Yoshiaki Kikuchi

The Functional Neuroanatomy of Maternal Love: Mother’s Response to Infant’s Attachment Behaviors

BACKGROUND Maternal love, which may be the core of maternal behavior, is essential for the mother-infant attachment relationship and is important for the infants development and mental health. However, little has been known about these neural mechanisms in human mothers. We examined patterns of maternal brain activation in response to infant cues using video clips. METHODS We performed functional magnetic resonance imaging (fMRI) measurements while 13 mothers viewed video clips, with no sound, of their own infant and other infants of approximately 16 months of age who demonstrated two different attachment behaviors (smiling at the infants mother and crying for her). RESULTS We found that a limited number of the mothers brain areas were specifically involved in recognition of the mothers own infant, namely orbitofrontal cortex (OFC), periaqueductal gray, anterior insula, and dorsal and ventrolateral parts of putamen. Additionally, we found the strong and specific mothers brain response for the mothers own infants distress. The differential neural activation pattern was found in the dorsal region of OFC, caudate nucleus, right inferior frontal gyrus, dorsomedial prefrontal cortex (PFC), anterior cingulate, posterior cingulate, thalamus, substantia nigra, posterior superior temporal sulcus, and PFC. CONCLUSIONS Our results showed the highly elaborate neural mechanism mediating maternal love and diverse and complex maternal behaviors for vigilant protectiveness.

Altered white matter fractional anisotropy and social impairment in children with autism spectrum disorder.

Individuals with autism spectrum disorder (ASD) have severe difficulties in social interaction and communication, as well as restricted and/or stereotyped patterns of behavior. Previous studies have suggested that abnormal neural connectivity might be associated with higher information processing dysfunction involving social impairment. However, the white matter structure in ASD is poorly understood. To explore this, we conducted a voxel-based, whole-brain diffusion tensor imaging (DTI) analysis to determine fractional anisotropy (FA), λ(1), λ(2) and λ(3) in high-functioning children with ASD compared with age-, gender-, and handedness-matched healthy control participants. We then investigated whether DTI parameters were associated with behaviorally measured social function. We found that FA and λ(1) were significantly lower in the ASD group than in the control group in the white matter around left dorsolateral prefrontal cortex (DLPFC), posterior superior temporal sulcus/temporo-parietal junction, right temporal pole, amygdala, superior longitudinal fasciculus, occipitofrontal fasciculus, mid- and left anterior corpus callosum, and mid- and right anterior cingulate cortex. The FA value in the left DLPFC was negatively correlated with the degree of social impairment in children with ASD. Higher λ(1) values were observed in the cerebellar vermis lobules in the ASD group. The white matter alterations in children with ASD were around cortical regions that play important roles in social cognition and information integration. These DTI results and their relationship to social impairment add to evidence of cerebral and cerebellar white matter structural abnormalities in ASD.

Language-related brain function during word repetition in post-stroke aphasics

We compared fMRI findings (using SPM99) obtained with repetition task in normal subjects with those of two patients with Brocas and Wernickes aphasia who received speech therapy and showed complete recovery. Both aphasic patients with left hemisphere damage who showed complete recovery exhibited activation of only the compensatory area in the right hemisphere during the repetition task. Recovery from Brocas aphasia involves reorganization and neuromodulation between the external temporopolar area and the anterior superior temporal area of the superior temporal gyrus, putamen and the inferior frontal gyrus, while that from Wernickes aphasia involves reorganization and neuromodulation between the superior temporal gyrus of the temporal region, the posterior supramarginal gyrus and inferior parietal lobule of the parietal region.

Temporal structure of implicit motor imagery in visual hand-shape discrimination as revealed by MEG.

WE investigated the spatio-temporal brain activity on the time scale of several milliseconds related to the mental rotation task requiring judgements of hand orientation, using a whole-cortex MEG (magnetoencephalography) system. Neuronal activity in the visual cortex was observed ∼100–200 ms from stimulus onset, and that in inferior parietal lobe followed (after 200 ms). Both of these activities showed a contralateral dominance to visual stimulus hemifield. Premotor activity started later than the inferior parietal lobe activity, and these activities partially overlapped. Activity in primary motor and/or motosensory areas was observed in some subjects. The whole-cortex neuromagnetic measurements provided the time course of activity in the human brain associated with the implicit motor imagery: visual cortex ← inferior parietal lobe ↔ premotor cortex. This process is considered to be the transformation process of retinotopic locations into a body-centered reference frame necessary for the mental rotation task.

