Yoshikatsu Ichimura

Inter-hemispheric desynchronization of the human MT+ during visually induced motion sickness

Visually induced motion sickness (VIMS) is triggered in susceptible individuals by stationary viewing of moving visual scenes. VIMS is often preceded by an illusion of self-motion (vection) and/or by inappropriate optokinetic nystagmus (OKN) responses associated with increased activity in the human motion-sensitive middle temporal area (MT+). Neuroimaging studies have reported predominant right hemispheric activation in MT+ during both vection and OKN, suggesting that VIMS may result from desynchronization of activity between left and right MT+ cortices. However, this possibility has not been directly tested. To this end, we presented VIMS-free and VIMS-inducing movies in that order while measuring the temporal correlations between corresponding left and right visual cortices (including MT+) using functional magnetic resonance imaging. The inter-hemispheric correlation was reduced significantly during the viewing of the VIMS-inducing movie compared to the control VIMS-free movie in the MT+ of subjects reporting VIMS, but not in insusceptible subjects. In contrast, there were no significant inter-hemispheric differences within VIMS-free or VIMS-inducing movie exposure for visual area V1, V2, V3, V3A or V7. Our findings provide the first evidence for an association between asynchronous bilateral MT+ activation and VIMS. Desynchronization of left and right MT+ regions may reflect hemispheric asymmetry in the activities of functional networks involved in eye movement control, vection perception and/or postural control.

Application of Electron Tracking Compton Camera (ETCC) in medical imaging

The Electron Tracking Compton Camera (ETCC) has the wide energy range (0.1-2 MeV). We upgrade the recoil electron readout circuit, and the tracking algorithm. Due to this improvement, the data acquisition rate is faster than before, and the imaging quality is increased. The performance of ETCC is checked by using the test-tube with F-18 water solution. We have developed the ETCC for new medical imaging device and succeeded in imaging the some imaging reagents. Thus, this detector has the possibility of new medical imaging.