Research institution: Indiana University
Research title: Feasibility and efficacy of working memory training in children with cochlear implants
Researchers: William Kronenberger, Ph.D., David Pisoni, Ph.D.
Training program used in research: Cogmed RM
Presented: Symposium on Cochlear Implants in Children – June 09, Seattle, WA
Purpose/Background: Cochlear implantation (CI) restores some components of hearing to a subset of deaf children, resulting in speech and language benefit in many cases. However, the success of implantation in producing optimal speech/language outcomes varies from child to child. Individual differences in underlying neurocognitive processes required for learning and consolidating temporal sequences (such as those received in auditory-language input) are likely to be responsible for a significant amount of this variability. One key process in this area is working memory, which is the ability to retain and manipulate symbolic representations of verbal information concurrently with other mental processing activities. Despite the importance of working memory for speech-language development, there has been no research attempting to enhance working memory as a method of improving speech-language outcomes in children with CIs. In this study, we investigate the feasibility and efficacy of a computer-based working memory training program for improving working memory capacity and related speech-language processes in deaf children with CIs.
Cochlear implantation (CI) treatment restores some components of hearing to a subset of deaf children, resulting in significant speech and language benefit in many cases. However, the success of implantation in producing optimal speech/language outcomes varies from child to child. Individual differences in underlying processes required for learning and consolidating temporal sequences (such as those received in auditory-language input) are likely to be responsible for a significant amount of this variability.
One key process in this area is working memory, which is defined as the ability to retain and manipulate information concurrently with other mental processing activities. Because language learning and development require the individual to follow, retain, and integrate a stream of auditory information, working memory is likely to be a core component of language development following CI.
Preliminary research from our group has demonstrated shorter verbal working memory spans in children with CIs. Moreover, CI users with longer verbal working memory spans demonstrate stronger performance on a range of spoken word recognition tasks. Hence, working memory may be a key component in the development of speech-language skills in CI users, and differences in working memory skills may explain some of the variability in post-implant speech-language outcomes. Despite the potential importance of working memory for speech-language learning and outcomes in the CI population, there has been no research attempting to modify working memory capacity as a method of improving speech-language outcomes in this clinical population. The goal of this research project is to improve clinical outcomes in children who receive CIs, by investigating the short-term effects of a novel working memory training program on working memory capacity and related speech-language processes.
A.1. Predictors of Post-Implantation Cognitive and Speech-Language Outcome
Early efforts to understand factors underlying variability in speech and language outcomes in children with CIs have focused on static global demographic and medical characteristics of the individual (such as age of implantation) or on technical characteristics of the implant (such as number of channels). Children implanted at younger ages display better speech-language outcomes than individuals implanted at older ages. Consistent with this finding, shorter length of auditory deprivation also predicts improved outcome (Kirk, Pisoni, & Miyamoto, 2000). Technical advances in the cochlear implant device have also produced dramatic improvements in audiological output and efficacy outcomes. This existing research has offered limited directions for intervention and auditory rehabilitation. Static global demographic variables such as age and duration of deafness cannot be manipulated in order to improve outcomes. Although technical advances in the CI device have improved the audiological experience of the entire population of individuals receiving implants, individual variability in outcomes of higher-order cognitive and language variables within this population has remained despite those improvements.
A.2. Neurocognitive Factors and Outcome Following Cochlear Implantation
Recent research shows that auditory deprivation and cochlear implantation affect more than a narrow set of speech-language processes. Auditory experience and language-based cognitive processing are a part of a wider, functionally integrated system of neurocognitive processes that develop throughout the lifespan (Geers and Moog, 1987; Ullman and Pierpont, 2005). These neurocognitive processes depend on language and auditory experience for their development, and they provide support for the continued development of language and auditory processing. Language development and use, for example, are critical components in the development of concentration, self-regulation, planning, and reasoning skills (Barkley, 1997). The quality of concentration and working memory skills, in turn, is related to auditory processing, vocabulary, and reasoning ability (Woodcock, McGrew, & Mather, 2001). This interrelationship of different domains of cognitive processes throughout development has been consistently supported by neuropsychological and imaging research (Frackowiak, Friston, Frith, Dolan, & Mazziotta, 1997).
Findings supporting the integration of auditory experience and language processing into a wider system of cognitive processing suggest that individual differences observed in auditory, speech, and language functioning in children with CIs may reflect variability in multiple integrated cognitive processes. If this is the case, then auditory deprivation and subsequent treatment with CI have a much greater impact on cognitive ability than is observed in auditory processing, speech, and language alone. The benefits of auditory input received after CI affect not only speech and language but also change the development of a network of cognitive functions including concentration, memory, sequencing, and organizational-integrative skills. Conversely, the ability of the individual to show benefit in these more general cognitive processes may have a profound effect on his or her ability to effectively use and benefit from the novel, complex auditory stimulation provided after cochlear implantation. This suggests that variability in speech and language outcomes following CI may be due to factors beyond the functioning of the implant alone and that these factors will likely reflect complex interactions among multiple cognitive processes.
Our work has shown that several areas of cognitive functioning, including working memory, are either at-risk or are related to outcome following CI. CI users score below age norms on measures of auditory working memory, such as memory for lists of digits forward and backward. Even when children with CIs were able to correctly recall items from three- and four-digit lists, their speed of retrieval from short-term memory was three times slower than that of a comparison group of age-matched normal-hearing children.
This suggests less efficient perceptual encoding and slower maintenance/retrieval of phonological representations in working memory. Additional research has found deficits in visual working memory in children with CI as well. Using a modification of the Simon memory game, Pisoni and colleagues (Cleary, Pisoni, & Geers, 2001; Pisoni & Cleary, 2004) found that children with CIs had shorter visual memory spans compared to normal hearing children.
Working memory is a core component of executive functioning, which involves planning, directing, monitoring, and controlling cognitive information and behavioral responses (Barkley, 1997). Individuals must hold information in working memory in order to comprehend the information, organize it into a broader context of understanding, and develop a meaningful and sequential plan of action. Continued use of working memory is essential for maintaining concentration, purposeful thinking, and mental effort during learning, because one must remember information as one is engaging in ongoing mental processing. Recent studies conducted by our research team have identified several potential weaknesses in key aspects of executive functioning in children with CIs. A sample of 12 children with CI’s had elevated scores relative to norms and relative to age-matched normal-hearing children on a parent-completed behavior checklist of working memory and related executive functioning deficits (Pisoni et al., 2007).