The role of lateral occipitotemporal junction and area MT/V5 in the visualanalysis of upper-limb postures

Humans, like numerous other species, strongly rely on the observation of ge stures of other individuals in their everyday life. It is hypothesized that the visual processing of human gestures is sustained by a specific functio nal architecture, even at an early prelexical cognitive stage, different fr om that required for the processing of other visual entities. In the presen t PET study, the neural basis of visual gesture analysis was investigated w ith functional neuroimaging of brain activity during naming and orientation tasks performed on pictures of either static gestures (upper-limb postures ) or tridimensional objects. To prevent automatic object-related cerebral a ctivation during the visual processing of postures, only intransitive postu res were selected, i.e., symbolic or meaningless postures which do not impl y the handling of objects. Conversely, only intransitive objects which cann ot be handled were selected to prevent gesture-related activation during th eir visual processing. Results clearly demonstrate a significant functional segregation between the processing of static intransitive postures and the processing of intransitive tridimensional objects. Visual processing of ob jects elicited mainly occipital and fusiform gyrus activity, while visual p rocessing of postures strongly activated the lateral occipitotemporal junct ion, encroaching upon area MT/V5, involved in motion analysis. These findin gs suggest that the lateral occipitotemporal junction, working in associati on with area MT/V5, plays a prominent role in the high-level perceptual ana lysis of gesture, namely the construction of its visual representation, ava ilable for subsequent recognition or imitation. (C) 2000 Academic Press.