The present invention relates to antibodies that -differentially -recognize- -multi- dimensional conformations- of- Aß- derived diffusible ligands, also known as ADDLs. The antibodies of the invention can distinguish between Alzheimer's Disease and control human brain extracts and are useful in methods of detecting ADDLs and diagnosing Alzheimer's Disease. The present antibodies also block binding of ADDLs to neurons, assembly of ADDLS, and tau phosphorylation and are there useful in methods for the preventing and treating diseases associated with soluble oligomers of amyloid ß 1-42.