|Budget Amount *help
¥4,200,000 (Direct Cost : ¥4,200,000)
Fiscal Year 2004 : ¥1,000,000 (Direct Cost : ¥1,000,000)
Fiscal Year 2003 : ¥900,000 (Direct Cost : ¥900,000)
Fiscal Year 2002 : ¥2,300,000 (Direct Cost : ¥2,300,000)
For the present project, three studies were conducted to investigate neural correlates of visual joint attention using fMRI.
First study was consisted of four cueing paradigms using a pattern of eyes (EYE) and an arrow (ARW) as a cue : EYE100 EYE500, ARW100, and ARW500. Subjects were instructed to respond to the target that was presented left or right to the central fixation randomly and irrelevantly to the direction of the precedent cue. Stimulus onset asynchrony of the cue to the target (SOA) was 100 (EYE100 and ARW100) or 500 (EYE500 and ARW500) msec. During EYE500, the left precentral sulcus (prCS) and the left intraparietal sulcus (IPS) were activated in contrast to EYE100. Generally, cueing effects of endogenous orienting at SOA=500 msec decrease in comparison with ones at SOA=100 msec. The result suggested that these areas might be involved in inhibition of responses that follow reflexive orienting induced by uninformative eye gaze.
In the second study, event-related functional ma
gnetic resonance imaging (fMRI) was used to specify the function of the fronto-parietal network during reflexive orienting induced by eye gaze. Valid cueing of EYE 100 activated the left prCS. The activation was significant in comparison with valid cueing of ARW100. Therefore, the function of the left prCS was specified as motor preparation that would follow reflexive orienting induced by eye gaze. Moreover, invalid cueing of EYE500 activated the right middle frontal gyrus (MFG) and the right inferior parietal lobule (IPL). These areas are involved in reorienting to the actual position where the target has been presented. Mentioned above, since the cueing effects of endogenous orienting decrease at SOA-500 msec, reorienting to the actual target may be facilitated. The right MFG and IPL activation would be corresponding to reorienting to the actual target.
In the third study, an index finger was used as a central cue instead of eyes. As like as the first study, we prepared four cueing paradigms using an index finger (IDX) and an arrow (ARW) as a cue : IDX100, IDX500, ARW100, and ARW500. In this study, the reaction times (RTs) were measured during fMRI scans. Since sex differences were detected in RTs, fMRI data were also analyzed for sex differences. For RT data, the cueing effect of IDX500 shown by males was smaller than one shown by females. For males, activation of the left medial superior frontal gyrus (dSFG) and the left supramarginal gyrus (SMG) was detected during all paradigms except for IDX100. The result suggests that males may succeed in ignoring the uninformative index finger and in inhibition of responses that follow reflexive orienting.
Overall, the present project suggests that 1) the dorsal fronto-parietal attention network may be involved in reflexive orienting by eye gaze and index finger, 2) that inhibition of reflexive orienting by eye gaze and index finger may activate the right ventral fronto-parietal attention network, and 3) activation of these areas may explain sex differences of RTs to eye gaze and index finger. Less