Hearing skills affected by APD

Because APD can be caused by dysfunction in any of a number of hearing pathways, circuits and centres in the brain, there are many possible effects.  Each case of APD will have its own pattern of disordered function.  Here are some effects of APD.

  • Unilateral weakness or inhibition of one ear (amblyaudia)
  • Impairment in:
    • pattern recognition (being able to recall and repeat very simple musical patterns of high and low pitch notes)
    • directional or spatial hearing and the related ability to hear against background noise
    • correctly hearing very fast changes at the start of speech sounds which can affect correctly hearing the sound (onset time discrimination)
    • detection of rapid changes in speech sounds (less than 20 thousandths of a second) measured by “gap detection” tests
    • remembering what has just been heard and the order of the sounds (auditory memory)
    • being able to maintain attention to auditory information (auditory attention)
    • correctly identifying and discriminating between speech sounds (phoneme discrimination, phonological awareness)

Some differences in brain function in people with APD can be seen on objective physiological tests such as

  • delayed electrical responses to certain speech sounds at the cortex of the brain (delayed cortical responses)
  • reduced brain activity to certain sounds on Functional Magnetic Resonance Imaging (FMRI)