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Chapter 14:
Cognitive Functions
Lateralization of Function
• Lateralization
Lateralization of Function
• The corpus callosum
– The anterior commissure.
– The hippocampal commissure.
– A few other small commissures.
Fig. 14-2, p. 418
Lateralization of Function
• The two hemispheres are not mirror images
of each other.
Lateralization of Function
• Each hemisphere of the brain gets input from
the opposite half of the visual world.
Fig. 14-3a, p. 419
Lateralization of Function
• Damage to the corpus callosum interferes
with the exchange of information between
hemispheres.
Lateralization of Function
• Split-brain people
Lateralization of Function
• Sperry (1974)
Lateralization of Function
• Immediately after surgery, each hemisphere
can only quickly and accurately respond to
information that reaches it directly.
– Smaller commissures allow a slower
response.
• The brain later learns use the smaller
connections:
• Difficulty integrating information between both
remains.
Lateralization of Function
• Right hemisphere damage
• Left hemisphere damage
Lateralization of Function
• right hemisphere
•
• left hemisphere
Lateralization of Function
• Some anatomical differences exist between
the hemispheres of the brain.
• Planum temporale
Fig. 14-9, p. 425
Lateralization of Function
• Damage to left hemisphere often results in
language deficiencies.
Lateralization of Function
• Being born with a condition where the corpus
callosum does not completely develop results
in extra development of the following:
– Anterior commissure
– Hippocampal commissure
Lateralization of Function
• The left hemisphere is dominant for speech in
95% of right-handed people.
• Left-handers
Lateralization of Function
• Recovery of language after damage to the
brain varies.
Lateralization of Function
• Rasmussen’s encephalopathy
Lateralization of Function
• Language recovery after brain damage
Evolution and Physiology of Language
• Human language is a complex form of
communication.
– Productivity
Evolution and Physiology of Language
• Human language is most likely a modification
of a behavior also found in other species.
• Chimpanzees
Evolution and Physiology of Language
• Bonobos or pygmy chimpanzees
Lateralization of Function
• Non-primates
Evolution and Physiology of Language
Studies of nonhuman language abilities
Evolution and Physiology of Language
•
•
Two categories of theories
1. “Language evolved as a by-product of
overall brain development.”
2. “Language evolved as an extra part of the
brain.”
Evolution and Physiology of Language
•
Problems associated with the “language as
a by-product of increased intelligence”
theory:
1. People with a full-size brain and normal
overall intelligence can show severe
language deficits.
2. People with impaired intelligence can
have normal language skills.
• Williams syndrome characterized by
metal retardation but skillful use of
language.
Fig. 14-14, p. 433
Evolution and Physiology of Language
• Evidence suggesting language evolved as an
extra brain module specialization includes:
– Language acquisition device
– Chomsky (1980)
Evolution and Physiology of Language
• Most researchers agree that humans have a
specially evolved “something” that enables
them to learn language easily.
Evolution and Physiology of Language
• Research suggests a critical period exists for
the learning of language.
Evolution and Physiology of Language
• Rare cases of children not exposed to
language indicates limited ability to learn
language later.
Evolution and Physiology of Language
• Most knowledge of brain mechanisms of
language come from the study of people with
brain damage:
– Broca’s area
– Aphasia
Evolution and Physiology of Language
• Broca’s aphasia/nonfluent aphasia
Fig. 14-15, p. 435
Evolution and Physiology of Language
• Wernicke’s area
• Wernicke’s aphasia
Table 14-1, p. 438
Evolution and Physiology of Language
• Dyslexia
Evolution and Physiology of Language
• Different kinds of dyslexics have different
reading problems.
• “Dysphonic dyslexics”
• “Dyseidetic dyslexics”
Evolution and Physiology of Language
• Most severe cases of “dyseidetic dyslexia”
result from brain damage that restricts the
field of vision.
Evolution and Physiology of Language
• One hypothesis to explain dyslexia
emphasizes a hearing impairment rather than
visual impairment.
Evolution and Physiology of Language
• Another hypothesis to explain dyslexia is
connecting vision to sound.
Evolution and Physiology of Language
• A final hypothesis relates dyslexia to
differences in attention.

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