Brain Attention Network May Be Altered in HIV Patients

Attention and concentration problems in patients with HIV infection may be associated with adaptation and overload of the brain attention network, researchers report in the August issue of the Annals of Neurology.

"HIV infects the brain and leads to decreased efficiency of the brain network. Therefore, the neural network adapts by reorganization and by using reserve brain regions...to compensate for the inefficiency during brain activation," lead investigator Dr. Linda Chang told Reuters Health

Dr. Chang of the University of Hawaii, Honolulu and colleagues used blood oxygen level dependent (BOLD) functional MRI to monitor brain activity in 18 HIV- positive patients and 18 seronegative controls.

The subjects wore display goggles attached to a personal computer. Movies were used to show a set of nonverbal visual-attention tasks involving tracking of moving balls.

Both groups showed similar accuracy and reaction times. However, the HIV infected patients demonstrated decreased activation in the normal visual attention network: the dorsal parietal, bilateral prefrontal and cerebellar regions. They also showed increased activation in adjacent or contralateral brain regions.

Cognitive performance, CD4 and viral load correlated with BOLD signal increases in the brain regions activated more in subjects with HIV infection. Moreover, there was less activation in regions that showed a saturation effect with increasing load.

The researchers conclude that HIV-associated brain injury reduces the efficacy of the normal attention network. Subsequent reorganization to maintain performance, they suggest, may exceed the brain reserve capacity and "lead to attention deficits and cognitive impairment."

"Detecting these subclinical changes in HIV patients before cognitive deficits [develop] is important for guiding future or preventive treatments," Dr. Chang added.

09/09/04

Ann Neurol 2004; 56: 259-272.