The salience network is activated during self-recognition from both first-person and third-person perspectives.

We usually observe ourselves from two perspectives. One is the first-person perspective, which we perceive directly with our own eyes, and the other is the third-person perspective, which we observe ourselves in a mirror or a picture. However, whether the self-recognition associated with these two perspectives has a common or separate neural basis remains unclear. To address this, we used functional magnetic resonance imaging to examine brain activity while participants viewed pretaped video clips of themselves and others engaged in meal preparation taken from first-person and third-person perspectives. We found that the first-person behavioral videos of the participants and others induced greater activation in the premotor-intraparietal region. In contrast, the third-person behavioral videos induced greater activation in the default mode network compared with the first-person videos. Regardless of the perspective, the videos of the participants induced greater activation in the salience network than the videos of others. On the other hand, the videos of others induced greater activation in the precuneus and lingual gyrus than the videos of the participants. These results suggest that the salience network is commonly involved in self-recognition from both perspectives, even though the brain regions involved in action observation for the two perspectives are distinct.

Early phase of pupil dilation is mediated by the peripheral parasympathetic pathway.

Pupil diameter fluctuates in association with changes in brain states induced by the neuromodulator systems. However, it remains unclear how the neuromodulator systems control the activity of the iris sphincter (constrictor) and dilator muscles to change the pupil size. The present study compared temporal patterns of pupil dilation during movement when each muscle was pharmacologically manipulated in the human eye. When the iris sphincter muscle was blocked with tropicamide, the latency of pupil dilation was delayed and the magnitude of pupil dilation was reduced during movement. In contrast, when the iris dilator muscle was continuously stimulated with phenylephrine, the latency and magnitude of rapid pupil dilation did not differ from the untreated control eye, but sustained pupil dilation was reduced until the end of movement. These results suggest that the iris sphincter muscle, which is under the control of the parasympathetic pathway, is quickly modulated by the neuromodulator system and plays a major role in rapid pupil dilation. However, the iris dilator muscle receives signals from the neuromodulator system with a slow latency and is involved in maintaining sustained pupil dilation.NEW & NOTEWORTHY By pharmacologically manipulating the pupil dilator and constrictor muscles of human eye separately, we found that the pupil constrictor muscle is a primary controller of rapid pupil dilation upon brain arousal. However, the pupil dilator muscle, which is innervated by the sympathetic nervous system and is generally considered as a major regulator of pupil dilation, is not involved in rapid pupil dilation, but was involved in long-lasting pupil dilation.

Pupil constriction via the parasympathetic pathway precedes perceptual switch of ambiguous stimuli.

Perceptual rivalry of ambiguous stimuli reflects the interaction of neural activity among multiple cortical regions. However, it remains unclear what drives a spontaneous perceptual alteration. We hypothesized that increased fluctuations in spontaneous neural activity due to arousal reduction drive the perceptual switch. Here, we show that the pupils shrank a few seconds prior to the onset of the spontaneous perceptual switch. Such pupil constriction was not observed before the exogenous perceptual switch. Pharmacological experiments confirmed that the pupil constriction disappeared when the peripheral parasympathetic pathway (pupil sphincter muscle) was blocked, but it remained intact when the peripheral sympathetic pathway (pupil dilator muscle) was manipulated. Furthermore, rapid pupil dilations with behavioral response are also mediated by the peripheral parasympathetic pathway. The present findings suggested that transient arousal drops, as denoted by the autonomic nervous modulation of pupil size, are involved in inducing the spontaneous perceptual switch of bistable stimuli.

Self-Face Activates the Dopamine Reward Pathway without Awareness.

The self-face advantage has been demonstrated not only at the supraliminal level, but also at the subliminal level. However, it remains unclear whether subliminal self-face processing involves the same neural networks as those for supraliminal self-face processing. Here, we show that the ventral tegmental area, a center of the dopamine reward pathway, exhibited greater activation to subliminal presentations of the self-face than those of the others' faces, whereas subliminal presentations of the others' faces induced activation in the amygdala, which generally responds to unfamiliar information. This self-other difference in brain response was consistently observed even when the facial configuration was modified without changing the shape of the facial parts. The present findings suggest that the dopamine reward pathway is involved in automatic self-advantage in face processing, and the subliminal self-other facial discrimination does not depend on information of the precise facial configuration.

