  As this account of the types of limitations that restrict cognition  demonstrates, the Abhidharma tradition seems unambiguous about the  ultimate basis for cognition: this is to be found in the sensory  domain itself, given that cognitions change following modifications  at the level of sense rather than in the mind (see AKBh ad  I, 45ab). In the case where changes in the mental stream occasion in  the absence of any sensory stimulus, these are said to be the result  of unconscious traces of past experience rather than endogenous to  mind itself.