Summary: New research from Stellenbosch University shows that HIV can affect the brain very early in infection, producing measurable changes in brain function even before common causes such as illness, fatigue or depression can fully explain cognitive symptoms.
Source: Stellenbosch University.
Stellenbosch University researchers report that HIV directly alters brain function during the early stages of infection.
Although clinicians have long observed cognitive and mood changes among people living with HIV—ranging from mild forgetfulness and low motivation to more severe cognitive disorders—it has remained unclear when neurobiological changes begin and whether those changes result directly from the virus or indirectly from generalized illness, stress or other factors.
Dr. Stéfan du Plessis, lead author of a series of papers published in AIDS and several international journals, explains that their findings indicate a direct impact of HIV on the brain. “Our research shows that HIV does have an impact on the brain and that these low-grade cognitive symptoms are likely not just function loss due to patients feeling sick, tired or depressed,” he says.
The research team used functional magnetic resonance imaging (fMRI) to compare brain activity in HIV-positive and HIV-negative individuals while they performed specific tasks designed to activate distinct brain regions. fMRI measures blood flow changes that correspond to neural activity, revealing which regions are recruited during particular cognitive, motor or reward-related tasks.
Importantly, HIV-positive participants in the study were physically and mentally well, had no history of drug abuse, and had not yet begun antiretroviral treatment (ART). This careful selection helped isolate the direct effects of the virus from other potential confounding factors.
The investigators observed reduced blood flow in the striatum of HIV-positive participants while they performed tasks involving higher motor functions. They also found diminished activation and reduced blood flow to the nucleus accumbens during a task involving a monetary reward. The nucleus accumbens plays a central role in motivation, reward processing and goal-directed behavior, and reduced responsiveness in this region can relate to apathy and lowered drive.
“The fMRI scans show how the HIV virus affects important parts of the brain involved with motivation,” says Du Plessis. He and his colleagues suggest that such functional changes could help explain why some people living with HIV struggle with medication adherence, daily tasks or maintaining regular activities—the virus itself may blunt motivation and reduce the drive to act.
In addition to functional changes, the team assessed structural differences in the frontal cortex, a brain region vulnerable to atrophy in HIV. They found a correlation between frontal lobe thinning and impaired brain function—the thinner the frontal cortex, the lower the measured functional capacity in those regions. This connection between structure and function reinforces the idea that HIV can produce early and measurable neurobiological effects.
Du Plessis emphasizes the clinical implications: “The study highlights a previously unknown functional effect that HIV has on the brain. We hope that these results will stimulate further studies to test the effects of antiretrovirals or other interventions that might improve brain function and therefore quality of life for people living with HIV.”
Previous research has estimated that up to half of people with HIV experience some form of cognitive impairment, ranging from subtle changes detectable only with specialized testing to more severe neurocognitive disorders. Before the advent of effective ART, many patients developed severe HIV-associated dementia; while ART has greatly reduced the incidence and severity of dementia, milder cognitive and motivational symptoms remain a concern.
Source: Wilma Stassen — Stellenbosch University
Publisher: Organized by NeuroscienceNews.com
Image source: Image in the public domain
Original research: The study is published in AIDS and other peer-reviewed journals.
MLA: Stellenbosch University. “HIV Targets the Brain During Early Infection.” NeuroscienceNews, 30 November 2017.
APA: Stellenbosch University (2017, November 30). HIV Targets the Brain During Early Infection. NeuroscienceNews.
Chicago: Stellenbosch University. “HIV Targets the Brain During Early Infection.” NeuroscienceNews. (accessed November 30, 2017).