Neuroscience: Past, Present, and Future

Origins of Neuroscience

• Nervous systems produce perception, thought, behavior, and emotion (it is us)

  • Questions free will & the presence of the “soul"

    • Can the nervous system make people more predisposed to things, such as crime?

• In prehistory, people knew how vital the brain is to life (i.e.: skull injuries made to inflict serious damage & trepanation [skull surgeries] to heal pain and remove evil spirits)

• In the ancient world, Egyptians believed your heart held your soul and memories (consciousness), not your brain (even though the reverse is true. Some writing indicated that they knew brain damage resulted in deficits

  • Hippocrates challenged this belief with his that the proximity of the eyes, ears, and nose to the brain indicated the brain’s importance in their processes

  • Galen discovering “ventricles” in the (sheep) brain made him think that these “pumps” fueled the brain’s function using four vital fluids, or humors

• In the Renaissance, Rene Descartes thought of the brain as a mechanical device run by pumps but that the mind & soul can overpower these mechanisms. (dualism - metaphysical and physical interaction) Believed that the mind is a spiritual entity that receives sensations and commands movements by communicating with the machinery of the brain via the pineal gland. Modern science disproves this

• In the Enlightenment, gray (soma) and white (axon) matter were discovered through dissections (white matter continuous with nerves in the body)

  • Delineation of the CNS: brain and spinal cord from the PNS: the nerves of the body

  • Observed the bumps (gyri) and grooves (sulci and fissures) are on the surface of everyone; this pattern, making the lobes of the brain, led to speculation of cerebral localized functions

• The 19th-century study of the brain concluded with four key insights:

  • Nerves as Wires: Luigi Galvani and Emil du Bois-Reymond discovered the nerves communicate with the brain via electricity that the brain can generate and that nerves contain nerve fibers that carry information

    • Charles Bell and Francois Mangendie concluded that nerve fibers within a nerve carry some information to the brain and spinal cord and others to the muscles and transmission is one-way. The two kinds of fiber are bundled together, yet segregate when they enter or exit the spinal cord

  • Localization of Specific Functions to Different Part of the Brain: Bell and Mangendie proposed that the origin of motor neurons is the cerebellum and the destination of the sensory fibers is the cerebrum. They tested this theory through the experimental ablation method, in which parts of the brain are systematically destroyed to determine their function.

    • Marie-Jean-Pierre Flourens concluded these same findings through his experimentation with animals, providing solid experimental support for his conclusions.

    • Franz Joseph Gall believed that bumps on the surface of the skull reflected bumps on the surface of the brain. His experiments with this theory led to the development of phrenology, which correlates the structure of the head with personality traits

    • Paul Broca, a French neurologist, found that the cerebrum functions were localized by studying the brain of a man who could not speak and finding a brain lesion in the left frontal lobe.

    • Other scientists would perform experiments to support cerebral localization using animal models.

  • The Evolution of Nervous Systems: Similar to Darwin’s conclusion of natural selection and traits stemming from common ancestors, the nervous systems of different species are thought to be from common ancestors as they have common mechanisms. This discovery has influenced how the nervous system is studied. Scientists use animal models, mainly rats, in experiments relating to the nervous system because of its similarities to the human nervous system.

  • The Neuron: The Basic Functional Unit of the Brain: With the advancement of microscopy, scientists were able to observe individual cells. Neurons/nerve cells were also discovered through this and studied. Controversy was raised about whether neurons were the basic unit of brain function and whether their axons fused like blood vessels to create a “nerve net.”

• Today, we use the scientific method in research:

  • Ask a question

  • Form a hypothesis

    • Make a prediction

  • Test your hypothesis with an experiment

  • Analyze results and evaluate your hypothesis

  • Communicate results