1 Why Hearing Is Important in Children

Carol Flexer, Jane R. Madell, Jace Wolfe, and Erin C. Schafer

Summary

This chapter focuses on the changing world for pediatric audiologists, brought about in large part by brain research and innovations in technology. Because hearing occurs in the brain, not in the ear, auditory neural development will be a focus of this chapter, including a discussion of neuroplasticity, auditory deprivation, and critical periods of auditory development. The hows and whys of spoken language enrichment and literacy development will also be addressed in this chapter. The bottom line is that pediatric audiologists have a key role in determining the future opportunities of a child with a hearing loss, and this chapter sets that precise tone for the rest of the book.

Keywords

hearing, hearing loss, deaf, hard of hearing, children, pediatrics, neuroplasticity, auditory brain, brain, listening, auditory deprivation, critical periods, audiology, language

1.1 Introduction to Pediatric Audiology

Approximately 12,000 new babies with hearing loss are identified every year, according to the National Institute on Deafness and Other Communication Disorders. In addition, estimates are that another 4,000 to 6,000 infants and young children between birth and 3 years of age who had passed the newborn screening test acquire late-onset hearing loss. Therefore, ~ 16,000 to 18,000 new babies and toddlers are identified with hearing loss per year, making hearing loss the most common birth defect.

Numerous studies over the decades demonstrate that when hearing loss of any degree is not adequately diagnosed and treated, it can negatively affect the speech, language, academic, emotional, and psychosocial development of young children.1,2 Therefore, the secondary effects of hearing loss adversely affect a child’s development as much as or more so than the hearing loss itself does.

Recently there has been a surge of technology and information about testing and managing hearing loss in infants and children. The impetus for this surge has been newborn hearing screening. As a result of identifying and treating hearing loss in neonates, we now are dealing with a vastly different population of children with hearing loss, a population that never existed before. With this new population, whose hearing loss is identified at birth, the secondary developmental and communicative deficits of hearing loss that were so common can now be prevented. What has happened in the field of hearing loss is revolutionary, and the pediatric audiologist is in the linchpin position.

How does the pediatric audiologist of today diagnose and treat this new population of babies and children with hearing loss and their families? How does audiology, as a (health) diagnosing and treating profession, collaborate with other health care providers, early interventionists, speech-language pathologists, teachers, and, of course, families in providing quality services? The first step is to recognize that, because of technology and brain neuroplasticity, everything that we used to know and believe about hearing loss has changed.

This chapter will begin with a discussion of the changing world for pediatric audiologists. Next, auditory neural development will be detailed, along with a discussion of neuroplasticity, auditory deprivation, and critical periods of auditory development. A new context for the word “deaf” will be posited, and the chapter will conclude with the distinction between hearing and listening.

1.2 Pediatric Audiology Is Changing

The popular book about change, Who Moved My Cheese? by Spencer Johnson, M.D. (1998), is particularly meaningful in the world of hearing loss.3 Changes brought about through technology and early hearing detection and intervention (EHDI) programs have permitted outcomes of listening and talking only dreamed of a few years ago. It is important to realize that the new outcomes available today do not invalidate the treatment decisions made by pediatric audiologists in the past. Audiologists did what was necessary with what was available at the time. For example, until the 1970s, children with bilateral hearing loss were routinely fitted with only one hearing aid.

With increased knowledge, we can now offer better services. Audiologists today do the best that can be done in today’s world. Tomorrow’s world will bring new possibilities, and we will need to “move with the cheese.” Our job as pediatric audiologists is to prepare today’s babies to be take-charge adults in the world of 2030, 2040, and 2050—not in the world of 1970, 1990, or even 2020. Because information and knowledge are the currencies of today’s cultures, listening, speaking, reading, writing, and electronic technologies must be made available to our babies and children to the fullest degree possible.

1.3 Hearing Occurs in the Brain

As a result of neurobiologic research, conversations about sensory input now focus on the brain. For example, we see with the brain; the eyes are the entryway to the brain for visual information. We smell with the brain; the nose is the pathway to the brain for olfactory stimuli. We hear with the brain; the ears are the doorway to the brain for sound/auditory information. Consequently, hearing loss is primarily a brain issue, not an ear issue; the problem with hearing loss is that it keeps sound from reaching the brain. Continuing with this analogy, hearing loss can be described as a doorway problem, not an ear problem. Hearing loss obstructs that doorway in various ways and to varying degrees, preventing auditory input from reaching the brain.

Hearing technologies break the doorway open to allow access, activation, stimulation, and development of auditory neural pathways with auditory information, including spoken language.

The child’s listening and spoken language outcomes are not determined by 16,000 (or likely much fewer) hair cells or by 30,000 auditory nerve fibers but by 100 billion neurons in the brain, processing 100 trillion pieces of information per second.4

There is substantial evidence that “hearing” is indeed the most effective modality for the teaching of spoken language (speech), reading, and cognitive skills.1,5,6,7,8,9,10 Furthermore, with today’s amplification technologies, including cochlear implants, and early identification and intervention, auditory brain access is available to babies with even the most profound deafness. This brain access allows the use of a developmental model of intervention that prevents the negative developmental outcomes of hearing loss that were so common a few years ago.

1.4 Neuroplasticity, Auditory Deprivation, Critical Periods, and Spoken Language Enrichment

Studies of brain development show that sensory stimulation of the auditory centers of the brain is critical and, indeed, influences the actual organization of auditory brain pathways.4,11,12,13,14,15,16,17,18 The fact is, the brain can organize itself only around the stimuli that it receives. If complete acoustic events are received, this is how the brain will be organized. Conversely, if hearing loss filters some or all speech sounds from reaching auditory centers of the brain, the brain will be organized differently. “When we want to remember (or learn) something we have heard, we must hear it clearly because memory can be only as clear as its original signal… muddy in, muddy out.”19 Signal enhancement, such as that provided by amplification technology, is really about brain stimulation, with subsequent development of auditory-neural pathways.

1.4.1 Review of Auditory Anatomy and Physiology

To fully appreciate auditory brain development, both in the presence of sufficient access to intelligible speech and in the context of auditory deprivation associated with untreated congenital hearing loss, it is useful to consider a brief review of auditory anatomy and physiology as well...