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Visual working memory (vWM) is an important ability required for various cognitive tasks although its neural underpinnings remain unclear. While many studies have focused on theta (4-7 Hz) and gamma (> 30 Hz) rhythms as a substrate of vWM, here we show that temporal signals embedded in alpha (8-12 Hz) and beta (13-30 Hz) bands can be a good predictor of vWM capacity. Neural activity of healthy human participants was recorded with magnetoencephalography when they performed a classical vWM task (change detection). We analyzed changes in inter-peak intervals (IPIs) of oscillatory signals along with an increase in WM load (a number of to-be-memorized items, 1-6). Results showed a load-dependent reduction of IPIs in the parietal and frontal regions, indicating that alpha/beta rhythms became faster when multiple items were stored in vWM. Furthermore, this reduction in IPIs was positively correlated with individual vWM capacity, especially in the frontal cortex. Those results indicate that vWM is represented as a change in oscillation frequency in the human cerebral cortex., Competing Interests: Declaration of competing interest The authors declare no competing financial interest., (Copyright © 2020. Published by Elsevier Inc.)

Neural oscillatory signals has been associated with many high-level functions (e.g. attention and working memory), because they reflect correlated behaviors of neural population that would facilitate the information transfer in the brain. On the other hand, a decreased power of oscillation (event-related desynchronization, ERD) has been associated with an irregular state in which many neurons behave in an uncorrelated manner. In contrast to this view, here we show that the human ERD is linked to the increased regularity of oscillatory signals. Using magnetoencephalography, we found that presenting a visual stimulus not only induced a decrease in power of alpha (8-12 Hz) to beta (13-30 Hz) rhythms in the contralateral visual cortex but also reduced the mean and variance of their inter-peak intervals (IPIs). This indicates that the suppressed alpha/beta rhythms became faster (reduced mean) and more regular (reduced variance) during visual stimulation. The same changes in IPIs, especially those of beta rhythm, were observed when subjects allocated their attention to a contralateral visual field. Those results revealed a new role of the event-related decrease in alpha/beta power and further suggested that our brain regulates and accelerates a clock for neural computations by actively suppressing the oscillation amplitude in task-relevant regions., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The primate visual system is assumed to comprise two main pathways: a ventral pathway for shape and color perception and a dorsal pathway for spatial processing and visuomotor control. Previous studies consistently reported strong activation in the dorsal pathway(especially in the inferior parietal region) induced by manipulable object images such as tools. However, it is controversial whether the dorsal pathway retains this preferential activity to tool images under unconscious perception. In the present study, we used magnetoencephalography (MEG) and investigated spatio-temporal dynamics of neural responses to visible and invisible tool images. A presentation of visible tool images elicited a strong neural response over the parietal regions in the left hemisphere peaking at 400 msec. This response unique to the processing of tool information in the left parietal regions was still observed when conscious perception of tool images was inhibited by interocular suppression. Furthermore, analyses of neural oscillation signals revealed a suppression of m rhythm (8-13 Hz), a neural index of movement execution or imagery,induced by both visible and invisible tools. Those results indicated that the neural circuit to process the tool information was preserved under unconscious perception, highlighting an implicit aspect of the dorsal pathway.

This study investigated how infants perceive and interpret human body movement. We recorded the eye movements and pupil sizes of 9- and 12-month-old infants and of adults (N=14 per group) as they observed animation clips of biomechanically possible and impossible arm movements performed by a human and by a humanoid robot. Both 12-month-old infants and adults spent more time looking at the elbows during impossible compared with possible arm movements, irrespective of the appearance of the actor. These results suggest that by 12 months of age, infants recognize biomechanical constraints on how arms move, and they extend this knowledge to humanoid robots. Adults exhibited more pupil dilation in response to the human's impossible arm movements compared with the possible ones, but 9- and 12-month-old infants showed no differential pupil dilation to the same actions. This finding suggests that the processing of human body movements might still be immature in 12-month-olds, as they did not show an emotional response to biomechanically impossible body movements. We discuss these findings in relation to the hypothesis that perception of others' body movements relies upon the infant's own sensorimotor experience., (Copyright © 2012 Elsevier Inc. All rights reserved.)

