Toshiaki Imada's research while affiliated with Chiba University and other places

Publications (73)

Article
Full-text available
Verbal interaction and imitation are essential for language learning and development in young children. However, it is unclear how mother–child dyads synchronize oscillatory neural activity at the cortical level in turn-based speech interactions. Our study investigated interbrain synchrony in mother–child pairs during a turn-taking paradigm of verb...
Article
No PDF available ABSTRACT This study examined how talker gender information may influence second language speech perception. The participants were ten right-handed male Japanese adults with normal hearing. The speech stimuli were two minimal pairs of English words, “heed-hod” and “head-had”, recorded from twenty male and twenty female native Englis...
Article
Full-text available
CONFERENCE ABSTRACT Human speech contains not only the linguistic content but also important information about speaker identity and affect. This study employed whole-head magnetoencephalography (MEG) to examine how brain activities were modulated by selective listening of phoneme, affect and gender information with different degrees of task diffic...
Article
No PDF available ABSTRACT This magnetoencephaalography (MEG) study investigated the effects of language experience in cue weighting of formant structure supporting native language neural commitment. The speech stimuli were a grid of /ra-la/ synthetic continuua with systematic variations of the second (F2) and third (F3) formants. The subjects were...
Article
Bilingual experience alters brain structure and enhances certain cognitive functions. Bilingualism can also affect mathematical processing. Reduced accuracy is commonly reported when arithmetic problems are presented in bilinguals’ second (L2) vs. first (L1) language. We used MEG brain imaging during mental addition to characterize spatiotemporal d...
Article
Full-text available
Pitch plays a crucial role in music and speech perception. Pitch perception is characterized by multiple perceptual dimensions, such as pitch height and chroma. Information provided by auditory signals that are related to these perceptual dimensions can be either congruent or incongruent. To create conflicting cues for pitch perception, we modified...
Article
Behavioral studies have shown that ramped sounds are judged to be louder and longer than damped sounds. Here we employed magnetoencephalography (MEG) to examine cortical processing of the perceptual temporal asymmetry. The participants were 6 normal-hearing right-handed male adults. The synthesized stimuli included three kinds, pure tone, piano not...
Article
Full-text available
This magnetoencephalography (MEG) study investigated evoked ON and OFF responses to ramped and damped sounds in normal-hearing human adults. Two pairs of stimuli that differed in spectral complexity were used in a passive listening task; each pair contained identical acoustical properties except for the intensity envelope. Behavioral duration judgm...
Article
Significance Infants discriminate speech sounds universally until 8 mo of age, then native discrimination improves and nonnative discrimination declines. Using magnetoencephalography, we investigate the contribution of auditory and motor brain systems to this developmental transition. We show that 7-mo-old infants activate auditory and motor brain...
Article
Full-text available
The development of speech perception shows a dramatic transition between infancy and adulthood. Between 6 and 12 months, infants' initial ability to discriminate all phonetic units across the world's languages narrows-native discrimination increases while non-native discrimination shows a steep decline. We used magnetoencephalography (MEG) to exami...
Article
Full-text available
Due to the rapid anatomical changes that occur within the brain structure in early human development and the significant differences between infant brains and the widely used standard adult templates, it becomes increasingly important to utilize appropriate age- and population-specific average templates when analyzing infant neuroimaging data. In t...
Conference Paper
This paper shows that pattern classification based on machine learning is a powerful tool to analyze human brain activity data obtained by magnetoencephalography (MEG). We propose a new weighting method using a multiple kernel learning (MKL) algorithm to localize the brain area contributing to the accurate vowel discrimination. Our MKL simultaneous...
Conference Paper
This paper shows that pattern classification based on machine learning is a powerful tool for analyzing human brain activity data obtained by magnetoencephalography (MEG). In our previous work, a weighting method using multiple kernel learning was proposed, but this method had a high computational cost. In this paper, we propose a novel and fast we...
Article
Full-text available
Behavioral studies show that bilinguals are slower and less accurate when performing mental calculation in their nondominant (second; L2) language than in their dominant (first; L1) language. However, little is known about the neural correlates associated with the performance differences observed between bilinguals' 2 languages during arithmetic pr...
