They believed the heart was the seat of thought and emotions, because it beat harder when we were feeling
Hippocrates concluded that the role should be assigned to the brain.
o Aristotle disagreed, saying the brain acted to calm the passions of the heart.
o Galen discounted this, saying that if it were so, then nerve endings would go to the heart, not the mind.
René Descartes, said that animals (including humans) are machines, and once set on this earth behave without any
He defined the term reflex: An automatic, stereotyped movement that is produced as a direct result of a stimulus.
He said that energy coming from an outside source would be reflected back through the nervous system to the
muscles, which would contract (we of course have a different explanation for this now.)
Descartes was a dualist, but he was the first to hypothesize a link between the brain and the mind:
o The mind controls movement, while the body provided information to the mind, via the brain.
o This interaction was said to take place in the pineal body, a small organ at the top of the brain stem.
o He noted that the brain contained fluid-filled VENTRICLES, and when the mind wanted to move, it tilted
the pineal body like a joystick, causing fluid to flow from the brain to the appropriate set of nerves.
Descartes used a model of moving bronze statues, which work in much the same way, to come to his conclusion.
Model: A mathematical or physical analogy for a physiological process; for example, computers have been used
as models for various functions of the brain.
It did not take long for this model to be tested experimentally, and to prove that Descartes was wrong.
Galvani discovered that electrical impulses toward a nerve cause the muscle to which it is attached to move,
regardless of activity in the brain. Therefore, the ability of a nerve to send a message to the muscles is a
characteristic of the tissue itself.
o A prominent nineteenth-century physiologist, who applied experimental techniques.
o Doctrine of specific nerve energies: Müller‘s conclusion that because all nerve fibers carry the same
type of message, sensory information must be specified by the particular nerve fibers that are active.
o Example, we receive optical information from auditory nerves, and auditory information from auditory
o Explanation: although the information sent is the same, the different nerves go to different parts of the
brain, and are thus interpreted differently.
o Removed various parts of animals‘ brains and observed their behavior;
o Brain ablation: The research method in which the function of a part of the brain is inferred by observing
the behaviors and animal can no longer perform after that part is damaged.
o Flourens claimed to have discovered regions of the brain that control heart rate and breathing, purposeful
movements, and visual and auditory reflexes.
o Applied the brian ablation technique to humans, by observing the behavior of those whose brains had
been damaged by strokes.
o Observations of those who could no longer speak, led him to conclude that there was an area in the left
side of the brain performing functions necessary for speech.
Gustav Fritsch and Eduard Hitzig:
o Applied a current to a dog‘s brain and observed the effects.
o Stimulation of specific parts of the brain led to contractions of specific muscles on the opposite side of the
body. This region is now called the PRIMARY MOTOR CORTEX.
Hermann von Helmholtz:
o Provided many great discoveries, including theories of color vision.
o He opposed Muller in that he believed all physiological phenomena can be subject to experimental
investigation (they are all mechanistic).