Neural correlates of beauty retouching to enhance attractiveness of self-depictions in women.

Beauty filters, while often employed for retouching photos to appear more attractive on social media, when used in excess cause images to give a distorted impression. The neural mechanisms underlying this change in facial attractiveness according to beauty retouching level remain unknown. The present study used functional magnetic resonance imaging in women as they viewed photos of their own face or unknown faces that had been retouched at three levels: no, mild, and extreme. The activity in the nucleus accumbens (NA) exhibited a positive correlation with facial attractiveness, whereas amygdala activity showed a negative correlation with attractiveness. Even though the participants rated others' faces as more attractive than their own, the NA showed increased activity only for their mildly retouched own face and the amygdala exhibited greater activation in the others' faces condition than the own face condition. Moreover, amygdala activity was greater for extremely retouched faces than for unretouched or mildly retouched faces for both conditions. Frontotemporal and cortical midline areas showed greater activation for one's own than others' faces, but such self-related activation was absent when extremely retouched. These results suggest that neural activity dynamically switches between the NA and amygdala according to perceived attractiveness of one's face.

Phylogeny and ontogeny of mental time.

Humans have mental time in our mind, apart from physical time that is a part of system that governs the physical world, and memory is our key cognitive ability for recognizing the passage of time. Recent studies have suggested that the memory system of several nonhuman animals may have an incidental nature, which is also a feature of episodic memory. In addition, apes, which are phylogenetically close to humans, have an ability to remember a single past event. In the case of humans, preverbal infants under the age of two are able to retain long-term memory of a single event and apply it to predict a future event. Thus, nonhuman animals and preverbal human infants both have their own specific mental time travel abilities, and there is a phylogenetic and ontogenic basis of full-fledged mental time travel that can be found in human adults.

Risk Factors Leading to Preference for Extreme Facial Retouching.

Young women posting their edited face photographs on social networking sites have become a popular phenomenon, but an excessively retouched face image sometimes gives a strange impression to its viewers. This study investigates what personal characteristics facilitate a bias toward an excessively edited face image. Thirty young Asian women evaluated the attractiveness and naturalness of their face images, which were edited in eight different levels-from mild to excessive-by expanding their eyes and thinning their chin. The mildly retouched face was evaluated as more attractive than the original face, but the excessively retouched face was evaluated as unattractive and unnatural in comparison with the original face. The preferred face edit level was higher for one's own face than for others. Moreover, participants with higher autism-spectrum quotient (AQ) scores were found to regard excessively edited face images as more attractive. The attention to detail subscale of the AQ showed a significant positive correlation with the preferred face edit level. The imagination subscale, on the contrary, showed a significant negative correlation with the preferred face edit level. The pupil response for self-face images was significantly larger than those for others' face images, but this difference decreased with higher AQ scores. This study suggests that an increased attractiveness in their mildly retouched face promotes this behavior of retouching one's own face, but autistic traits, which are insensitive to the creepiness of the excessively retouched face, might pose a potential risk to inducing retouch dependence.

Blink synchronization is an indicator of interest while viewing videos.

The temporal pattern of spontaneous blinks changes greatly depending on an individual's internal cognitive state. For instance, when several individuals watch the same video, blinks can be synchronized at attentional breakpoints. The present study examined the degree of this blink synchronization, as reflecting an interest level, while viewing various video clips. In the first experiment, participants interested in soccer, shogi (Japanese chess), or a specific musical group watched a video clip related to each category and rated their interest level after viewing. Results revealed that blink synchronization increased with a rise in interest level in the video clips of soccer and shogi. Moreover, while blink synchronization increased when viewing preferred video clips for the soccer and music group fans, synchronization decreased when viewing videos from the other categories, except for the shogi fans. In contrast, the blink rates did not correlate with the interest level on the video content but changed with the number of shot transitions of it. In the second experiment, participants viewed a video in which a professional salesperson gave descriptions of several products for a few minutes each. When participants reported an interest in the product, blinks were synchronized to the salesperson's blinks. However, when feeling uninterested, blink synchronization did not occur. These results suggest that blink synchronization could be used as an involuntary index to assess a person's interest.

