Transcript Brain and Behavior

Brain and Behavior
Chapter 1
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?
Understanding by Analogy
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Metaphors have always been drawn from
discoveries in the physical world: fluid
mechanics, windmills, man as machine.
Discarded theories:
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Fluid in ventricles, flow of humors (Galen)
Body as machine explained by mechanics
Nerves as hollow tubes full of gas or fluid
Vibrating “aetherial Medium”
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.
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.
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.
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.
Organizational Principles
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Two hemispheres – left, right
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Each with four distinct lobes:
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Frontal – thinking, planning, control of movement
Parietal – tactile sensation, body image, space
Occipital – vision
Temporal – hearing, learning and memory, emotion
Each lobe has folds:
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Gyri (gyrus) – crests (flat areas)
Sulci (sulcus) – grooves (areas folded in)
Organization (Cont.)
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Contralateral control:
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The left hemisphere controls the right side of the
body.
The right hemisphere controls the left side of the
body.
Sensory information from one side of the body is
interpreted by the opposite brain hemisphere.
Some brain functions are localized to a
hemisphere.
Localization of Language
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Aphasia – a difficulty of language caused by
brain injury (such as with stroke).
Broca – described patients who can
understand language but not speak.
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Results from damage to Broca’s area.
Wernicke – described patients who can speak
but not understand language.
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Results from damage to Wernicke’s area.
A Language Circuit
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Wernicke’s areas and Broca’s areas are part of
a connected circuit for receiving and
producing language.
Wernicke predicted conduction aphasia – a
disorder produced by breaking the connection
between the two regions.
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Results in paraphasia – omitting and substituting
parts of speech. Also, inability to repeat phrases.
Brodmann Areas
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Different areas of the brain with different
functions have different kinds of neurons.
Brodmann mapped the areas based on the
kinds of cells found:
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Cytoarchitectonic method
52 functionally distinct areas identified by
number.
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.