Accumulation System: Distributed Neural Substrates of Perceptual Decision Making Revealed by fMRI Deconvolution.

Neural substrates of evidence accumulation have been a central issue in decision-making studies because of the prominent success of the accumulation model in explaining a wide range of perceptual decision making. Since accumulation-shaped activities have been found in multiple brain regions, which are called accumulators, questions regarding functional relations among these accumulators are emerging. This study employed the deconvolution method of functional magnetic resonance imaging (fMRI) signals from human male and female participants during object-category decision tasks, taking advantage of the whole-brain coverage of fMRI with improved availability of temporal information of the deconvolved activity.

Stochastic process underlying emergent recognition of visual objects hidden in degraded images.

When a degraded two-tone image such as a "Mooney" image is seen for the first time, it is unrecognizable in the initial seconds. The recognition of such an image is facilitated by giving prior information on the object, which is known as top-down facilitation and has been intensively studied. Even in the absence of any prior information, however, we experience sudden perception of the emergence of a salient object after continued observation of the image, whose processes remain poorly understood.

Language comprehension dependent on emotional context: a magnetoencephalography study.

In communication, language can be interpreted differently depending upon the emotional context. To clarify the effect of emotional context on language processing, we performed experiments using a cross-modal priming paradigm with an auditorily presented prime and a visually presented target. The primes were the names of people that were spoken with a happy, sad, or neutral intonation; the targets were interrogative one-word sentences with emotionally neutral content.

Phase-interpolated averaging for analyzing electroencephalography and magnetoencephalography epochs.

Stimulus-locked averages of electroencephalography (EEG) and magnetoencephalography (MEG) epochs reveal characteristic waveforms. EEG/MEG generation models to have reconstruct such waveforms have been recently proposed. These models assume that evoked, phase-modulated, and amplitude-modulated activities occur solely or simultaneously.

Inference in alpha rhythm phase and amplitude modeled on Markov random field using belief propagation from electroencephalograms.

Alpha rhythm is a major component of spontaneous electroencephalographic (EEG) data. We develop a novel method that can be used to estimate the instantaneous phases and amplitudes of the alpha rhythm with high accuracy by modeling the alpha rhythm phase and amplitude as Markov random field (MRF) models. By using a belief propagation technique, we construct an exact-inference algorithm that can be used to estimate instantaneous phases and amplitudes and calculate the marginal likelihood.

Masked immediate-repetition-priming effect on the early lexical process in the bilateral anterior temporal areas assessed by neuromagnetic responses.

A masked priming paradigm has been used to measure unconscious and automatic context effects on the processing of words. However, its spatiotemporal neural basis has not yet been clarified. To test the hypothesis that masked repetition priming causes enhancement of neural activation, we conducted a magnetoencephalography experiment in which a prime was visually presented for a short duration (50 ms), preceded by a mask pattern, and followed by a target word that was represented by a Japanese katakana syllabogram.

Phase-compensated averaging for analyzing electroencephalography and magnetoencephalography epochs.

Stimulus-locked averaging for electroencephalography and/or megnetoencephalography (EEG/MEG) epochs cancels out ongoing spontaneous activities by treating them as noise. However, such spontaneous activities are the object of interest for EEG/MEG researchers who study phase-related phenomena, e.g.

Neuroimaging study on brain asymmetries in situs inversus totalis.

Situs inversus totalis (SI) is a rare condition in which all visceral organs are arranged as mirror images of the usual pattern. The objective of this study was to determine whether SI individuals have reversed brain asymmetries. We performed a neuroimaging study on 3 SI subjects and 11 control individuals with normally arranged visceral organs.

Neural activations correlated with reading speed during reading novels.

Functional magnetic resonance imaging was used to measure neural activations in subjects instructed to silently read novels at ordinary and rapid speeds. Among the 19 subjects, 8 were experts in a rapid reading technique. Subjects pressed a button to turn pages during reading, and the interval between turning pages was recorded to evaluate the reading speed.

Early neural activation for lexico-semantic access in the left anterior temporal area analyzed by an fMRI-assisted MEG multidipole method.

To determine the time and location of lexico-semantic access, we measured neural activations by magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) and estimated the neural sources by fMRI-assisted MEG multidipole analysis. Since the activations for phonological processing and lexico-semantic access were reported to overlap in many brain areas, we compared the activations in lexical and phonological decision tasks. The former task required visual form processing, phonological processing, and lexico-semantic access, while the latter task required only visual form and phonological processing, with similar phonological task demands for both tasks.

Phonological influences on lexicosemantic processing of kanji words.

To investigate the phonological influences on the lexicosemantic process with a strong orthographic constraint, we used kanji (morphogram) homophone words and measured, using magnetoencephalography, the neural activities during the silent reading of prime-target pairs. The primes were phonologically the same as or different from the targets or pseudocharacters. The neural activities in the left posterior temporal and inferior parietal areas became weaker with phonological repetition.

Brownian motion, fluctuation and life.

The measurements of dynamic behaviors of biomolecules in relation to their functions have been allowed using single molecule measurements. Thermal Brownian motion causes random step motion of motor proteins and structural fluctuation of protein molecules between multiple states. In hierarchic structure of life, the fluctuation is modulated.

Discrete stochastic process underlying perceptual rivalry.

In perceptual rivalry such as ambiguous figure perception and binocular rivalry, the conscious percept spontaneously alternates between two stable interpretations of an unchanging stimulus. It is well known that the time intervals of the perceptual alternation follow a gamma distribution (GD), but its implication for the alternation mechanism has not been clarified. We examined quantitatively GDs fitted to alternation intervals, and found that the shape-determining parameter alpha of the GDs took natural numbers.