Transient heart rate acceleration in association with spontaneous eyeblinks.

The reason why people spontaneously blink several times more frequently than is necessary for ocular lubrication has been a mystery. However, spontaneous eyeblinks selectively occur at attentional breakpoints of information processing, suggesting the involvement of spontaneous eyeblink in attentional disengagement from external stimuli. Physiological activity also changes considerably according to attention state. Heart rate decreases when attention is directed at stimuli, while it increases as attention is released. Therefore, we examined the temporal dynamics between spontaneous eyeblinks and instantaneous heart rate under natural circumstances. Our results showed that the heart rate momentarily increases after each spontaneous eyeblink while participants were freely viewing a movie or listening to a story. This phenomenon was consistently observed even when the participants were placed in a dark room. The skin conductance level on the fingers also increased after each spontaneous eyeblink, suggesting that the blink-related heart rate acceleration was induced by an increase in sympathetic nervous system activity. In contrast, no heart rate acceleration was observed to accompany spontaneous eyeblinks at rest or volitional eyeblinks. These results demonstrated that the generation of spontaneous eyeblinks and the activity of the autonomic nervous system are correlated under attentional influence of natural circumstances.

Development of long-term event memory in preverbal infants: an eye-tracking study.

The development of long-term event memory in preverbal infants remains elusive. To address this issue, we applied an eye-tracking method that successfully revealed in great apes that they have long-term memory of single events. Six-, 12-, 18- and 24-month-old infants watched a video story in which an aggressive ape-looking character came out from one of two identical doors. While viewing the same video again 24 hours later, 18- and 24-month-old infants anticipatorily looked at the door where the character would show up before it actually came out, but 6- and 12-month-old infants did not. Next, 12-, 18- and 24-month-old infants watched a different video story, in which a human grabbed one of two objects to hit back at the character. In their second viewing after a 24-hour delay, 18- and 24-month-old infants increased viewing time on the objects before the character grabbed one. In this viewing, 24-month-old infants preferentially looked at the object that the human had used, but 18-month-old infants did not show such preference. Our results show that infants at 18 months of age have developed long-term event memory, an ability to encode and retrieve a one-time event and this ability is elaborated thereafter.

The right angular gyrus controls spontaneous eyeblink rate: A combined structural MRI and TMS study.

Spontaneous eyeblink rates vary greatly between people, from several to a few dozen blinks per minute. Nevertheless, it remains unknown which brain region controls generation of spontaneous eyeblinks. To investigate this issue, the present study examined brain anatomy, which reflects inter-individual variability in eyeblink rate using structural magnetic resonance images with voxel-based morphometry (VBM) in 57 participants. The gray matter volume of the right angular gyrus (rAG) was positively associated with an increased eyeblink rate. Next, we examined whether eyeblink rate decreased when activity in the rAG was disrupted by transcranial magnetic stimulation (TMS) with a protocol of continuous theta burst stimulation: TMS of the rAG decreased eyeblink rate by 16%. In contrast, sham stimulation did not significantly affect eyeblink rate. The results from the structural MRI and TMS experiments suggest that the rAG is involved in controlling the generation of spontaneous eyeblinks in humans.

Short-latency allocentric control of saccadic eye movements.

