Subjects in the fMRI were either shown images of objects alone or hands grasping these objects. Reliably, the object-only stimuli activated the contralateral ventral visual pathway. In the case of grasping stimuli where the hand was presented in the opposite visual hemifield from the object, contralateral activation of the dorsal and ventral visual pathways was seen. When subjects were asked to focus their attention on either object or grasping hand, activation was pronounced in the ventral or dorsal visual streams, respectively.
Most importantly, the study affirms that there really isn’t a single fundamental visual representation in the brain — the representation used to recognize an object is not the same as the representation used to pick up that object. Because of the different functions of these tasks, this probably doesn’t sound too surprising but, to me, it is surprising! What we consciously see is neurally separate from what our motor system is “seeing” and the break between the two pathways happens quite early in visual processing.
Like the mirror neuron work, this provides further evidence in the “seeing is believing/doing” vein. As the author of the news and views summary points out, this work
remind[s] us once more that (ultimately) the brain did not evolve to enable us to think; it evolved to enable us to act.
Lastly, this type of idea is the basis of Rodolfo Llinas’s elegant book i of the vortex, which I’ve been reading recently. So far, it’s great and I recommend it highly!