Être touché : une action immobile, fondation de notre développement

National audienceAt the start of my research, touch was not yet my object of study. It was a means of eliciting neuronal activity in babies' brains, the characteristics of which I could then study. As my work on brain development progressed, it became clear to me that this sense, neglected by neuroscientists, held untapped potential, not only for understanding how the newborn brain makes sense of its environment, but also for elucidating the pathological mechanisms of neurodevelopmental disorders (which include autism spectrum disorders, attention deficit disorders with or without hyperactivity, and dys learning disorders). In this chapter, through my scientific journey, I set out to develop this potential of the tactile sense to understand how our brain functions or dysfunctions at the beginning of life.Au début de mes travaux de Recherche, le toucher n’était pas encore mon objet d’étude. Il était un moyen de susciter dans le cerveau des bébés une activité neuronale dont je pourrais ensuite étudier les caractéristiques. Au fur et à mesure de la progression de mes travaux sur le développement cérébral, il m’apparut que ce sens négligé des neuroscientifiques recelait un potentiel inexploité, non seulement pour comprendre comment le cerveau du nouveau-né donne du sens à son environnement, mais aussi pour élucider les mécanismes pathologiques des troubles du neurodéveloppement (qui comprennent notamment les troubles du spectre de l’autisme, les troubles de l’attention avec ou sans hyperactivité, ou les troubles des apprentissages dits « dys »). Dans ce chapitre, à travers mon cheminement scientifique, j’entreprends de développer ce potentiel du sens tactile pour comprendre comment notre cerveau fonctionne ou dysfonctionne au début de la vie

Psychobiological foundations of early sensori motor development and implications for neonatal care

International audienceIn mammals, somatosensation and chemosensation are the first sensory systems by which the developing organism becomes acquainted with its environment (Segond, 2008). Somatosensory perception includes tactile, thermal and pain perception through cutaneous receptors, as well as postural and movement information through muscle and tendon receptors. Chemosensory perception includes the olfactory, gustatory and trigeminal systems, involved in nutrition, social interactions, and emotional reactivity and regulation. In humans, these two systems emerge in utero and prepare the foetus for neonatal life. Because of this developmental heterochrony, they are the foundation of cognitive and affective development (Humphrey, 1970; Lecanuet & Schaal, 1996; Schaal, 2000; Schaal, Hummel, & Soussignan, 2004). Although the importance of these ontogenetically and phylogenetically earlier systems for individual development has been acknowledged for a long time, they are the least studied in the human neonate, compared with later modalities such as audition (Fitzgerald & Andrews, 1994; Streri, Hevia, Izard, & Coubart, 2013). Clinicians dealing with premature and other fragile newborns have initiated a regain of interest for these perceptions by suggesting therapeutic interventions in these modalities, but their efforts are impeded by the lack of fundamental knowledge that could drive their hypotheses and frame their observations. In this chapter, we propose a framework to study neonatal psychobiological development focusing on tactile and chemical senses. We want to emphasize how these senses are crucial modalities to understand very early development, and how they can bring rational arguments and testable hypotheses to the growing field of sensory therapies and developmental care in preterm and term neonates. We hope that these modalities will attract more attention from both researchers and clinicians in the future

Somatosensory prediction among preschool children: a cross-sectional study

International audienceBackground: Sensory prediction (SP) is the ability to anticipate future stimulations on the basis of previous sensory inputs. It is related to mismatch detection (MMD, the ability to detect an unusual or deviant stimulus among familiar ones), and to repetition suppression (RS, the reduction of neuronal activity when a stimulus is repeated or becomes irrelevant). This work aims to describe somatosensory RS, MMD, and SP in neurotypical preschool children. We hypothesize a deactivation in the somatosensory cortex when a tactile stimulation is repeated, a fronto-central mismatch response to deviant stimuli, and a somatosensory activation with late frontal components when the stimulation is unexpectedly omitted. Method: We aim at including 60 children from 3 age groups: 2, 4, and 6 years old. Brain activity is measured using 128-channels electroencephalography (EEG). The vibrotactile oddball-omission protocol contains 290 trials (200ms-long vibrations that feel like moving on the skin on the anterior part of the forearm). RS is quantified by comparing amplitudes of potentials evoked by the first (familiarization) and the last (control) 40 standard trials. In between, 30 deviant stimuli (movement is reversed) are presented among standards and used to evaluate the MMD (amplitude difference between deviants and standard), and 30 omissions to evaluate SP (significant neuronal activation compared to baseline in the absence of an expected stimulus). So far (N=13), we observe a strong RS from 2 years of age. We need more participants to analyze MMD and SP. General implications: There is still little information on tactile processing in children despite the importance of this modality in understanding sensory impairments associated with neurodevelopmental disorders. If somatosensory predictive mechanisms can be quantified from 2 years old, they could be used as early markers to screen for atypical neurodevelopment among vulnerable populations, such as premature neonates

