T Takeda

Tokyo Medical and Dental University, Edo, Tōkyō, Japan

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Publications (12)11.37 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The human primary motor cortex during a unilateral finger reactive movement to visual stimuli was examined by magnetoencephalography (MEG) measurement. The brain activity related to movement execution (the motor activity contralateral to the movement side) was estimated based on movement onset conditions and reaction times. The movement onset conditions were: (1) a simple reaction time task with a visual stimulus, (2) a Go/NoGo task with different colored stimuli and (3) a Go/NoGo task with different position stimuli. Dipole source estimation was done, and the time course of the motor activity was calculated. The results showed that not only the visual response but also the contralateral motor activity was evoked by the stimulus in all cases, and even when the NoGo stimulus was given. The motor activity in the primary motor cortex was conjectured to consist of two dominant components: the first component for the movement preparation and the second component for the movement execution. Because the first component happened with a constant delay time from the stimulus even in the NoGo case, the first component, coming through a fast pathway for signals from visual stimulus processing to the motor cortex without any intervening cognitive processing, was conjectured to make the motor cortex prepare for the forthcoming movement onset automatically regardless of the stimulus instruction.
    Cognitive Brain Research 11/1999; 8(3):229-39. · 3.77 Impact Factor
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    ABSTRACT: Using magnetoencephalography (MEG) and a taste stimulator with rapid-rise time, we previously located the primary gustatory area in the human cerebral cortex and also investigated the relation between the onset latency of the gustatory-evoked magnetic fields (GEM) and reaction times (RT) in different taste qualities. In the present study, we investigated the temporal process from receptors to the higher brain in taste detection based on the results of the GEM and RT of different tastes. We used 100 mM, 300 mM and 1 M NaCl and 3 mM saccharine. The duration of each stimulus was 400 ms. The interstimulus interval was approximately 30 s. The temperature of both taste solution and deionized water was maintained the same as that of the tongue. Four subjects participated in this experiment. The 64-channel whole-head SQUID system (CTF Systems Inc., Canada) was used to measure GEM. The sampling rate was 250 Hz, and the low-pass filter was 40 Hz. In each subject, GEM and RT to a given taste were measured separately by applying 40 trials of stimulation. After each trial of both measurements, subjects showed a perceived intensity by using their fingers. In the GEM study, the trials contaminated with eye movements were rejected and the remaining trials were averaged. Averaged GEM were super-imposed on the same sheet with all 64 channels to measure the onset latency of GEM from the stimulus onset. RT and onset latencies of GEM were longer for saccharine than NaCl, and the value of RT minus the onset latency of GEM from RT, presumably indicating the time for higher brain process plus motor process, did not differ between 3 mM saccharine and 1 M NaCl. With increased concentrations of NaCl, RT became shorter, but onset latencies of GEM remained constant. Sweet taste took a longer time than salty taste at receptor process including the time for diffusion to receptors.
    Annals of the New York Academy of Sciences 12/1998; 855:493-7. · 4.31 Impact Factor
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    ABSTRACT: We investigated the spatio-temporal brain activity on the time scale of several milliseconds related to the mental rotation task requiring judgements of hand orientation, using a whole-cortex MEG (magnetoencephalography) system. Neuronal activity in the visual cortex was observed approximately 100-200 ms from stimulus onset, and that in inferior parietal lobe followed (after 200 ms). Both of these activities showed a contralateral dominance to visual stimulus hemifield. Premotor activity started later than the inferior parietal lobe activity, and these activities partially overlapped. Activity in primary motor and/or motosensory areas was observed in some subjects. The whole-cortex neuromagnetic measurements provided the time course of activity in the human brain associated with the implicit motor imagery: visual cortex-->inferior parietal lobe<-->premotor cortex. This process is considered to be the transformation process of retinotopic locations into a body-centered reference frame necessary for the mental rotation task.
    Neuroreport 05/1998; 9(6):1127-32. · 1.64 Impact Factor
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    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.
    Neuroreport 06/1997; 8(7):1657-61. · 1.64 Impact Factor
  • T Takeda, H Endo, K Hashimoto
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    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
  • Electroencephalography and clinical neurophysiology. Supplement 02/1996; 47:133-41.
  • Electroencephalography and clinical neurophysiology. Supplement 02/1996; 47:121-7.
  • Electroencephalography and clinical neurophysiology. Supplement 02/1996; 47:273-81.
  • Electroencephalography and clinical neurophysiology. Supplement 02/1996; 47:283-91.
  • Electroencephalography and clinical neurophysiology. Supplement 02/1996; 47:449-57.
  • Electroencephalography and Clinical Neurophysiology/Electromyography and Motor Control 08/1995; 97(4):124-124.
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    T Takeda, H Endo, K Hashimoto
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    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 [3]. 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.