The Influence of Targeted Right Ear Auditory Training on Verbal Output in Down Syndrome Individuals

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Findings from dichotic listening studies suggest individuals with Down syndrome (DS) exhibit a unique pattern of lateralization for language, which is syndrome specific and is the reverse of typical functional cerebral lateralization (Grouis, Ypsilanti, & Koidou, 2013). Along with advanced neuroimaging, these observations provide supportive evidence that an individual with DS most accurately perceives language through the left ear, interprets language through the right hemisphere and transfers processed information across the cerebrum to the left hemisphere for speech response (Chua, Weeks, & Elliot, 1996). Children and adolescents with DS exhibit a decreased utterance length and poor intelligibility as syntactic complexity increases (Martin et al., 2009). Individuals with DS are less likely to use verbally provided information in verbal and motor planning (Heath et al., 2005). Along with increased verbal and manual response times, this verbal-motor bias indicates a pattern of cerebral specialization for language specific to the DS population (Heath et al., 2005). The relative influence of each contributing factor is difficult to determine and may vary from one individual to another; however, the combination of cerebral and motor functional atypia exacts detrimental effects on speech and language development in this specialized population (Stoel-Gammon, 2001). These observations encourage attempts to facilitate expressive language use in the DS population.

Current literature does not address the use of targeted right ear auditory training as a strategy to de-confound the observed delay in language processing. A question that remains unaddressed is whether intentional strengthening of the weaker right ear in treatment design can facilitate communication of auditory information for speech sounds to the left auditory cortex and improve verbal production. The purpose of this study is to measure the functional effect of targeted right ear training in a randomized population of DS clients. It is hypothesized that targeted auditory training utilizing Applied Behavior Technologies, The Listening Program Level-One to strengthen the weaker right ear in DS individuals with confirmed left ear advantage (LEA) will result in a measurable increase in expressive verbal output. Increased output may provide data to support the hypothesis that preferential ear training can strengthen the neural pathway leading from right ear to left hemisphere.

The results of this study have new implications as to the extent of cerebral lateralization and its influence on the functional capabilities in Down syndrome individuals. In addition, this study suggests new directions in research focusing on the use of targeted auditory training as a way of therapeutically influencing neuroplasticity.