title: Declined neural efficiency in cognitively stable human immunodeficiency virus patients.
abstract: OBJECTIVE
  To determine whether brain activation changes in clinically and neurocognitively normal human immunodeficiency virus (HIV)-infected and in HIV-seronegative control (SN) participants over a 1-year period.
  
  
  METHODS
  Functional magnetic resonance imaging (fMRI) was performed in 32 SN and 31 HIV patients (all with stable combination antiretroviral treatment) at baseline and after 1 year. Each participant performed a set of visual attention tasks with increasing attentional load (from tracking two, three, or four balls). All HIV and SN participants had normal neuropsychological function at both examinations.
  
  
  RESULTS
  Over 1 year, HIV patients showed no change in their neurocognitive status or in task performance during fMRI. However, HIV patients showed significant 1-year increases in fMRI signals in the prefrontal and posterior parietal cortices for the more difficult tasks, whereas SN control participants showed only decreases in brain activation in these regions. This resulted in significant interactions between HIV status and time of study in left insula, left parietal, left temporal, and several frontal regions (left and right middle frontal gyrus, and anterior cingulate).
  
  
  CONCLUSIONS
  Because fMRI task performance remained unchanged in both groups, the HIV patients appeared to maintain performance by increasing usage of the attention network, whereas the control participants reduced usage of the attention network after 1 year. These findings suggest improved efficiency or a practice effect in the SN participants but declined efficiency of the neural substrate in HIV patients, possibly because of ongoing brain injury associated with the HIV infection, despite their apparent stable clinical course.
authors.affiliation: Department of Medicine, University of Hawaii at Manoa, and the Queen's Medical Center, Honolulu, HI 96813, USA. tmernst@hawaii.edu
authors.forename: Thomas
authors.initials: T
authors.lastname: Ernst
authors.forename: Renat
authors.initials: R
authors.lastname: Yakupov
authors.forename: Helenna
authors.initials: H
authors.lastname: Nakama
authors.forename: Grace
authors.initials: G
authors.lastname: Crocket
authors.forename: Michael
authors.initials: M
authors.lastname: Cole
authors.forename: Michael
authors.initials: M
authors.lastname: Watters
authors.forename: Mary Lynn
authors.initials: ML
authors.lastname: Ricardo-Dukelow
authors.forename: Linda
authors.initials: L
authors.lastname: Chang