AUDITORY PROCESSING DISORDERS

Even more than our ability to hear, it is our early experiences with language that determine how well we will be able to hear and understand speech. In the brain it is cognition that drives perception, and perhaps nowhere is that more clearly seen than in auditory processing.

When we hear speech, sounds enter our ears and strike the tympanic membranes (ear drums), causing them to vibrate like a drum. These vibrations travel across the empty space of the auditory tube (the Eustachian tube) and into the cochlea. The cochlea is lined with tiny hair cells, each of which are tuned to respond to specific frequencies of sound. As the pressure wave travels down the cochlea the membrane wall bounces, causing certain hair cells to bend and spark a signal down the auditory nerve.

Notice in the picture above that there are a cluster of three tubes sitting just in front of the cochlea. These are the vestibular organs, positioned to provide coordinate information to the brain about where the head is in space. They are filled with fluid and lined with hair cells; when the head tilts, fluid moves and bends the hair cells, signalling the brain with its location. The vestibular nerve exits the vestibular organs and joins the auditory nerve coming off the cochlea; this "auditory-cochlear" nerve becomes the 8th cranial nerve in the brain, sending signals to the auditory cortex. Anything that interferes with hearing or vestibular functions (e.g. like ear infections, tumors, etc.) will affect how these language areas of the brain become wired during development.

When fluid in the middle ear, tumors, or even ear wax interferes with the sound wave as it passes from ear drum to cochlea, we call this a "conductive hearing loss." Consonants, particularly consonants in the upper frequencies, are much weaker than the powerful vowel sounds will be lost.

A conductive hearing loss in the first few months of life, even if it is only temporary and mild, can dramatically alter the way the brain hears language. Missing the high-pitched consonants like th, f, s, h, t and k, for example, will significantly damage a child's ability to hear English langaueg sounds accurately, making speech incomprehensible at times. If this type of hearing loss is experienced throughout the critical period for language development (1-7 months), language may not develop at all. If it is experienced to a lesser degree or after the critical period, a less severe form of auditory processing disorder may develop.

While difficulty discriminating high-pitched consonants creates one form of auditory processing disorder, there are others as well. A "figure/ground" disorder refers to problems hearing speech in background noise; a "speed of processing" disorder refers to difficulty hearing rapid changes in speech such as word endings and tense markers, and a "disorder of auditory attention" refers to difficulty ignoring one speaker while listening to another (like we do at a party when we listen to our conversational partner and ignore everyone else speaking nearby).

SYMPTOMS OF AUDITORY PROCESSING PROBLEMS

• frequently misunderstanding what was said

• having difficulty following directions

• frequently ignoring others when they talk

• frequently being "off topic" or seeming inattentive

• having reading comprehension problems

• having fine motor difficulties or poor handwriting

• having difficulty matching, building or copying complex images

• emotional immaturity

• difficulty in school in spite of average or above average intelligenc

  DIAGNOSTIC TESTING

• SCAN-C or SCAN-A, vestibular screen, handwriting sample, bilateral attention test

COSTS: $450; $27 for SCAN test alone

Three of the four types of auditory processing disorders (figure/ground, speed of processing and auditory attention) can be dramatically improved with intervention since they are learned skills. The other type, which involves dificulty hearing high-pitched consonants, can be improved thorugh intervention to the point that it has a minimal impact on learning and social interactions.

Please be aware that rewiring perceptual networks takes a great deal of time and effort and that good results require several years of dedicated intervention. However, since auditory processing problems can interfere with a wide range of social, emotional, cogntive and academic skills throughout life if left untreated, it is well worth the time, effort, and expense involved to help children with processing disorders improve auditory skills..

Intervention methods are determined based on the results of individual testing and may include:

• learning strategies for correctly guessing partially heard words

• improving grammar and vocabulary

• activities and exercises to improve skills impaired by poor auditory perception (these are skills: processed by the angular gyrus and adjacent areas that process meaning in language, spatial relationships between body and objects, fine motor control, symbolic learning, reading music and conceptual math)

• practicing describing, explaining and locating objects and people through language

• using videos to practice auditory attention, memory and perception skills

• figure/ground exercises for both hearing and vision

COSTS: 140 per hour (two 30 minute sessions weekly)