Link between soluble Aβ pathology and cognitive impairment. Correlation between average levels of soluble (a, b) and insoluble (c, d) Aβ42 and Aβ40 and the magnitude of cognitive impairments in transgenic animals, during the temporal progression of the AD-like amyloid pathology. A cognitive index was calculated based on the animals’ performance throughout all phases of the two behavioral paradigms employed, and expressed as a z score. Average values were analyzed with linear regression. Note the negative correlation between cognition and the levels of soluble Aβ42 peptides but not with soluble Aβ40.