Fetal eye movements in response to a visual stimulus

At First Sight: Fetal Eye Movements Reveal a Preference for Face-Like Configurations From 26 Weeks of Gestation

Previous research indicates that both adults and newborns show enhanced electrophysiological and behavioral responses to schematic face-like configurations (FCs-three dots composing a downward-pointing triangle), as compared to the inverted configurations (ICs). Even fetuses, when exposed to light stimuli projected through the uterine wall, preferentially orient their heads toward FCs rather than ICs. However, when this effect emerges along the third trimester of pregnancy and in relation to the maturation of which brain structures is still unknown. Here, to provide a sensitive measure of fetal preference for FCs along the whole third trimester, fetal lens movements in response to FCs and ICs was monitored with 2D-ultrasound. In a series of three experiments, fetuses were recruited at 26, 31, and 37 weeks of gestational age and were presented with both flashing and continuous light stimuli. Our results showed that significantly more lens movements were observed in response to continuous as compared to flashing light stimuli. Furthermore, lens movements linearly increased within the third trimester and, regardless of the time-point, significantly more lens movements were observed in response to FCs versus ICs. We also found a significant correlation in the first time-point, wherein the greater the FCs versus ICs differential response the larger the thalamic nuclei dimension. These findings suggest that FC preference is already present at the beginning of the third trimester, as soon as thalamocortical projections are established.

I like the way you move: how animate motion affects visual attention in early human infancy

The ability to detect animates (as compared with inanimates) rapidly is advantageous for human survival. Due to its relevance, not only the adult human brain has evolved specific neural mechanisms to discriminate animates, but it has been proposed that selection finely tuned the human visual attention system to prioritize visual cues that signal the presence of living things. Among them, animate motion-i.e., the motion of animate entities -, is one of the most powerful cues that triggers humans' attention. From a developmental point of view, whether such specialization is inborn or acquired through experience is a fascinating research topic. This mini-review aims to summarize and discuss recent behavioral and electrophysiological research that suggests that animate motion has an attentional advantage in the first year of life starting from birth. Specifically, the rationale underlying this paper concerns how attention deployment is affected by animate motion conveyed both by the movement of a single dot and, also, when the single dot is embedded in a complex array, named biological motion. Overall, it will highlight the importance of both inborn predispositions to pay attention preferentially to animate motion, mainly supported by subcortical structures, and the exposure to certain experiences, shortly after birth, to drive the cortical attentional visual system to become the way it is in adults.

Trajectories of brain and behaviour development in the womb, at birth and through infancy

Birth is often seen as the starting point for studying effects of the environment on human development, with much research focused on the capacities of young infants. However, recent imaging advances have revealed that the complex behaviours of the fetus and the uterine environment exert influence. Birth is now viewed as a punctuate event along a developmental pathway of increasing autonomy of the child from their mother. Here we highlight (1) increasing physiological autonomy and perceptual sensitivity in the fetus, (2) physiological and neurochemical processes associated with birth that influence future behaviour, (3) the recalibration of motor and sensory systems in the newborn to adapt to the world outside the womb and (4) the effect of the prenatal environment on later infant behaviours and brain function. Taken together, these lines of evidence move us beyond nature-nurture issues to a developmental human lifespan view beginning within the womb.

The key to understanding core knowledge resides in the fetus

What Babies Know outlines a compelling case for why infancy research is fundamental for conceptualizing what it is to be human. There is another period in human development that is relatively inaccessible, yet is more important. In order to truly understand the nature of core knowledge, perception, and cognition, we must start not with the infant, but with the fetus.

Spatial Single-cell Analysis Decodes Cortical Layer and Area Specification

The human cerebral cortex, pivotal for advanced cognitive functions, is composed of six distinct layers and dozens of functionally specialized areas1,2. The layers and areas are distinguished both molecularly, by diverse neuronal and glial cell subtypes, and structurally, through intricate spatial organization3,4. While single-cell transcriptomics studies have advanced molecular characterization of human cortical development, a critical gap exists due to the loss of spatial context during cell dissociation5,6,7,8. Here, we utilized multiplexed error-robust fluorescence in situ hybridization (MERFISH)9, augmented with deep-learning-based cell segmentation, to examine the molecular, cellular, and cytoarchitectural development of human fetal cortex with spatially resolved single-cell resolution. Our extensive spatial atlas, encompassing 16 million single cells, spans eight cortical areas across four time points in the second and third trimesters. We uncovered an early establishment of the six-layer structure, identifiable in the laminar distribution of excitatory neuronal subtypes by mid-gestation, long before the emergence of cytoarchitectural layers. Notably, while anterior-posterior gradients of neuronal subtypes were generally observed in most cortical areas, a striking exception was the sharp molecular border between primary (V1) and secondary visual cortices (V2) at gestational week 20. Here we discovered an abrupt binary shift in neuronal subtype specification at the earliest stages, challenging the notion that continuous morphogen gradients dictate mid-gestation cortical arealization6,10. Moreover, integrating single-nuclei RNA-sequencing and in situ whole transcriptomics revealed an early upregulation of synaptogenesis in V1-specific Layer 4 neurons, suggesting a role of synaptogenesis in this discrete border formation. Collectively, our findings underscore the crucial role of spatial relationships in determining the molecular specification of cortical layers and areas. This work not only provides a valuable resource for the field, but also establishes a spatially resolved single-cell analysis paradigm that paves the way for a comprehensive developmental atlas of the human brain.

