The Poz-itive Brain

     Even when antiretroviral therapy is effective, individuals with HIV still sustain damage to the central nervous system—which includes the brain.  And unfortunately, detecting these changes early and reliably is far from an easy feat.

     There’s good news, however.  Recently, a test was conducted that examines brain waves to evaluate just how well that organ processes sound.  This new study is providing insight into the effect of the virus on the brain.

     This study, published in Clinical Neurophysiology, involved a collaborative effort between Dartmouth’s Geisel School of Medicine and the Auditory Neuroscience Laboratory at Northwestern University.  Its findings are shedding further light into how the brain’s auditory system may provide a window into how HIV affects the brain.

     Dr. Jay Buckey, Jr., a professor of medicine at Geisel and co-leader of the study, stated, “’Initially, we thought we’d find that HIV affects the ear, but what seems to be affected is the brain’s ability to process sound’.” 

     To test this hypothesis, the researchers employed FFR (speech-evoked frequency-following response).  This test records brain waves from scalp electrodes while sounds common to everyday speech (for example, “ba,”  “da,” “ ga”) are played into the ear.  According to the leaders of the study, the test offers an objective, non-invasive way to record brain waves and then assess the brain’s auditory functions.

      Nina Kraus, Ph.D., a neurobiologist at Northwestern and study co-leader with Dr. Buckey, stated, “’There are many acoustic ingredients in speech, such as pitch, timing, harmonics, and phrase.  The FFR enables us to play speech sounds into the ear of study participants and figure out how good a job the brain is doing processing these different acoustic ingredients’.”

     When comparing the FFR results of 68 HIV-poz adults to 59 HIV-negative adults,  the investigators found that the auditory-neurophysiological responses to certain speech cues were disrupted in HIV-poz adults– even though they performed normally on hearing tests.  This confirmed that these hearing difficulties are rooted in the central nervous system.

     Kraus elaborated, “’When the brain processes sound, it’s not like a volume knob where all of the acoustic ingredients are either processed well or poorly.  With the FFR, we’re able to see which aspects of auditory processing are affected or diminished and ask:  ‘Is there a specific neural signature that aligns itself with HIV’?”

     Kraus and her colleagues hope that FFR can also aid in assessing the effects of concussions and Alzheimer’s on the brain.

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