Broca's region subserves imagery of motion: A combined cytoarchitectonic and fMRI study

Broca's region in the dominant cerebral hemisphere is known to mediate the production of language but also contributes to comprehension. Here, we repo rt the differential participation of Broca's region in imagery of motion in humans. Healthy volunteers were studied with functional magnetic resonance imaging (fMRI) while they imagined movement trajectories following differe nt instructions. Imagery of right-hand finger movements induced a cortical activation pattern including dorsal and ventral portions of the premotor co rtex, frontal medial wall areas, and cortical areas lining the intraparieta l sulcus in both cerebral hemispheres. Imagery of movement observation and of a moving target specifically activated the opercular portion of the infe rior frontal cortex. A left-hemispheric dominance was found for egocentric movements and a right-hemispheric dominance for movement characteristics in space. To precisely localize these inferior frontal activations, the fMRI data were coregistered with cytoarchitectonic maps of Broca's areas 44 and 45 in a common reference space. It was found that the activation areas in t he opercular portion of the inferior frontal cortex were localized to area 44 of Broca's region. These activations of area 44 can be interpreted to po ssibly demonstrate the location of the human analogue to the so-called mirr or neurones found in inferior frontal cortex of nonhuman primates. We sugge st that area 44 mediates higher-order forelimb movement control resembling the neuronal mechanisms subserving speech. Hum. Brain Mapping 11:273-285, 2 000. (C) 2000 Wiley-Liss, Inc.