Tau deposition refers to the accumulation of abnormal tau protein aggregates in the brain, which is a characteristic feature of several neurodegenerative disorders, including Alzheimer's disease (AD), frontotemporal dementia (FTD), and certain forms of Parkinson's disease (PD), among others. In neuroimaging, techniques such as positron emission tomography (PET) using radioligands targeting tau can visualize and quantify tau deposition in the brain. These imaging methods enable researchers and clinicians to detect the presence of abnormal tau aggregates and assess their distribution and severity.