User blog comment:Xilinoc/Ch. 585 - The Headless Star 4/@comment-24509822-20140618112048/@comment-24282510-20140619055512

All i got to say is there is a diffence between zanpakuto and zanpakuto spirit. Since a zanpakuto is more or less a medium (i guess you can say that) for which a zanpakuto spirits acts. Aizen would have a weaken form of absolute hypnosis. Not to mention the binds on him likely weaken it even more.

The way i took it back then and still think it was his zanpakuto merged with him.