A monoclonal antibody or antigen-binding fragment thereof, wherein the antibody or antigen-binding fragment: a) binds tau in normal human brain tissue and b) does not binds tau in human Alzheimer's disease brain tissue, wherein the antibody is selected from the group consisting of a) an antibody comprising a heavy chain CDR1 region of SEQ ID NO:201, a heavy chain CDR2 region of SEQ ID NO:202, and a heavy chain CDR3 region of SEQ ID NO:203, a light chain CDR1 region of SEQ ID NO:204, a light chain CDR2 region of SEQ ID NO:205 and a light chain CDR3 region of SEQ ID NO:206, b) an antibody comprising a heavy chain CDR1 region of SEQ ID NO:207, a heavy chain CDR2 region of SEQ ID NO:208, and a heavy chain CDR3 region of SEQ ID NO:209, a light chain CDR1 region of SEQ ID NO:210, a light chain CDR2 region of SEQ ID NO:211 and a light chain CDR3 region of SEQ ID NO:212, c) an antibody comprising a heavy chain CDR1 region of SEQ ID NO:222, a heavy chain CDR2 region of SEQ ID NO:223, and a heavy chain CDR3 region of SEQ ID NO:224, a light chain CDR1 region of SEQ ID NO:225, a light chain CDR2 region of SEQ ID NO:173 and a light chain CDR3 region of SEQ ID NO:226, d) an antibody comprising a heavy chain CDR1 region of SEQ ID NO:238, a heavy chain CDR2 region of SEQ ID NO:239, and a heavy chain CDR3 region of SEQ ID NO:240, a light chain CDR1 region of SEQ ID NO:241, a light chain CDR2 region of SEQ ID NO:173 and a light chain CDR3 region of SEQ ID NO:242, e) an antibody comprising a heavy chain CDR1 region of SEQ ID NO:243, a heavy chain CDR2 region of SEQ ID NO:244, and a heavy chain CDR3 region of SEQ ID NO:245, a light chain CDR1 region of SEQ ID NO:246, a light chain CDR2 region of SEQ ID NO:173 and a light chain CDR3 region of SEQ ID NO:212, f) an antibody comprising a heavy chain CDR1 region of SEQ ID NO:243, a heavy chain CDR2 region of SEQ ID NO:247, and a heavy chain CDR3 region of SEQ ID NO:248, a light chain CDR1 region of SEQ ID NO:249 a light chain CDR2 region of SEQ ID NO:173 and a light chain CDR3 region of SEQ ID NO:212, and g) an antibody comprising a heavy chain CDR1 region of SEQ ID NO:250, a heavy chain CDR2 region of SEQ ID NO:251, and a heavy chain CDR3 region of SEQ ID NO:252, a light chain CDR1 region of SEQ ID NO:254, a light chain CDR2 region of SEQ ID NO:254 and a light chain CDR3 region of SEQ ID NO:255. a) an antibody comprising a heavy chain CDR1 region of SEQ ID NO:201, a heavy chain CDR2 region of SEQ ID NO:202, and a heavy chain CDR3 region of SEQ ID NO:203, a light chain CDR1 region of SEQ ID NO:204, a light chain CDR2 region of SEQ ID NO:205 and a light chain CDR3 region of SEQ ID NO:206, b) an antibody comprising a heavy chain CDR1 region of SEQ ID NO:207, a heavy chain CDR2 region of SEQ ID NO:208, and a heavy chain CDR3 region of SEQ ID NO:209, a light chain CDR1 region of SEQ ID NO:210, a light chain CDR2 region of SEQ ID NO:211 and a light chain CDR3 region of SEQ ID NO:212, c) an antibody comprising a heavy chain CDR1 region of SEQ ID NO:222, a heavy chain CDR2 region of SEQ ID NO:223, and a heavy chain CDR3 region of SEQ ID NO:224, a light chain CDR1 region of SEQ ID NO:225, a light chain CDR2 region of SEQ ID NO:173 and a light chain CDR3 region of SEQ ID NO:226, d) an antibody comprising a heavy chain CDR1 region of SEQ ID NO:238, a heavy chain CDR2 region of SEQ ID NO:239, and a heavy chain CDR3 region of SEQ ID NO:240, a light chain CDR1 region of SEQ ID NO:241, a light chain CDR2 region of SEQ ID NO:173 and a light chain CDR3 region of SEQ ID NO:242, e) an antibody comprising a heavy chain CDR1 region of SEQ ID NO:243, a heavy chain CDR2 region of SEQ ID NO:244, and a heavy chain CDR3 region of SEQ ID NO:245, a light chain CDR1 region of SEQ ID NO:246, a light chain CDR2 region of SEQ ID NO:173 and a light chain CDR3 region of SEQ ID NO:212, f) an antibody comprising a heavy chain CDR1 region of SEQ ID NO:243, a heavy chain CDR2 region of SEQ ID NO:247, and a heavy chain CDR3 region of SEQ ID NO:248, a light chain CDR1 region of SEQ ID NO:249 a light chain CDR2 region of SEQ ID NO:173 and a light chain CDR3 region of SEQ ID NO:212, and g) an antibody comprising a heavy chain CDR1 region of SEQ ID NO:250, a heavy chain CDR2 region of SEQ ID NO:251, and a heavy chain CDR3 region of SEQ ID NO:252, a light chain CDR1 region of SEQ ID NO:254, a light chain CDR2 region of SEQ ID NO:254 and a light chain CDR3 region of SEQ ID NO:255.