Ž . International Journal of Psychophysiology 26 1997 431442 Alpha EEG activity and subcortical pathologyin HIV infection T. Baldeweg  , J.H. Gruzelier Academic Department of Psychiatry, Charing Cross and Westminster Medical School, St. Dunstan’s Road, L ondon W6 8RP, UK Abstract Ž . Quantitative electroencephalographic QEEG investigations of patients with HIV-1 infections were made to detect early signs of HIV brain involvement. QEEG data were recorded in a prospective controlled cohort study together with standardised clinical, immunological and neuropsychological tests. Subject groups were HIV-seronega- tive controls, HIV-seropositive subjects with asymptomatic infection, and HIV-seropositive subjects with symptomatic infection exclusing AIDS defining illnesses. Marked increase in background alpha amplitude preceded cognitive and neurological impairment in the symptomatic stage of infection. Elevation of alpha amplitude was also associated with change in psychiatric status. Antiretroviral medication suppressed this alpha elevation, supporting the usefulness of QEEG in monitoring drug CNS effects. In the context of clinical, neuropathological and brain imaging data it is suggested that these changes in the alpha rhythm are the earliest, albeit unspecific, signs of HIV brain involvement, reflecting the predominantly subcortical prominence of the pathological process.  1997 Elsevier Science B.V. Keywords: Electroencephalography; HIV; Alpha activity 1. Introduction 1.1. Neuropathophysiology The clinical picture of AIDS may be severely complicated by a number of neurological and psychopathological conditions which are due to the neurotropism of the human immunodefi- Ž . ciency virus type 1 HIV-1 . HIV-1 enters the brain shortly after seroconversion, which in some patients may manifest as an aseptic meningitis. However, the virus remains latent during the  Corresponding author. asymptomatic stage of infection when the still functioning immune system is able to suppress viral replication and spread. The inevitable de- cline in systemic immune competence is mainly due to progressive loss of T-lymphocytes carrying Ž . the CD4-receptor T-helper cells . Once the num- ber of CD4 lymphocytes in the peripheral blood has dropped below 200 cellsr l, which often co- incides with the occurrence of the first AIDS-def- ining infections, patients are at increased risk of suffering from CNS disorders. These can be due to either ‘primary’ HIV-1 induced pathology or ‘secondary’ pathology due to opportunistic infec- tions and neoplasms of the brain. ‘Primary’ HIV-1 induced CNS neuropathology 0167-8760r97r$17.00  1997 Elsevier Science B.V. All rights reserved. Ž . PII S0167-8760 97 00780-0