1. Chapter 14: Cognitive Functions

2. Lateralization of Function
Lateralization of function refers to the idea that each hemisphere of the brain is specialized for different functions.
Each hemispheres is connected to the contralateral (opposite) side of the body.
Example: skin receptors and muscles on the right side of the body are connected to the left hemisphere
Each hemisphere processes visual information from the opposite side of the world.

3. Lateralization of Function
The left and right hemisphere exchange information primarily through a set of axons called the corpus callosum.
Other areas that exchange information include:
The anterior commissure.
The hippocampal commissure.
A few other small commissures.
Information crosses to the other hemisphere with only a brief delay.

5. Lateralization of Function
The two hemispheres are not mirror images of each other.
Division of labor between the two hemispheres is known as lateralization.
In most humans the left side is specialized for language.
The corpus callosum allows each hemisphere of the brain access to information from both sides.

6. Lateralization of Function
Each hemisphere of the brain gets input from the opposite half of the visual world.
The visual field is what is visible at any moment.
Light from the right half of the visual field shines into the left half of both retinas.
Light from the left visual field shines onto the right half of both retinas.

7. Lateralization of Function
The left half of each retina connects to the left hemisphere.
The right half of each retina connects to the right hemisphere.
Half of the axons from each eye cross to the opposite side of the brain at the optic chiasm.
The auditory system is arranged differently in that each ear sends the information to both sides of the brain.

9. Lateralization of Function
Damage to the corpus callosum interferes with the exchange of information between hemispheres.
Epilepsy is a condition characterized by repeated episodes of excessive synchronized neural activity.
Mainly due to decreased release of the inhibitory neurotransmitter GABA.
Physicians once cut the corpus callosum to prevent the seizure from spreading to the opposite side of the body.

10. Lateralization of Function
People who have undergone surgery to the corpus callosum are referred to as split-brain people.
Spit brain people maintain normal intellect and motivation but they tend to:
Use hands independently in a way others cannot.
Respond differently to stimuli presented to only one side of the body.

12. Lateralization of Function
Sperry (1974) revealed subtle behavioral differences for spilt brain people.
Because the left side of the brain is dominant for language in most people, most split brain people:
Have difficulty naming objects briefly viewed in the left visual field.
A small amount of information can still be transferred via several smaller commissures.

14. 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.

16. Lateralization of Function
Right hemisphere is better at perceiving emotions.
Damage to parts of the right hemisphere causes difficulty perceiving other’s emotions, failure to understand humor and sarcasm, and a monotone voice.
Left hemisphere damage increases ability to accurately judge emotion.
Associated with decreased interference from the left hemispheres.

18. Lateralization of Function
The right hemisphere is also better at comprehending spatial relationships.
In general, the left hemisphere seems to focus more on visual details, and the right hemisphere focuses more on visual patterns.

20. Lateralization of Function
Some anatomical differences exist between the hemispheres of the brain.
The planum temporale is an area of the temporal cortex that is larger in the left hemisphere in 65% of people.
Difference are slightly greater for people who are strongly right handed.

22. MRI studies indicate that the a big difference in the ratio of left to right planum temporale is related to increased language performance.
Damage to left hemisphere often results in language deficiencies.
Left side seems to be specialized for language from the very beginning in most people.

23. Lateralization of Function
The corpus callosum matures gradually through the first 5 to 10 years.
Thus, young children have difficulty comparing information from the left and right hand.

24. 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 - connects the anterior parts of the cerebral cortex.
Hippocampal commissure - connects the left and right hippocampus.
Allows better performance on some tasks compared split-brain people.

25. Lateralization of Function
The left hemisphere is dominant for speech in 95% of right-handed people.
Left-handers are more variable
Most left-handers have left-hemisphere
Some have right-hemisphere or mixed-dominance for speech.
also reversed for spatial perception
Research on hemisphere dominance should not be over-emphasized
Behaviors require use of both

26. Evolution and Physiology of Language
Human language is a complex form of communication.
Compared to other species, human language has high productivity.
Productivity - the ability to produce new signals to represent new ideas.

27. Evolution and Physiology of Language
Human language is most likely a modification of a behavior also found in other species.
Chimpanzees use language but it differs from humans:
Seldom use symbols in new original combinations.
Use of symbols lacks productivity.
Use of symbols is primarily used to request and not describe.
Production of requests is better than understanding other’s requests.

29. Evolution and Physiology of Language
Bonobos or pygmy chimpanzees resemble humans more than other primates.
show better comprehension of human language:
Understand more than they can produce.
Use symbols/names to describe objects.
Request items not seen.
Use symbols to describe past events.
Make original, creative requests.