Simultaneous EEG-fNIRS explore sensory prediction as a screening tool for neurodevelopmental disorders

International audienceSensory prediction (SP) is the ability to anticipate future stimulations on the basis of previous sensory inputs. It is related to another basic skill named repetition suppression (RS) which is the reduction of activity in the brain when a stimulation is repeated or becomes irrelevant. Oddball protocols, in which a rare deviant stimulus (target) appears randomly in a sequence of frequent repeated stimuli, and stimulus omission protocols, in which an expected (based on repetition) stimulus is omitted, are usually used to highlight these skills. For example, 2-3 months old infants present a decreasing neuronal response to repeated stimuli in the sensory cortices, and an increase of activity in sensory and frontal cortices during a deviant stimulation (Dehaene-Lambertz and Dehaene, 1994). Recent studies indicate that children born preterm (born before 37 weeks of gestational age, GA) and children with neurodevelopmental disorders (such as autism spectrum disorder or attention-deficit disorder) may have altered sensory prediction and repetition suppression. Infants born preterm have lower brain activation during sensory prediction tasks compared to full-term infants (Emberson et al, 2017; Boldin et al, 2018). Gonzalez-Gadea et al. (2015) demonstrated that children with neurodevelopmental disorders (NDD) could have different brain responses to both expected and unexpected deviant stimuli compared to controls in an auditory oddball protocol.The prevalence of neurodevelopmental disorders (NDD) is higher in the premature population (Johnson et al, 2011) and both prematurity and NDD are associated with sensory deficits, especially tactile hypo- or hypersensitivity, suggesting a common mechanism for altered RS and SP in prematurity and NDD.The aim of this work is to describe somatosensory repetition suppression and prediction from birth to 6 years of age in both neurotypical and neuroatypical children. We hypothesize that neurotypical children will have a larger RS and SP in somatosensory and frontal cortices compared to children born preterm or children with NDD.To test these hypotheses, we built a 17 minutes tactile omission protocol designed to generate RS and SP responses. Brain activity will be measured with electroencephalography (EEG) and functional Near Infrared Spectroscopy (fNIRS).Data will be analyzed using a mixed model analysis between conditions (first 50 stimuli, last 50 stimuli, standard, omission and postomission), age group (0, 2, 4, 6 years old) and neurodevelopmental status (neurotypical, degree of prematurity, neurodevelopmental disorder).We aim at including 160 children from birth to 6 years old, divided in 4 age groups (N=40 per group): premature newborns, 2 years old, 4 years old and 6 years old. Each group will be divided in 2 subgroups (N=20) sketching the neuroatypical and neurotypical developmental trajectories: at birth, half of the participants will be extremely premature (born before 32 weeks GA) and the other late premature (born after 34 weeks GA), at 2 and 4 years old, half of the participants will be born premature and the other half at term, and in the 6 years old group, half will be diagnosed with a NDD and the other half will be neurotypical.The protocol contains 300 stimuli divided in 3 parts. The first and the last 50 stimuli are standard and used to measure RS. In between, 40 blocks of four stimuli and one omission each, are used to evaluate SP. Each stimulus is a 200ms vibration that feels like moving on the skin on the anterior part of the forearm. Interstimulus interval is jittered between 2 and 4s. Omissions generate a 7s interval instead. Stimulation is delivered by custom-made vibratory matrices (Caylar SAS, Villebon-sur-Yvette, France). The matrix for newborns contains a column of 4 vibrators, the one for children contains 3 columns of 6 vibrators.Newborn brain activity will be recorded at 35 weeks of corrected GA during natural sleep in the neonatal intensive care unit of the University hospital of Caen, France. Children brain activity will be recorded in the laboratory while they watch moving circles on a screen with classical music. Children of 4 and 6 years old will also undergo behavioral, motor and cognitive evaluations in order to compare brain measures with development.Neuronal activity is measured using a 128 channels EEG (Magstim EGI, Eugene OR, USA) at 1000 Hz sampling rate. Impedance is kept under 50kΩ. The data are processed using Magstim EGI software Netstation: bandpass filtered (1-20Hz) then segmented (-100-900ms for the standard, and 7000ms for the omissions). Segments are visually inspected to remove artifacts before averaging. We apply baseline correction to all the segments at 100ms before stimulus onset. Using Matlab (The Mathworks, Inc. Natick MA, USA), we calculate amplitude and latencies of evoked potentials in three electrodes placed over the contralateral somatosensory cortex, and two electrodes placed over the posterior superior frontal gyrus. We calculate the difference between first and last 50 stimuli response averages to quantify RS in both regions of interest. The amplitude of potentials evoked by omissions is used to quantify SP. Newborn brain activity will also be recorded with simultaneous fNIRS (Imagent, ISS, Champaign IL, USA) at 690nm and 830nm, with 2 detectors and 8 sources placed over the two regions of interest (somatosensory and posterior frontal). Data will be processed using Homer3 software (www.bu.edu/neurophotonics/research/fnirs) (Conversion of light intensity to Optical Density (OD), bandpass filtering, Δ OD to hemoglobin concentrations, motion artifact removal and block average). In Matlab we will compare the difference between first and last 50 stimuli response (oxygenated hemoglobin concentration changes during the 3s following stimulus onset, relative to baseline: ∆HbO) averages to quantify RS. The amplitude of the hemodynamic response to omissions (both event-based and block-based) will be used to quantify SP.For EEG, we will compare values of RS and SP in both areas of interest using a mixed model analysis between conditions, age group and neurodevelopmental status.For fNIRS, we will compare values of RS and SP in both areas of interest using a mixed model analysis between conditions and neurodevelopmental status, for event-based and block-based responses.Finally, we will compare fNIRS and EEG responses in each condition to evaluate consistency between techniques, and determine which is most sensitive to neurodevelopment

