[Show abstract][Hide abstract] ABSTRACT: Introduction The study of human brain mechanism in cognitive science has become active recently due to the advancement of non-invasive brain measurement methods. In some experimental studies, reaction time tasks like button press have been used to analyze cognitive performance. However, few studies have been done to examine the human brain mechanism in the reaction time task. It has been reported in fMRI and PET studies that there are some differences in the motor activity between a self-paced movement (SPM) and an externally triggered movement (ETM) [1, 2]. Although there have been reported many MEG studies related to SPM [3, 4], not much is known about motor activity during ETM [5, 6]. By the way, it was recently reported that the primary motor cortex (MI) was not only structurally [7, 8] but also functionally inhomogeneous  and was differently activated depending on the task. It is important, not only for the motion control study but for the cognitive science, to examine the cha
[Show abstract][Hide abstract] ABSTRACT: We carried out multi-dipole estimation and pursued spatio-temporal brain activity on a time scale of several milliseconds during an auditory discrimination task using a whole-cortex type SQUID system. Neuronal activities were estimated in the medial (hippocampus, parahippocampal gyrus, etc.) and lateral temporal cortices (superior and middle temporal gyri, etc.), the dorsolateral prefrontal cortex (middle and inferior frontal gyri, etc.) and the parietal cortex (supramarginal gyrus, etc.) in the 280-400 ms latency range. The activity in the posterior hippocampal region was the most prominent and long-lasting in parallel with the activities in the other regions. Therefore, the posterior hippocampal region is a central structure engaged in auditory discrimination. The whole-cortex neuromagnetic measurements provided the possibility of imaging the time-varying activities of the human cortico-hippocampal neural networks.
[Show abstract][Hide abstract] ABSTRACT: Three dimensional optometer (TDO) can measure dynamic accommodation, eye movement and pupil diameter simultaneously, while subjects are looking at visual objects by moving their eyes. While three-dimensional visual stimulator (TVS) can present independent binocular targets changing its distance, direction and image size. Using the TDO and the TVS, simultaneous accommodation and vergence responses toward a real image and/or a stereoscopic image created by the TVS were measured. It was found that the accommodation toward the stereoscopic image showed peculiar responses that had less amplitude compared with the response toward the real image, and recede movement of accommodation from the initial peak in the response. A 64-channel whole-cortex magnetoencephalography (MEG) system was also used to study the control mechanism of the accommodation by the central nervous system. A special relay lens system has been developed both to impose visual stimuli and to measure accommodation responses with a dynamic refractometer. Using these systems, MEG and accommodation responses were measured simultaneously. Consequently, an accommodation response toward stepwise stimuli was found after about 300 ms from the onset of the stimuli. Two highly synchronized MEG responses probably related to the accommodative control were found at about 100, 200 ms from the onset of the stimuli prior to the accommodative response
Engineering in Medicine and Biology Society, 1997. Proceedings of the 19th Annual International Conference of the IEEE; 01/1997
[Show abstract][Hide abstract] ABSTRACT: 1 Introduction Visual accommodation is a mysterious function which has drawn strong attention from many vision researchers but long prevented accurate analysis, because there have been few appropriate measurement apparatuses. Every person more or less has troublesome with accommodation by myopia, hyperopia and/or presbyopia during his/her life. As it has strong relationship with three-dimensional perception, it is now drawing further attention in order to develop human friendly three-dimensional displays. We have developed several apparatus [1,2] to measure accommodation under natural visual environments and found various new phenomena about accommodation characteristics . Then, we have introduced MEG system to record brain responses directly together with accommodation response. This paper report brief explanation of the apparatus and its application first. Next it reports the simultaneous recording of accommodation response and accommodation related MEG. The study revealed a probable control center of accommodation and detail temporal characteristics.