Language teaching/Cochlear implants and language instruction

Introduction
Cochlear implants allow individuals with profound hearing loss to regain or develop speech and verbal language ability by providing auditory stimulation via electrical impulses. Speech and language ability varies among individuals, with many cochlear implant recipients developing age appropriate linguistic ability. Research in this field has looked at language ability of cochlear implant recipients in comparison to hearing individuals and/or deaf individuals on a variety of dimensions. Ability to produce accurate speech, ability to understand speech and writing and reading ability have all been studied. This chapter will be devoted to the topic of cochlear implants and language development in prelingually deaf children. It will begin with a review of some basic information about cochlear implants. It will then review two common methods of language instruction, namely oral communication and total communication. Empirical evidence examining speech perception, production and development following implantation and language instruction will also be examined.

What is a cochlear implant?
A cochlear implant is a piece of medical technology that restores and/or improves hearing and speech ability in deaf individuals. Approximately 199,000 people worldwide have a cochlear implant. The implant consists of a portion embedded in the skull and a portion worn exterior on the side of the head. The internal portion of the implant comprises a receiver and a transmission coil. The external portion includes a microphone, radio transmitter and speech processor.

Learning Exercise
Watch the video below to learn about the basics of cochlear implants and language instruction. The video provides a summary of important information outlined in the introduction of this chapter. See the learning exercise at the end of the chapter for questions that test your knowledge of the entire chapter.

Parts of a Cochlear Implant
External
 * Microphone: Detects sound in environment
 * Speech Processor: Organizes sounds detected in the environment.
 * Radio Transmitter: Consists of a coil and magnet that transmit information received from speech processor via an electric impulse

Internal
 * Receiver and Stimulator: Have electric circuits that control electric impulses that are delivered via the auditory nerve
 * Microelectrode Array: Inserted onto the bottom of the basilar membrane in the cochlea. This allows the damaged cochlea to function.  It consists of a group of electrodes which receive the sound information in the form of an electrical impulse and direct the impulse to the auditory nerve.

Who is eligible for a cochlear implant?
Candidates for cochlear implants are individuals with severe to profound deafness. Cochlear implants are effective for individuals with conductive deafness. Conductive deafness occurs from damage to the cochlea in the ear, which inhibits the supply of sound information to the brain via the auditory nerve. Cochlear implants work to restore hearing by stimulation of the auditory nerve. For this reason, cochlear implants they are not an effective treatment for individuals with nerve deafness. This type of deafness occurs when the auditory nerve is damaged, often from infection or injury and does not currently have an effective treatment. Generally, surgery is most beneficial when performed at a younger age. Ideal candidates are very young children, however adults can also benefit. We will discuss age of implantation more later in the chapter. Cochlear implantation candidacy is always determined by a team of medical professionals including audiologists, otologists, surgeons and speech therapists. Potential candidates complete a full medical history and several hearing tests to determine their eligibility for the surgery. The American Speech Language Hearing Association outlines the following criteria for cochlear implants for children:
 * Profound hearing loss in both ears
 * No success with hearing aid use
 * In good general health
 * Have a realistic understanding of the benefits of cochlear implants
 * Are willing to participate in rehabilitation and intensive therapies following surgery
 * Plan to make use of education support

How does it work?
Cochlear implants facilitate hearing by taking on the role of the cochlea and providing electrical stimulation to the auditory nerve. Individuals with conductive deafness have damaged hair cells in the cochlea. These hair cells are responsible for responding to sound and sending information to the auditory nerve. The auditory nerve is responsible for delivering sound information to the brain. The electrodes implanted in the cochlea replace the function of the damaged hair cells, and with the other internal and external portions of the implant, relay sound information to the brain. The sound quality provided by the cochlear implant is often described as muffled or disjointed, but significantly improves hearing in the recipient. The poor sound quality can be attributed to the limited signal output of the implant, with the signal reaching the higher auditory centres at only a fraction of what it would normally. Cochlear implants do not completely restore hearing, extensive training and rehabilitation is required in order for individuals to learn how to perceive sound.

Methods of Language Instruction
Following implantation, children must begin specialized learning programs in order to develop age appropriate language abilities. Because children have had a period of time prior to the implant without auditory stimulation, and the sound quality received from the implant is degraded, they will require extra training in order to make up for the period of deprivation. Cochlear implant recipients will need to learn to discriminate between sounds, understand spoken and language and learn how to reproduce sounds in the form of written language. Significant controversy has surrounded the best way to teach language to children prior to receiving and following cochlear implant surgery. Two methods of instruction have been developed, namely oral and total communication. In this section we will review the benefits of each type of language instruction and discuss current research comparing methods.

Oral Communication
In the oral communication method of instruction, children are taught exclusively spoken language. This is a challenging method of instruction, because children must learn to hear, decode and produce speech using their limited experience with hearing to guide their learning. Children's initially limited language ability may hinder their ability to communicate using only verbal communication.

Total Communication
In the total communication method of instruction, children are taught both spoken and signed language. This method of communication allows the child to fully express themselves using both spoken and signed language. A possible drawback of this method is that children may rely too heavily on signed language, which may come more naturally to them, and therefore do not make as significant progress in their spoken language ability.

