Executive Functioning and Language Development in Children with Cochlear Implants

“Hearing loss is primarily a brain issue, not an ear issue”

(Flexer, 2011)

“…deaf children are not simply hearing children who cannot hear”

(Marschark & Knoors, 2012)

The benefits of cochlear implants (CIs) are well-established for restoring some attributes of hearing and allowing for spoken language development in prelingually-deaf children. However, effects of hearing loss may extend beyond spoken language skills alone to include other domains of neurocognitive functioning. Because the brain is an integrated organ that develops based on experience, changes in exposure to hearing, language, and other experience-related factors have downstream influences on neurocognitive functioning. Furthermore, because language is supported by multiple neurocognitive functions such as attention, reasoning, and memory, a reciprocal relationship exists between language and other domains of neurocognitive functioning, with each influencing and supporting the other. Therefore, understanding and explaining neurocognitive functioning in children with CIs is critical for improving language functioning and quality of life.

A subdomain of neurocognitive functioning that is dependent in part on auditory and language experiences is executive functioning (EF). EF is an umbrella set of neurocognitive functions responsible for the active regulation of cognitive, behavioral, and emotional processes in the service of planned, organized, controlled, goal-driven thinking and behavior (Diamond, 2013). Multiple subdomains of EF exist, including working memory (WM), inhibition, flexibility-shifting, planning, organization, and controlled attention for efficient/fast processing (Barkley, 2012; Kronenberger & Pisoni, in press). Hearing provides valuable stimulation and practice with EF to the developing child through experiences such as selective attention (focusing on a specific auditory stimulus), resisting distraction (screening out competing auditory stimuli that are not the focus of attention), sequential processing/tracking (sustaining attention and processing effort on a sequence of auditory stimuli), and sensory integration (integrating auditory stimuli with visual, tactile, olfactory, and other stimuli) (Kral, Kronenberger, Pisoni, & O’Donoghue, 2016; Kronenberger & Pisoni, in press). Evidence from studies of music exposure (Bialystok & DePape, 2009; Slevc, Davey, Buschkuehl, & Jaeggi, 2016), sequential processing (Conway, Pisoni, Anaya, Karpicke, & Henning, 2011) , and early deafness (Kral et al., 2016) support the beneficial role of auditory experience for development of EF. Spoken language, which is facilitated by auditory experience, also enhances the development and use of EF by serving as a tool to control focus and behavior (self-talk), to maintain goals and sequential steps in mind (by representing goals and steps using language), to assist WM (actively holding information in mind using language), and to organize complex information (representing ideas with language) (Byrd, Van Der Veen, McNamara, & Berg, 2004; Fatzer & Roebers, 2012; Petersen, Bates, & Staples, 2015; Zelazo, Müller, Frye, & Marcovitch, 2003). Thus, deprivation of early auditory experience from deafness, and restoration of some components of hearing (and spoken language) with a CI, may influence EF outcomes in prelingually deaf children who receive CIs.

EF is also a significant factor supporting the development and deployment of language skills by providing concentration and mental effort to enhance language learning and processing. Research supports the important role of domains of EF such as WM in the acquisition of language skills and fund of verbal information in normal hearing (NH) children (Gathercole & Baddeley, 1993; Gathercole, Brown, & Pickering, 2003). Furthermore, several models (such as the Ease of Language Understanding [ELU] (Rönnberg et al., 2013) and Framework for Understanding Effortful Learning [FUEL] (Pichora-Fuller et al., 2016) models) have been developed to explain the important role that controlled mental effort and working memory have during complex, challenging speech-language processing. According to these models, simple language processing, such as speech perception under ideal conditions by NH children or rapid access to well-specified vocabulary in the mental lexicon, occurs through a fast, automatic processing channel that requires little concentration or mental effort. However, challenging, complex processing, including speech perception under challenging conditions, requires active, controlled processing that places more demands on EF components such as controlled effort and WM. For children with CIs, speech perception and access to the mental lexicon is more demanding and challenging than for NH children, making the use of EF more important for language processing for children with CIs (Kronenberger & Pisoni, in press).

In order to explain the relationship between hearing, spoken language, and EF in children with CIs in the context of many other biological, psychological, and social influences on language and EF, we have proposed an Auditory Neurocognitive Model (ANM; Figure 1) (Kronenberger & Pisoni, in press). This model recognizes the influences of auditory experience on language and EF, as well as the influence of EF on language, which occur within a broader context of biopsychosocial influences on the neurocognitive development of the child. By identifying the network of influences on the reciprocal relationship between language and EF, the ANM specifies important domains of neurocognitive functioning that may explain outcomes and serve as targets for intervention.

Figure 1.

Auditory-Neurocognitive Model

Empirical research has supported the basic tenets of the ANM. Children with CIs are at elevated risk for EF delays relative to NH children, although the majority of children with CIs develop EF skills in the average range (Kronenberger, Beer, Castellanos, Pisoni, & Miyamoto, 2014; Kronenberger, Colson, Henning, & Pisoni, 2014; Kronenberger, Pisoni, Henning, & Colson, 2013). Approximately 1/3 of children with CIs have been found to have clinically significant EF delays, a rate 2–5 times that of NH peers (Kronenberger, Beer, et al., 2014; Kronenberger, Pisoni, Henning, et al., 2013). Cross-sectional and longitudinal studies have consistently found associations between some components of EF – especially verbal working memory, controlled fluency-speed, inhibition, and concentration – and language outcomes, and associations between EF and language are stronger in children with CIs than in NH children (Harris et al., 2013; Kronenberger, Colson, et al., 2014; Kronenberger, Pisoni, Harris, et al., 2013; Pisoni, Kronenberger, Roman, & Geers, 2011). Recently, a pilot experimental study has found that reducing access to EF adversely affects real-time speech-language processing of children with CIs more than NH peers (Kronenberger, Henning, Ditmars, & Pisoni, under review). Reviews of research in this area have found overwhelming and consistent evidence of the reciprocal/bidirectional hearing-language-EF relationship, and have identified significant limitations in research studies that contradict this relationship (Kronenberger & Pisoni, in press).

Models linking hearing, language, and EF in prelingually deaf children with CIs have important clinical and translational implications: Routine assessment of neurocognitive functioning, especially EF, should be integrated into outcome evaluations for children who receive CIs. Children who are at-risk for EF delays should be targeted for EF interventions, guided by tenets of models such as the ANM as well as existing evidence-based EF treatments (Diamond & Lee, 2011). Because speech-language skills and EF skills are closely intertwined, improvement in EF may be a target or a by-product of speech-language interventions, and, conversely, treatment components that improve EF may be effective in producing better spoken language performance in challenging settings. Families may benefit from education about EF and language outcomes in order to embed children with CIs in family environments that model, encourage, and teach EF. Finally, new research should evolve beyond comparisons of CI and NH samples to investigate factors explaining the wide variability in EF outcomes within the population of CI users and to test novel interventions to improve EF.