Increased subcortical neural activity among HIV+ individuals during a lexical retrieval task.
Deficits in lexical retrieval, present in approximately 40% of HIV+ patients, are thought to reflect disruptions to frontal-striatal functions and may worsen with immunosuppression. Coupling frontal-striatal tasks such as lexical retrieval with functional neuroimaging may help delineate the pathophysiologic mechanisms underlying HIV-associated neurological dysfunction.



We examined whether HIV infection confers brain functional changes during lexical access and retrieval. It was expected that HIV+ individuals would demonstrate greater brain activity in frontal-subcortical regions despite minimal differences between groups on neuropsychological testing. Within the HIV+ sample, we examined associations between indices of immunosuppression (recent and nadir CD4+ count) and task-related signal change in frontostriatal structures. Method16 HIV+ participants and 12 HIV- controls underwent fMRI while engaged in phonemic/letter and semantic fluency tasks. Participants also completed standardized measures of verbal fluency



HIV status groups performed similarly on phonemic and semantic fluency tasks prior to being scanned. fMRI results demonstrated activation differences during the phonemic fluency task as a function of HIV status, with HIV+ individuals demonstrating significantly greater activation in BG structures than HIV- individuals. There were no significant differences in frontal brain activation between HIV status groups during the phonemic fluency task, nor were there significant brain activation differences during the semantic fluency task. Within the HIV+ group, current CD4+ count, though not nadir, was positively correlated with increased activity in the inferior frontal gyrus and basal ganglia.



During phonemic fluency performance, HIV+ patients recruit subcortical structures to a greater degree than HIV- controls despite similar task performances suggesting that fMRI may be sensitive to neurocompromise before overt cognitive declines can be detected. Among HIV+ individuals, reduced activity in the frontal-subcortical structures was associated with lower CD4+ count.
Department of Psychiatry and Biobehavioral Sciences, University of California Los Angeles, 740 Westwood Plaza C8-746, Los Angeles, CA 90095, USA. Electronic address: athames@mednet.ucla.edu.
April D
AD
Thames
Department of Psychiatry and Biobehavioral Sciences, University of California Los Angeles, 740 Westwood Plaza C8-746, Los Angeles, CA 90095, USA.
Philip
P
Sayegh
Department of Psychiatry and Biobehavioral Sciences, University of California Los Angeles, 740 Westwood Plaza C8-746, Los Angeles, CA 90095, USA.
Kevin
K
Terashima
University of California San Francisco Medical Center, 505 Parnassus Ave, San Francisco, CA 94143, USA.
Jessica M
JM
Foley
Department of Psychiatry and Biobehavioral Sciences, University of California Los Angeles, 740 Westwood Plaza C8-746, Los Angeles, CA 90095, USA.
Andrew
A
Cho
Department of Psychiatry and Biobehavioral Sciences, University of California Los Angeles, 740 Westwood Plaza C8-746, Los Angeles, CA 90095, USA; Department of Psychology, California State University Northridge, 18111 Nordhoff St, Northridge, CA 91330, USA.
Alyssa
A
Arentoft
Department of Psychiatry and Biobehavioral Sciences, University of California Los Angeles, 740 Westwood Plaza C8-746, Los Angeles, CA 90095, USA; VA Greater Los Angeles Healthcare System, 11301 Wilshire Blvd, Los Angeles, CA 90073, USA.
Charles H
CH
Hinkin
Department of Psychiatry and Biobehavioral Sciences, University of California Los Angeles, 740 Westwood Plaza C8-746, Los Angeles, CA 90095, USA.
Susan Y
SY
Bookheimer
D001921:Brain / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001931:Brain Mapping; D002560:Cerebrovascular Circulation / Q000502:physiology; D005260:Female; D015658:HIV Infections / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000523:psychology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010100:Oxygen / Q000097:blood; D010700:Phonetics; D012660:Semantics; D013060:Speech / Q000502:physiology*
D010100:Oxygen
HIV; Immunosuppression; Lexical retrieval; Neuroimaging; Verbal fluency