Early Ideas about Brain and Behavior

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Early Ideas about Brain and Behavior
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Mind, Brain and Behavior

• Neuroscientists want to unify the science of the
  mind with the science of the brain.
• Actions of the brain underlie all behavior.
• What we call mind is a range of functions carried
  out by the brain.
• Neural science explains behavior in terms of
  brain activities.
• Where does psychology fit?

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Where Does Mind Reside?

• Which part of the body is the seat of the soul,
  the repository of memory?
• Aristotle (384-322 B.C.) said the heart.
• Hippocrates (460-379 B.C.) said the brain.
• Galen (130-200 A.D.) agreed with Hippocrates
• Cerebrum vs cerebellum
• Ventricles do the work

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19th Century Views

• By the 1800s, the nervous system had been
  completely dissected and gross anatomy described.
• Injury to the brain disrupts functioning.
• Brain communicates with the body via nerves.
• The brain has parts that probably perform
  different functions.
• The brain follows laws of nature and operates
  like a machine.

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Understanding by Analogy

• Metaphors have always been drawn from discoveries
  in the physical world fluid mechanics,
  windmills, man as machine.
• Modern analogies
• Mind as switchboard
• Mind as computer

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Discarded Theories

• Fluid in ventricles, flow of humors
• Galen
• Body as machine explained by mechanics
• Nerves as hollow tubes full of gas or fluid
• Descartes
• Nerves as wires
• Galvani, du Bois-Reymond, Muller, Helmholtz

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The Discovery of the Neuron

• Golgi developed a silver staining method that
  revealed the cell body and projections of the
  neuron.
• Ramon y Cajal used the technique to show that
  neurons do not quite touch.
• Neurons are a network of separate (discrete)
  cells that communicate.
• Galvani showed that the signaling is electric.

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Nissl Stain
Golgi Stain
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Localization vs Distribution

• Are specific functions carried out in specific
  regions of the brain?
• Are functions an emergent property of brain
  activity as a whole?
• Todays neuroscience still debates this.
• The answers appear somewhere between the two
  extremes.

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Two Alternative Views

• Cellular connectionism
• Individual neurons are the signaling elements of
  the nervous system, arranged in functional groups
• Supported by empirical observations of Ramon y
  Cajal, Wernicke, Jackson, Sherrington.
• The aggregate field view
• All regions of the brain participate in all
  mental functions.
• Mind is NOT completely biological

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The Localization Debate

• Gall the brain consists of 35 organs
  corresponding to mental faculties.
• Observable through bumps on the head.
• Phrenology anatomical basis for personology
• Flourens all perceptions, all volitions
  occupy the same seat
• Aggregate field view
• A reaction against strict materialism (mind not
  completely biological).

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The Discovery of Localization

• Imaging techniques that show the brain in action
  confirm that certain functions are carried out in
  specific areas of the brain.
• This was difficult to see early on because of
  parallel processing
• Each function is subserved by more than one
  neural pathway.
• When one pathway is damaged, others may
  compensate, making localization harder to see.

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Support for the Field View

• Lashley found that the greater the lesions, the
  greater the impairment in functioning.
• No matter where lesions were made, learning was
  impaired.
• Mass action -- brain mass, not specific regions
  was most important to functioning.
• Maze learning involves multiple functions, so it
  is unsuitable for studying localization.

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The Current View

• Functions consist of multiple processes that
  occur in specific areas of the brain.
• Imaging studies reveal the different processes,
  called elementary operations.
• Processing is both serial and parallel.
• Even the simplest mental activity requires
  coordination of processes in multiple areas of
  the brain.
• Such processing appears introspectively seamless.