From which regions of the brain do conscious representations of visual stimuli emerge? This is an important but controversial issue in neuroscience because some studies have reported a major role of the higher visual regions of the ventral pathway in conscious perception, whereas others have found neural correlates of consciousness as early as in the primary visual areas and in the thalamus. One reason for this controversy has been the difficulty in focusing on neural activity at the moment when conscious percepts are generated in the brain, excluding any bottom-up responses (not directly related to consciousness) that are induced by stimuli. In this study, we address this issue with a new approach that can induce a rapid change in conscious perception with little influence from bottom-up responses. Our results reveal that the first consciousness-related activity emerges from the higher visual region of the ventral pathway. However, this activity is rapidly diffused to the entire brain, including the early visual cortex. These results thus integrate previous "higher" and "lower" views on the emergence of neural correlates of consciousness, providing a new perspective for the temporal dynamics of consciousness.

The role of sensory information in motor control has been studied, but the cortical processing underlying cross-modal relationship between visual and somatosensory information for movement execution remains a matter of debate. Visual estimates of limb positions are congruent with proprioceptive estimates under normal visual conditions, but a mismatch between the watched and felt movement of the hand disrupts motor execution. We investigated whether activation in somatosensory areas was affected by the discordance between the intended and an executed action. Subjects performed self-paced thumb movement of the left hand under normal visual and mirror conditions. The Mirror condition provided a non-veridical and unexpected visual feedback. The results showed activity in the primary somatosensory area to be inhibited and activity in the secondary somatosensory area (SII) to be enhanced with voluntary movement, and neural responses in the SII and parietal cortex were strongly affected by the unexpected visual feedback. These results provide evidence that the visual information plays a crucial role in activation in somatosensory areas during motor execution. A mechanism that monitors sensory inputs and motor outputs congruent with current intension is necessary to control voluntary movement., (Copyright © 2011. Published by Elsevier Inc.)

Visual working memory (VWM) is known as a highly capacity-limited cognitive system that can hold 3-4 items. Recent studies have demonstrated that activity in the intraparietal sulcus (IPS) and occipital cortices correlates with the number of representations held in VWM. However, differences among those regions are poorly understood, particularly when task-irrelevant items are to be ignored. The present fMRI-based study investigated whether memory load-sensitive regions such as the IPS and occipital cortices respond differently to task-relevant information. Using a change detection task in which participants are required to remember pre-specified targets, here we show that while the IPS exhibited comparable responses to both targets and distractors, the dorsal occipital cortex manifested significantly weaker responses to an array containing distractors than to an array containing only targets, despite that the number of objects presented was the same for the two arrays. These results suggest that parietal and occipital cortices engage differently in distractor processing and that the dorsal occipital, rather than parietal, activity appears to reflect output of stimulus filtering and selection based on behavioral relevance.

Numerous studies have demonstrated effects of spatial attention within single sensory modalities (within-modal spatial attention) and the effect of directing attention to one sense compared with the other senses (intermodal attention) on cortical neuronal activity. Furthermore, recent studies have been revealing that the effects of spatial attention directed to a certain location in a certain sense spread to the other senses at the same location in space (cross-modal spatial attention). The present study used magnetoencephalography to examine the temporal dynamics of the effects of within-modal and cross-modal spatial and intermodal attention on cortical processes responsive to visual stimuli. Visual or tactile stimuli were randomly presented on the left or right side at a random interstimulus interval and subjects directed attention to the left or right when vision or touch was a task-relevant modality. Sensor-space analysis showed that a response around the occipitotemporal region at around 150 ms after visual stimulation was significantly enhanced by within-modal, cross-modal spatial, and intermodal attention. A later response over the right frontal region at around 200 ms was enhanced by within-modal spatial and intermodal attention, but not by cross-modal spatial attention. These effects were estimated to originate from the occipitotemporal and lateral frontal areas, respectively. Thus the results suggest different spatiotemporal dynamics of neural representations of cross-modal attention and intermodal or within-modal attention.

Previously, we used near-infrared spectroscopy (NIRS) to measure infant's brain activity during face processing by detecting changes in hemodynamic responses, oxy-Hb, deoxy-Hb, and total-Hb concentrations [1,2]. We found that the right temporal cortex of the brain was activated when infants looked at upright frontal faces rather than inverted faces, and at the frontal view as well as the profile view on 8-month-olds. In the present study, we investigated 7- and 8-month-olds' brain activity related to the perception of mother's and stranger's faces by NIRS. The finding was that oxy-Hb and total-Hb concentrations in the right temporal cortex increased against the baseline during presentation of the mother's face. For strangers' faces, the total-Hb concentration in the right temporal cortex was greater than the baseline. By contrast, oxy- and total-Hb concentrations in the left temporal cortex increased only in the presentation of mother's face. The great activity in the right temporal region for faces irrespective of familiarity was consistent with a predominance of the right temporal cortex found previously in infants [1,2] as well as functional magnetic resonance imaging (fMRI) studies in adults [3,4]. In contrast to the activity in the right temporal cortex, the greater hemodynamic response in the left temporal cortex was observed only in the mother's face condition. These findings suggest that the processing of the mother's face enhances activity in bilateral temporal cortex. This is the first study to clarify the location of brain activity in infants related to the perception of their mother's face., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

