For example, hearing loss has been associated with smaller brain volumes and lower white matter microstructural integrity, and this could slow cognitive processing. Additionally, hearing loss has been associated with tau pathology, an early indicator of Alzheimer disease. Other hearing loss–related changes to the brain may include dysfunctional neurotransmission due to decreased levels of GABA receptors, cortical thinning, and reduced gray matter volume, particularly in primary auditory cortex within the temporal lobe. This evidence concerns the gene MAPT and hearing loss disorder.