Thesis defense Lennart Verhagen (Donders Series 86)

23 March 2012

Promotor: Prof.dr. A. Postma, copromotors: Dr. H.C. Dijkerman, dr. I. Toni

How to grasp a ripe tomato?

Fortunately, we don’t have to think about this when we are standing in the supermarket after a busy day. We carefully grasp that ripe tomato without effort. Such a fluent integration of abstract knowledge (“that tomato is ripe”) and spatial information (“it is there”) is actually extraordinary. While modern computers beat grandmasters in chess, not even the best robot grasps a ripe tomato as easily as humans do, and similarly, no other animal uses tools, let alone gestures, as proficiently.

In his thesis entitled “How to grasp a ripe tomato” neuroscientist Lennart Verhagen describes the fundamental mechanisms of the interaction between abstract and spatial processing in the guidance of grasping movements. For this research he measured the brain activity of participants using fMRI and EEG, but also directly interfered with brain processes using transcranial magnetic stimulation (TMS).

Previously, it was assumed that movements are primarily spatially planned (“the object is there”), and that abstract knowledge is added as icing on the cake (“but don’t squeeze too hard”). However, this technologically innovating research shows that abstract and spatial information are already integrated at the initiation of the movement planning. A coarse framework of the intended movement is constructed (“this is again a ripe tomato that you should grasp like this”) in a brain network that is, not by accident, also strongly active during tool use and gesture production. This interaction between abstract and motoric domains forms the foundation of many characteristically human movements.