Article
Infants change from universal language‐general listeners to language‐specific listeners in the first year of life. Studies show that statistical learning affects this change. As learning ensues, the power of statistical information subsides and a reliance on learned categories emerges. We posited that phonetic processing is anchored by two strategi...
Article
Full-text available
In this study, behavioral and brain measures were taken to assess the effects of training a Japanese adult subject to perceptually distinguish English /l/ and /r/. Behavioral data showed significant improvement in identifying both trained and untrained speech stimuli. Correspondingly, neuromagnetic results showed enhanced mismatch field responses i...
Article
Full-text available
The present study used magnetoencephalography (MEG) to examine perceptual learning of American English /r/ and /l/ categories by Japanese adults who had limited English exposure. A training software program was developed based on the principles of infant phonetic learning, featuring systematic acoustic exaggeration, multi-talker variability, visibl...
Article
Amplitude modulation (AM) provides very important auditory information for the perception of complex sounds by normal listeners as well as cochlear implant users. The present study used a 122-channel whole-head magnetoencephalography (MEG) system to record auditory responses to amplitude-modulated pure tones and broadband noises in six healthy male...
Article
In adults, neural responses to the acoustic properties of native and non-native speech sounds differ. Recent magnetoencephalography (MEG) studies indicate that two regions of the brain, the superior temporal area and inferior parietal area (Broca's), in both the left and right hemispheres, may contribute to how the adult brain responds to the acous...
Article
Magnetoencephalography (MEG) provides a safe, noninvasive method for studying the developing brain by offering reliable localization of the brain regions activated during speech processing. However technical challenges make recording awake infants difficult. The small size of the infant head in the adult-sized helmet results in a low signal-to-nois...
Article
Language acquisition involves neural commitment to language‐specific auditory patterns, which may interfere with second language learning. This magnetoencephalography study tested whether perceptual interference could occur at the preattentive level. Auditory mismatch field (MMF) responses were recorded from ten American and ten Japanese adult subj...
Article
Discriminative responses to tones, harmonics, and syllables in the left hemisphere were measured with magnetoencephalography in neonates, 6-month-old infants, and 12-month-old infants using the oddball paradigm. Real-time head position tracking, signal space separation, and head position standardization were applied to secure quality data for sourc...
Article
Full-text available
The present study investigated whether the human mirror-neuron system exhibits gender differences. Neuromagenetic mu (approximately 20 Hz) oscillations were recorded over the right primary motor cortex, which reflect the mirror neuron activity, in 10 female and 10 male participants while they observed the videotaped hand actions and moving dot. In...
Article
This phonetic study examined neural encoding of within-and cross- category information as a function of language experience. Behavioral and magnetoencephalography (MEG) measures for synthetic /ba-wa/ and /ra-la/ stimuli were obtained from ten American and ten Japanese subjects. The MEG experiments employed the oddball paradigm in two conditions. On...
Article
Studies suggest that exact mathematical terms (numbers, multiplication tables) are stored in the language in which they were originally learned. Bilingual adults are less accurate and slower when doing exact mathematical calculations using their non-dominant language. Approximate mathematical calculations appear not to be affected by language. The...
Article
Full-text available
Linguistic experience alters an individual's perception of speech. We here provide evidence of the effects of language experience at the neural level from two magnetoencephalography (MEG) studies that compare adult American and Japanese listeners' phonetic processing. The experimental stimuli were American English /ra/ and /la/ syllables, phonemic...
Article
Magnetoencephalography (MEG) detects the brain's magnetic fields as generated by neuronal electric currents arising from synaptic ion flow. It is noninvasive, has excellent temporal resolution, and it can localize neuronal activity with good precision. For these reasons, many scientists interested in the localization of brain functions have turned...
Article
Full-text available
In the biomagnetic inverse problem, it is important that the optimal method be selected, especially when estimating internal electrical sources for higher functions with poor information about their source profile. In this paper, internal sources of brain magnetic fields associated with short-term memory processes were estimated by: 1) a nonlinear...
Article
Introduction According to human patient studies [1], the lesion in the inferior temporal cortex and/or in the parietal areas causes the agnosia. There are two types of agnosia; apperceptive agnosia and association agnosia. According to Farah [2], the apperceptive agnosia patients seem to have adequate elementary visual functions and general cogniti...
