Radial density function for R1282 immunoreactive deposits

We assessed $N=989$ R1282 immunoreactive deposits in the 4 PSAPP mice. In Fig. 4(a) and (b), the solid curve, $\rho(r)$ for all deposits, shows a constant neuronal density as a function of distance from the center of the R1282 immunoreactive deposit. This curve is flat except close to the origin, where there is a weak decrease in neuronal density. This curve is consistent with the view that there is not an appreciable effect on neuronal density when all $A\beta$ deposits are considered as a single population. However, to test the hypothesis that a subset of $A\beta$ deposits is toxic, we analyzed $A\beta$ deposits subdivided by size (effective radius $R$) and optical density (dotted, dashed and long-dashed curves in Fig. 4(a) and (b)). Although all graphs flatten out and converge towards the same neuronal density beyond $R = 50\mu m$ from the center of mass of the $A\beta$ deposit, in smaller distances the larger and more dense $A\beta$ deposits are associated with a focal reduction in neuronal density. There is an approximately 20% reduction in neuronal density within the larger or denser $A\beta$ deposits (larger than $R = 12\mu m$ in size).