Studies of the brain became more sophisticated after the invention of the microscope and the development of a staining procedure by Gamillo Golgi (1843-1926) during the late 1890s. The procedure used a silver chromate salt to reveal the structures of individual neurons; for the first time, you were able to see what single neurons looked like. Santiago Ramón y Cajal (1852-1934), considered to be the father of modern neuroscience, used this technique to form the neuron doctrine, the hypothesis that the neuron is the functional unit of the brain. In 1906, Santiago Ramón y Cajal shared the Nobel Prize with Golgi for summarizing evidence of the neuron doctrine (Shepherd, 1991).

George Barger (1878-1939) and Henry Dale (1875-1968) discovered norepinephrine, or noradrenaline in 1911.  An increase in norepinephrine from the sympathetic nervous system increases the rate of contractions of the heart. Later, in 1914, Henry Dale first identified acetylcholine as a possible neurotransmitter and demonstrated its importance in the nervous system (Kandel, 2000).

Walter Rudolph Hess, in 1928, reported that stimulation to the hypothalamus resulted in “affective” responses, inducing behaviors from excitement to apathy. In 1929, Karl Lashley (1890–1958) attempted to localize memory in the brain through lesion experiments in rats. He searched for engams, his word for the neural components of memory. He also defined “equipotentiality” and “mass action”. From the 1930s to the 1950s, Wilder Penfield (1891-1976) and Theodore Rasmussen (1910-2002) mapped the motor and sensory homunculus, or visual representation of the concept of “the body within the brain”, and illustrated the localization of function in the human brain (Martensen, 2004).

In the 1940s, Alan Hodgkin (1914-1998), Andrew Huxley (1917-2012), and Bernard Katz (1911-2003) explained electrical activity of neurons by concentration gradients of ions and movement of ions through pores. These findings were based on nerve action potentials, the impulses that enable an organism to be coordinated by a central nervous system (Finger, 1994).

In 1949, Donald Hebb (1904-1985) introduces a synaptic learning rule, which becomes known as the Hebb rule. The Hebb rule is often summarized as “Cells that fire together, wire together.” This theory explained the adaptation of neurons in the brain during the learning process, and attempts to explain “associative learning.”

Comments are closed.