31. Evolution and Physiology of Language
Explanations include:
Perhaps bonobos have greater language potential than other chimpanzees
Language training began early with subjects
Subjects were also allowed to learn through observation and imitation in addition to formal training

32. Lateralization of Function
Non-primates also display some aspects of spoken language.
The African gray parrot show a great ability for imitating sounds and also using sounds meaningfully.
Example: Alex the gray parrot.

35. Evolution and Physiology of Language
Studies of nonhuman language abilities:
Give insights to how best to teach language to those who do not learn it easily.
Examples: Brain damaged people or children with autism.
Indicate that language evolved from a precursor found in other species
Illustrate the ambiguity of our concept of language.
Creates demand for more precise definition.

36. Evolution and Physiology of Language
Two categories of theories attempt to explain the human ability to learn language more easily than other species.
“Language evolved as a by-product of overall brain development.”
“Language evolved as a brain specialization.”

37. Evolution and Physiology of Language
Problems associated with the “language as a by-product of increased intelligence” theory:
People with a full-size brain and normal overall intelligence can show severe language deficits.
People with impaired intelligence can have normal language skills.
Williams syndrome characterized by metal retardation but skillful use of language.

39. Evolution and Physiology of Language
Evidence suggesting language evolved as an extra brain module specialization includes:
Language acquisition device is a built in mechanism for acquiring language.
Evidence comes from the ease at which most children develop language.
Chomsky (1980) further suggests the poverty of stimulus argument: children do not hear many examples of some of the grammatical structures they acquire.

40. Evolution and Physiology of Language
Most researchers agree that humans have a specially evolved “something” that enables them to learn language easily.
Certain brain areas are indeed necessary for language.
But same areas are also necessary for other tasks (memory and music perception).
Exactly how humans evolved language is unknown but is perhaps due to the pressure for social interaction.

41. Evolution and Physiology of Language
Research suggests a sensitive period exists for the learning of language.
No early language exposure can lead to permanent impairment
Learning of a second language differs as a function of age:
Children excel at learning pronunciation and unfamiliar aspects of grammar.
No sharp cutoff exist for second language learning.
Earlier the better

42. Evolution and Physiology of Language
Rare cases of children not exposed to language indicates limited ability to learn language later.
Deaf children unable to learn spoken language and not given the opportunity to learn sign language while young reveals:
Little development of skill at any language later.
Early exposure to some language increases ability to learn another language later.

43. Evolution and Physiology of Language
Most knowledge of brain mechanisms of language come from the study of people with brain damage:
Broca’s area is a part of the frontal lobe of the left cerebral cortex near the motor cortex.
Damage results in some language disability.
Aphasia refers to a condition in which there is severe language impairment.

45. Evolution and Physiology of Language
Broca’s aphasia/nonfluent aphasia refers to serious impairment in language production, usually due to brain damage.
Also have comprehension deficits when sentence structure is complex
Omission of most pronouns, prepositions, conjunctions, auxiliary verbs, tense and number endings during speech production.
Difficulty understanding the same kinds of words they omit (prepositions and conjunctions).

46. Evolution and Physiology of Language
Broca’s aphasia is usually accompanied by comprehension deficits when:
The sentence meaning depends on prepositions, word endings or unusual word order.
Broca’s area thus seems to be critical for the understanding of some, but not all, aspects of grammar.

48. Evolution and Physiology of Language
Wernicke’s area is an area of the brain located near the auditory part of the cerebral cortex.
Wernicke’s/ fluent aphasia is characterized by impaired language comprehension and the impaired ability to remember the names of objects
Sometimes called “fluent aphasia” because the person can still speak smoothly.
Recognition of items is often not impaired; ability to find word is impaired.

49. Evolution and Physiology of Language
Typical characteristics of Wernicke’s aphasia include:
Articulate speech / fluent speech except with pauses to find the right word.
Difficulty finding the right word - anomia refers to the difficulty recalling the name of objects.
Poor language comprehension - difficulty understanding spoken and written speech (especially nouns and verbs).

50. Broca’s Aphasia and Wernicke’s Aphasia
Type
Pronunciation
Content of Speech
Comprehension
Broca’s aphasia
Poor
Mostly nouns and verbs, omits prepositions and other grammatical connectives
Impaired if the meaning depends on complex grammar
Wernicke’s aphasia
Unimpaired
Grammatical but often nonsensical; has trouble finding the right word, especially names of objects
Seriously impaired

51. Evolution and Physiology of Language
Bilingual speakers process multiple languages in the same areas of the brain.
Languages are not kept in separate areas
Language areas in temporal and frontal cortex grow thicker than average in those that are fluent in two languages from early childhood.

52. Evolution and Physiology of Language
Bilinguals (con’t)
Those that are more adept at one language, show greater brain activity for the second language.
Switching between languages activates the frontal cortex, temporal cortex and basal ganglia
Brain must work hard to prime one set of words while inhibiting another

53. Evolution and Physiology of Language
No other species develops music to the same extent
Has many parallels to language
Broca’s area strongly activated
Suggest we use language areas of the brain when we compose music.

