I Brain activation during executed (EM) and imagined movements (IM) of the right and left hand was studied in 10 healthy right-handed subjects using functional magnetic resonance imagining (fMRI). Low electromyographic (EMG) activity of the musculi ºexor digitorum superªcialis and high vividness of the imagined movements were trained prior to image acquisition. Regional cerebral activation was measured by fMRI during EM and IM and compared to resting conditions. Anatomically selected regions of interest (ROIs) were marked interactively over the entire brain. In each ROI activated pixels above a t value of 2.45 (p < 0.01) were counted and analyzed. In all subjects the supplementary motor area (SMA), the premotor cortex (PMC), and the primary motor cortex (M1) showed signiªcant activation during both EM and IM; the somatosensory cortex (S1) was signiªcantly activated only during EM. Ipsilateral cerebellar activation was decreased during IM compared to EM. In the cerebellum, IM and EM differed in their foci of maximal activation: Highest ipsilateral activation of the cerebellum was observed in the anterior lobe (Larsell lobule H IV) during EM, whereas a lower maximum was found about 2-cm dorsolateral (Larsell lobule H VII) during IM. The prefrontal and parietal regions revealed no signiªcant changes during both conditions. The results of cortical activity support the hypothesis that motor imagery and motor performance possess similar neural substrates. The differential activation in the cerebellum during EM and IM is in accordance with the assumption that the posterior cerebellum is involved in the inhibition of movement execution during imagination. I

The capacity to voluntarily regulate emotions is critical for mental health, especially when coping with aversive events. Several neuroimaging studies of emotion regulation found the amygdala to be a target for downregulation and prefrontal regions to be associated with downregulation. To characterize the role of prefrontal regions in bidirectional emotion regulation and to investigate regulatory influences on amygdala activity and peripheral physiological measures, a functional magnetic resonance imaging (fMRI) study with simultaneous recording of self-report, startle eyeblink, and skin conductance responses was carried out. Subjects viewed threat-related pictures and were asked to up- and downregulate their emotional responses using reappraisal strategies. While startle eyeblink responses (in successful regulators) and skin conductance responses were amplified during upregulation, but showed no consistent effect during downregulation, amygdala activity was increased and decreased according to the regulation instructions. Trial-by-trial ratings of regulation success correlated positively with activity in amygdala during upregulation and orbitofrontal cortex during downregulation. Downregulation was characterized by left-hemispheric activation peaks in anterior cingulate cortex, dorsolateral prefrontal cortex, and orbitofrontal cortex and upregulation was characterized by a pattern of prefrontal activation not restricted to the left hemisphere. Further analyses showed significant overlap of prefrontal activation across both regulation conditions, possibly reflecting cognitive processes underlying both up- and downregulation, but also showed distinct activations in each condition. The present study demonstrates that amygdala responses to threat-related stimuli can be controlled through the use of cognitive strategies depending on recruitment of prefrontal areas, thereby changing the subject's affective state.

Functional magnetic resonance imaging (fMRI) was employed to determine areas of activation in the cerebellar cortex in 46 human subjects during a series of motor tasks. To reduce the variance due to differences in individual anatomy, a specific transformational procedure for the cerebellum was introduced. The activation areas for movements of lips, tongue, hands, and feet were determined and found to be sharply confined to lobules and sublobules and their sagittal zones in the rostral and caudal spino-cerebellar cortex. There was a clear symmetry mirroring at the midline. The activation mapped as two distinct homunculoid representations. One, a more extended representation, was located upside down in the superior cerebellum, and a second one, doubled and smaller, in the inferior cerebellum. The two representations were remarkably similar to those proposed by Snider and Eldred [1951] five decades ago. In the upper representation, an intralimb somatotopy for the right elbow, wrist, and fingers was revealed. The maps seem to confirm earlier electrophysiological findings of sagittal zones in animals. They differ, however, from micromapping reports on fractured somatotopic maps in the cerebellar cortex of mammals. We assume that the representations that we observed are not solely the result of spatial integration of hemodynamic events underlying the fMRI method and may reflect integration of afferent peripheral and central information in the cerebellar cortex.

Reorganization after early brain injuries is not only determined by the maturational stage of the CNS at the time of the insult (timing), but also by the structural properties, location and extent of the lesion. This study addresses the impact of different lesion extents on the type of reorganization induced in a cohort of patients with lesions of uniform structure and location (unilateral periventricular defects) and similar timing (early third trimester of pregnancy). Twelve young adult patients with congenital hemiparesis and 10 age-matched controls were studied. The severity of structural damage to hand motor projections of the cortico-spinal tract was assessed on semi-coronal MRI reconstructions along anatomical landmarks of cortico-spinal tract somatotopy. The functional integrity of these crossed cortico-spinal projections in the affected hemisphere, as well as the presence of any abnormal ipsilateral projections to the paretic hand, was examined by transcranial magnetic stimulation (TMS). Cortical activation during simple voluntary hand movements was studied by functional MRI (fMRI). Patients with small lesions (SL; n = 4) and only mild hand motor impairment possessed intact crossed cortico-spinal projections to the paretic hand, whereas no motor response could be elicited by TMS of the affected hemisphere in those with large lesions (LL; n = 6) and more severe hand motor impairment. Evidence for compensatory recruitment of the unaffected hemisphere was found in both subgroups. In the SL group, fMRI demonstrated ipsilateral activation of premotor areas, without any abnormal projections to the paretic hand originating from these sites. In the LL group, such abnormal ipsilateral projections to the paretic hand were indeed found, and fMRI confirmed cortical activation of an abnormal ipsilateral hand motor representation in the primary sensorimotor region of the unaffected hemisphere. Two patients with intermediate-sized lesions presented combined features of both groups (SL, LL). In conclusion, this study provides evidence that the type of cortico-spinal reorganization depends on the extent of the brain lesion. We propose that involvement of the ipsilateral hemisphere can be (i) of the premotor type, i.e. without ipsilateral motor projections but with significant activation of ipsilateral premotor areas, or (ii) of the primary motor type, i.e. with abnormal ipsilateral cortico-spinal projections to the paretic hand.

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