The BioMAP (Biological Marker of Auditory Processing) is a neurophysiological test used to quickly and objectively identify disordered processing of sound that has been associated with learning impairments in many children. Unlike traditional brainstem evoked response recordings using clicks or tone bursts, the BioMAP uses a complex speech syllable that reflects the acoustic and phonetic characteristics of sounds that present difficulties for disordered populations. Over the past decade Dr. Nina Kraus and her colleagues at the Auditory Neuroscience Lab at Northwestern University have evaluated the evoked brainstem responses of more than 1000 children, and have found that the BioMAP acts as a unique biological marker for those learning disabled children with central auditory processing disorders that have a high likelihood of benefiting from an auditory training program.
Traditionally, assessment of disorders of language, learning, and auditory processing has relied heavily on behavioral measures that may be inherently confounded by cognitive, perceptual, and attentional variables which limit the reliability and validity of these tests. As a supplement to diagnostic tools typical of clinical assessment, the BioMAP has the potential to provide a measure that is objective and non-invasive, enabling professionals to assess more fully the auditory processing abilities of children.
A joint partnership between the Auditory Neuroscience Lab and Bio-logic Systems Corporation has been formed to translate this research to the marketplace.
Background of The BioMAP
Children and adults diagnosed with learning disabilities exhibit highly variable perceptual and cognitive profiles. Many factors can contribute to the diagnosis of a learning problem. These include variations in basic perceptual physiology and higher levels of cognitive function and attention, experientially developed compensatory mechanisms, exposure to previous remedial interventions and differing interpretations of diagnostic categories by clinicians.
The remediation and rehabilitation of children with auditory-based processing disorders involves numerous clinical approaches. One of the most promising interventions utilizes computer-based, auditory training paradigms that have been commercially available for about a decade. The BioMAP (Biological Marker of Auditory Processing) offers an important set of biological measures for assessing the efficacy of auditory training and allows for a determination of which children are the best candidates for such training.
An accurate manifestation of stimulus timing in the auditory brainstem is a hallmark of normal perception. Recording the brainstem’s response to sound has long been established as a valid and reliable means of assessing the integrity of the neural transmission of acoustic stimuli. Transient acoustic events induce a pattern of voltage fluctuations in the brainstem, resulting in a familiar waveform yielding information about brainstem nuclei along the ascending central auditory pathway. Disruptions in this systematic progression on the order of fractions of milliseconds are clinically significant in the diagnosis of hearing loss and brainstem pathology.
To further our understanding of the functional relationship between the acoustic structure of speech and the brainstem’s response, a valid and reliable means was developed by which to characterize the neural activity of the brainstem in response to the speech sound /da/ (see figure). We have labeled this technique “BioMAP”. Measures of both timing and magnitude are used to describe brainstem neural activity to speech, which is characterized by rapid temporal changes and complex spectral distributions. Timing measures provide insight into (1) the accuracy with which brainstem nuclei synchronously respond to acoustic stimuli (e.g., peak latency, inter-peak interval, and slope), and (2) the fidelity with which the response mimics either the stimulus or another response (e.g., stimulus-to-response correlations, and inter-response correlations). Magnitude measures provide information about (1) the robustness with which the brainstem nuclei respond to acoustic stimuli and (2) the size of a given spectral component within the response.
A growing body of literature from our lab that has evaluated speech-evoked brainstem response differences between normal children and children with learning problems indicates that brainstem measures relating to the encoding of linguistic information can serve as a biological marker for auditory function in children with language-based learning problems, such as dyslexia. A consistent finding is that about one third of children with language-based learning problems exhibit a unique pattern of auditory neural activity that easily distinguishes them from the larger population of children with learning problems.
From this basic research we have developed a method by which to identify learning disabled children with preconscious, subcortical, disordered auditory processing of sound. We have found that the BioMAP can identify those learning disabled children with a high likelihood of benefiting from an auditory training program.
Clinical Application
To date, there has been no electrophysiological test in the clinical test battery to objectively assess the central auditory function of a child with suspected language-based learning problems. Traditionally, central auditory processing evaluations have consisted of behavioral measures. These measures are often subjective in nature, raising questions of reliability in the diagnostic process. Further, these evaluations may be inherently confounded by non-perceptual variables (e.g., attention, memory, motivation, failure to understand the task, large variability etc.) causing many professionals to question the validity and reliability of these tests. Just as electrophysiological testing has become an important tool in the assessment of peripheral hearing, the availability of a clinical assessment tool that is valid, objective (does not rely on the listener’s response), and non-invasive, would enable professionals to assess more fully the auditory processing abilities of children.
