The AP Bio curriculum covers some biochem topics that would be directly relevant to your intended major. While the AP Chem curriculum covers mostly inorganic chem, some of the content in the curriculum will be directly related to the concepts you will cover in Organic Chem, which will likely be one of the most difficult courses in your intended major.
I would look at your performance in prior bio and chem courses. If you have A’s in both, then choose the one that you feel you would benefit the most from in terms of another year of introductory science instruction. If you don’t have A’s in both, take the one in which you received the lower grade. You will probably need to take the introductory course in both bio and chem for your intended major. As a neuro/cog sci major, you likely won’t be able to test out of these classes even with a 5 on the AP exams, but the AP curriculum and tests are great prep for these courses.
Everyone’s prior advice about taking one year of each (Bio, chem and physics) is also a priority. You will want a solid foundation in all three before taking the required intro courses in these classes for science majors.