Technology-aided assessment of sensorimotor function in early infancy

A HAND USE AND GRASP SENSOR SYSTEM IN MONITORING INFANT FINE MOTOR DEVELOPMENT

Objective

To assess the feasibility of a hand use and grasp sensor system in collecting and quantifying fine motor development longitudinally in an infant's home environment.

Design

Cohort study. Researchers made home visits monthly to participating families to collect grasp data from infants using a hand use and grasp sensor.

Setting

Data collection were conducted in each participant's home.

Participants

A convenience sample of 14 typical developmental infants were enrolled from 3 months to 9 months of age. Two infants dropped out. A total of 62 testing sessions involving 12 infants were available for analysis (N=12).

Interventions

At each session, the infant was seated in a standardized infant seat. Each instrumented toy was hung on the hand use and grasp sensor structure, presented for 6 minutes in 3 feedback modes: visual, auditory, and vibratory.

Main Outcome Measures

Infant grasp frequency and duration, peak grasping force, average grasping force, force coefficient of variation, and proportion of bimanual grasps.

Results

A total of 2832 recorded grasp events from 12 infants were analyzed. In linear mixed-effects model analysis, when interacting with each toy, infants’ peak grasp force, average grasp force, and accumulated grasp time all increased significantly with age (all P<.001). Bimanual grasps also occupied an increasingly greater percentage of infants’ total grasps as they grew older (bar toy P<.001, candy toy P=.021).

Conclusions

We observed significant changes in hand use and grasp sensor outcome measures with age that are consistent with maturation of grasp skills. We envision the evolution of hand use and grasp sensor technology into an inexpensive and convenient tool to track infant grasp development for early detection of possible developmental delay and/or cerebral palsy as a supplement to clinical evaluations.

An fMRI Compatible Smart Device for Measuring Palmar Grasping Actions in Newborns

Grasping is one of the first dominant motor behaviors that enable interaction of a newborn infant with its surroundings. Although atypical grasping patterns are considered predictive of neuromotor disorders and injuries, their clinical assessment suffers from examiner subjectivity, and the neuropathophysiology is poorly understood. Therefore, the combination of technology with functional magnetic resonance imaging (fMRI) may help to precisely map the brain activity associated with grasping and thus provide important insights into how functional outcomes can be improved following cerebral injury. This work introduces an MR-compatible device (i.e., smart graspable device (SGD)) for detecting grasping actions in newborn infants. Electromagnetic interference immunity (EMI) is achieved using a fiber Bragg grating sensor. Its biocompatibility and absence of electrical signals propagating through the fiber make the safety profile of the SGD particularly favorable for use with fragile infants. Firstly, the SGD design, fabrication, and metrological characterization are described, followed by preliminary assessments on a preterm newborn infant and an adult during an fMRI experiment. The results demonstrate that the combination of the SGD and fMRI can safely and precisely identify the brain activity associated with grasping behavior, which may enable early diagnosis of motor impairment and help guide tailored rehabilitation programs.

Somatotopic Mapping of the Developing Sensorimotor Cortex in the Preterm Human Brain

In the mature mammalian brain, the primary somatosensory and motor cortices are known to be spatially organized such that neural activity relating to specific body parts can be somatopically mapped onto an anatomical "homunculus". This organization creates an internal body representation which is fundamental for precise motor control, spatial awareness and social interaction. Although it is unknown when this organization develops in humans, animal studies suggest that it may emerge even before the time of normal birth. We therefore characterized the somatotopic organization of the primary sensorimotor cortices using functional MRI and a set of custom-made robotic tools in 35 healthy preterm infants aged from 31 + 6 to 36 + 3 weeks postmenstrual age. Functional responses induced by somatosensory stimulation of the wrists, ankles, and mouth had a distinct spatial organization as seen in the characteristic mature homunculus map. In comparison to the ankle, activation related to wrist stimulation was significantly larger and more commonly involved additional areas including the supplementary motor area and ipsilateral sensorimotor cortex. These results are in keeping with early intrinsic determination of a somatotopic map within the primary sensorimotor cortices. This may explain why acquired brain injury in this region during the preterm period cannot be compensated for by cortical reorganization and therefore can lead to long-lasting motor and sensory impairment.

Functional Laterality of Task-Evoked Activation in Sensorimotor Cortex of Preterm Infants: An Optimized 3 T fMRI Study Employing a Customized Neonatal Head Coil

Background

Functional magnetic resonance imaging (fMRI) in neonates has been introduced as a non-invasive method for studying sensorimotor processing in the developing brain. However, previous neonatal studies have delivered conflicting results regarding localization, lateralization, and directionality of blood oxygenation level dependent (BOLD) responses in sensorimotor cortex (SMC). Amongst the confounding factors in interpreting neonatal fMRI studies include the use of standard adult MR-coils providing insufficient signal to noise, and liberal statistical thresholds, compromising clinical interpretation at the single subject level.

Patients / methods

Here, we employed a custom-designed neonatal MR-coil adapted and optimized to the head size of a newborn in order to improve robustness, reliability and validity of neonatal sensorimotor fMRI.

Thirteen preterm infants with a median gestational age of 26 weeks were scanned at term-corrected age using a prototype 8-channel neonatal head coil at 3T (Achieva, Philips, Best, NL). Sensorimotor stimulation was elicited by passive extension/flexion of the elbow at 1 Hz in a block design. Analysis of temporal signal to noise ratio (tSNR) was performed on the whole brain and the SMC, and was compared to data acquired with an ‘adult’ 8 channel head coil published previously. Task-evoked activation was determined by single-subject SPM8 analyses, thresholded at p < 0.05, whole-brain FWE-corrected.