In this study, the cortical dynamics of the visual change detection process were investigated using an oddball paradigm similar to that used in auditory mismatch negativity studies. When subjects watched a silent movie, color stimuli were presented using 280 dual color LEDs arranged along the frame of the video screen. Task-irrelevant red and blue color stimuli were presented randomly at a probability of 10% and 90%, respectively, in one session and vice versa for the other one, and we traced brain responses using magnetoencephalography. Results show that activation in the middle occipital gyrus (MOG) was significantly enhanced for the infrequent stimulus, while early activities in Brodmann's area 17/18 were comparable for the frequent and infrequent stimuli. These results suggest that automatic visual change detection is associated with the MOG activity.

Detecting a visual change was suggested to relate closely to the visual sensory memory formed by visual stimuli before the occurrence of the change, because change detection involves identifying a difference between ongoing and preceding sensory conditions. Previous neuroimaging studies showed that an abrupt visual change activates the middle occipital gyrus (MOG). However, it still remains to be elucidated whether the MOG is related to visual change detection based on sensory memory. Here we tried to settle this issue using a new method of stimulation with blue and red LEDs to emphasize a memory-based change detection process. There were two stimuli, a standard trial stimulus and a deviant trial stimulus. The former was a red light lasting 500 ms, and the latter was a red light lasting 250 ms immediately followed by a blue light lasting 250 ms. Effects of the trial-trial interval, 250 approximately 2000 ms, were investigated to know how cortical responses to the abrupt change (from red to blue) were affected by preceding conditions. The brain response to the deviant trial stimulus was recorded by magnetoencephalography. Results of a multi-dipole analysis showed that the activity in the MOG, peaking at around 150 ms after the change onset, decreased in amplitude as the interval increased, but the earlier activity in BA 17/18 was not affected by the interval. These results suggested that the MOG is an important cortical area relating to the sensory memory-based visual change-detecting system., (Copyright 2010 Elsevier Inc. All rights reserved.)

The quick detection of dynamic changes in multisensory environments is essential to survive dangerous events and orient attention to informative events. Previous studies have identified multimodal cortical areas activated by changes of visual, auditory, and tactile stimuli. In the present study, we used magnetoencephalography (MEG) to examine time-varying cortical processes responsive to unexpected unimodal changes during continuous multisensory stimulation. The results showed that there were change-driven cortical responses in multimodal areas, such as the temporo-parietal junction and middle and inferior frontal gyri, regardless of the sensory modalities where the change occurred. These multimodal activations accompanied unimodal activations, both of which in general had some peaks within 300 ms after the changes. Thus, neural processes responsive to unimodal changes in the multisensory environment are distributed at different timing in these cortical areas.

Williams syndrome is known for uneven cognitive abilities. Visuospatial difficulties such as a failure in constructing objects are considered to be characteristic and may influence the copying of Japanese semantic characters, kanji. In contrast to previous investigations, which were done mainly cross-sectionally, this study focused on the developmental aspects of the symptoms, to get a better view of the mechanism. Developmental changes in visuospatial abilities (including copying two-dimensional figures, three-dimensional figures, and kanji) in four boys with Williams syndrome, ages 4 to 11 years, were longitudinally observed for 6-9 years. The Benton's three-dimensional block construction tests and the Yerkes test were also performed. Some of the results were compared with those of mental age-matched children. The observation revealed improvements in performance for copying two-dimensional figures, as well as for copying kanji, in the Williams syndrome participants; however, copying three-dimensional figures tended to remain difficult, especially if in a transparent view. Obtaining three-dimensional information using pictorial cues seemed to remain difficult for the Williams syndrome participants even at the later stage of study monitoring. This difficulty might be correlated with the core dysfunction of Williams syndrome.

