Search

Broca's region in the dominant cerebral hemisphere is known to mediate the production of language but also contributes to comprehension. Here, we report 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 different instructions. Imagery of right-hand finger movements induced a cortical activation pattern including dorsal and ventral portions of the premotor cortex, frontal medial wall areas, and cortical areas lining the intraparietal sulcus in both cerebral hemispheres. Imagery of movement observation and of a moving target specifically activated the opercular portion of the inferior 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 the 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 possibly demonstrate the location of the human analogue to the so-called mirror neurones found in inferior frontal cortex of nonhuman primates. We suggest that area 44 mediates higher-order forelimb movement control resembling the neuronal mechanisms subserving speech. Hum. Brain Mapping 11:273-285, 2000. (C) 2000 Wiley-Liss, Inc.

To determine task-specific activations of the human brain in individual subjects, we applied pixel-by-pixel t-map statistics to the regional cerebral perfusion data obtained sequentially by dynamic scanning of [15O]-butanol with positron emission tomography (PET). The listmode data were binned into frames of 2 sec, and multiple corresponding pixel-by-pixel activation-minus-control subtractions were used for t-map calculation. The subtraction frames covering 10–40 sec after tracer arrival in the brain showed the activation-related increase of regional cerebral perfusion. A mismatch of the activation and control data by 2 sec resulted in a mean error of

We compare estimates of three-dimensional brain activity extracted from averaged and from selected single-trial rnagnetoencephalographic signals, in order to study activation sequences related to motor preparation, inhibition, and movement, cued on two tones (Sl and 52). We studied all possible hand-ear combinations in a right-handed subject in both initiation and inhibition, and found some marked differences between combinations. Averaging revealed activity in the right motor cortex in all combina- tions requiring movement inhibition, irrespective of laterality of finger and ear, and in the contralateral motor cortex during movement (but considerably reduced for the task with the practiced ear and finger). These activation patterns are seen in single trials with variability of latency but not position. In the average signal, a long silent period between the warning and imperative stimuli is seen; in single trials, however, recurring sequences of activation linking frontal and posterior areas are seen throughout the analysis period in all combinations. These results show that single-trial analysis is needed to understand all the significant neural correlates of this task.