Results

Using a custom-designed neonatal MR-coil, we found significant positive BOLD responses in contralateral SMC after unilateral passive sensorimotor stimulation in all neonates (analyses restricted to artifact-free data sets = 8/13). Improved imaging characteristics of the neonatal MR-coil were evidenced by additional phantom and in vivo tSNR measurements: phantom studies revealed a 240% global increase in tSNR; in vivo studies revealed a 73% global and a 55% local (SMC) increase in tSNR, as compared to the ‘adult’ MR-coil.

Conclusions

Our findings strengthen the importance of using optimized coil settings for neonatal fMRI, yielding robust and reproducible SMC activation at the single subject level. We conclude that functional lateralization of SMC activation, as found in children and adults, is already present in the newborn period.

Sensorized toys for measuring manipulation capabilities of infants at home

Preterm infants, i.e. babies born after a gestation period shorter than 37 weeks, spend less time exploring objects. The quantitative measurement of grasping actions and forces in infants can give insights on their typical or atypical motor development. The aim of this work was to test a new tool, a kit of sensorized toys, to longitudinally measure, monitor and promote preterm infants manipulation capabilities with a purposive training in an ecological environment. This study presents preliminary analysis of grasping activity. Three preterm infants performed 4 weeks of daily training at home. Sensorized toys with embedded pressure sensors were used as part of the training to allow quantitative analysis of grasping (pressure and acceleration applied to toys while playing). Each toy was placed on the midline, while the infant was in supine position. Preliminary data show differences in the grasping parameters in relation to infants age and the performed daily training. Ongoing clinical trial will allow a full validation of this new tool for promoting object exploration in preterm infants.

Early intervention in neurodevelopmental disorders: underlying neural mechanisms

Neurodevelopmental disorders affect motor, cognitive, language, learning, and behavioural development with lifelong consequences. Early identification of infants at risk for neurodevelopmental disorders is a major prerequisite for intervention programmes. This ensures that interventions which aim to positively modify the natural history of these disorders can start in the first weeks or months of life. As indicated by recent scientific evidence, gene abnormalities or congenital brain lesions are not the sole determinants for the neurodevelopmental outcome of affected infants. In fact, environment and experience may modify brain development and improve the outcome in infants at risk for neurodevelopmental disorders. In this review, we analyse the complexity and sensitivity of the brain to environmental stimuli, highlighting clinical effects of early intervention, mainly reported so far in preterm infants, and summarizing the effects of enriched environment on human and animal models. Finally, we discuss some new approaches to early intervention, based on recent neurophysiological theories and new breakthroughs in biotechnologies for diagnosis and rehabilitation.

Sensorized graspable devices for the study of motor imitation in infants

Researches regarding neonatal imitation are of great clinical interest since they can provide evidences of an innate mechanism underlying action understanding; the study can be led through the analysis of infants' spontaneous movements, like grasping, that are recognized as markers of neural activity. To this aim, a portable and non-intrusive device has been designed and developed to measure infants' grasping during the presentation of specific visual stimuli. The device is composed of two soft handles with embedded pressure sensors. During trials action observation should produce an increase of the measured pressure exerted by the infant's hand, according to the imitation-based paradigm of the defined clinical protocol. The final prototype has been tested within a pilot study and it has been proved to be suitable for monitoring infants' imitation abilities, meeting all the clinical specifications in terms of size, weight, safety and sensitivity. Preliminary acquired results are a starting point to clarify mechanisms related to imitation and sensorimotor system growth. The present methodology could be employed to boosts investigation on the development of mirror neurons in infants.

An Automated System for the Analysis of Newborns' Oral-Motor Behavior

The assessment of oral-motor behavior (OMB) represents one the earliest noninvasive ways to evaluate newborns' well-being and neuromotor behavior. This work aimed at developing a new low-cost, easy-to-use and noninvasive system for a technology-aided assessment of newborns' OMB during bottle feeding. A SUcking MOnitoring Device (SUMOD) was designed and developed to be easily integrated on a typical feeding bottle. A software system was developed to automatically treat and analyze the acquired data: proper algorithms for a fully automatic segmentation and features extraction are proposed and implemented. A set of measures of motor control and coordination are introduced and implemented for the specific application to the OMB analysis. Experimental data were collected on two groups of newborns (healthy versus low birth weight) with the SUMOD in a clinical setting.

Maturation of Sensori-Motor Functional Responses in the Preterm Brain

Preterm birth engenders an increased risk of conditions like cerebral palsy and therefore this time may be crucial for the brain's developing sensori-motor system. However, little is known about how cortical sensori-motor function matures at this time, whether development is influenced by experience, and about its role in spontaneous motor behavior. We aimed to systematically characterize spatial and temporal maturation of sensori-motor functional brain activity across this period using functional MRI and a custom-made robotic stimulation device. We studied 57 infants aged from 30 + 2 to 43 + 2 weeks postmenstrual age. Following both induced and spontaneous right wrist movements, we saw consistent positive blood oxygen level–dependent functional responses in the contralateral (left) primary somatosensory and motor cortices. In addition, we saw a maturational trend toward faster, higher amplitude, and more spatially dispersed functional responses; and increasing integration of the ipsilateral hemisphere and sensori-motor associative areas. We also found that interhemispheric functional connectivity was significantly related to ex-utero exposure, suggesting the influence of experience-dependent mechanisms. At term equivalent age, we saw a decrease in both response amplitude and interhemispheric functional connectivity, and an increase in spatial specificity, culminating in the establishment of a sensori-motor functional response similar to that seen in adults.