A fronto-parietal circuit for object manipulation in man: evidence from anfMRI-study

Functional magnetic resonance imaging (fMRI) was used to localize brain are as active during manipulation of complex objects. In one experiment subject s were required to manipulate complex objects for exploring their macrogeom etric features as compared to manipulation of a simple smooth object (a sph ere). In a second experiment subjects were asked to manipulate complex obje cts and to silently name them upon recognition as compared to manipulation of complex not recognizable objects without covert naming. Manipulation of complex objects resulted in an activation of ventral premotor cortex [Brodm ann's area (BA) 44], of a region in the intraparietal sulcus (most probably corresponding to the anterior intraparietal area in the monkey), of area S II and of a sector of the superior parietal lobule. When the objects were c overtly named additional activations were found in the opercular part of BA 44 and in the pars triangularis of the inferior frontal gyrus (BA 45). We suggest that a fronto-parietal circuit for manipulation of objects exists i n humans and involves basically the same areas as in the monkey. It is prop osed that area SII analyses the intrinsic object characteristics whilst the superior parietal lobule is related to kinaesthesia.