Auditory training (AT) is a fundamental component of the comprehensive approach to the treatment and management of listening difficulties seen in (central) auditory processing disorder ([C]APD).1 A growing body of literature has documented the effectiveness of direct auditory skills remediation to improve auditory function and listening skills, as revealed by both behavioral and electrophysiological outcome.1-3 While a number of parameters can be altered to customize AT, this brief article focuses on the stimulus used in AT tasks and, specifically, on the use of musical stimuli to enhance auditory function.
THE CASE FOR MUSIC
Why use music in AT? Music and speech represent the most cognitively complex uses of acoustic information by humans and both take advantage of the dynamic modulation of acoustic parameters.4 Music activates a widespread bilateral network of brain regions (frontal, temporal, parietal, and subcortical) related to attention, working memory, semantic and syntactic processing, motor functions, and emotional processing.5-7 Music seems to enhance various functions, including attention, learning, communication, and memory. Therefore, it offers considerable potential in neurorehabilitation.8
Music has been used to improve phonological processing and spelling in dyslexia9 and communication in autism.10 Melodic intonation therapy (intoning phrases, and tapping out rhythms and stress patterns) has been used following stroke to enhance recovery of speech.11 Some individuals diagnosed with (C)APD exhibit difficulties learning songs and nursery rhymes and poor musical and singing skills, making music a logical stimulus choice for treatment. Music taxes timing skills and exercises temporal processing that underlies the resolution of prosodic detail. Prosodic (i.e., intonation contours of voice, stress patterns, and rhythm) and melodic (i.e., succession of notes in musical phrase) pitch perception rely on common neural systems,12 and speech and music perception are both dependent on low-level, automatic, bottom-up processes and higher-level, schema-driven, top-down processes. Music is enjoyable and engaging, two characteristics that render it a powerful stimulus for the intensive effort required for effective AT.
BENEFITS OF MUSICAL TRAINING
Musical training leads to heightened fine-grained frequency discrimination and working memory, and improved ability to listen in noise.13 Enhanced late potentials (i.e., P2) following musical AT in children and adults demonstrate the potential of music to alter cortical representation.14 Based on fMRI and behavioral measures, Gaab and colleagues concluded that musical experience may improve rapid spectrotemporal processing and augment the efficiency of traditional language regions.15 Foxton et al. suggested that AT using contour discrimination tasks and training on a musical instrument may aid in both the improvement of pitch contour perception skills and literacy.16 Musicians show more robust and efficient neural responses in subcortical and cortical regions that support language,12,17 demonstrating that musical experience and training may tune the brain and facilitate processing of both music and language.
Finding no neural, cognitive, motor, or musical differences between a group of children beginning musical training and a control group, Norton and colleagues concluded that musical training itself (rather than inherent differences in auditory processing skills or enhanced musical aptitude) leads to improved non-musical auditory processing abilities and altered brain function.18 Recent studies have demonstrated the utility of musical AT with cochlear implant recipients.19, 20 In fact, a new clinical test of musical perception specifically for use with this population has been developed.21 Clearly, extensive AT with music may lead to perceptual benefits for auditory processing of speech such that musical stimuli should benefit AT for individuals with (C)APD.
TYPES OF MUSICAL TRAINING
Musical AT may include basic auditory discrimination training using tones and tone glides, as well as musical auditory discrimination training requiring discrimination of contour, rhythm, meter, and timbre. Similarly, discriminating between instruments or chords trains auditory discrimination. Pattern, contour, and rhythm discrimination, recognition, and identification can be trained using keyboard cadences, as well as with nursery rhymes and poetry. The childhood game Musical Chairs is an example of an informal activity useful for training vigilance and temporal resolution. The familiar game Name that Tune exercises interhemispheric transfer, as do dichotic melodies, singing, extracting lyrics from songs, and playing an instrument requiring bimanual coordination.
While the evidence outlined above provides a basis for using musical stimuli in AT, additional research and clinical investigations will ultimately determine its utility in comprehensive intervention for (C)APD.
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