Activation also involves stimulating mental models that can be modified or tuned to help learners incorporate new knowledge into what they already know. Andre (1997) cited research that showed themes can serve as an organising structure if they are relevant to the content being taught. However! Irrelevant themes that have been shoehorned in to instruction in an attempt to promote motivation can actually increase the cognitive load required to engage with the content presented.
Link: Merrill’s first principles of instruction