Functional brain imaging as an objective measure of speech perception performance in adult cochlear implant users

In this study we examined the role of functional brain imaging of regional cerebral bloodflow (rCBF) with the use of single photon emission computed tomography (SPECT) for the objective measurement of brain performance in adult cochlear implant (CI) users during speech perception. The subjects consisted of nine normal-hearing and eight CI individuals who watched a 15-min videotape under two conditions: (1) a visual-only presentation; and (2) a left-monaural audio and visual presentation. Cortical activations were observed bilaterally in Brodmann areas 41, 42, 21, 22 and 38 for normal-hearing control subjects. Bilateral activations were also observed in CI individuals who demonstrated high performance on open-set speech recognition tasks; however, activations were smaller in both amplitude and extent than those observed for normal-hearing individuals. CI individuals with minimal open-set recognition demonstrated only unilateral activation of auditory cortex in the hemisphere contralateral to the ear of implantation. These data support SPECT as a tool for objectively documenting cortical activations in adult CI users.