Does brain activity at rest reflect adaptive strategies? Evidence from speech processing after cochlear implantation.

In functional neuroimaging studies, task-related activity refers to the signal difference between the stimulation and rest conditions. We asked whether long-term changes in the sensory environment may affect brain activity at rest. To answer this question, we compared regional cerebral blood flow between a group of normally hearing controls and a group of cochlear-implanted (CI) deaf patients. Here we present evidence that long-term alteration of auditory experience, such as profound deafness followed by partial auditory recuperation through cochlear implantation, leads to functional cortical reorganizations at rest. Without any visual or auditory stimulation, CI subjects showed changes of cerebral blood flow in the visual, auditory cortex, Broca area, and in the posterior temporal cortex with an increment of activity in these areas from the time of activation of the implant to less than a year after the implantation.