Neonatal eyelid conditioning during sleep

Detection of regularities in auditory sequences before and at term-age in human neonates

During the last trimester of gestation, fetuses and preterm neonates begin to respond to sensory stimulation and to discover the structure of their environment. Yet, neuronal migration is still ongoing. This late migration notably concerns the supra-granular layers neurons, which are believed to play a critical role in encoding predictions and detecting regularities. In order to gain a deeper understanding of how the brain processes and perceives regularities during this stage of development, we conducted a study in which we recorded event-related potentials (ERP) in 31-wGA preterm and full-term neonates exposed to alternating auditory sequences (e.g. "ba ga ba ga ba"), when the regularity of these sequences was violated by a repetition (e.g., ``ba ga ba ga ga''). We compared the ERPs in this case to those obtained when violating a simple repetition pattern ("ga ga ga ga ga" vs. "ga ga ga ga ba"). Our results indicated that both preterm and full-term neonates were able to detect violations of regularity in both types of sequences, indicating that as early as 31 weeks gestational age, human neonates are sensitive to the conditional statistics between successive auditory elements. Full-term neonates showed an early and similar mismatch response (MMR) in the repetition and alternating sequences. In contrast, 31-wGA neonates exhibited a two-component MMR. The first component which was only observed for simple sequences with repetition, corresponded to sensory adaptation. It was followed much later by a deviance-detection component that was observed for both alternation and repetition sequences. This pattern confirms that MMRs detected at the scalp may correspond to a dual cortical process and shows that deviance detection computed by higher-level regions accelerates dramatically with brain maturation during the last weeks of gestation to become indistinguishable from bottom-up sensory adaptation at term.

Learning during sleep in humans - A historical review

Sleep helps to consolidate previously acquired memories. Whether new information such as languages and other useful skills can also be learned during sleep has been debated for over a century, however, the sporadic studies' different objectives and varied methodologies make it difficult to draw definitive conclusions. This review provides a comprehensive overview of the history of sleep learning research conducted in humans, from its empirical beginnings in the 1940s to the present day. Synthesizing the findings from 51 research papers, we show that several studies support the notion that simpler forms of learning, such as habituation and conditioning, are possible during sleep. In contrast, the findings for more complex, applied learning (e.g., learning a new language during sleep) are more divergent. While there is often an indication of processing and learning during sleep when looking at neural markers, behavioral evidence for the transfer of new knowledge to wake remains inconclusive. We close by critically examining the limitations and assumptions that have contributed to the discrepancies in the literature and highlight promising new directions in the field.

Perinatal attention, memory and learning during sleep

The perinatal brain is well equipped to react to the environment during sleep. Several lines of research in animals and humans prior to and immediately after birth have documented the capability to respond, to process and remember patterns of stimulation. In this article, we will summarize recent findings as well as previous work documenting the memory and learning capacities of the developing brain during sleep and wake states. The role of these sleep state dependent processes may play in the ability to adapt to the postnatal environment will be discussed.

How babies learn: The autonomic socioemotional reflex

BACKGROUND

Human and animal research has long documented the negative effects of early traumatic events on long-term development and socioemotional behavior. Yet, how and where the body stores these memories remains unclear. Current theories propose that the brain stores such memory in the subcortical limbic system. However, a clear theory of change with testable hypothesis has yet to emerge.

AIMS

In this paper, we review the classical Pavlovian conditioning learning tradition, along with its functional variant. Then, we review calming cycle theory, which builds upon the idea that mother/infant learning is distinct from other types of learning, requiring a new set of assumptions in light of functional Pavlovian conditioning.

CONCLUSION

Calming cycle theory states that learning of behaviors associated with subcortical autonomic physiology is separate and distinct from learning of behaviors associated with cortical physiology. Mother/infant autonomic learning starts in the uterine environment via functional Pavlovian co-conditioning that is stored as conditional reflexes within the dyad's autonomic nervous systems. These reflexes are preserved transnatally as autonomic socioemotional reflexes (ASRs), which can be used to monitor mother-infant relational health. The functional Pavlovian co-conditioning mechanism can be exploited to change the physiological/behavioral reflex response. The theory provides a well established learning mechanism, a theory of change and a method of change, along with a set of hypotheses with which to test the theory. We present evidence from a randomized controlled trial with prematurely born infants and their mothers that supports calming cycle theory.

