<unk>  brain samples are limited resources, because it is extremely difficult for a researcher to get a hold of an individual’s brain. The researchers ask their participants or the families to consent to allowing them to study the loved one's brain, however there has been a falling rates of consent in the last few years. Subsequently researchers have to use indirect methods to study the locations and processes of the brain. Another limitation to<unk>  is the continuous funding and the time it takes to conduct a longitudinal study.<unk>  longitudinal<unk>  usually take place at the time of assessment until the time of death about 20–30 years.
Postmortem studies
Molecular pathology
Viral neuronal tracing
Neuroproteomics
Molecular genetics
Digital autopsy
Brain fingerprinting
Clinical neuropsychology