Spatio-temporal brain activity related to rotation method during a mental rotation task of three-dimensional objects: An MEG study

During mental rotation tasks, subjects perform mental simulation to solve tasks. However, detailed neural mechanisms underlying mental rotation of three-dimensional (3D) objects, particularly, whether higher motor areas related to mental simulation are activated, remain unknown. We hypothesized that environmental monitoring-a process based on environmental information and is included in motor execution-is as a key factor affecting the utilization of higher motor areas. Therefore, using magnetoencephalography (MEG), we measured spatio-temporal brain activities during two types (two-dimensional (2D) and 3D rotation tasks) of mental rotation of 3D objects. Only the 3D rotation tasks required subjects to mentally rotate objects in a depth plane with visualization of hidden parts of the visual stimuli by acquiring and retrieving 3D information. In cases showing significant differences in the averaged activities at 100-ms intervals between the two rotations, the activities were located in the right dorsal premotor (PMd) at approximately 500 ms. In these cases, averaged activities during 3D rotation were greater than those during 2D rotation, implying that the right PMd activities are related to environmental monitoring. During 3D rotation, higher activities were observed from 200 to 300 ms in the left PMd and from 400 to 700 ms in the right PMd. It is considered that the left PMd is related to primary motor control, whereas the right PMd plays a supplementary role during mental simulation. Further, during 3D rotation, late higher activities related to mental simulation are observed in the right superior parietal lobule (SPL), which is connected to PMd.

Imitation behavior is sensitive to visual perspective of the model: an fMRI study

Imitation behavior and accompanying brain activity can be affected by the perspective of the model adopted. The present study was designed to understand the effect of a model’s perspective in terms of the view (1st person vs. 3rd person) and the anatomical congruency of the limb between the model and the performer (congruent vs. incongruent). Eighteen young participants observed video clips of a model’s finger-lifting behavior and lifted the same finger on their right hand as quickly as possible. Half of the video clips were filmed from the view of the participant (the 1st person view), whereas the other half were filmed from the perspective of facing a mirror (the 3rd person view). Each video clip depicted the finger lifting of the model’s right (congruent) or left (incongruent) hand. Comparisons of the latency to imitate among the four perspective conditions showed significantly shorter latency for the 1st person-congruent and 3rd person-incongruent conditions. Hemodynamic measurements with functional magnetic resonance imaging showed that shorter latency was explained with less involvement of the brain areas that are activated when a task is relatively complex. The brain areas considered to be a part of neural substrates of imitation were significantly activated under the 1st person view conditions regardless of the hand congruency. These findings suggest that, although the latency to imitate finger lifting was determined by the complexity of the task induced with the model’s perspective, imitation behavior seemed to be more effectively guided with the models filmed from the 1st person view.

Human cortico-hippocampal activity related to auditory discrimination revealed by neuromagnetic field

WE carried out multi-dipole estimation and pursued spatio-temporal brain activity on a time scale of several milliseconds during an auditory discrimination task using a whole-cortex type SQUID system. Neuronal activities were estimated in the medial (hippocampus, parahippocampal gyrus, etc.) and lateral temporal cortices (superior and middle temporal gyri, etc.), the dorsolateral prefrontal cortex (middle and inferior frontal gyri, etc.) and the parietal cortex (supramarginal gyrus, etc.) in the 280–400 ms latency range. The activity in the posterior hippocampal region was the most prominent and long-lasting in parallel with the activities in the other regions. Therefore, the posterior hippocampal region is a central structure engaged in auditory discrimination. The whole-cortex neuromagnetic measurements provided the possibility of imaging the time-varying activities of the human cortico-hippocampal neural networks.