Background: To segregate luminance-related, face-related and non-specific components involved in spatio-temporal dynamics of cortical activations to a face stimulus, we recorded cortical responses to face appearance (Onset), disappearance (Offset), and change (Change) using magnetoencephalography., Results: Activity in and around the primary visual cortex (V1/V2) showed luminance-dependent behavior. Any of the three events evoked activity in the middle occipital gyrus (MOG) at 150 ms and temporo-parietal junction (TPJ) at 250 ms after the onset of each event. Onset and Change activated the fusiform gyrus (FG), while Offset did not. This FG activation showed a triphasic waveform, consistent with results of intracranial recordings in humans., Conclusion: Analysis employed in this study successfully segregated four different elements involved in the spatio-temporal dynamics of cortical activations in response to a face stimulus. The results show the responses of MOG and TPJ to be associated with non-specific processes, such as the detection of abrupt changes or exogenous attention. Activity in FG corresponds to a face-specific response recorded by intracranial studies, and that in V1/V2 is related to a change in luminance.

Using random dots blinking (RDB), which reflects the activity of the higher visual area related to face perception, the following stimuli were presented. (1) Upright: a schematic face; (2) Inverted: the Upright stimulus inverted; and (3) Scrambled: the same contour and features as in Upright but with the spatial relation distorted. Clear negative components (N-ERP250) were identified at approximately 250 ms after stimulus onset. At the T5 and T6 electrodes, the peak latency was significantly longer for Inverted and Scrambled than for Upright. At the P4 electrode, the maximum amplitude was significantly larger for Scrambled than for Upright and Inverted. These results indicate that the delayed latency for Inverted and Scrambled reflects the involvement of the additional analytic processing caused by the configural distortion, and that the increase in amplitude for Scrambled indicates the existence of further processing caused by the distortion of the spatial relationship between the contour and features.

To understand the processing of facial expressions in terms of social communication, it is important to clarify how they are influenced by environmental stimuli such as natural scenes or objects. We investigated how and when neural responses to facial expressions were modulated by both a natural scene and an object containing emotional information. A facial expression stimulus (fearful/neutral) was presented after a scene or object stimulus (fearful/neutral), and then event-related potentials were recorded from both the onset of scene and facial expression presentation. As in previous studies, for the presentation of the scenes and objects positive-going waves at around 200-500 ms were observed for unpleasant visual stimuli at the Pz and Cz electrodes when the stimuli were intact; however, such a response was not observed when the stimuli were scrambled. During the subsequent facial expression presentation period, although we could not identify a significant interaction between the contextual information and facial expression in the N170 component, we observed a significant interaction in the P2 component: the P2 amplitude of the fearful cued was significantly larger than that of the neutral cued condition when the face was fearful, and the P2 amplitude of the neutral face was significantly larger than that of the fearful face condition when the preceding stimulus was neutral. These findings show that an adjacent, non-face stimulus containing emotional information influences the subsequent processing of facial expressions up to 260 ms, and even in cases when the two stimulus categories are different.

We recorded event-related potentials (ERPs) to investigate the interhemispheric difference of the N170 component for upright and inverted face perception in detail in fifteen healthy subjects. This is the first ERP study focusing on interhemispheric differences for face perception by showing faces in the hemifield. The face inversion effect, the prolonged latency and enhanced amplitude were found in both hemispheres. We found that the peak latency of the N170 following both upright and inverted face stimulation showed no significant difference between each hemisphere, though the N170 latency for the inverted face in the left hemisphere was shorter than that in the right hemisphere. The N170 recorded from the hemisphere ipsilateral to the stimulated hemifield showed unique findings. The interhemispheric time difference of the N170 between the right and the left hemispheres when the inverted face was presented in the left hemifield was significantly shorter than in the other three conditions. This unique finding may indicate that the conduction time from the right to the left for inverted face perception is faster than the other conditions, or that the left hemisphere specifically processed the inverted face very rapidly after receiving signals from the right hemisphere. If the N170 was generated by some, at least two, temporally overlapping activities, the different style of a summation of these activities may cause the unique findings found in this study. In conclusion, by presenting face stimuli in the hemifields, we could identify several new findings regarding the N170 component related to the face inversion effect.

Pain is an unpleasant sensation, and at the same time, it is always subjective and affective. Ten healthy subjects viewed 3 counterbalanced blocks of images from the International Affective Picture System: images showing painful events and those evoking emotions of fear and rest. They were instructed to imagine pain in their own body while viewing each image showing a painful event (the imagination of pain). Using functional magnetic resonance imaging, we compared cerebral hemodynamic responses during the imagination of pain with those to emotions of fear and rest. The results show that the imagination of pain is associated with increased activity in several brain regions involved in the pain-related neural network, notably the anterior cingulate cortex (ACC), right anterior insula, cerebellum, posterior parietal cortex, and secondary somatosensory cortex region, whereas increased activity in the ACC and amygdala is associated with the viewing of images evoking fear. Our results indicate that the imagination of pain even without physical injury engages the cortical representations of the pain-related neural network more specifically than emotions of fear and rest; it also engages the common representation (i.e., in ACC) between the imagination of pain and the emotion of fear.