Article
this paper, we calculated the estimation errors of position and moment of the dipole localized by this single dipole method using locally selected channels rather than all channels of the whole-head measurement system
Article
The present study investigated brain plasticity in Japanese adults learning the English /l–r/ distinction. Both behavioral and brain (MEG) measures were used. Training was designed to mimic the listening experience of infants who are exposed to the exaggerated acoustic events contained in infant‐directed speech (‘‘motherese’’). A multimedia softwar...
Article
This study investigated, for American adolescents, whether the learning of non-native speech contrasts in one prosodic domain (Mandarin Chinese tones) would influence the processing of non-native contrasts in another prosodic domain (Mandarin Chinese intonation). Two groups of 14-year-old American teenagers were tested using the functional magnetic...
Conference Paper
Full-text available
The pilot study shows strong effects of language experience in behavioral and MEG results. A full report is shown in Zhang et al. (2005). Effects of language experience: neural commitment to language-specific auditory patterns. Neuroimage, 26(3), 703-720.
Article
To find out which brain regions are responsible for the mental construction and recognition of a kanji character initiated by visually presented kanji radicals, rather than by information retained in the memory, a left hen radical and the corresponding right tsukuri radical were simultaneously presented randomly to either the left or right visual f...
Chapter
The Japanese language has three writing systems: kanji script, or ideograms, hiragana script, or phonograms and katakana script, another type of phonograms. Modern Japanese has 71 hiragana and 71 katakana characters, which have one-to-one correspondence. A hiragana character has only one phonetic value, which represents a mora, or a syllable, in sp...
Chapter
Previous studies of somatosensory evoked potentials (SEPs) and fields (SEFs) have shown that high-frequency signals in the range of 300–900 Hz concur with the primary response (N20 and N20m) of the somatosensory cortex [1],[2]. However, the physiological mechanisms of the high-frequency oscillations remained undetermined. We addressed the issue by...
Article
To investigate the characteristics of visual short-term memory in humans, brain magnetic fields evoked during a delayed paired comparison task were recorded using a whole-head neuromagnetometer. The visual stimulus consisted of a circle with different colors in each quadrant. In the memory condition, subjects reacted with the index finger, when the...
Article
The mental rotation task has been reported to activate the human parietal and extra-striate areas, based on the results of fMRI and PET analysis. In the present study, we investigated the dynamic properties of the distributed cortical activity related to mental rotation processes at high temporal resolution by means of brain magnetic field measurem...
Article
N1m is an auditory evoked brain magnetic field with a magnitude of 100 fT order observed over the auditory cortex, 100 ms after the onset of auditory stimuli. The N1m is often used as a landmark of functional localization in the cortex. However, the mechanism of the N1m has not yet been clarified. The N1m peak amplitude and latency are dependent on...
Article
The distal-proximal representations of the finger and palm in the first somatosensory cortex (SI) were studied in humans. Somatosensory evoked magnetic fields (SEFs) from 11 subjects were measured, following mechanical stimulation of the skin by using a 122 channel whole head SQUID system. Sensory stimulus comprising of a 10 ms vibration at the fre...
Article
Full-text available
We investigated the dynamic properties of the distributed cortical activity related to mental rotation processes at high temporal resolution by means of brain-magnetic-field measurements and a linear inversion algorithm. Distributed neural activities during the mental rotation and control tasks were estimated for six subjects, and the differences i...
Article
Objective: Frequency organization in the human somatosensory cortex was studied. Design and methods: Somatosensory evoked magnetic fields (SEFs) from 12 subjects were measured following vibratory stimulation of the index finger by using a 122 channel whole head SQUID system. Sensory stimuli comprising a 40 ms vibration at frequencies of 50, 100,...
Article
To investigate the characteristics of short-term memory in the human brain, magnetoencephalograms (MEGs) evoked by a delayed paired comparison task were recorded. A visual stimulus, a circle with a different color in each quadrant, was presented. In the memory task, subjects were requested to move the index finger when the second stimulus (TEST) wa...
Conference Paper
In this study, a dynamic estimation of the current distribution in a mental rotation task from the measurements of the brain magnetic field was presented. The authors used a current reconstruction algorithm based on the weighted minimum-norm estimation (WMNE) with the weighing factors calculated from the results of simplified multiple signal classi...