Somatosensory prediction in preschool children: a preliminary ERP study

International audienceSensory prediction (SP) is the ability to anticipate future stimulations on the basis of previous sensory inputs. It is related to repetition suppression (RS) which is the reduction of activity in the brain when a stimulus is repeated or becomes irrelevant. Oddball protocols, in which a rare deviant stimulus (target) appears randomly in a sequence of frequent, repeated stimuli, and stimulus omission protocols in which an expected stimulus is omitted, are used to highlight these skills. Recent studies indicate that children born preterm and children with neurodevelopmental disorders (NDD) may have altered sensory prediction and repetition suppression (Emberson et al, 2017; Gonzalez-Gadea et al, 2015). The prevalence of NDD is higher in children born prematurely (Johnson et al, 2011) and both prematurity and NDD are associated with sensory deficits, especially tactile hypo- or hypersensitivity, suggesting a common mechanism for altered RS and SP in prematurity and NDD. The aim of this work is to describe somatosensory repetition suppression and prediction of neurotypical preschool children. We included four neurotypical children from 4 to 5 years old. We built an 18 minutes vibrotactile oddball-omission protocol designed to generate RS and SP responses (Fig. 1). The protocol contains 290 trials: 200ms-long vibrations that feel like moving on the skin on the anterior part of the forearm. The first (familiarization) and the last (control) 40 stimuli are standard and used to measure RS. In between, 30 blocks of seven stimuli, containing five standards, one deviant (movement is reversed) and one omission each, are used to evaluate SP. Brain activity is measured using 128-channels EEG (Magstim EGI®).Event-related analysis (Fig. 2) shows that the amplitude of the N140 evoked potential is weaker for the control phase compared to the familiarization in the somatosensory cortex for every subject, indicating robust somatosensory RS. For stimuli presented just after an unexpected omission (post-omission stimuli), a mismatch negativity was observed in the somatosensory cortex and a positive mismatch response in the frontal cortex from 400ms after stimulus onset. In the deviant condition, we observed positive mismatch response in both somatosensory and frontal cortices from 400ms to 600ms after stimulus onset.There is currently little information on tactile processing in children, despite studies showing the importance of this modality in understanding sensory impairments associated with NDD. Here we describe robust repetition suppression of tactile stimuli in neurotypical children, and we continue including subjects from 2 to 6 years of age, with a preterm-born group and a NDD group, to compare with these findings. We need to pursue the inclusions to interpret post-omission results indicating tactile prediction and deviant discrimination. In particular, a positive mismatch response was unexpected and needs to be further investigated. This study will provide important insights into tactile processing and sensory prediction in the tactile modality in preschoolers with various neurodevelopmental profiles

