Quantitative Assessment of Cortical Auditory-tactile Processing in Children with Disabilities

Summary

Objective and easy measurement of sensory processing is extremely difficult in nonverbal or vulnerable pediatric patients. We developed a new methodology to quantitatively assess infants and children's cortical processing of light touch, speech sounds, and the multisensory processing of the 2 stimuli, without requiring active subject participation or causing discomfort in vulnerable patients.

Abstract

Objective and easy measurement of sensory processing is extremely difficult in nonverbal or vulnerable pediatric patients. We developed a new methodology to quantitatively assess children's cortical processing of light touch, speech sounds and the multisensory processing of the 2 stimuli, without requiring active subject participation or causing children discomfort. To accomplish this we developed a dual channel, time and strength calibrated air puff stimulator that allows both tactile stimulation and sham control. We combined this with the use of event-related potential methodology to allow for high temporal resolution of signals from the primary and secondary somatosensory cortices as well as higher order processing. This methodology also allowed us to measure a multisensory response to auditory-tactile stimulation.

Introduction

The study of developing cortical sensory processes is essential to understanding the basis for most higher order functions. Sensory experiences are responsible for much of the brain's organization through infancy and childhood, laying the foundation for complex processes such as cognition, communication, and motor development^1-3. Most pediatric studies of sensory processes focus on auditory and visual domains, mainly because these stimuli are easiest to develop, standardize, and test. However, tactile processing is of particular interest in infants and children as it is the first sense to develop in the fetus^4,5, and somatosensory information....

Protocol

1. Assessment of Response to Light Touch

1. Place the electrode net (e.g. 128-channels geodesic sensor net) on child or infant's head. Adjust sensors for full contact using warm saline solution. If on a child, ensure child is sitting comfortably in parent or caregiver lap. If on an infant, ensure that infant is lightly swaddled and either held in caregiver's arms or in a supine position in an open crib.
2. Position a 1 mm nozzle 0.5 cm below the tip of the index finger of the tested hand. Place finger for a young child or palm for an infant in a mold holder and secure with Velcro tape proximal and distal to joint to ensure consist....

Results

Assessment of light touch (Figure 3):

Characteristics of the cortical response to tactile stimulation using the Puffer system: The patterns of peaks in response to the puff are very similar to the cortical responses obtained using median nerve stimulation in normal adults^10,11. The early response (P50, N70, P100 peaks) primarily reflects activity in the primary sensory cortex¹² and does not require awareness of stimulation........

Discussion

This novel combination of air puff and ERP (referred to as the "Puffer system") to measure cortical processing of light touch and tactile-auditory responses is well tolerated by young children with disabilities and by infants. This holds true for unisensory and multisensory versions, and whether the attentional component is added or not in the case of young children. The reasons for the success of this methodology in assessing a young and vulnerable population are due to both the use of an innocuous tactile stimu.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Geodesic sensor net	EGI, Inc., Eugene, OR	depends on size
Net Station EEG software v. 4.2	EGI, Inc., Eugene, OR	NA
E-Prime stimulus control application	PST, Inc. Pittsburgh, PA	NA
Manometer (model 6 in, 0-60 psi)	H. O. Trerice Co, Oak Park, MI
Custom Puffer setup	Nathalie Maitre