15. and it's a bit boring. Neuroscience is a study of the nervous system, of the brain. What we know about the brain can be divided into 3 or 4 categories...
1: neurochemistry/neurotransmitters… it was discovered a hundred years ago that communication between nerves at their synapses is a chemical event involving neurotransmitters (chemicals). Over the decades more and more details have been unraveled by numerous researchers. There are a handful of major transmitters (e.g acetylcholine, dopamine, GABA), and dozens of minor ones.
2. gross anatomy and connectivity. The gross anatomy has been studied for even longer, and now with ever more sophisticated tools. We used to do "ablations" studies: when you kill a nerve body its axons die off and you can trace their connections. (Or a stain (and poison) horseradish peroxidase will spread down the axons.) Now we have functional MRI (fMRI) (and PET scans and other techniques) to see what areas are active and when.
3. behavioral studies: I said 3 or 4 because I'm not sure how much we've learned from this aspect of study. The big names are Pavlov, Lorenz and Tinbergen (ethology). We have not learned that much of any importance (I think) from Skinner and the "Behaviourists", but there are many other observers, some crossing disciplines - like Sherrington's work on reflexes at the beginning of the 20th century…
4. connectivity and nerve nets: here there are some luminary names, like Sherrington, and Golgi, who started staining nerves: (the illustration is of Cajal's drawing using Golgi's stain.) Neurophysiologists, throughout the 20th century, made small steps in studying the functionality of these connections. Some of the most striking work is in the physiology of vision. Hubel and Weisel pieced together the connectivity of six orders of neurons in the cat's visual system so we can see how it's wired to perceive the orientation of edges, and the direction of movements. This work from the 1950s and 1960s is a stunning piece of research , (footnote: The neurophysiology of vision, actually begins before Hubel and Weisel. In the 30s and 40s the concept of "surround contrast" fields in the retina was pieced together. This traces 3 orders of neuron, how they begin to look for contrast. (see: Neural Networks on my website). Hubel and Weisel worked on the organization of 4th, 5th, and 6th order of visual neurons in the brain tracing out how cells are wired to pay attention to edges and movement, the orientation of edges, the direction of movements. (again, see: Neural Networks on my website)and it is still the state of the art.
5(?). observation and introspection tell us little about the brain, but something about the "mind". Freud's speculations about/discovery of the unconscious, repression and resistance are significant. Introspection may show that if we can suspend the verbal (and verbal conceptional) mind, we will experience very interesting changes in our state of consciousness.)