It is generally accepted that the neural circuits that are implicated in saccade control use retinotopically coded target locations. However, several studies have revealed that nonretinotopic representation is also used. This idea raises a question about whether nonretinotopic coding is egocentric (head or body centered) or allocentric (environment centered). In the current study, we hypothesized that allocentric coding may play a crucial role in immediate saccade control. To test this hypothesis, we used an immediate double-step saccade task toward two sequentially flashed targets with a frame in the background, and we examined whether the end point of the second saccade was affected by a transient shift of the background that participants were told to ignore. When the background was shifted transiently upward (or downward) during the flash of the second target, the second saccade generally erred the target downward (or upward), which was in the direction opposite to the shift of the background. The effect on the second saccade became significant within 150 ms after the frame was presented for decoding and was built up for 200 ms thereafter. When the second saccade was not adjusted, a small, corrective saccade followed within 300 ms. The effect scaled linearly with the shift size up to 3° for a noncorrective second saccade and up to 6° for a corrective saccade. The present results show that an allocentric location of a target is rapidly represented by the brain and used for controlling saccades. NEW & NOTEWORTHY: We found that the saccade end point was shifted from the actual target position toward the direction expected from allocentric coding when a large frame in the background was transiently shifted during the period of target presentation. The effect occurred within 150 ms. The present study provides direct evidence that the brain rapidly uses allocentric coding of a target to control immediate saccades.

A group of very preterm children characterized by atypical gaze patterns.

OBJECTIVE: Very preterm (VP) children are at risk for social difficulties, including autism spectrum disorder (ASD). This study used eye tracking to determine viewing behaviors that may reflect these difficulties. DESIGN: The gaze patterns of 47 VP (mean gestational age: 28weeks, mean birth weight: 948g, and mean chronological age: 49months) were assessed while viewing dynamic social scenes and compared with those of 25 typically developing (TD) and 25 children with ASD. The temporo-spatial gaze patterns were summarized on a two-dimensional plane using multidimensional scaling (MDS) and the median of the TD children was used to characterize the gazes of the VP children. Time spent viewing the face was also compared. RESULTS: The VP children formed two clusters: one had a mean MDS distance comparable to that of TD group (n=32; VP-small), and the other had a larger mean distance comparable to that of ASD group (n=15; VP-large). The VP-large were similar to the ASD group by spending significantly less time viewing the face. Their performance was comparable to the TD during the initial 1s, but they could not remain focused on the face thereafter. CONCLUSIONS: The VP children were objectively classified into two groups based on gaze behaviors. One group was comparable to TD children, whereas the other had difficulty maintaining attention and exhibited atypical viewing behaviors similar to those of the ASD group. Our method may be useful in identifying VP children at higher risk for experiencing social difficulties.

Automatic facial mimicry in response to dynamic emotional stimuli in five-month-old infants.

Human adults automatically mimic others' emotional expressions, which is believed to contribute to sharing emotions with others. Although this behaviour appears fundamental to social reciprocity, little is known about its developmental process. Therefore, we examined whether infants show automatic facial mimicry in response to others' emotional expressions. Facial electromyographic activity over the corrugator supercilii (brow) and zygomaticus major (cheek) of four- to five-month-old infants was measured while they viewed dynamic clips presenting audiovisual, visual and auditory emotions. The audiovisual bimodal emotion stimuli were a display of a laughing/crying facial expression with an emotionally congruent vocalization, whereas the visual/auditory unimodal emotion stimuli displayed those emotional faces/vocalizations paired with a neutral vocalization/face, respectively. Increased activation of the corrugator supercilii muscle in response to audiovisual cries and the zygomaticus major in response to audiovisual laughter were observed between 500 and 1000 ms after stimulus onset, which clearly suggests rapid facial mimicry. By contrast, both visual and auditory unimodal emotion stimuli did not activate the infants' corresponding muscles. These results revealed that automatic facial mimicry is present as early as five months of age, when multimodal emotional information is present.

Eyeblink Synchrony in Multimodal Human-Android Interaction.

