Reivindicaciones

1. A non-human transgenic animal wherein GSK-3β protein is over-expressed in the animal, wherein expression of the GSK-3β protein is under the control of a tet-regulated conditional GSK-3β expression system, having a tTA transgene under the control of the CamKIIa promoter, such that increased levels of tau phosphorylation are found in the hippocampus, but not in the cortex or striatum. 2. A transgenic animal according to claim 1, in which GSK-3β is the only enzyme which is over-expressed. 3. A transgenic animal according to claim 1, in which GSK-3β is the only protein which is over-expressed. 4. A transgenic animal according to any proceeding claim, which is a mammal. 5. A transgenic animal according to claim 4, where the mammal is a mouse, rat or primate. 6. The use of a transgenic animal according to any proceeding claim as a model for Alzheimer's disease. 7. A use of a transgenic animal according to any of claims 1 to 5, in the testing of a drug or therapy to treat neurodegenerative diseases. 8. A method of identification of a therapy useful in the treatment of Alzheimer's disease, comprising administering the therapy to the transgenic animal according to any of claims 1 to 5 and monitoring for an effect on pathology or behaviour.