While previous studies in psychology demonstrated that humans can respond more quickly to the stimuli at attended than unattended locations, it remains unclear whether attention also accelerates the speed of perceptual neural activity in the human brain. One possible reason for this unclarity would be an insufficient spatial resolution of previous electroencephalography (EEG) and magnetoencephalography (MEG) techniques in which neural signals from multiple brain regions are merged with each other. Here, we addressed this issue by combining MEG with a novel stimulus-presentation technique that can focus on neural signals from higher visual cortex where the magnitude of attentional modulation is prominent. Results revealed that the allocation of spatial attention induces both an increase in neural intensity (attentional enhancement) and a decrease in neural latency (attentional acceleration) to the attended compared to unattended visual stimuli (Experiment 1). Furthermore, an attention-induced behavioural facilitation reported in previous psychological studies (Posner paradigm) was closely correlated with the neural 'acceleration' rather than 'enhancement' in the visual cortex (Experiment 2). In addition to bridging a gap between previous psychological and neurological findings, our results demonstrated a temporal dynamics of attentional modulation in the human brain.

We previously examined the cortical processing in response to somatosensory, auditory and noxious stimuli, using magnetoencephalography in humans. Here, we performed a similar analysis of the processing in the human visual cortex for comparative purposes. After flash stimuli applied to the right eye, activations were found in eight cortical areas: the left medial occipital area around the calcarine fissure (primary visual cortex, V1), the left dorsomedial area around the parietooccipital sulcus (DM), the ventral (MOv) and dorsal (MOd) parts of the middle occipital area of bilateral hemispheres, the left temporo-occipito-parietal cortex corresponding to human MT/V5 (hMT), and the ventral surface of the medial occipital area (VO) of the bilateral hemispheres. The mean onset latencies of each cortical activity were (in ms): 27.5 (V1), 31.8 (DM), 32.8 (left MOv), 32.2 (right MOv), 33.4 (left MOd), 32.3 (right MOv), 37.8 (hMT), 46.9 (left VO), and 46.4 (right VO). Therefore the cortico-cortical connection time of visual processing at the early stage was 4-6 ms, which is very similar to the time delay between sequential activations in somatosensory and auditory processing. In addition, the activities in V1, MOd, DM, and hMT showed a similar biphasic waveform with a reversal of polarity after 10 ms, which is a common activation profile of the cortical activity for somatosensory, auditory, and pain-evoked responses. These results suggest similar mechanisms of the serial cortico-cortical processing of sensory information among all sensory areas of the cortex.

To clarify the latency of the earliest cortical activity in visual processing, electroretinograms (ERGs) and visual evoked magnetic fields (VEFs) following flash stimulation were recorded simultaneously in six human subjects. Flash stimuli were applied to the right eye and ERGs were recorded from a skin electrode placed on the lower lid. ERGs showed two major deflections in all subjects: an eyelid-negativity around 20 ms and a positivity around 60 ms corresponding to an a- and b-waves, respectively. The mean onset and peak latency of the earliest component of VEFs (37 M) was 30.2 and 36.9 ms, respectively. There was a linear correlation between the peak latency of the a-wave and the onset latency of the 37 M (r=0.90, P=0.011). When a single equivalent current dipole analysis was applied to the 37 M, four out of six subjects showed highly reliable results. The generator of the 37 M was estimated to be located in the striate cortex in all four subjects. Since post-receptoral activities in the retina are expected to start around the peak of the a-wave (20 ms), the early cortical activity, which appears 10 ms later than the a-wave peak, is considered to be the earliest cortical activity following flash stimulation.

The objective of this study was to reveal the oscillatory activity in the occipitotemporal area related to the visual perception of the letters of first (L1) and second languages (L2) and pseudoletters. We recorded neuromagnetic signals while Korean native speakers were exposed to a phonogram of Korean, acquired at school age as their L1 (Hangul), that of Japanese, learned in adulthood as a L2 (Kana) and pseudoletter (Pseudo), and quantified the event-related desynchronization (ERD) and synchronization (ERS). In all conditions, sustained ERDs in the alpha band were observed in both hemispheres. ERD for Pseudo was gradually attenuated after approximately 400-500 ms after stimulus onset, whereas both Hangul and Kana produced stronger and longer-lasting ERD. ERD for Kana showed a broader alpha band than Hangul. Furthermore, transient ERSs in the gamma band around 70 Hz were observed between 100 and 400 ms in the bilateral occipitotemporal areas. In the left hemisphere, gamma band oscillations showed similar enhancement in all conditions, suggesting that gamma band activity in the left occipitotemporal area might be enhanced not only by the bottom-up process as visual perception but also by the top-down process as attention to prelexical visual stimuli. In the right hemisphere, gamma band ERS was stronger for Hangul than Pseudo and no differences were shown between Kana and Pseudo. The differences of oscillatory activity in the alpha and gamma bands suggest that neuronal networks, including the occipitotemporal area, are related to the visual perception of letters differing between L1 and L2.

