Keisuke Toyama

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Source current estimation from MEG measurement is an ill-posed problem that requires prior assumptions about brain activity and an efficient estimation algorithm. In this article, we propose a new hierarchical Bayesian method introducing a hierarchical prior that can effectively incorporate both structural and functional MRI data. In our method, the(More)
It has been empirically established that the cerebral cortical areas defined by Brodmann one hundred years ago solely on the basis of cellular organization are closely correlated to their function, such as sensation, association, and motion. Cytoarchitectonically distinct cortical areas have different densities and types of neurons. Thus, signaling patterns(More)
The dopamine system has been implicated in guiding behavior based on rewards. The pedunculopontine tegmental nucleus (PPTN) of the brainstem receives afferent inputs from reward-related structures, including the cerebral cortices and the basal ganglia, and in turn provides strong excitatory projections to dopamine neurons. This anatomical evidence predicts(More)
Humans can acquire appropriate behaviors that maximize rewards on a trial-and-error basis. Recent electrophysiological and imaging studies have demonstrated that neural activity in the midbrain and ventral striatum encodes the error of reward prediction. However, it is yet to be examined whether the striatum is the main locus of reward-based behavioral(More)
Independent component analysis (ICA) is a new, simple and powerful idea for analyzing multi-variant data. One of the successful applications is neurobiological data analysis such as electroencephalography (EEG), magnetic resonance imaging (MRI), and magnetoencephalography (MEG). However, many problems remain. In most cases, neurobiological data contain a(More)
The telomerase activity and length of telomeres of peripheral blood mononuclear cells obtained from 124 healthy individuals aged 4–95years was measured. Telomerase activity level was semiquantitatively assessed by a fluorescent-telomeric repeat amplification protocol (fluorescent-TRAP) using an internal telomerase assay standard, fluorescent primers and an(More)
The role of inhibitory Golgi cells in cerebellar function was investigated by selectively ablating Golgi cells expressing human interleukin-2 receptor alpha subunit in transgenic mice, using the immunotoxin-mediated cell targeting technique. Golgi cell disruption caused severe acute motor disorders. These mice showed gradual recovery but retained a(More)
The responses of neurons in the primate and cat primary visual cortices (V1s) to the stimuli within their classical receptive fields (CRFs) are markedly suppressed by the surrounding stimuli outside CRFs. In the present study, we show that a similar suppressive effect occurs for visually evoked magnetic responses in the human visual cortex. The initial peak(More)
We analysed the laminar distribution of transmembrane currents from embryonic (E) day 17 until adulthood after selective thalamic stimulation in slices of rat forebrain to study the development of functional thalamocortical and cortico-cortical connections. At E18 to birth a short-latency current sink was observed in the subplate and layer 6, which was(More)
To examine the neural mechanism underlying illusory-contour perception, we measured the magnetic responses of the human visual cortex to an abutting-line grating inducing illusory contours (test stimulus) and a non-abutting-line grating (control stimulus) using the technique of magnetoencephalography (MEG). In the initial latency period of 60-80 ms, the MEG(More)