Neuroscience and the Study of Behavior

Outline:

• Study of Behavior
  • Comparative Psychology
  • Ethology
• Neuroscience
• Neuroethology

History: Neuroscience

• Stone Age surgeons cut holes into the skull, probably to release "evil spirits" as the cause of headaches or strange behaviors
• Aegyptians: embalmed the body but carefully extracted the brain from the skull and - trashed it - deeming it unnecessary for an after life
• Greeks: Noting the rich vascular supply of the brain, Aristotle concluded that it had to be an organ to cool the blood
• Romans: As doctor of Roman gladiators Galen obviously noted the behavioral deficits that arise from traumatic injuries to head and brain. Life (pneuma , i.e. breath) takes three forms: the brain forms the center of sensory perceptions and movement; the heart regulates blood and body temperature and the liver is the center of nutrition and metabolism. On epilepsy he writes: "In all forms it is the brain which is diseased; either the sickness originates in the brain itself,... or it rises in sympathy into the brain from the cardiac orifice of the stomach... Seldom, however, it can have its origin in any part of the body... and then rises to the head in a way which the patient can feel..."
• Middle Ages: Mental illnesses as punishment for committed sins, tiral of god, or the result of possession by demons
• 17th Century:
  • Rene Descartes (1596-1650) describes the pineal gland as the control center of the body and mind
• 18th Century:
  • Antony von Leeuwenhoek (1632-) describes a nerve fiber in cross section
  • Luigi Galvani (1737-1798) electrical stimulation of frog nerves
• 19th Century:
  • Jan Evangelista Purkinje, Robert Remak, Wilhelm His: Anatomy and physiology of nerve cells
• 20th Century:
  • Sir Charles Scott Sherrington (1857-1952) research on neuron function: "Behavior is motion" ... and other nobel prize winners
  • Modern Psychiatry: The "happyness cure" to mentall illness - from lobotomy and electro-convulsive therapy to the pharmacological ice picks of today
  • Despite Decade of the Brain (1990-1999) all neurological disorders still without real therapy. The brain as the seat of our most noble deeds and most primitive impulses

Scientists

Neuroethology

The study of the proximate mechanisms (i.e., performance and control) of behavior considers the inclusion of "top-down" approaches as essential. It commonly starts with a characterization of behaviors (robust, repeatable, biologically relevant, and often stereotyped) and progresses with questions about sensory stimuli, predictions for underlying "computations”, or the study of motor control. In the process, Neuroethology addresses questions such as:

• How does the nervous system gain a view of the outside world?
• How does it pattern and regulate movement?
• How is information derived from experience stored in the brain?
• What are the physiological mechanisms underlying motivational states?

It specifically relates such considerations to more basic findings in Neuroscience, which has provided us with detailed information on the general mechanisms by which neurons talk to each other. Neuroethology often utilizes dedicated systems which communicate along labelled lines. Sensory systems convert signal energy into electric impulses (e.g. sound perception; graded to all-or-none), while motor systems translate neural activity into behavior (e.g. escape in crayfish, goldfish).

Scientists

• Walter Hess (Nobelprize 1949)
• Erich von Holst
• Walter Heiligenberg - social behavior and communication via electric signals in electric fish
• Mark Konishi - auditory sensory map in prey-capture of Owls
• Franz Huber - acoustic signalling in courtship and aggression of crickets

Basic Organization of Nervous Systems

Structures of the nervous system (e.g., the human brain) are composed of different, basic cell types: mostly neurons (or nerve cells) and glial cells. A generalized neuron features a series of different, basic components with cell body (i.e., a region of the neuron containing the nucleus), axon (an elongated process for long-distance signalling), axon terminals (the site of information transfer to other cells), and dendrites (highly-branched processes largely involved in receiving and integrating incoming information). Based on functional considerations nerve cells may be classified as sensory neurons (which encode information about the surrounding world), interneurons (which are involved in information processing), and motor neurons (which activate muscle fibers and control muscular contraction). Glial cells surround neurons in the nervous system and support, protect, and communicate with their surround. Glia come in many shapes and size, such as Oligodendrocytes, Astrocytes, Ependymal cells, Microglia, Special glial cells in the central nervous system and Schwann cells, Satellite/Capsule cells, Enteric (gut) glia in the peripheral nervous system. Astrocyte control the specific environment of neurons necessary for succesful signaling. They provide electrical insulation (myelin) of axonal lines (oligodendrocyte for CNS and Schwann cell for PNS myelination). Microglial cells, which line the ventricles of the brain, act as immune cells in CNS. In addition to neurons and glia the brain contains cells making up blood vessels and connective tissues enclosing sheaths.

White (fiber) matter consists of myelinated axons that largely run the longitudinally in the body. Gray (neuronal) matter contains the cell bodies, dendrites, synapses and blood vessels.

Scientists

• Santiago Ramon y Cajal (Nobelprize 1906)
• Camillo Golgi (Nobelprize 1906)