Backward masking is one of the potent ways to reveal the neural mechanism of visual awareness in humans. Although previous neuroimaging studies have reported that the visual masking involves the attenuation of hemodynamic signals to the masked stimulus in visual ventral regions such as the fusiform and inferior temporal gyrus, the temporal profiles of this attenuation as a whole neural population is mostly unclear. Here we used magnetoencephalography and investigated the neural response changes in higher visual region induced by backward masking. The combination of our previous random dot blinking method with the sensor-based analysis isolated the neural responses in the higher visual cortex relating to shape perception. The results revealed that, as the visibility of the target stimulus was reduced by the mask following it, the neural response to the target in the ventral regions showed gradual decreases both in its peak amplitude and peak latency. Furthermore, this decrease in the peak amplitudes was significantly correlated with the behavioral accuracy of the target identification, while the peak latency was not. These results indicate that backward masking simultaneously produces two types of neural changes in higher visual regions: attenuation of the populational neural activity itself and temporal interruption of this activity by the subsequent mask response. Especially, our data suggest that the response attenuation in higher visual response is a main cause of the perceptual impairment observed in the backward masking paradigm.

We have been studying the underlying mechanisms of face perception in humans using magneto- (MEG) and electro-encephalography (EEG) including (1) perception by viewing the static face, (2) differences in perception by viewing the eyes and whole face, (3) the face inversion effect, (4) the effect of gaze direction, (5) perception of eye motion, (6) perception of mouth motion, and (7) the interaction between auditory and visual stimuli related to the vowel sounds. In this review article, we mainly summarize our results obtained on 3, 5, and 6 above. With the presentation of both upright and inverted unfamiliar faces, the inferior temporal cortex (IT) centered on the fusiform gyrus, and the lateral temporal cortex (LT) near the superior temporal sulcus were activated simultaneously, but independently, between 140 and 200 ms post-stimulus. The right hemisphere IT and LT were both active in all subjects, and those in the left hemisphere in half of the subjects. Latencies with inverted faces relative to those with upright faces were longer in the right hemisphere, and shorter in the left hemisphere. Since the activated regions under upright and those under inverted face stimuli did not show a significant difference, we consider that differences in processing upright versus inverted faces are attributable to temporal processing differences rather than to processing of information by different brain regions. When viewing the motion of the mouth and eyes, a large clear MEG component, 1M (mean peak latency of approximately 160 ms), was elicited to both mouth and eye movement, and was generated mainly in the occipito-temporal border, at human MT/V5. The 1M to mouth movement and the 1M to eye movement showed no significant difference in amplitude or generator location. Therefore, our results indicate that human MT/V5 is active in the perception of both mouth and eye motion, and that the perception of movement of facial parts is probably processed similarly.

Neuroimaging studies have reported that the left superior temporal cortical area is activated by visually presented words. In the present study, we recorded cortical magnetic responses evoked by visual words and examined the effect of phonological repetition (e.g., hair-hare) on left superior temporal cortical activity, using pairs of homophonic Japanese words as stimuli. Unlike English, Japanese has a large number of homophone pairs with a totally different orthography. By taking advantage of this feature of the Japanese writing system, the effect of phonological repetition can be solely examined without being confounded by the effect of orthographic similarity. Magnetic responses were recorded over the bilateral temporal sites of the brain while subjects silently read words. The words were presented one by one; a quarter of them was immediately followed by a homophonic word. Clear magnetic responses in the latency range of 300-600 msec were observed in the left hemisphere, and the responses to the homophones were smaller than those to the first presented words. In the right hemisphere, clear responses were not consistently recorded in the same latency range, and no effect of phonological repetition was observed. The sources of the responses recorded over the left hemisphere were estimated to be in the left superior temporal cortical area adjacent to the auditory cortex and the source strength as well as the magnetic responses showed a reduction by phonological repetition. This result suggests that the activity in the left superior temporal cortical area is associated with access to the phonological representation of words.

