Analysis of Β-amyloid (AΒ) deposition in the temporal lobe in Alzheimer's disease using Fourier (spectral) analysis

Abstract

Aim: To determine the spatial pattern of β-amyloid (Aβ) deposition throughout the temporal lobe in Alzheimer's disease (AD). Methods: Sections of the complete temporal lobe from six cases of sporadic AD were immunolabelled with antibody against Aβ. Fourier (spectral) analysis was used to identify sinusoidal patterns in the fluctuation of Aβ deposition in a direction parallel to the pia mater or alveus. Results: Significant sinusoidal fluctuations in density were evident in 81/99 (82%) analyses. In 64% of analyses, two frequency components were present with density peaks of Aβ deposits repeating every 500-1000 μm and at distances greater than 1000 μm. In 25% of analyses, three or more frequency components were present. The estimated period or wavelength (number of sample units to complete one full cycle) of the first and second frequency components did not vary significantly between gyri of the temporal lobe, but there was evidence that the fluctuations of the classic deposits had longer periods than the diffuse and primitive deposits. Conclusions: (i) Aβ deposits exhibit complex sinusoidal fluctuations in density in the temporal lobe in AD; (ii) fluctuations in Aβ deposition may reflect the formation of Aβ deposits in relation to the modular and vascular structure of the cortex; and (iii) Fourier analysis may be a useful statistical method for studying the patterns of Aβ deposition both in AD and in transgenic models of disease. © 2010 Blackwell Publishing Ltd.