TUESDAY, SEPTEMBER 27, 2016

Brain scans reveal cognitive deficits in older HIV patients

Using brain scans, Georgetown University Medical Center neuroscientists conducted a pilot study that showed cognitive deficits in older adults who have HIV.

The participants in the study took a standard neuropsychology test that examined cognitive functions, executive functions and daily functions. The standard neuropsychology test involves solving problems and/or answering questions and can be completed on the computer or with pencil/paper. Unlike MRI scans that show images and structures of the brain, a standard neuropsychology test examines how well the brain is working while performing certain functions.

As the subjects took the test, functional MRI (fMRI) scans showed their brain activity. While participants were performing an alternating face-gender/word-semantic task, the scans revealed cognitive deficits in HIV-positive individuals when compared to similar healthy subjects.

Executive functions or cognitive control is defined as the processes that allow information processing and behavior to vary depending on one’s environment and current goals.

During the scans, the participants were shown superimposed face-word images and were cued (unpredictably) to judge the gender of a face (male versus female) or the meaning of the word (e.g., animate for “tiger” and inanimate for “table”). A switch after the cue in task often leads to an increase in reaction time and a decrease in accuracy, which is known as a switching cost.

The HIV-positive subjects were significantly slower in adjusting to change in tasks, which correlates with brain dysfunctions in the dorsal anterior cingulate cortex (dACC), one of the key executive regions. This collar-shaped area is near the front of the brain, and damage to this region has been linked to many cognitive impairments.

Neurologist and lead author of the study Xiong Jiang and epidemiologist Manya Magnus said this new study’s findings should be taken with caution as it is a pilot study with a small sample size. But if the findings are verified in future studies with larger and better-controlled samples, “it could suggest that brain dysfunction might affect a larger proportion of HIV-infected individuals than previously recognized, especially in those who are 50 years or older.”

This cognitive deficit is known as HIV-associated neurocognitive disorder (HAND). HAND affects approximately 30 to 60 percent of HIV-positive individuals.

“This would represent a significant public health challenge since the population of persons living with HIV is rapidly aging; overcoming this challenge will require researchers, medical practitioners, patients and family members/caregivers to work together to address this question,” Jiang said.

Although some symptoms of HAND include motor dysfunction and affected cognitive functions such as memory and executive function, depending on the severity of the disease, a patient may be asymptomatic. There are studies examining whether drugs with higher blood-brain-barrier penetration will be better to prevent/treat HAND than drugs with lower penetration, but the results have been conflicting, so additional research is needed.

Jiang and Manya also suggest further research is needed in better identifying and characterizing HAND in those who may be asymptomatic and unable to detect with methods currently available.

“The ultimate goal for us is to use fMRI to better understand how HIV-disease affects brain function, and to develop fMRI techniques that can serve as a non-invasive biomarker for early diagnosis and interventional therapies,” said Jiang and Manya.

The study was published in the journal AIDS Care in November.