Fearnley and Less studied the brain of 36 control subjects, aged 21 to 91 years, who were recruited at the United Kindong Parkinson's Disease Society Brain Bank (UKPDSBB). They observed a linear reduction of pigmented nigal neurons with advancing age in the pars compacta of the caudal substatia nigra at the rate of 4.7% per decade. there was a characteristic regional distribution of nigral cell loss that was fundamentally different from that in patients with varius stages of Parkinson Disease.