Currently, efforts are underway to commercialize the BioMAP as a clinical tool for the identification of children with a range of learning disorders. It is our hope and expectation that the BioMAP will have considerable value, not only as a clinically useful tool to assist in the selection of children who are candidates for auditory-based intervention training, but also as a means of assessing the changes brought about by this training.
Link to slide presentation
Publications Relevant to BioMAP
Kraus N & Nicol T (2005) Brainstem origins for cortical "what" and "'where" pathways in the auditory system. TRENDS in Neurosciences 28: 176 - 181.
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Download Adobe Acrobat PDF) Wible B, Nicol T, Kraus N. (2005) Correlation between brainstem and cortical auditory processes in normal and language-impaired children. Brain 128: 417 - 423.
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Download Adobe Acrobat PDF)Russo N, Nicol T, Musacchia G, Kraus, N. (2004) Brainstem responses to speech syllables. Clinical Neurophysiology 115: 2021-2030.
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Download Adobe Acrobat PDF)Wible B, Nicol T & Kraus N. (2004) Atypical brainstem representation of onset and formant structure of speech sounds in children with language-based learning problems. Biological Psychology 67: 299-317.
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Download Adobe Acrobat PDF)Hayes E, Tiippana K, Nicol T, Sams M & Kraus, N. (2003) Integration of heard and seen speech: a factor in learning disabilities in children. Neuroscience Letters 351:46-50.
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Download Adobe Acrobat PDF)Cunningham J, Nicol T, King CD, Zecker SG & Kraus N. (2002) Effects of noise and cue enhancement on neural responses to speech in auditory midbrain, thalamus and cortex. Hear Res 169:97-111.
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Download Adobe Acrobat PDF)Training
Russo N, Nicol T, Zecker S, Hayes E, Kraus N. (2005). Auditory training improves neural timing in the human brainstem. Behavioural Brain Research 156: 95-103.
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Download Adobe Acrobat PDF)Warrier CM, Johnson KL, Hayes E, Nicol T & Kraus N. (2004) Learning impaired children exhibit timing deficits and training-related improvements in auditory cortical responses to speech in noise. Experimental Brain Research 157: 431-441.
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Download Adobe Acrobat PDF)Hayes E, Warrier CM, Nicol T, Zecker SG & Kraus N. (2003) Neural plasticity following auditory training in children with learning problems. Clinical Neurophysiology 114:673-684.
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Download Adobe Acrobat PDF)King C, Warrier CM, Hayes E & Kraus N. (2002) Deficits in auditory brainstem encoding of speech sounds in children with learning problems. Neurosci Lett 319:111-115.
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Download Adobe Acrobat PDF)Cunningham J, Nicol T, Zecker SG & Kraus N. (2001) Neurobiologic responses to speech in noise in children with learning problems: Deficits and strategies for improvement. Clin Neurophysiol 112:758-767.
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Download Adobe Acrobat PDF)Invited Reviews
Wible B, Nicol T, Kraus N (2005) Encoding of complex sounds in an animal model: Implications for understanding speech perception in humans. In: Auditory Cortex: Towards a Synthesis of Human and Animal Research, Konig R, Heil P, Budinger E and Scheich H (eds.), Lawrence Erlbaum Associates, Oxford, pp 241-254.
Nicol T, Kraus N (2005) How can the neural encoding and perception of speech be improved? In: Plasticity and Signal Representation in the Auditory System, Merzenich M and Syka S (eds.) Springer, New York, pp 259-270.
Nicol T, Kraus N (2004) Speech-sound encoding: Physiological manifestations and behavioral ramifications. In: Clinical Neurophysiology Supplement 57: 624-630.
Kraus N & Nicol T. (2003) Aggregate neural responses to speech sounds in the central auditory system. Speech Communication 41:35-47.
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Download Adobe Acrobat PDF)Link to Recent Media Coverage
Link to Listening, Learning and the Brain Project
Link to Auditory Neuroscience Laboratory
