SOUND TO SYMBOL

iPad Apps Based on Preverbal Elemental Music

    All of the aspects of language that an infant can perceive at birth and all of those aspects that are learned during the first year of life are musical

           - Brandt et al 2012    

Why Auditory Cognition?

Written By Dr. Thea Kuddo 10/03/2016

Why is it important to build capacity to auditory perception and cognition?

Auditory cognition is a set of processes by which ​​​​​​​​​​​​​​the ​brain makes sense of the sound world. THESE PROCESSES ARE FUNDAMENTAL FOR SPOKEN LANGUAGE LEARNING. Without auditory cognition, sounds don't have meaning for us. Auditory cognitive processes require SEVERAL BRAIN NETWORKS TO WORK TOGETHER: 

                                                        complex sound perception 
​                                                        visual cues
                                                        attention
                                                        auditory working memory 
                                                        long-term memory 
                                                        emotional systems

​ ​​
HOW DO WE BUILD OUR AUDITORY CAPACITY FOR UNDERSTANDING SPOKEN LANGUAGE?

The development of the auditory system is necessary for understanding SPEECH and other COMPLEX SOUNDS. Building the capacity for EFFICIENT auditory perception begins before birth and continues into adulthood. Auditory perception development during the early years requires ACCESS TO BASIC FEATURES OF SOUNDS like FREQUENCY and INTENSITY, as well as DETECTION OF CHANGES in these features over time. The higher order processes like FORMING AUDITORY OBJECTS, LOCALIZING SOUNDS, UNDERSTANDING SPEECH, AND PERCEIVING MUSIC are involved in the auditory perception development as well. While full adult performance in virtually all auditory aspects develops by adolescence, SOUND FEATURE CODING takes place during the early years of life. Most fundamental sound features are well encoded by 6 months of age in typically developing children.
 MAKING SENSE OF THE AUDITORY WORLD around us requires
                                                                                 
        1.  interacting  with auditory stimulation


        2. distinguishing  between basic features of sounds: frequency, intensity, duration,
            timbre

                a. Frequency discrimination refers to our ability to detect a change in the

                frequency of a pure tone. Adults can detect 0.2-0.3% differences for frequencies in
                the range of 250-4000Hz. Children have poorer frequency discrimination: studies
                show that during the first year of life infants improve their frequency detection from
                3.5% at 3 months of age to 2% at 12 months of age. Frequency discrimination
                requires memory; memory for pitch develops through childhood.

                b. Intensity discrimination refers​ to our ability to detect a difference between the
                intensities of two sounds. The smallest intensity change adults can detect is 10% of
                the baseline intensity of white noise. Development of intensity discrimination starts
                in infancy and continues into school age. Memory and attention have an important
                role in intensity discrimination.

                c. Duration discrimination refers to our ability to detect a change in the duration

                of a sound. The ability to discriminate between the duration of sounds develops
                around 6-8 years of age. Studies show that very few 4-year olds have an adult-like
                duration discrimination. 

                d. Timbre discrimination refers to our ability to detect changes in the spectrum of

                frequencies of a complex sound. Recognizing and distinguishing familiar sounds
                such as different vowels or different instruments playing identical notes, involves
                efficient spectral shape discrimination. Infants of 7.5 -8 months can discriminate
                between spectral shapes while ignoring irrelevant acoustic features.

                e. Loudness perception. Loudness is related to sound intensity. Loudness is a very

                important percept: it determines the dynamic range of human hearing. Studies
                show that children aged 8-12 years show adult-like growth to loudness for narrow
                band noises of 500-2000 Hz.


       3.  higher order tasks:
                               
               a. Forming auditory objects/mapping sounds onto meaning/auditory scene    

              analysis:
              our auditory brain organizes concurrent sounds in the environment into groups or
              auditory objects, and assigns meanings to these. Newborns and very young infants
              have the basic capacity to do so in a similar way to adults. Organizing the world in
              terms of objects is a necessary requirement for cognitive development. Streaming
              sounds into auditory objects affects an infant's ability to selectively attend to relevant
              target sounds. Stream segmentation development continues until adolescence.

              b. Localizing sound objects in space: sound localization refers to our ability to

             identify the direction of a sound source. Studies suggest that the ability to localize
             sound is mature by 6-8 years of age.

             c. Speech and music perception



​DEVELOPMENTAL PLASTICITY OF THE CENTRAL AUDITORY SYSTEM 

Plasticity is defined as the ability of neurons and neural networks to alter their structure as a result of stimulation. Auditory stimulation is essential for central auditory system development. The height of synaptic density in the auditory cortex occurs around 3.5-4 years of age. Studies indicate without appropriate experience, the synapses likely remain incompetent in terms of auditory processing. 





References:
1. Romand R. and Varela-Nieto I. 2014 Development of Auditory and Vestibular Systems Fourth Edition. Academic Press: Elsevier inc.
2. Warren RM. 2013 Auditory Perception: An Analysis and Synthesis Third Edition. Cambridge University Press.
3. Greenberg S. and Ainsworth WA. 2006 Listening to Speech. An Auditory Perspective . Psychology Press.







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