Functional anatomy of reaching and grasping - from the frontal cortex to the brainstem
fMRI studies of the functional anatomy of reaching and grasping in humans are particularly challenging because of severe technical limitations of the methods at hand. Whereas direct neurophysiological measurements are possible in non-human primates, any transfer and confirmation of the respective findings must face the fact that only much less sensitive methods are available for humans. On the other hand, only experiments with humans can address the impressive human flexibility in action control. In particular, functional magnetic resonance imaging and neuropsychological studies in patients with brain damage considerably expanded our knowledge about action control in humans. I will present results from two series of fMRI experiments. On the one hand we inspected the impact of object recognition on cortical networks of grasping. Beyond the demonstration of the impact of recognition on signals in 'kinematic' cortical areas, these experiments emphasised the desperate need for the acquisition of precise behavioural data in neuroimaging experiments of motor tasks. On the other hand, we demonstrated that the cerebral cortex doesn't tell the whole story of goal-directed action control in humans. One of the phylogenetically oldest visual structures of the vertebrates' brain, the optic tectum, houses a population of reach-related neurons. This anatomical overlap suggests interesting functional interpretations based on already available descriptions of the oculomotor system and shows that our understanding of the anatomy of the human action system is still far from being complete.