VALIDATING HEARING AID FITTING THROUGH BEHAVIORAL ASSESSMENT OF SPEECH DISCRIMINATION USING VRISD
(VISUAL REINFORCEMENT INFANT SPEECH DISCRIMINATION)
WHY IS THERE A NEED FOR A BEHAVIORAL ASSESSMENT PROCEDURE FOR INFANT SPEECH DISCRIMINATION?
Because of the limitations of parent report, there is a critical need to develop an objective behavioral measure of speech discrimination that can be reliable and valid for infants who are prelinguistic. Auditory discrimination is the current standard for validation of hearing aid fitting of individuals from 2.5 years of age. Physiological CAEP AOR assessment provides information that the brain can detect differences in speech stimuli. However, hearing is a behavioral cognitive auditory response. Therefore, in order to assure that the sounds processed at the level of the cortex are actually perceived by the child as different sounds, a valid and reliable behavioral procedure is needed.
A behavioral procedure needs to be done as soon after the fitting of amplification and can provide specific information about what the child is hearing with the amplification, An objective assessment, the VRISD procedure was developed in the 1970s to use conditioned head-turn to assess speech discrimination in infants 6 months to 30 months of age (Moore, Wilson, Thompson, 1977). Because infants with HL were not being identified in infancy, the technique was not used with children with HL. Uhler et al (2010) demonstrated that toddlers with HL can demonstrate prelinguistic discrimination ability with amplification using a conditioned head turn response. The VRISD procedure can be used to provide an objective measurement of auditory prelinguistic discrimination.
The original VRISD research protocol required 30 trials and used a statistical procedure that could determine differences between groups but not individual mastery of the phoneme discrimination. Uhler et al (2010) and Fredrickson (2010) developed a stopping criterion because infant performance was subject to fatigue and habituation. A statistical procedure for indicating mastery of the discrimination was also established. Infants are capable of discriminating 5 contrasts in about a 30 minute session. One goal of the study will be to choose the 5 representative contrasts that will provide the most appropriate information for hearing aid fitting requires research on the developmental hierarchy of contrast difficulty. The majority of infants can perform the VRISD task between 7 and 9 months of age.
Children will be conditioned to turn to a visual reinforcer when they hear a change in stimul (Uhler et al., 2010; Fredrickson, 2010). For example, the child will hear simple vowel sounds such as “ah” and “ee” or consonant sounds such as “s” and “sh”. One phoneme will be the background stimuli and will play repeatedly. Correct head turns will be reinforced through a video reinforce with cartoon characters. In the VRISD procedure, stimulus-change trials are mixed with control (no change) trials on a random basis. Infant responses fall in one of 4 categories: hits (correct response), misses, false positives, and correct rejections. A binomial probability statistic will be used to determine whether the child’s performance reaches criterion. Each contrast will receive a Pass/Fail score.
CRITERIA FOR PARTICIPANT INCLUSION AND EXCLUSION: Criteria for inclusion of children with HL will be (a) no evidence of significant developmental delays as documented by a parental checklist as well as no secondary disabilities, (b) HL identified per the Colorado State Guidelines for Newborn Hearing Screening, (c) full time use of amplification, (d) demonstrated ability to complete a conditioned head turn via visual reinforcement audiometry (VRA), (e) currently enrolled in early intervention, and (f) either English or Spanish is the primary language spoken in the home.
Criteria for exclusion will be (a) auditory neuropathy, (b) the presence of a secondary disability, (c) history of chronic middle ear infections (d) born earlier than 35 weeks gestation, and (e) abnormal tympanometry on the day of testing. Additional exclusion criteria for children with NH include: failing newborn hearing screening and concern of HL.
DEGREE AND TYPE OF HEARING LOSS (HL):
Degree of HL will be determined using the three-frequency pure tone average (PTA) of 500, 1000 and 2000 Hz of the hearing thresholds obtained via ABR/ASSR and VRA when the infants are 7 months of age. Participants will be categorized by HL according to better PTA threshold ranges and placed in groups based on NH or degree of sensorineural HL
For the hearing test, Visual Reinforcement Audiometry, VRA, a standard clinical procedure used with children 6 – 24 months of age, will be used. Tympanometric screening will check for the presence of middle ear fluid. The screening will be administered by a registered audiologist. Only children who have normal tympanograms (Type A or Type B (if pressure equalization tubes are present)) will proceed with testing. Testing will be postponed for those children whose tympanograms are abnormal.
Both children with normal hearing and children with hearing loss will be included in these studies.