Sensory integration (Part 3) – The Auditory System
THE ANATOMICAL REVIEW – REGISTRATION
Sound waves enter the ear canal through the pinna. The waves now move to the tympanic membrane. After the tympanic membrane is the middle ear where the auditory waves travel over the incus, stapes and malleus. The waves now move into the inner ear into the cochlea. The cochlea has 3 fluid-filled sections: Scala media, scala tympani and the scala vestibuli. The scala media contains endolymp. The organ of Corti is situated here. The organ of Corti transforms mechanic waves into electric signals, via the hair cells, that can be transported through the neurons. The scala tympani and vestibuli are located within the bony labyrinth. This is filled with perilymph. The neurons take the electric signals to the brain via the vestibulocochlear nerve. The electric signals are processed at the following points before reaching the thalamus: cochlear nuclei, superior olivary complex and the inferior colliculus. The signals are then sent to the temporal lobe where the primary auditory cortex is situated.
THE AUDITORY SYSTEM AND SENSORY INTEGRATION
Types of modulation difficulties: over-responsive, under-responsive and sensory-craving.
o Distracted by sounds not normally heard by others
o Fearful of the some sounds: flushing toilet, vacuum cleaner, hairdryer, squeaky shoes, dog barking
o Startled by loud or unexpected sounds
o Distracted by background noise
o Frequently asks people to be quiet
o Avoid areas where sounds are too loud: movie theatre, musical theatres, etc.
o Holds hands over ears
o Gets easily irritated by certain sounds e.g. person eating an apple or popcorn, a ringing telephone, the frequency of someone voice, dogs barking, etc.
o Often doesn’t respond to own name
o Often doesn’t respond to verbal cues e.g. direct questions
o Difficulty understanding or remembering what was said
o Appear oblivious of certain sounds
o Asks directions to be repeated
Sensory craving behaviour
o Uses a loud voice
o Makes background noise
o Enjoys noisy places
Any limitations here is addressed by a speech therapist.
Auditory processing is the ability of the brain to recognize and interpret what you hear, thus it’s all about understanding, interpreting and organizing the information that we hear.
Which auditory abilities do we have?
The ability to find the source of a sound
The ability to follow a sound
The ability to remember what was heard
The ability to put into order what was heard and to repeat it logically
The ability to compare and contrast environmental sounds
The ability to distinguish between which sounds are important and which are background noises
The ability to relate a novel sounds to a familiar sound
The ability to unite various ideas into a coherent whole
The ability to maintain focus on what is being heard
Children with auditory processing dysfunction confused words sounding nearly the same e.g. sun/fun even more so when in a noisy environment. The level of the child’s language ability and ability to follow instructions can be assessed to determine if there may be are a sensory dysfunction says SPD (Australia, SPD Australia, 2013). A child’s hearing should always be tested before a diagnosis of auditory sensory processing dysfunction can be made.
These children need to be referred to an audiologist to first determine if his/her hearing is functional and then to a speech therapist for evaluation and possible treatment.