Unravelling the functional development of vertebrate pathways controlling gaze

Animals constantly redirect their gaze away or towards relevant targets and, besides these goal-oriented responses, stabilizing movements clamp the visual scene avoiding image blurring. The vestibulo-ocular (VOR) and the optokinetic reflexes are the main contributors to gaze stabilization, whereas the optic tectum integrates multisensory information and generates orienting/evasive gaze movements in all vertebrates. Lampreys show a unique stepwise development of the visual system whose understanding provides important insights into the evolution and development of vertebrate vision. Although the developmental emergence of the visual components, and the retinofugal pathways have been described, the functional development of the visual system and the development of the downstream pathways controlling gaze are still unknown. Here, we show that VOR followed by light-evoked eye movements are the first to appear already in larvae, despite their burrowed lifestyle. However, the circuits controlling goal-oriented responses emerge later, in larvae in non-parasitic lampreys but during late metamorphosis in parasitic lampreys. The appearance of stabilizing responses earlier than goal-oriented in the lamprey development shows a stepwise transition from simpler to more complex visual systems, offering a unique opportunity to isolate the functioning of their underlying circuits.

Fetal movements: the origin of human behaviour

The study of the onset and ontogeny of human behaviour has made it clear that a multitude of fetal movement patterns are spontaneously generated, and that there is a close association between activity and the development of peripheral and central structures. The embryo starts moving by 7.5 week's gestation; 2 to 3 weeks later, a number of movement patterns including general movements, isolated limb and head movements, hiccup, and breathing movements, appear. Some movements (e.g. yawning, smiling, 'pointing'; we show these in eight videos in this review) precede life-long patterns; others have intrauterine functions, such as sucking/swallowing for amniotic fluid regulation, breathing movements for lung development, or eye movements for retinal cell diversity. In cases of developmental brain dysfunction, fetal general movements alter their sequence and gestalt, which suggests a dysfunction of the developing nervous system. The scarcity of longitudinal studies calls for further comprehensive research on the predictive value of prenatal functional deviations. What this paper adds Motor output can occur in the absence of sensory input. Structural development is activity-dependent. Fetal general movements are among the first movement patterns to occur. Pregnancy-related and maternal factors impact quantity and modulation of fetal general movements. Prenatal general movement assessment has not yet brought the expected breakthrough.

Infancy studies come of age: Jacques Mehler's influence on the importance of perinatal experience for early language learning

In this paper, we pay homage to Jacques Mehler's empirical and theoretical contributions to the field of infancy studies. We focus on studies of the ability of the human fetus and newborn to attend to, learn from, and remember aspects of the environment, in particular the linguistic environment, as a part of an essential dynamic system of early influence. We provide a selective review of Mehler's and others' studies that examined the perinatal period and helped to clarify the earliest skills and predilections that infants bring to the task of language learning. We then highlight findings on newborns' perceptual skills and biases that motivated a shift in researchers' focus to fetal learning to better understand the role of the maternal voice in guiding newborns' speech perception. Finally, we point to the inspiration drawn from these perinatal approaches to more full-scale empirical treatments of how prenatal experience and behavior have come to be recognized as essential underpinnings to the earliest mental architectures of human cognition.

Fetal eye movements in response to a visual stimulus

INTRODUCTION

In 2D ultrasound, the lens of the fetal eye can be distinguished as white circles within the hypoechoic eyeball, and eye movements can be visualized from about 15 weeks' gestation. It has been shown that from 31 weeks gestational age the fetal sensory system is capable of directed vision if enough light is available.

METHODS

We have developed a light source for delivering visual stimuli to be seen by the fetal eye, using laser dot diodes emitting at 650 nm. The 2D component of 94 fetal ultrasound scans (mean gestational age 240 days), where the light stimulus was presented, was coded to determine whether the eyes moved in response to the stimuli independent of any head movement.

RESULTS

The light stimulus significantly provoked head and eye movements, but after the light was withdrawn the head stopped moving, yet the eyes continued to move.

CONCLUSION

This provides evidence for visual attention mechanisms that can be controlled through eye movements that are independent of head movements prior to birth.