Cortical activation shortly after cochlear implantation

We evaluated the cortical activations in postlingually deaf cochlear implant (CI) users in the early period (0-2 months) of CI usage. The subjects were 8 early CI users and 8 normal subjects. With tone burst stimuli (1 kHz) delivered to the right side, strong and broad activation of the ipsilateral (right) primary auditory cortex with 2 peaks and weaker activation of the contralateral (left) temporal lobe were observed in early CI users, in a clear contrast with the normal subjects in whom activation was observed in a small area of the contralateral (left) primary cortex. With word stimuli, activation of the superior frontomedian cortex presumably including the supplementary motor area and the neighboring cingulate gyri was observed in early CI users, which was absent in normal subjects. The activation in the immediate association cortices near the primary area was lower in early CI users, while the periphery of the association cortex seemed to be more mobilized.