We reported the changes of brain responses during sleep following auditory, visual, somatosensory and painful somatosensory stimulation by using magnetoencephalography (MEG). Surprisingly, very large changes were found under all conditions, although the changes in each were not the same. However, there are some common findings. Short-latency components, reflecting the primary cortical activities generated in the primary sensory cortex for each stimulus kind, show no significant change, or are slightly prolonged in latency and decreased in amplitude. These findings indicate that the neuronal activities in the primary sensory cortex are not affected or are only slightly inhibited during sleep. By contrast, middle- and long-latency components, probably reflecting secondary activities, are much affected during sleep. Since the dipole location is changed (auditory stimulation), unchanged (somatosensory stimulation) or vague (visual stimulation) between the state of being awake and asleep, different regions responsible for such changes of activity may be one explanation, although the activated regions are very close to each other. The enhancement of activities probably indicates two possibilities, an increase in the activity of excitatory systems during sleep, or a decrease in the activity of some inhibitory systems, which are active in the awake state. We have no evidence to support either, but we prefer the latter, since it is difficult to consider why neuronal activities would be increased during sleep.

We recorded event-related potentials (ERP) in response to images of faces with a straight gaze (straight eyes) and eyes averted (averted eyes). Peak latencies of ERP components showed no significant change between straight eyes and averted eyes, but amplitude for averted eyes, particularly when averted to the right, was significantly larger than that for straight eyes at the lateral temporal electrode of the right hemisphere. Single-unit recordings in monkeys and neuroimaging studies in humans have revealed activity in the lateral temporal region, mainly the superior temporal sulcus, and a clinical study demonstrated the importance of the right hemisphere when viewing gaze direction. This is the first systematic neurophysiological report to confirm these findings using ERP.

We developed a visual 3D model of a space module and analyzed whether activity in the auditory cortex is influenced by rotating the image using magnetoencephalography. We presented 1,000 Hz pure tone as an auditory stimulus in four different visual conditions: (1) RR: a virtual image rotated around the center, (2) VR: images rotated vertically, (3) HR: images rotated horizontally and (4) ST: the images did not rotate. We compared the difference in the auditory evoked component among the conditions. The dipoles were estimated to lie in Heschl’s gyrus. The dipole moment was significantly larger for RR and VR than for ST in the right hemisphere. Investigating the inter-hemispheric differences in each visual condition, the dipole moments for RR and VR were significantly larger in the right hemisphere than the left hemisphere. Auditory activity was influenced by visual movement inducing self-motion perception and the effect of such visual movement on the auditory cortex was right-dominant. [ABSTRACT FROM AUTHOR]

A flash is perceived to lag spatially behind a moving object even when the two retinal images are physically aligned (flashlag effect, FLE). Here we show that this robust illusion can be diminished by a knowledge of letters in the observer's brain. When moving and f lashed segments in the FLE made the shape of a Kanji letter (ideographic characters used in Japan), the magnitude of the illusory lag perceived by Japanese subjects was significantly reduced compared to when conventional geometric (nonletter) segments were used. This diminishment was not observed when a pseudo-Kanji letter was presented to Japanese subjects or when non-Japanese English-speakers (who do not have a knowledge of Kanji) saw a real Kanji letter, indicating that the reduction in the FLE was induced by a retrieval of the knowledge (shapes of letters) stored in the observer's brain. Furthermore, measurements of neural activities by magnetoencephalography showed that the initial brain response, in which the effect of the knowledge became evident, occurred as early as 160 msec after the appearance of the f lashed segment. These results demonstrated a substantial influence of knowledge on the flash-lag illusion and further suggest a rapid response of the knowledge-based perceptual pathway in the human brain. [ABSTRACT FROM AUTHOR]

Abstract: We developed a new method of color-opponent flicker (COF) stimulation, and investigated behavioral responses for object discrimination at the around threshold frequency of COF stimulation. Pairs of figures, a face, flower, the letter “G” and a random pattern, were drawn with a red and green checkerboard with a black mesh. COF stimulation was produced by presenting pairs of figures alternately (red–green–red–green–) at various frequencies (30–120Hz). A discrimination task for objects during COF stimulation was performed by 16 healthy subjects. Threshold frequency of COF stimulation was between 50 and 75Hz. The accuracy rate for face discrimination was significantly higher than those for other objects (p <0.01, ANOVA with Fisher''s PLSD multiple comparisons test). The present COF stimulation technique could be useful to investigate subliminal processes of the visual system, and the present results indicate a higher sensitivity and selectivity for face discrimination than those for other objects. [Copyright &y& Elsevier]

