Methods for detecting α-synuclein oligomers in vivo comprise administering an antibody to an individual suspected of carrying soluble α-synuclein, wherein the antibody is produced from a stabilized soluble α-synuclein oligomer and is capable of binding the stabilized soluble α-synuclein oligomer, wherein the stabilized soluble α-synuclein oligomer has a lower formation rate to a non-soluble aggregated form than a non-stabilized soluble oligomer of the α-synuclein, and wherein the antibody is labelled with a detectable marker and detecting the presence of any complex formed between the antibody and soluble α-synuclein by detection of the marker.
