Katsuyuki Sakai

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Transcranial magnetic stimulation (TMS) over the human primary motor cortex (M1) evokes motor responses in the contralateral limb muscles. The latencies and amplitudes of those responses depend on the direction of induced current in the brain by the stimuli (Mills et al. 1992, Werhahn et al. 1994). This observation suggests that different neural elements(More)
Our voluntary behaviors are thought to be controlled by top-down signals from the prefrontal cortex that modulate neural processing in the posterior cortices according to the behavioral goal. However, we have insufficient evidence for the causal effect of the top-down signals. We applied a single-pulse transcranial magnetic stimulation over the human(More)
In order to locate the site of action of transcranial magnetic stimulation (TMS) within the human motor cortices, we investigated how the optimal positions for evoking motor responses over the scalp corresponded to the hand and leg primary-motor areas. TMS was delivered with a figure-8 shaped coil over each point of a grid system constructed on the skull(More)
Remarkable human performance, such as playing the violin, is often based on motor skills that, once acquired, are retained for a long time. To examine how motor skills are retained, we trained monkeys and humans extensively to perform many visuomotor sequences and examined their performance after a long retention period of up to 18 months. For both monkeys(More)
 Subthreshold transcranial magnetic stimulation (TMS) over the motor cortex can shorten the simple reaction time in contralateral arm muscles if the cortical shock is given at about the same time as the reaction stimulus. The present experiments were designed to investigate whether this phenomenon is due to a specific facilitatory effect on cortical(More)
Silvia A. Bunge,1 Jonathan D. Wallis,2 Amanda Parker,3 Marcel Brass,4 Eveline A. Crone,1,5 Eiji Hoshi,6 and Katsuyuki Sakai7 1Department of Psychology and Center for Mind and Brain, University of California at Davis, Davis, California 95616, 2Helen Wills Neuroscience Institute and Department of Psychology, University of California at Berkeley, Berkeley,(More)
The prefrontal cortex (PFC) is thought to modulate the neural network state in favor of the processing of task-relevant sensory information prior to the presentation of sensory stimuli. However, this proactive control mechanism cannot always optimize the network state because of intrinsic fluctuation of neural activity upon arrival of sensory information.(More)
The dorsal and ventral parts of the lateral prefrontal cortex have been thought to play distinct roles in decision making. Although its dorsal part such as the frontal eye field (FEF) is shown to play roles in accumulation of sensory information during perceptual decision making, the role of the ventral prefrontal cortex (PFv) is not well-documented.(More)
The visual perception of words is known to activate the auditory representation of their spoken forms automatically. We examined the neural mechanism for this phonological activation using transcranial magnetic stimulation (TMS) with a masked priming paradigm. The stimulation sites (left superior temporal gyrus [L-STG] and inferior parietal lobe [L-IPL]),(More)
Percutaneous coronary intervention (PCI) was performed for chronic total occlusion of the proximal right coronary artery in a 70-year-old male with unstable angina. The forceful manipulation of the guide catheter led to an aortocoronary dissection involving the right Valsalva sinus and the ascending aorta. Intracoronary ultrasound (ICUS) showed the(More)