The Debate
There has been significant debate in the medical and educational communities surrounding the best method of language instruction for children to use following cochlear implantation. Traditionally, the oral communication method was preferred, valuing spoken language over signed language. More recently sign language has been acknowledged as a rich and complex language that may be useful for individuals with hearing loss to learn in combination with other methods. In this section we will review some of the research comparing total and oral communication. A substantial body of research has found numerous benefits associated with oral communication. Oral communication was found to be more effective for measures of spoken word recognition, speech intelligibility and expressive language ability as well as speech perception and overall language skills. Oral communication may also facilitate speech production. Based on measures of consonant-production accuracy, receptive spoken vocabulary and expressive vocabulary in pre-operatively deaf children, researchers found that oral communication can be useful for facilitating expressive and receptive vocabulary. . The oral communication method is often supported by evidence that children’s language ability will be hindered by their tendency to “fall back on” signing as an easy method of communication if they are taught total communication. However, there is no conclusive evidence that total communication discourages spoken language development. Tye-Murray, Spencer, and Woodworth. studied children taught using total communication and found there was great variation in the type of communication style children adopted. When taught both signed and oral language, many children used both to communicate and some chose spoken language exclusively. Spencer and Woodworth concluded that exposing children to sign language does not mean they will adopt it as their prinicipal form of communication. Geers. found children taught in total communication used sign to express words 50% of the time and language 77%. Sign and spoken language were often used together, yet language was still predominant. Other research has also supported total communication as a valid method of instruction for cochlear implant recipients. It is clear that research has not conclusively found one type of instruction be superior. Recent research has shown more positive language development associated with oral communication. The preference for oral communication is often justified by the fact that this method forces children to rely on their oral language ability to express themselves. In the total communication method, children may fall back on signed language, hindering their ability to develop a full oral vocabulary. More research is required to examine the differences in language outcomes between the two programs.

Cochlear Implants and Language Ability
Previous research has demonstrated that cochlear implants significantly improve language ability. This improvement is further enhanced by implantation at a young age. Currently, cochlear implantation surgery is conducted on children as young as 12 months. Numerous studies have concluded that implantation at a young age is associated with better language outcomes  Specifically, implantation before age 2.5 is associated with better speech and vocabulary  This may be because children have a shorter period of auditory deprivation and are therefor are at less of a disadvantage when testing age appropriate language skills. Further reading about cochlear implants and age of implantation are available at the end of this chapter. Our focus for the remainder of the chapter will be on looking at three dimensions of language ability, namely speech production, speech perception and reading, and examining children’s abilities on these three dimensions following cochlear implantation as well as factors that contribute to their development.

Speech Perception
Cochlear implantation facilitates dramatic improvement in speech perception. Children progress from perceiving 0 words per minute to 44 within five years of receiving the implant. Speech perception continues to improve between childhood and adolescence, this increase mirrors increases in speech production (to age 10 level). Despite these dramatic improvements, speech perception in individuals with cochlear implants is impaired compared to hearing individuals. Studies have concluded that speech perception ability in cochlear implant users reaches levels similar to that of a person with 70-90 db of hearing loss. Speech perception in cochlear implant users is especially impaired by distractions such as background noise or low volume and pitch. These impairments are due to the imperfect nature of the cochlear implant. Although it provides auditory stimulation, the implant is not able to provide the same information that hearing individuals get from the auditory world.

Speech Production
''Developing spoken language ability is an important benefit of using a cochlear implant. In this section current research on speech production will be discussed.'' Following cochlear implantation, children show dramatic improvements in speech production. The most dramatic improvements in speech intelligibility are seen in the first three years following implantation. For example, Blamey et al found that speech intelligibility (measured by percent of unintelligible syllables in conversation) significantly improved from only 10% intelligible after using a cochlear implant for 3 months to 95% intelligible at a three year follow up. This research illustrates that the dramatic increase in sound quality that a cochlear implant provides has a significant impact on speech production. This increase in speech ability is further enhanced if implantation occurs at a young age. If a children receives a cochlear implant between 12 and 16 mos they are likely to achieve age appropriate speech ability earlier (by 4.5 years of age) than peers who received implants later. Early implantation may also allow children with cochlear implants to enter public school during the primary grades. Speech production continues to improve during the six years following implantation. After this period, improvement in speech production tend to plateau.

Overall speech production ability following cochlear implant surgery varies amount children. Previous research has chronicled the significant improvement in speech production ability in the six years following implantation. Speech production has been found to improve 22% between the elementary and high school years. Although cochlear implants provide users with a tremendous advantage over their deaf peers in their ability to produce speech, their speech production is variable and often lags behind levels of hearing children. Greers found 50% of cochlear implant users had language ability at an age appropriate level. Specifically, prelingually deaf children with cochlear implants seemed to be impaired in sentence recall tasks due to memory deficits for spoken and written language. Cochlear implant users excell at expressive voaculary tests, with 58% scoring at an age appropriate level.