Cortical Processing of Multimodal Sensory Learning in Human Neonates

Following birth, infants must immediately process and rapidly adapt to the array of unknown sensory experiences associated with their new ex-utero environment. However, although it is known that unimodal stimuli induce activity in the corresponding primary sensory cortices of the newborn brain, it is unclear how multimodal stimuli are processed and integrated across modalities. The latter is essential for learning and understanding environmental contingencies through encoding relationships between sensory experiences; and ultimately likely subserves development of life-long skills such as speech and language. Here, for the first time, we map the intracerebral processing which underlies auditory-sensorimotor classical conditioning in a group of 13 neonates (median gestational age at birth: 38 weeks + 4 days, range: 32 weeks + 2 days to 41 weeks + 6 days; median postmenstrual age at scan: 40 weeks + 5 days, range: 38 weeks + 3 days to 42 weeks + 1 days) with blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (MRI) and magnetic resonance (MR) compatible robotics. We demonstrate that classical conditioning can induce crossmodal changes within putative unimodal sensory cortex even in the absence of its archetypal substrate. Our results also suggest that multimodal learning is associated with network wide activity within the conditioned neural system. These findings suggest that in early life, external multimodal sensory stimulation and integration shapes activity in the developing cortex and may influence its associated functional network architecture.

Sleep, Little Baby: The Calming Effects of Prenatal Speech Exposure on Newborns' Sleep and Heartrate

In a pilot study, 34 fetuses were stimulated daily with a maternal spoken nursery rhyme from week 34 of gestation onward and re-exposed two and five weeks after birth to this familiar, as well as to an unfamiliar rhyme, both spoken with the maternal and an unfamiliar female voice. During auditory stimulation, newborns were continuously monitored with polysomnography using video-monitored hdEEG. Afterward, changes in sleep–wake-state proportions during familiar and unfamiliar voice stimulation were analyzed. Our preliminary results demonstrate a general calming effect of auditory stimulation exclusively in infants who were prenatally “familiarized” with a spoken nursery rhyme, as evidenced by less waking states, more time spent in quiet (deep) sleep, and lower heartrates. A stimulation naïve group, on the other hand, demonstrated no such effects. Stimulus-specific effects related to the familiarity of the prenatally replayed voice or rhyme were not evident in newborns. Together, these results suggest “fetal learning” at a basic level and point to a familiarization with auditory stimuli prior to birth, which is evident in the first weeks of life in behavioral states and heartrate physiology of the newborn.

Sleep deprivation directly following eyeblink-conditioning impairs memory consolidation

The relation between sleep and different forms of memory formation continues to be a relevant topic in our daily life. Sleep has been found to affect cerebellum-dependent procedural memory formation, but it remains to be elucidated to what extent the level of sleep deprivation directly after motor training also influences our ability to store and retrieve memories. Here, we studied the effect of disturbed sleep in mice during two different time-windows, one covering the first four hours following eyeblink conditioning (EBC) and another window following the next period of four hours. Compared to control mice with sleep ad libitum, the percentage of conditioned responses and their amplitude were impaired when mice were deprived of sleep directly after conditioning. This impairment was still significant when the learned EBC responses were extinguished and later reacquired. However, consolidation of eyeblink responses was not affected when mice were deprived later than four hours after acquisition, not even when tested during a different day-night cycle for control. Moreover, mice that slept longer directly following EBC showed a tendency for more conditioned responses. Our data indicate that consolidation of motor memories can benefit from sleep directly following memory formation.

