Abstract
Cells responding to the observation of goal-directed hand actions have been recorded in the anterior portion of the superior temporal sulcus (STS) of the macaque (Perrett et al., 1989). From here, information about the characteristics of the action is sent via parietal lobe to frontal cortex involved in motor planning (Rizzolatti and Craighero, 2004). However, the extent and location of the STS regions responding to vision of hand actions remains unclear.
Four macaques were scanned while they fixated videos showing object-directed and mimicked hand grasping actions (Nelissen et al., 2005). Static frames and scrambled videos were used as controls. In previous experiments, six different STS motion sensitive regions were functionally defined (Nelissen et al., Soc. Neurosci. Abstr., 2003), including MT/V5, ventral and dorsal MST, FST, a motion responsive region anterior to FST, termed lower superior temporal (LST) region and the middle portion of STP (STPm).
Observation of hand grasping actions activates lower bank (MT/V5) and fundus (FST) in the caudal part of the STS. Anterior to FST, responses were found both in the lower (LST) and upper bank (middle STP). Finally, in the rostral portion of the STS, activations were restricted mainly to the lower bank. This activation pattern by observation of hand actions was similar for isolated hand videos and person acting videos. These data suggest that multiple motion pathways may arise from MT/V5: while MST is involved in control of locomotion and pursuit, a second pathway processing actions projects from MT/V5 to more ventral and rostral STS regions.
This work was supported by grants GOA 2005/18, IUAP 05/04 and MIRROR project QLGR-CT-2002-00746