Sensory maps and brain development the midbrain auditory nucleus had receptive fields independent of nature and intensity of the sound. Roger Sperry proposed a chemical gradient model for eye rotation and for neuronal wiring diagram. Retinal neurons and target cells had identification tags in the form of chemical gradients so that the projection of neurons would be orderly. For a topographic map of the visual world, the map first forms during neural development via molecular signals, such as chemospecific matching between molecular gradients. The molecular basis of sensory maps and brain development is a field that is being actively explored. The most recent work has
Nanoparticles for drug delivery to the brain that it can bind and undergo endocytosis. Another mechanism is "adsorption mediated transcytosis", where electrostatic interactions are involved in mediating nanoparticle crossing of the BBB. Cationic nanoparticles (including cationic liposomes) are of interest for this mechanism, because their positive charges assist binding on the brain's endothelial cells. Using TAT-peptides, a cell-penetrating peptide, to functionalize the surface of cationic nanoparticles can further improve drug transport into the brain. In contrast to the above mechanisms, a delivery with magnetic fields doesn't strongly depend on the biochemistry of the brain. In this case, nanoparticles are literally pulled across the BBB via application of