As the result of recent progress in technology of communication robot, robots are becoming an important social partner for humans. Behavioral synchrony is understood as an important factor in establishing good human-robot relationships. In this study, we hypothesized that biasing a human's attitude toward a robot changes the degree of synchrony between human and robot. We first examined whether eyeblinks were synchronized between a human and an android in face-to-face interaction and found that human listeners' eyeblinks were entrained to android speakers' eyeblinks. This eyeblink synchrony disappeared when the android speaker spoke while looking away from the human listeners but was enhanced when the human participants listened to the speaking android while touching the android's hand. These results suggest that eyeblink synchrony reflects a qualitative state in human-robot interactions.

Blink and you'll miss it: the role of blinking in the perception of magic tricks.

Magicians use several techniques to deceive their audiences, including, for example, the misdirection of attention and verbal suggestion. We explored another potential stratagem, namely the relaxation of attention. Participants watched a video of a highly skilled magician whilst having their eye-blinks recorded. The timing of spontaneous eye-blinks was highly synchronized across participants. In addition, the synchronized blinks frequency occurred immediately after a seemingly impossible feat, and often coincided with actions that the magician wanted to conceal from the audience. Given that blinking is associated with the relaxation of attention, these findings suggest that blinking plays an important role in the perception of magic, and that magicians may utilize blinking and the relaxation of attention to hide certain secret actions.

Similar impressions of humanness for human and artificial singing voices in autism spectrum disorders.

People with autism spectrum disorder (ASD) exhibit impairments in the perception of and orientation to social information related to humans, and some people with ASD show higher preference toward human-like robots than other humans. We speculated that this behavioural bias in people with ASD is caused by a weakness in their perception of humanness. To address this issue, we investigated whether people with ASD detect a subtle difference between the same song sung by human and artificial voices even when the lyrics, melody and rhythm are identical. People without ASD answered that the songs sung by a human voice evoked more impressions of humanness (human-likeness, animateness, naturalness, emotion) and more positive feelings (warmth, familiarity, comfort) than those sung by an artificial voice. In contrast, people with ASD had similar impressions of humanness and positive feelings for the songs sung by the human and artificial voices. The evaluations of musical characteristics (complexity, regularity, brightness) did not differ between people with and without ASD. These results suggest that people with ASD are weak in their ability to perceive psychological attributes of humanness.

Automatic representation of a visual stimulus relative to a background in the right precuneus.

Our brains represent the position of a visual stimulus egocentrically, in either retinal or craniotopic coordinates. In addition, recent behavioral studies have shown that the stimulus position is automatically represented allocentrically relative to a large frame in the background. Here, we investigated neural correlates of the 'background coordinate' using an fMRI adaptation technique. A red dot was presented at different locations on a screen, in combination with a rectangular frame that was also presented at different locations, while the participants looked at a fixation cross. When the red dot was presented repeatedly at the same location relative to the rectangular frame, the fMRI signals significantly decreased in the right precuneus. No adaptation was observed after repeated presentations relative to a small, but salient, landmark. These results suggest that the background coordinate is implemented in the right precuneus.

Blink-related dynamic switching between internal and external orienting networks while viewing videos.

Humans spontaneously generate eyeblinks every few seconds. However, because this blink rate is several times more common than is required for ocular lubrication, the function of most spontaneous eyeblinks remains unknown. Because spontaneous eyeblinks tend to occur at implicit breakpoints in video stories, I hypothesized that spontaneous eyeblinks play an active role in attentional disengagement from external stimuli. Consistent with this, we previously found that spontaneous eyeblinks involve the concurrent deactivation of the dorsal attention network and activation of the default mode network when individuals are viewing videos. However, this previous study examined only the upper brain regions to increase the temporal resolution of the data. Therefore, the present study examined whether the temporal and subcortical regions exhibited blink-related activations or deactivations using the same visual stimuli as in the previous study. Data revealed that the bilateral hippocampus and cerebellum showed a prominent but momentary activation after the blink onset. In contrast, a blink-related deactivation was observed in both the right ventral and dorsal attention networks. These results suggest that spontaneous eyeblinks are involved in the attentional disengagement from external visual information via the massive and dynamic alteration of brain activity between the external and internal orienting networks.