Transcript September 27

Early Ideas about Brain
and Behavior
Mind, Brain and Behavior
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Neuroscientists want to unify the science of
the mind with the science of the brain.
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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?
Where Does Mind Reside?
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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:
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Cerebrum vs cerebellum
Ventricles do the work
19th Century Views
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By the 1800’s, 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.
Understanding by Analogy
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Metaphors have always been drawn from
discoveries in the physical world: fluid
mechanics, windmills, man as machine.
Modern analogies:
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Mind as switchboard
Mind as computer
Discarded Theories
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Fluid in ventricles, flow of humors
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Body as machine explained by mechanics
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Galen
Nerves as hollow tubes full of gas or fluid
Descartes
Nerves as “wires”
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Galvani, du Bois-Reymond, Muller, Helmholtz
The Discovery of the Neuron
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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.
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Neurons are a network of separate (discrete) cells
that communicate.
Galvani showed that the signaling is electric.
Nissl Stain
Golgi Stain
Localization vs Distribution
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Are specific functions carried out in specific
regions of the brain?
Are functions an emergent property of brain
activity as a whole?
Today’s neuroscience still debates this.
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The answers appear somewhere between the two
extremes.
Two Alternative Views
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Cellular connectionism:
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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:
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All regions of the brain participate in all mental
functions.
Mind is NOT completely biological
The Localization Debate
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Gall – the brain consists of 35+ organs
corresponding to mental faculties.
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Observable through bumps on the head.
Phrenology – anatomical basis for personology
Flourens – “…all perceptions, all volitions
occupy the same seat…”
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Aggregate field view
A reaction against strict materialism (mind not
completely biological).
The Discovery of Localization
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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
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Each function is subserved by more than one
neural pathway.
When one pathway is damaged, others may
compensate, making localization harder to see.
Support for the Field View
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Lashley found that the greater the lesions, the
greater the impairment in functioning.
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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.
The Current View
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Functions consist of multiple processes that
occur in specific areas of the brain.
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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.
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Such processing appears introspectively seamless.