Sensory Prediction and Repetition Suppression in the tactile modality as early markers of executive attention development at preschool age

International audienceThe tactile modality, the first to develop, is the foundation of cognitive development. Sensory Prediction (SP) is a core mechanism sustained by our perceptions and allows the brain to anticipate future stimulations on the basis of previous sensory inputs (Friston, 2005). Repetition Suppression (RS) refers to the reduction of activity in the brain when a predicted stimulus is repeated or becomes irrelevant. Sensory Prediction in the tactile modality was suggested as an early precursor of cognitive development (Dumont et al., 2022). Predictive mechanisms may form the basis of executive attention development by sustaining self-regulation processes such as habituation or anticipation (Bubic et al., 2010).The aim of this study is to investigate how tactile prediction and other tactile processing phenomena are related to executive attention development at preschool age

Is tactile perception related with attention development?

International audienceThis poster presents behavioral and cerebral measurements of the project MEDiATE. The project aims at identifying precursors of executive attention that can serve as early markers for attention disorder screening. In the first study, we demonstrate that tactile sensory processing is related with executive functions in everyday situations. In the follow-up study, preliminary data show Repetition Suppression (RS) and deviance detection in the tactile modality. During the Child ANT, we do not observe a strong difference between congruent and incongruent conditions, suggesting that our sample of children perform well on this task. To further investigate the relationship between brain evoked potentials for tactile sensory processing and attention, we need a larger sample of children, including younger children and children with high developmental risk or NDD, who may show larger differences between the congruent and incongruent conditions Such findings could help to promote new screening and remediation tools for attention deficits based on the quality of tactile sensory processing

Is tactile perception related with attention development?

International audienceThis poster presents behavioral and cerebral measurements of the project MEDiATE. The project aims at identifying precursors of executive attention that can serve as early markers for attention disorder screening. In the first study, we demonstrate that tactile sensory processing is related with executive functions in everyday situations. In the follow-up study, preliminary data show Repetition Suppression (RS) and deviance detection in the tactile modality. During the Child ANT, we do not observe a strong difference between congruent and incongruent conditions, suggesting that our sample of children perform well on this task. To further investigate the relationship between brain evoked potentials for tactile sensory processing and attention, we need a larger sample of children, including younger children and children with high developmental risk or NDD, who may show larger differences between the congruent and incongruent conditions Such findings could help to promote new screening and remediation tools for attention deficits based on the quality of tactile sensory processing

Is tactile perception related with attention development?

International audienceThis poster presents behavioral and cerebral measurements of the project MEDiATE. The project aims at identifying precursors of executive attention that can serve as early markers for attention disorder screening. In the first study, we demonstrate that tactile sensory processing is related with executive functions in everyday situations. In the follow-up study, preliminary data show Repetition Suppression (RS) and deviance detection in the tactile modality. During the Child ANT, we do not observe a strong difference between congruent and incongruent conditions, suggesting that our sample of children perform well on this task. To further investigate the relationship between brain evoked potentials for tactile sensory processing and attention, we need a larger sample of children, including younger children and children with high developmental risk or NDD, who may show larger differences between the congruent and incongruent conditions Such findings could help to promote new screening and remediation tools for attention deficits based on the quality of tactile sensory processing

Sensory Prediction and Repetition Suppression in the tactile modality as early markers of executive attention development at preschool age

International audienceThe tactile modality, the first to develop, is the foundation of cognitive development. Sensory Prediction (SP) is a core mechanism sustained by our perceptions and allows the brain to anticipate future stimulations on the basis of previous sensory inputs (Friston, 2005). Repetition Suppression (RS) refers to the reduction of activity in the brain when a predicted stimulus is repeated or becomes irrelevant. Sensory Prediction in the tactile modality was suggested as an early precursor of cognitive development (Dumont et al., 2022). Predictive mechanisms may form the basis of executive attention development by sustaining self-regulation processes such as habituation or anticipation (Bubic et al., 2010).The aim of this study is to investigate how tactile prediction and other tactile processing phenomena are related to executive attention development at preschool age