 22 (Figs 4 and 5). On the 1‐back task, HIV participants showed greater activation than SN controls (FDR corrected, p  < 0.0001) in frontal regions, with local maxima at the left cingulate gyrus (Brodmann's area [BA] 24), left medial frontal gyrus (BA 6), and right middle frontal gyrus (BA 9; Supplementary Table 1).…”

“…(2) To assess the neural correlates of adaptive WMT, we performed blood‐oxygenated‐level–dependent (BOLD) functional magnetic resonance (MR) imaging (MRI) (fMRI) to evaluate changes in the neural network at 1 and 6 months after the training. Based on previous work, we expect HIV patients to show a baseline reorganized or adapted WM network, with lesser activation within the normal WM network, but greater activation in the reserve networks, compared to controls 20, 21, 22, 23, 24. After the adaptive WMT, improved efficiency in the neural networks would lead to decreased activation in the extent and magnitude of the BOLD signal in both groups.…”

The Role of Host Genetics in the Susceptibility for HIV-associated Neurocognitive Disorders

“…Further, functional neuroimaging studies have shown that individuals with the met allele do better on neuropsychological tests of executive functioning and working memory, which presumably assess prefrontal cortical function (Egan et al 2001;Goldberg et al 2003;Mattay et al 2003). Such findings are particularly relevant to HIV, as a recent neuroimaging study suggested reduced neural processing capacity in working memory networks in those with HIV (Tomasi et al 2006). …”

The effects of HIV on P300 are moderated by familial risk for substance dependence: Implications for a theory of brain reserve

“…BR theory views premorbid variables, such as VIQ, educational attainment, or brain size, as important factors explaining the wide variation in functional outcomes after brain disease or injury across patients with similar structural deficits. It has been invoked by investigators studying HIV/AIDS (Stern et al, 1996;Tomasi et al, 2006), dementia (Spitznagel and Tremont, 2005;Zhang et al, 1990), Alzheimer's Disease (Bennett et al, 2003;Scarmeas et al, 2004;Stern et al, 1994), multiple sclerosis (Cader et al, 2006), and other disorders (Farmer et al, 2002;Kesler et al, 2003;Ropacki et al, 2003), as well as normal aging .…”