Abstract: The present study used magnetoencephalography (MEG) to investigate human MT/V5 activity when observing changes in eye gaze. Subjects viewed a face in which the eyes changed to look either directly at (BACK) or away from (AWAY) the subject in a series of apparent motion conditions. BACK involved 2 directions, from left to center (LC) and from right to center (RC). Likewise, AWAY involved 2 directions, from center to left (CL) and from center to right (CR). A clear MEG component, 1M, was elicited with all eye gaze changes. Mean peak latency was 157 ms and was unaffected by stimulus condition. The equivalent current dipole (ECD) was localized to human MT/V5. Two main effects were noted: (1) ECD moment was significantly larger for BACK than for AWAY; and (2) 1M ECD locations were more posterior for AWAY than for BACK. Gaze direction, with LEFT involving CL and RC and RIGHT involving CR and LC, showed no significant effects. These data indicate that MT/V5 responds to gaze direction rather than eye position, and that eye movements directed at the viewer elicit the strongest effects. Processing of gaze change is NOT sensitive to eye direction per se but rather is modulated by eye gaze relative to the viewer. [Copyright &y& Elsevier]

Abstract: Grapheme-color synesthesia is a phenomenon in which achromatic letters/digits automatically induce particular colors. When multiple letters are integrated into a word, some synesthetes perceive that all those letters are changed into the same color, reporting lexical color to that word. Previous psychological studies found several “rules” that determine those lexical colors. The colors to most words are determined by the first letters of the words, while some words in ordinal sequences have their specific colors. Recent studies further reported the third case where lexical colors might be influenced by semantic information of words. Although neural mechanisms determining those lexical colors remained unknown, here we identified three separate neural systems in the synesthete's brain underlying three rules for illusory coloring of words. In addition to the occipito-temporal and parietal regions previously found to be associated with the grapheme-color synesthesia, neural systems for lexical coloring extended to linguistic areas in the left inferior frontal and anterior temporal regions that were engaged in semantic analyses of words. Those results indicate an involvement of wider and higher neural networks than previously assumed in a production of synesthetic colors to visual stimuli and further showed a multiplicity of synesthetic mechanisms represented in the single brain. [Copyright &y& Elsevier]

Abstract: We often fail to consciously detect an unexpected object when we are engaged in an attention-demanding task (inattentional blindness). The inattentional blindness which is induced by visual short-term memory (VSTM) load has been proposed to result from a suppression of temporo-parietal junction (TPJ) activity that involves stimulus-driven attention. However, the fact that, inversely proportional to TPJ activity, intraparietal sulcus (IPS) activity correlates with VSTM load renders questionable the account of inattentional blindness based only on TPJ activity. Here, we investigated whether the TPJ is solely responsible for inattentional blindness by decoupling IPS and TPJ responses to VSTM load and then using the same manipulation to test the behavioral inattentional blindness performance. Experiment 1 showed that TPJ activity was not suppressed by task-irrelevant load while the IPS responded to both task-relevant and task-irrelevant load. Although the TPJ account of inattentional blindness predicts that the degree of inattentional blindness should track TPJ activity, we found in Experiment 2 that inattentional blindness was induced not only by task-relevant load but also by task-irrelevant load, showing inconsistency between the extent of inattentional blindness and TPJ response. These findings suggest that inattentional blindness can be induced without suppression of TPJ activity and seem to offer the possibility that the IPS contributes to conscious perception. [ABSTRACT FROM AUTHOR]

Humans perceive motion when numerous small dots pattern is followed by one of the same pattern but with all the dots shifted a little in one direction. When the amount of shift exceeds a level humans no more perceive motion even though physical visual information does not change. Using this stimulus, we addressed to elucidate the temporal structure of the neural activity related to this apparent motion perception. The magnetic responses to the random-dot patterns with various amounts of shift were measured while the subjects were performing a direction discrimination task. A significant magnetic response amplitude change occurred with three distinct peaks when the response inducing apparent motion was compared with those inducing no motion without change in the response latencies. The major difference occurred at about 110, 140, 210 ms after the stimulus onset. The response origin was always within the occipitotemporal area. The results indicate that the neural activity for the perception of apparent motion can be measured by MEG that occur at least 110 ms after the stimulus onset possibly in the human MT+. Three distinct peaks in the response difference may represent the sequential multiple neural process proposed theoretically though further study is necessary to prove. [Copyright &y& Elsevier]