More recently, brain scans have directly linked these conditions with changes in levels of neurotransmitters — chemicals that convey messages across neurons — or alterations in the number or structure of
neurons in different brain areas.
Gatti, C., Cantelmi, M. G., Brunetti, M., Gaiti, A., Calderini, G., and Teolato, S. Effect of chronic treatment with phosphatidyl serine on phospholipase A1 and A2 activities
in different brain areas of 4 month and 24 month old rats.
Certain types of memory are
encoded in different brain areas, and depending on where Sacktor injects the inhibitor in his animals, he can zap away different categories of memory.
Previously, researchers had two theories about how neurons in the motor cortex might control movement: One was that these neurons fired in patterns that represent more abstract commands, such as «move your arm to the right,» and then
neurons in different brain areas would translate those instructions to guide the muscle contractions that make the arm move; the other was that the motor cortex neurons would actually send directions to the arm muscles, telling them how to contract.