HIERARCHICAL-CLUSTERING INTO GROUPS OF HUMAN BRAIN-REGIONS ACCORDING TO ELEMENTAL COMPOSITION

Thirteen brain regions were dissected from both hemispheres of fifteen 'normal' ageing subjects (8 females, 7 males) of mean age 79+/-7 year s. Elemental compositions were determined by simultaneous application of particle induced X-ray emission (PIXE) and Rutherford backscatterin g (RBS) analyses using a 2 MeV, 4 nA proton beam scanned over 4 mm(2) of the sample surface. Elemental concentrations were found to be depen dent upon the brain region and hemisphere studied. Hierarchical cluste r analysis was applied to group the brain regions according to the sam ple concentrations of eight elements. The resulting dendrogram is pres ented and its clusters related to the sample compositions of grey and white matter.