Neuroscience by Picture - A

Based on the picture, guess these neuroscience-themed answers starting with the letter A.

Picture Credit:
Picture 2 by Quasar Jarosz (https://creativecommons.org/licenses/by-sa/3.0/); modified
Picture 4 by https://www.scientificanimations.com (https://creativecommons.org/licenses/by-sa/4.0/); modified
Picture 7 by Helixitta (https://creativecommons.org/licenses/by-sa/4.0/); modified
Picture 8 by James.mcd.nz (https://creativecommons.org/licenses/by-sa/4.0/); modified
Picture 11 by Cancer Research UK (https://creativecommons.org/licenses/by-sa/4.0/deed.en); modified
Picture 12 by BruceBlaus (https://creativecommons.org/licenses/by-sa/4.0/deed.en); modified
Picture 13 by Leevanjackson (https://creativecommons.org/licenses/by-sa/4.0/); modified
Picture 14 by P.j.duncan88 (https://creativecommons.org/licenses/by-sa/4.0/deed.en); unmodified
Picture 15 by CFCF (https://creativecommons.org/licenses/by-sa/4.0/deed.en); modified

All other pictures are in the public domain and were partially modified by me.