54. Evolution and Physiology of Language
Dyslexia is a specific impairment of reading in a person with adequate vision and adequate skills in other academic areas.
More common in boys.
Linked to at least four genes that produce deficits in cognition or hearing

55. Evolution and Physiology of Language
In some cases, dyslexia is associated with mild abnormality in various brain structures.
More likely to have a bilateral symmetrical cerebral cortex.
Less arousal in the parietal and temporal cortex while reading

56. Evolution and Physiology of Language
Research and literature is often confusing:
Different people have different types of reading problems
Small number have impaired control of eye movements
Most have auditory problems

57. Evolution and Physiology of Language
Some researchers distinguish:
“Dysphonic dyslexics” have trouble sounding out words.
Attempt to remember them as a whole.
“Dyseidetic dyslexics” fail to recognize a word as a whole.
Read slowly and have particular trouble with irregularly spelled words.

58. Evolution and Physiology of Language
Most severe cases of “dyseidetic dyslexia” result from brain damage that restricts the field of vision.
Characterized by the following:
only seeing one letter a time
short eye movements
very slow reading
difficulty with long words

59. Evolution and Physiology of Language
Most people with dyslexia have auditory problems
Brain scans show less than normal response to speech sounds
Trouble detecting the temporal order of sounds
But not just impaired hearing
Perhaps connecting vision to sound or paying attention to different aspects of sound.

60. Evolution and Physiology of Language
A final hypothesis relates dyslexia to differences in attention.
Reading requires the shifting of attention.
People with dyslexia do not shift their attention in the same way.
Effective treatment may be for dyslexics to focus on one word at a time.

62. Attention Conscious is a difficult concept to define
Researchers use the operational definition:
“If a person reports the presence of one stimulus but can not report the presence of the second, he or she was conscious of the first and not the second”
Almost synonymous with attention

63. Attention
Psychologist have noted the phenomenon of inattentional blindness:
Of all that your eyes see, you are conscious of only those few things to which you direct your attention
While observing a complex scene, you will not notice if something changes slowly

64. Attention
Exploration of which types of brain activity are conscious are to present a single stimulus and differentiate brain activity between the occasions with and without consciousness.
Stimulus initially activates primary visual cortex in both conditions
More strongly activated in the conscious condition and activity spreads to several additional areas.

65. Attention Consciousness depends upon the amount of brain activity.
Increasing attention to a stimulus also increases brain activity.
A conscious stimulus also induces a precise synchrony of responses in neurons over various areas of the brain

66. Attention
Binocular rivalry are slow and gradual shifts of the eye sweeping form one side to another.
Stimulus seen by each eye evokes a particular pattern of brain responses.
Research shows that switching to each stimulus is accompanied by a shift in a pattern of activity over a large portion of the brain.

70. Attention Research suggest consciousness is a threshold phenomenon
If a stimulus activates enough neurons to a sufficient extent, the activity reverberates, magnifies, and extends over much of the brain.
If a stimulus fails to reach that level, the pattern fades away.

71. Attention
Meaningful stimuli capture our attention faster than meaningless stimuli.
Somehow brain has to know that it was meaningful before it became conscious.
Indicates:
Much of brain activity is unconscious
Subtle effects on behavior by unconscious stimuli can exist.

73. Attention Delays exist between an event and our consciousness of it.
Phi phenomenon occurs when we see a dot in one position alternating with a similar dot nearby
Appears as if the dot is moving back and forth.
Reveals that perceptions of events after can also alter changes in event that occurred before.

74. Attention “Inattention” or “neglect” is the opposite of attention.
Spatial neglect is a tendency to ignore the left side of the body and its surroundings or the left side of objects.
Often associated with damage to the right hemisphere of the brain.

75. Attention
Exact location of the damage to the right hemisphere can affect the details of what the person neglects.
Damage to the inferior part of the right parietal cortex leads to the neglect of everything to the left of their own body.
Damage to the superior temporal cortex neglect the left side of objects, regardless of location.

76. Attention
Problems of neglect are associated with attention and not sensation.
Someone with neglect can see an entire letter enough to say what it is.
The same person ignores the left half when asked to cross out all the letters that compose a word.

77. Attention
Several procedures can increase attention to the neglected side:
telling the person to pay attention to the left side.
telling the person to look left while feeling an object with the left hand or hearing a sound from the left side.
A touch stimulus briefly increases attention to one side of the body or the other.
Crossing of the hands in front of the body also decreases neglect to the left side.

79. Attention
Many patients with spatial neglect also have deficits with spatial working memory and with shifting attention, even when location is irrelevant.
Thus, problems associated with neglect extend to many aspect of attention rather than simply the left-right dimension.