Gait impairment during complex walking in older adults is thought to result from a progressive failure to compensate for deteriorating peripheral inputs by central neural processes. It is the primary hypothesis of this paper that failure of higher cerebral adaptations may already be present in middle-aged adults who do not present observable gait impairments. We therefore compared metabolic brain activity during steering of gait (i.e., complex locomotion) and straight walking (i.e., simple locomotion) in young and middle-aged individuals. Cerebral distribution of [18F]-fluorodeoxyglucose, a marker of brain synaptic activity, was assessed during over ground straight walking and steering of gait using positron emission tomography in seven young adults (aged 24±3) and seven middle-aged adults (aged 59±3). Brain regions involved in steering of gait (posterior parietal cortex, superior frontal gyrus, and cerebellum) are retained in middle-age. However, despite similar walking performance, there are age-related differences in the distribution of [ 18F]-FDG during steering: middle-aged adults have (i) increased activation of precentral and fusiform gyri, (ii) reduced deactivation of multisensory cortices (inferior frontal, postcentral, fusiform gyri), and (iii) reduced activation of the middle frontal gyrus and cuneus. Our results suggest that pre-clinical decline in central sensorimotor processing in middle-age is observable during complex walking.