Article
Auditory evoked cortical responses, electric. N1 and magnetic N1m, increase when the interstimulus interval (ISI) increases. We assumed that the response to a tone is mainly affected by the immediately preceding ISI, by the immediately preceding pause between stimuli (PBS) and by the previous stimulus duration (PSD). These 3 values are connected by...
Conference Paper
Visually evoked magnetoencephalograms (MEGs) associated with a delayed-match paradigm were measured to obtain functional information related to short-term memory processes. A delayed-match paradigm was introduced. The paradigm consists of a four-color-stimuli; a pair of circles with four differently-colored regions. The subjects retain the first im...
Article
High-frequency potential oscillations in the range of 300-900 Hz have recently been shown to concur with the primary response (N20) of the somatosensory cortex in awake humans. However, the physiological mechanisms of the high-frequency oscillations remained undetermined. We addressed the issue by analyzing magnetic fields during wakefulness and sl...
Article
A conventional equivalent current dipole estimation provides one of the quantitative measures to evaluate the discrepancy between two single-dipole-like magnetic field patterns, though there is one problem; all stimulus positions in the visual field do not necessarily contribute to the generation of a single-dipole-like magnetic field. Another impo...
Article
This letter shows that a portable visual stimulator for MEG measurements can be realized using an optical fiber bundle and a CRT display system offering high brightness and high speed raster scanning, and that MEGs with neither magnetic contamination nor jitter can be measured by the stimulator.
Article
The spatio-temporal organization of the human primary auditory response (N19 and P30) was determined by analyzing magnetic fields from the right hemisphere evoked by monaural clicks to the left ear. The magnetic response consisted of peaks corresponding to electrical N19 (N19m) and P30 (P30m) within 40 msec after stimulation. However, the onset of...
Article
Magnetic compound action fields (CAFs) over the right arm were measured from 63 sensor positions with two 7-channel SQUID gradiometer systems following electrical stimulation of the index and little fingers as well as the ring finger separately. The wave forms of the CAFs were primarily biphasic, corresponding to the depolarization and repolarizati...
Article
Full-text available
The dependence of the auditory evoked brain magnetic responses on the interstimulus interval (ISI), as well as on the stimulus onset asynchrony (SOA), was examined by using pure tone stimuli. Several papers have shown that the auditory evoked responses, N1 and N1m, increase as the SOA increases, which is explained by refractoriness. The peak latenc...
Article
Magnetic compound action fields (CAFs) over the right arm were measured from 63 sensor positions with two 7-channel SQUID gradiometer systems following electrical stimulation of the median nerve at the wrist. The field mapping of the CAFs revealed a propagating quadrupolar pattern with the leading depolarization and trailing repolarization fronts....
Article
Full-text available
We recorded neuromagnetic fields from 4 Japanese subjects, mainly over the left temporal, parietal and occipital areas, responding to visual stimuli presented for 100 ms every 1.3 1.7 s at lower left visual field. In two subjects the right hemisphere was also measured. The stimuli were randomly presented a kanji characters (50%) or a random dot pat...
Article
The purpose of this study is to make a quantitative search for possibility of deterministic dynamics in MEG (Magnetoencephalogram) data by analysing the correlation dimensions. The time series data of MEG are analyzed not only by the conventional G-P (Grassberger-Procaccia) algorithm but also by an improved estimator of the correlation dimension pr...

Citations

... Researchers estimate that almost half of dementia cases are attributable to modifiable risk factors including physical inactivity and depression [44]. Studies [45] indicate that engaging in healthy lifestyles behaviors across multiple domains including physical activity, cognitive engagement, and stress management can slow cognitive decline [46]- [51] and promote brain neuroplasticity [52], [53]. There currently exists a gap in the design of methods to assist midlife and older adults in learning to incorporate such healthy behaviors into their everyday lives in a way that leads to sustained, holistic behavior change. ...
... Our stimuli were generalized versions of classic Shepard tones. The original Shepard tones proved pivotal in trying to disentangle the contribution of two putative cues to pitch termed chroma and pitch height [52,65]. Our generalized Shepard tones further allowed the independent manipulation of two types of acoustic dimensions, SFS and SE, which could be crossed with properties of harmonicity and inharmonicity. ...
