HIV directly affects the brain, Stellenbosch researchers discover
HIV directly affects the brain in the early stages of the infection‚ Stellenbosch University researchers have discovered.
It has long been known that many people with HIV experience cognitive symptoms such as depression and forgetfulness, but it was unclear whether they were caused by the patients’ physical illness‚ or whether HIV had a direct effect 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‚" said Dr Stéfan du Plessis‚ lead author of a series of articles about the research published in "AIDS" and other international journals.
Using functional magnetic-resonance imaging (fMRI) — a scan that shows how blood flows to certain parts of the brain when a person performs certain tasks or experiences certain emotions — Du Plessis and his team compared the brain activity of people with HIV to those without HIV.
They found that HIV-positive participants had less blood flow in the striatal region of the brain while performing tasks involving higher motor functions. They also observed little action or blood flow to the nucleus accumbens — the section of the brain involved with motivation‚ apathy and enthusiasm — of HIV-positive patients while performing a task involving a monetary reward.
"The fMRI scans show how the HI virus affects important parts of the brain involved with motivation. We theorise that this could happen to such an extent that patients are often simply not motivated enough to take their medication‚ or even get out of bed‚" said Du Plessis‚ who conducted the research as part of his PhD in psychiatry.
The researchers also studied the structure of the frontal cortex‚ a brain region that atrophies in HIV patients. They discovered a link between the levels of atrophy and brain functional impairment — the thinner the frontal lobe was‚ the lower the levels of function.
"The study highlights a previously unknown functional effect that HIV has on the brain," said Du Plessis. "We hope these results will stimulate further studies to test the effects of antiretrovirals‚ or other interventions‚ that could improve brain function and, therefore, the lives and well-being of patients with HIV."
Earlier studies have shown that up to 50% of people with HIV may suffer from cognitive impairment‚ ranging from subtle impairment, detectable only through sophisticated cognitive tests‚ to severe psychosis. Prior to the introduction of antiretroviral therapy, many patients developed severe HIV-related dementia. The therapy has markedly improved the symptoms of dementia in HIV-positive people.