Chapter 14: Cognitive Functions. Lateralization of Function Lateralization.

Chapter 14:Cognitive Functions

Lateralization of Function

• Lateralization


• The corpus callosum

– The anterior commissure.– The hippocampal commissure.– A few other small commissures.

Fig. 14-2, p. 418


• The two hemispheres are not mirror images of each other.


• Each hemisphere of the brain gets input from the opposite half of the visual world.

Fig. 14-3a, p. 419


• Damage to the corpus callosum interferes with the exchange of information between hemispheres.


• Split-brain people


• Sperry (1974)


• 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.


• Right hemisphere damage

• Left hemisphere damage


• right hemisphere•

• left hemisphere


• Some anatomical differences exist between the hemispheres of the brain.

• Planum temporale

Fig. 14-9, p. 425


• Damage to left hemisphere often results in language deficiencies.


• Being born with a condition where the corpus callosum does not completely develop results in extra development of the following:– Anterior commissure

– Hippocampal commissure


• The left hemisphere is dominant for speech in 95% of right-handed people.

• Left-handers


• Recovery of language after damage to the brain varies.


• Rasmussen’s encephalopathy


• Language recovery after brain damage

Evolution and Physiology of Language

• Human language is a complex form of communication.

– Productivity


• Human language is most likely a modification of a behavior also found in other species.

• Chimpanzees


• Bonobos or pygmy chimpanzees


• Non-primates


Studies of nonhuman language abilities


• 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.”


• 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


• Evidence suggesting language evolved as an extra brain module specialization includes:– Language acquisition device

– Chomsky (1980)


• Most researchers agree that humans have a specially evolved “something” that enables them to learn language easily.


• Research suggests a critical period exists for the learning of language.


• Rare cases of children not exposed to language indicates limited ability to learn language later.


• Most knowledge of brain mechanisms of language come from the study of people with brain damage:– Broca’s area

– Aphasia


• Broca’s aphasia/nonfluent aphasia

Fig. 14-15, p. 435


• Wernicke’s area

• Wernicke’s aphasia

Table 14-1, p. 438


• Dyslexia


• Different kinds of dyslexics have different reading problems.

• “Dysphonic dyslexics”

• “Dyseidetic dyslexics”


• Most severe cases of “dyseidetic dyslexia” result from brain damage that restricts the field of vision.


• One hypothesis to explain dyslexia emphasizes a hearing impairment rather than visual impairment.


• Another hypothesis to explain dyslexia is connecting vision to sound.


• A final hypothesis relates dyslexia to differences in attention.

Chapter 14: Cognitive Functions. Lateralization of Function Lateralization.

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Transcript of Chapter 14: Cognitive Functions. Lateralization of Function Lateralization.