... Given this fact, the present investigation followed up our recent study (Cheng et al., 2019) in training Chinese adults to learn the English /i/-/ɪ/ contrast and further tested the hypothesis that increasing the amount of acoustic variability along the secondary dimension (i.e., vowel duration) can induce successful learning independent of talker variability. Specifically, Cheng et al. (2019) adopted an improved HVPT paradigm first introduced by Zhang et al. (2000), Zhang et al. (2009) by incorporating several important features to simulate "enriched" exposure for facilitating speech learning. In addition to incremental levels of talker variability across the training sessions, one salient feature was the structured support of adaptive scaffolding by introducing decremental levels of acoustic exaggeration inspired by benefits of the infantdirected speech that is more acoustically variable than speech directed to adults to category learning (Burnham et al., 2002;Kitamura et al., 2001;Kitamura & Burnham, 2003;Kuhl et al., 1997;Uther et al., 2007). ...
... Specific temporal and parietal regions in the brain become specialized for native language processing with focal and efficient activation. (b) The effects of NLNC are self-reinforcing and bidirectional – it enhances the detection of compatible higher-order linguistic patterns, while at the same time hindering the detection of non-conforming patterns contained in foreign languages, as shown behaviorally (Iverson et al., 2003) and neurally at the preattentive level (Zhang et al., 2006). (c) Neural commitment is not irreversible – Enriched exposure can induce substantial plasticity in the adult brain for second language learning. ...
... Audition is known to mark more strongly the onset than the offset of auditory events (Philips, Hall, & Boehnke, 2002). In addition, the strength of the mark is a function of the rate of change in intensity of the onset and offset ramp (Phillips et al., 2002; see also Deneux et al., 2016;Lu, Liang, & Wang, 2001;Zhang, et al., 2016). We may observe a subjective counterpart of this difference in loudness perception: the beginning of a sound is the portion of the sound that contributes most to the overall loudness of the sound (Dittrich & Oberfeld, 2009). ...
... www.praat.org). The interstimulus interval was 1200 msec, as used in previous studies (Eilers et al, 1979;Zhang et al, 2000). Table 2 provides a summary of the contrasts including fundamental frequencies, and Table 3 provides a summary of place of articulation and voicing characteristics. ...
... We observed MMNs when metric structure was violated in such a way, that the input could not be predicted by the meter established in the previous bars. Previously MMNms have been found to disruptions of a regular sequence of identical sounds (Ford and Hillyard, 1981; Imada et al., 1993; Nordby et al., 1988). Takegata et al. (2001) have shown that MMN increase in size, when a strong regularity, created by two different sounds, is violated compared with a situation where the two different sounds do not establish a common temporal framework. ...
... Uno es el proceso de detección del cambio acústico con la activación bilateral y el otro, el procesamiento fonético específico, el cual está lateralizado a la corteza auditiva izquierda. Así, el aprendizaje fonético de un segundo lenguaje, como hablantes de japonés en entrenamiento para aprender el contraste /r-l/ en inglés, muestra un cambio más prominente en el hemisferio izquierdo que en el derecho (Zhang, Kuhl, Imada, Kotani & Pruitt, 2001). Sin embargo, Kasai et al. (2001) reportaron que la MMNm de los japoneses a los tonos puros y a los cambios intracategóricos de una vocal fue predominante en el hemisferio derecho, mientras que la MMN a los cambios en las categorías de vocales fueron bilaterales. ...
... These findings suggest the existence of a potential "sensitive " period for structural brain development, that is important for language, and which precedes the behavioral transition in language processing that occurs between 6 and 12 months of age. In other words, brain structural development may be an essential first step in the dramatic transition observed both in behavior and measures of neural function ( Kuhl et al., 2014 ;Zhao et al., 2021 ) observed at 11-12 months of age. This would be consistent with the concept that functional activity is reliant on already existing structural scaffolding, a logically intuitive idea. ...
... MTM was generated according to the procedure illustrated in Figure 2. GTM models were constructed with runGTM function of ugtm [49], which is a python package that implements GTM [36,37]. In the training of GTM models using the runGTM function, the following parameters were used: k = 28, m = 2, where k is the sqrt of the number of GTM nodes, m is the sqrt of the number of radial basis function centers, and other parameters were set to default. ...