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.