Somatosensory prediction in preschool children: a preliminary ERP study

Abstract

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