Complex sentence: The condition is normally caused by brain injury or illness which disrupts the brain's ability to process what the sound means, believed to be due to a disruption of the "what" pathway in the brain (1).
Split into simpler sentences: The condition is normally caused by brain injury or illness which disrupts the brain's ability to process what the sound means. It is believed to be due to a disruption of the "what" pathway in the brain (1).