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

Abstract

To determine the spatial pattern of beta-amyloid (Abeta) deposition throughout the temporal lobe in Alzheimer's disease (AD). Sections of the complete temporal lobe from six cases of sporadic AD were immunolabelled with antibody against Abeta. Fourier (spectral) analysis was used to identify sinusoidal patterns in the fluctuation of Abeta deposition in a direction parallel to the pia mater or alveus. 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 Abeta deposits repeating every 500-1000 microm and at distances greater than 1000 microm. 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. (i) Abeta deposits exhibit complex sinusoidal fluctuations in density in the temporal lobe in AD; (ii) fluctuations in Abeta deposition may reflect the formation of Abeta 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 Abeta deposition both in AD and in transgenic models of disease.