Stapedial reflex threshold predicts individual loudness tolerance for people with autistic spectrum disorders.

People with autism spectrum disorder (ASD) frequently show the symptoms of oversensitivity to sound (hyperacusis). Although the previous studies have investigated methods for quantifying hyperacusis in ASD, appropriate physiological signs for quantifying hyperacusis in ASD remain poorly understood. Here, we investigated the relationship of loudness tolerance with the threshold of the stapedial reflex and with contralateral suppression of the distortion product otoacoustic emissions, which has been suggested to be related to hyperacusis in people without ASD. We tested an ASD group and a neurotypical group. The results revealed that only the stapedial reflex threshold was significantly correlated with loudness tolerance in both groups. In addition to reduced loudness tolerance, people with lower stapedial reflex thresholds also exhibited higher scores on the Social Responsiveness Scale-2.

Developmental changes in intralimb coordination during spontaneous movements of human infants from 2 to 3 months of age.

Human infants show a variety of spontaneous movements in the first few months of life. Although the pattern of spontaneous movements changes at approximately 2 months of age, the precise mechanism that governs the developmental changes in intralimb coordination remains unclear. In the present study, we focused on knee-ankle coordination during spontaneous movements of human infants from 2 to 3 months of age. Multiple attitude sensors were used to measure three-dimensional angular motion of knee and ankle joint motions. We acquired a one-dimensional time series of the knee joint angle around the putative hinge joint and a two-dimensional time series of ankle motions on the putative sagittal and frontal plane. First, we found that 3-month-old infants show a significant predominance to extend their knee joints, remarkably so on the left side. To quantify dissociated motions of the knee and ankle, we calculated the temporal correlation and the regression slope between them. We observed that 3-month-old infants moved their ankle joints more independently of knee motions than 2-month-old infants. Finally, we found that dissociated motions of the knee and ankle simultaneously develop with knee extension predominance. The developmental change from synchronization to dissociation of intralimb joint movements during spontaneous movements suggests that the development of the cortical and/or subcortical mechanism may mediate selective activation and inhibition of joint motions at approximately 2 months of age.

Reward sensitivity differs depending on global self-esteem in value-based decision-making.

Global self-esteem is a component of individual personality that impacts decision-making. Many studies have discussed the different preferences for decision-making in response to threats to a person's self-confidence, depending on global self-esteem. However, studies about global self-esteem and non-social decision-making have indicated that decisions differ due to reward sensitivity. Here, reward sensitivity refers to the extent to which rewards change decisions. We hypothesized that individuals with lower global self-esteem have lower reward sensitivity and investigated the relationship between self-esteem and reward sensitivity using a computational model. We first examined the effect of expected value and maximum value in learning under uncertainties because some studies have shown the possibility of saliency (e.g. maximum value) and relative value (e.g. expected value) affecting decisions, respectively. In our learning task, expected value affected decisions, but there was no significant effect of maximum value. Therefore, we modelled participants' choices under the condition of different expected value without considering maximum value. We used the Q-learning model, which is one of the traditional computational models in explaining experiential learning decisions. Global self-esteem correlated positively with reward sensitivity. Our results suggest that individual reward sensitivity affects decision-making depending on one's global self-esteem.

Species-specific Posture of Human Foetus in Late First Trimester.

The ontogeny associated with the arm-hanging posture, which is considered ape-specific, remains unknown. To examine its ontogeny, we measured foetal movements of 62 human foetuses aged 10-20 gestation weeks using four-dimensional sonography. We observed that the first-trimester foetuses show this particular species-specific posture. After 11 weeks of gestation, all foetuses showed the arm-hanging posture, and the posture was most frequently observed at 14-16 weeks of gestation. Moreover, this posture often involved extension of both arms and both legs, indicating that it is not myogenic but neurogenic. Furthermore, early ontogeny suggests that it originates because of subcortical activity. Such posture extension bias and persistence indicates that vestibulospinal tract maturation involves the ontogeny of arm-hanging posture during 14-16 weeks of gestation.

Emergence and development of embodied cognition: a constructivist approach using robots.

A constructivist approach to cognition assumes the minimal and the simplest set of initial principles or mechanisms, embeds them in realistic circumstances, and lets the entire system evolve under close observation. This paper presents a line of research along this approach trying to connect embodiment to social cognition. First, we show that a mere physical body, when driven toward some task goal, provides a clear information structure, for action execution and perception. As a mechanism of autonomous exploration of such structure, "embodiment as a coupled chaotic field" is proposed, with experiments showing emergent and adaptive behavior. Scaling up the principles, a simulation of the fetal/neonatal motor development is presented. The musculo-skeletal system, basic nervous system, and the uterus environment are simulated. The neural-body dynamics exhibit spontaneous exploration of a variety of motor patterns. Lastly, a robotic experiment is presented to show that visual-motor self-learning can lead to neonatal imitation.

A translational model to determine rodent's age from human foetal age.

To understand the prenatal origin of developmental and psychiatric disorders, studies in laboratory animals are imperative. However, the developmental pace differs between humans and animals; hence, corresponding human ages must be estimated to infer the most vulnerable developmental timings in humans. Because rats and mice are extensively used as models in developmental research, a correspondence between human foetal ages and rodents' ages must be precisely determined; thus, developing a translational model is of utmost importance. Optimizing a translational model involves classifying the brain regions according to developmental paces, but previous studies have conducted this classification arbitrarily. Here we used a clustering method and showed that the brain regions can be classified into two groups. To quantify the developmental pace, we gathered data for a range of development events in humans and rodents and created a linear mixed model that translates human developmental timings into the corresponding rat timings. We conducted an automatic classification of brain regions using an EM algorithm and obtained a model to translate human foetal age to rat age. Our model could predict rat developmental timings within 2.5 days of root mean squared error. This result provides useful information for designing animal studies and clinical tests.

Eye movement activity in normal human fetuses between 24 and 39 weeks of gestation.

Rapid eye movement (REM) sleep occurs throughout a relatively large proportion of early development, and normal REM activity appears to be required for healthy brain development. The eye movements (EMs) observed during REM sleep are the most distinctive characteristics of this state. EMs are used as an index of neurological function postnatally, but no specific indices of EM activity exist for fetuses. We aimed to identify and characterize EM activity, particularly EM bursts suggestive of REM periods, in fetuses with a gestational age between 24 and 39 weeks. This cross-sectional study included 84 normal singleton pregnancies. Fetal EMs were monitored using real-time ultrasonography for 60 min and recorded as videos. The videos were manually converted into a time series of EM events, which were then analyzed by piecewise linear regression for various EM characteristics, including EM density, EM burst density, density of EMs in EM bursts, and continuous EM burst time. Two critical points for EM density, EM burst density, and density of EMs in EM bursts were evident at gestation weeks 28-29 and 36-37. Overall EM activity in human fetuses increased until 28-29 weeks of gestation, then again from 36-37 to 38-39 weeks of gestation. These findings may be useful for creating indices of fetal neurological function for prognostic purposes.