Cognitive Impact of Cerebellar Non-invasive Stimulation in a Patient With Schizophrenia

Cerebellum plays a role in the regulation of cognitive processes. Cerebellar alterations could explain cognitive impairments in schizophrenia. We describe the case of a 50 years old patient with schizophrenia whom underwent cerebellar transcranial direct current stimulation (tDCS). In order to study the effect of cerebellar stimulation on cognitive functions, the patient underwent a neuropsychological assessment and an eyeblink conditioning (EBC) protocol. Although the effect of brain stimulation cannot be only assessed in a single-case study, our results suggest that cerebellar stimulation may have an effect on a broad range of cognitive functions typically impaired in patients with schizophrenia, including verbal episodic, short term, and working memory. In addition to neuropsychological tests, we evaluated the cerebellar function by performing EBC before and after tDCS. Our data suggest that tDCS can improve EBC. Further clinical trials are required for better understanding of how cerebellar stimulation can modulate cognitive processes in patients with schizophrenia and healthy controls.

Sleep in Infancy: A Concept Analysis

PROBLEM

Sleep has historically been defined by adult standards that fail to recognize the dynamic physiologic process in the first year of life.

ELIGIBILITY CRITERIA

A literature review and concept analysis were conducted to examine what is known about sleep in infancy. Studies were included if sleep was objectively measured and healthy infants 0 to 12 months old were the focus of the study.

SAMPLE

Of 647 records identified, 348 were assessed for eligibility and 20 studies were included in the review of the literature.

RESULTS

Sleep in infancy is a time of evolving sleep architecture, sleep consolidation, and extensive neural activity resulting in neurodevelopment.

CONCLUSIONS

It is imperative to recognize the critical role of sleep for optimal infant neurodevelopment on the part of healthcare providers and society at large.

IMPLICATIONS

Efforts should be made to protect sleep periods in both healthy and hospitalized infants. The proposed definition has the potential to improve the care of healthy and hospitalized infants by preserving and promoting neurodevelopment.

Emergence of mature cortical activity in wakefulness and sleep in healthy preterm and full-term infants

Study Objectives

Cortical activity patterns develop rapidly over the equivalent of the last trimester of gestation, in parallel with the establishment of sleep architecture. However, the emergence of mature cortical activity in wakefulness compared with sleep states in healthy preterm infants is poorly understood.

Methods

To investigate whether the cortical activity has a different developmental profile in each sleep-wake state, we recorded 11-channels electroencephalography (EEG), electrooculography (EOG), and respiratory movement for 1 hr from 115 infants 34 to 43 weeks-corrected age, with 0.5-17 days of postnatal age. We characterized the trajectory of δ, θ, and α-β oscillations in wakefulness, rapid eye movement (REM) sleep, and non-REM sleep by calculating the power spectrum of the EEG, averaged across artifact-free epochs.

Results

δ-Oscillations in wakefulness and REM sleep decrease with corrected age, particularly in the temporal region, but not in non-REM sleep. θ-Oscillations increase with corrected age in sleep, especially non-REM sleep, but not in wakefulness. On the other hand, α-β oscillations decrease predominantly with postnatal age, independently of sleep-wake state, particularly in the occipital region.

Conclusions

The developmental trajectory of δ and θ rhythms is state-dependent and results in changed cortical activity patterns between states with corrected age, which suggests that these frequency bands may have particular functional roles in each state. Interestingly, postnatal age is associated with a decrease in α-β oscillations overlying primary visual cortex in every sleep-wake state, suggesting that postnatal experience (including the first visual input through open eyes during periods of wakefulness) is associated with resting-state visual cortical activity changes.

Cerebellar-dependent associative learning is impaired in very preterm born children and young adults

Preterm birth incorporates an increased risk for cerebellar developmental disorders likely contributing to motor and cognitive abnormalities. Experimental evidence of cerebellar dysfunction in preterm subjects, however, is sparse. In this study, classical eyeblink conditioning was used as a marker of cerebellar dysfunction. Standard delay conditioning was investigated in 20 adults and 32 preschool children born very preterm. Focal lesions were excluded based on structural magnetic resonance imaging. For comparison, an equal number of matched term born healthy peers were tested. Subgroups of children (12 preterm, 12 controls) were retested. Preterm subjects acquired significantly less conditioned responses (CR) compared to controls with slower learning rates. A likely explanation for these findings is that preterm birth impedes function of the cerebellum even in the absence of focal cerebellar lesions. The present findings are consistent with the assumption that prematurity results in long-term detrimental effects on the integrity of the cerebellum. It cannot be excluded, however, that extra-cerebellar pathology contributed to the present findings.