Factors that Influence Speech Production
35% of variation in speech production can be explained by the following factors
 * Age: Children who receive a cochlear implant at a young age generally develop better speech production ability than those who receive the implant as an older child or adult.
 * Hearing aid use prior to cochlear implant: Children who used hearing aids prior to receiving the cochlear implant have better speech production ability.
 * Time since cochlear implant surgery: This factor explains the most variability in cochlear implant users speech production ability. Longer time since implant is associated with improved speech production.
 * Gender: Females develop stronger speech production ability than males.
 * Parental Education: Having educated parents is associated with speech outcomes. This can be attributed to higher socio-economic status among educated parents, more parental involvement and better access to resources.
 * IQ: IQ is a predictor of language ability in both hearing and deaf children. Higher IQ is associated with better language ability.

Reading
Deafness significantly impairs an individual’s ability to learn to read. Studies of deaf high school graduates have revealed very poor reading ability, averaging at the fourth grade level. Further, 50% of deaf individuals are illiterate. The challenge of progressing beyond a basic level of reading ability is often referred to as the “fourth grade barrier” due to the fact that it is difficult for deaf individuals to learn to read beyond the fourth grade level. An important tool for improving reading ability in deaf individuals is cochlear implants. Cochlear implants have been associated with significantly improved reading ability on a variety of measures. In this section a variety of research evidence will be reviewed, detailing improvements in reading ability following cochlear implantation.

Current research has found that children with cochlear implants achieve significantly higher reading levels than then deaf children without implants. Cochlear implants have been shown to improve children’s scores on a variety of reading measures including reading comprehension, reading accuracy and standardized reading tests (Moog, 2002). Young elementary school children with cochlear implants show impressive improvements in vocabulary. On measures of word accuracy and comprehension, elementary school children have shown to reach grade level expectations at high rates (60 and 70% respectively). Spencer et al 1991 research study found that of school aged children and teens between grades 4-12 with cochlear implants, 54% were reading at a fourth grade level or higher. Compared to a similar sample of deaf children using hearing aids and other conventional hearing technology, only 8-14% achieved a fourth grade reading level.

Cochlear implants provide children with a clear advantage in reading comprehension when compared to deaf peers, however, they may still not be reaching reading levels of hearing children. Developing age-appropriate reading ability poses extra challenges for individuals with profound deafness due to their limited spoken vocabulary and lack of phonological awareness. Perfetti & Sandak (2000) characterized this challenge as due to an “incomplete spoken language system and demands of reading a speech based system””. Cochlear implant users make significant improvements in reading ability in years following implantation, however when tested later in high school there is variability in improvements in reading ability. Geers' longitudinal study of high school students with cochlear implants found that reading ability at appropriate grade level decreased as children aged. 56% achieved an appropriate level in elementary school, while 44% achieved age appropriate scores in high school. Researchers found great variability in ability in high school student. Other research by Geers in speech and hearing has found 44-66% of high school students have average reading ability, yet continue to be impaired by very poor spelling, writing and phonological knowledge.

Factors that Influence Reading Ability (Connor & Swolan, 2004)

 * Pre-implant vocabulary: In both deaf and hearing children, a larger vocabulary prior to learning to read is correlated with stronger reading abilities.
 * Language skills: Strong spoken language ability is associated with better reading ability.  This may be due to increased vocabulary, better phonetic understanding, etc
 * Age of implantation: Children who receive a cochlear implant at a younger age generally make better progress in reading ability
 * Socioeconomic status: children from lower SES generally achieve worse reading ability than their higher SES peers. This can be contributed to factors such as lack of opportunity, stress, constraints of single parent household, etc.

Learning Exercise
Test your knowledge of the content of this chapter with questions below. 1. How does a cochlear implant differ from a hearing aid? 2. Who can benefit from a cochlear implant? 3. How does a cochlear implant transmit sound?

Complete the following table: ''Using the information in this table, write a short essay supporting either oral or total communication. Use research to support your position.''

Case Study Using the research presented in this chapter, answer the questions, in short essay form, posed at the end of each case description.

Case 1: Ella is a 6 year old female who will be receiving a cochlear implant. Ella was born deaf. She has used a hearing aid since she was born. Ella comes from a low income family. Ella's family doctor believes she is in general good heath, with an average IQ for her age. Ella lives with her two hearing parents who are excited for the opportunity for Ella to be able to hear. Imagine that you are Ella's doctor. Outline the factors detailed in this case study that may affect Ella's speech production and perception abilities. Provide evidence from research to support these predictions. Ella's parents are wondering about her language abilities after the implant. Detail what sort of information you would provide to Ella's parents to help them support her transition with the cochlear implant including communication styles and what type of language ability they can expect Ella to develop.

Case 2: Sean is a five year old hearing child. He is a strong student in school and loves to read. Abbey is a five year old who received a cochlear implant at 18 months old. Abbey has been taught to hear and speak using oral communication. She has made significant improvements over the past five years. Explain the possible similarities and differences between Sean and Abbey's hearing ability, speech perception, speech production and reading ability. What factors might explain these similarities and differences?