Gender Differences of Brain Activity in the Conflicts Based on Implicit Self-Esteem

There are gender differences in global and domain-specific self-esteem and the incidence of some psychiatric disorders related to self-esteem, suggesting that there are gender differences in the neural basis underlying ones own self-esteem. We investigated gender differences in the brain activity while subjects (14 males and 12 females) performed an implicit self-esteem task, using fMRI. While ventromedial prefrontal cortex (vmPFC) was significantly activated in females, medial and dorsomedial PFC (dmPFC) were activated in males in the incongruent condition (self = negative) compared with the congruent condition (self = positive). Additionally, scores on the explicit self-esteem test were negatively correlated with vmPFC activity in females and positively correlated with dmPFC activity in males. Furthermore, the functional relationships among the regions found by direct gender comparisons were discussed based on the somatic-marker model. These showed that, compared to males, females more firmly store even the incongruent associations as part of their schematic self-knowledge, and such associations automatically activate the neural networks for emotional response and control, in which vmPFC plays a central role. This may explain female cognitive/behavioral traits; females have more tendency to ruminate more often than males, which sometimes results in a prolonged negative affect.

Emotional discrimination during viewing unpleasant pictures: timing in human anterior ventrolateral prefrontal cortex and amygdala

The ventrolateral prefrontal cortex (VLPFC) and amygdala have critical roles in the generation and regulation of unpleasant emotions, and in this study the dynamic neural basis of unpleasant emotion processing was elucidated by using paired-samples permutation t-tests to identify the timing of emotional discrimination in various brain regions. We recorded the temporal dynamics of blood-oxygen-level-dependent (BOLD) signals in those brain regions during the viewing of unpleasant pictures by using functional magnetic resonance imaging (fMRI) with high temporal resolution, and we compared the time course of the signal within the volume of interest (VOI) across emotional conditions. Results show that emotional discrimination in the right amygdala precedes that in the left amygdala and that emotional discrimination in both those regions precedes that in the right anterior VLPFC. They support the hypotheses that the right amygdala is part of a rapid emotional stimulus detection system and the left amygdala is specialized for sustained stimulus evaluation and that the right anterior VLPFC is implicated in the integration of viscerosensory information with affective signals between the bilateral anterior VLPFCs and the bilateral amygdalae.

Magnetoencephalographic measurements during two types of mental rotations of three-dimensional objects

Neural mechanisms of higher-order cognitive processes are hard to study by using nonhuman primates. Of these mechanisms, the mental rotation task is the one of the best studied. When subjects decide whether two shapes presented at various orientations are the identical or mirror images, their reaction time increases with the angle of rotation between the shapes. Recent magnetic resonance imaging (MRI) and magnetoencephalographic (MEG) studies revealed that activities of the premotor area and/or the parietal association area are related to the angular difference between two objects. However, there are two kinds of degree of difficulty in the mental rotation task of three-dimensional objects. One is based on the angular difference and the other is based on the rotation method itself. Keeping these two difficulties in mind, this paper evaluates the activities for a mental rotation task . Here, the performance of the subjects are sufficient as judged by measuring response time prior to MEG experiment. Results reveal that the activities in the right occipital area contralateral to the left visual stimulus field were found in eight out of 12 cases in the range of 150-200 ms. On the other hand, no activities were found in the left. These results are consistent with contralateral dominance of the anatomical connection. fMRI researches showed activities of both parietal association area for the mental rotation of three-dimensional object. In this study, activities of these areas were estimated in both 2-D and 3-D rotation. In addition to this result, the number of subjects, whose activities of posterior part of both parietal association areas were estimated, was increased in 3-D rotation compared with 2-D rotation. From this result, it is implied that these activities are related to the degree of difficulties of rotation method itself. In addition to these result, activities were observed in the posterior part of parietal association area ipsilateral to those in the premotor area in two out of four cases in 2-D rotation and in three out of three cases in 3-D rotation. 3-D rotation requires subjects to imagine the invisible parts of visual stimuli for judging whether the visual stimulus is an identical pair or not. It is believed that this requirement activates the fronto-parietal circuit which is used in visuo-motor tasks.