Understanding physiology of motor system

1. Functions of Brain
Shittu LAJ

2. Psychology
Cognitive
Neuroscience
Computational Sciences /
Artificial intelligence
Neuroscience
Brain functions-scope and different subsets

3. Events that occurred in the 19th Century paved the
way for brain study
• Mind-brain identity evidence
- phrenology
- brain damaged patients
- Broca, Alzheimer, Wernicke
- Aggregate field view of the brain.
- Cellular Connectionism
• Darwin’s theory of evolution

4. Franz Joseph Gall (1757-1828)

5. Phrenology
• Gall proposed that discrete regions of the cerebral
cortex control specific functions.
• Brain does not act as a unitary organ but is divided into
at least 35 organs.
• Each “organ” corresponds to a specific mental faculty.
• Center for each mental function increased in size as a
result of use.
• As each center grew, it was thought to cause the
overlying skull to protrude.

6. Phrenology – Cont’d
• Creating patterns of bumps and ridges on the
skull.
• Thus, indicated regions of the brain, which were
most developed.
• Correlating personality with bumps – develop
an anatomical basis for describing character
traits.

7. Pierre Flourens
• Specific sites in brain are
not responsible for specific
behaviors.
• All regions participate in
every mental function.
• Injury to specific area would
affect all higher functions
equally.
• Aggregate field view of the
brain.

8. Views of Cortical Function
Setting the stage for Aphasia
Phrenology – the cortex is a mosaic of specific functions,
abstract mental attributes are located in & represented by
single, functionally specific cortical areas
Aggregate field – mental functions are represented
diffusely throughout the brain
Cellular Connectionism – individual neurons are the
signaling units of the brain; they are arranged in functional
groups & connect in a precise fashion

9. Pierre Paul Broca (1824-1880)
• 8 patients who understood
language but could not speak
• No problems with tongue, mouth
or vocal cords
• Utter isolated words but couldn’t
speak grammatically or in full
sentences, or write
• Lesion in posterior frontal lobe
(Broca’s Area)
• “We speak with the left
hemisphere” (‘nous parlons avec
l’hemisphere gauche’)

10. Carl Wernicke (1848-1905)
• Described a new type of aphasia
- impairment of comprehension
rather than execution (receptive
rather than expressive).
• Patient could speak but not
understand language.
• Lesions in posterior temporal
lobe.

11. Wernicke – Continue
• Language involves separate
motor & sensory programs, each
governed by separate cortical
regions
• Motor program: Broca’s area (near
motor area for mouth, tongue & vocal
cords)
• Sensory language interpretation
program: Wernicke’s area (near
auditory & association cortex)

12. Areas in the Cerebral Cortex Involved in
Language
Wernicke’s area – processes
auditory input for language &
important to the understanding of
speech.
Broca’s area – controls production
of speech. Lies near motor area
that controls mouth & tongue
movements.
Wernicke’s area communicates with
Broca’s area via the arcuate
fasciculus (lesions here produce
Disconnection Aphasia)
Wernicke’s Area
Broca’s Area Arcuate FasciculusArcuate Fasciculus

13. Specific Regions of the Cortex Involved in Language
(PET Scan)

14. Karl Lashley (1920’s) -
Last Attack on Localization of Function
• Severity of learning deficits in
rats depended on extent of
damage, not precise location.
• Equipotentiality (or Mass Action)
– particular brain areas are not
specialized, but all parts
participate in all functions
• Ideas were accepted for years

15. Lateralization of Function-introduction
• Lateralization of function refers to the concept
that each hemisphere of the brain is
specialized for different functions.
• Each hemispheres controls the contralateral
(opposite) side of the body.
– Example: skin receptors and muscles
mainly on the right side of the body.
– Each hemisphere sees the opposite side of
the world.

16. Cerebral Lateralization
• Cerebral dominance:
–Specialization of one hemisphere.
• Left hemisphere:
–More adept in language and analytical
abilities.
–Damage:
• Severe speech problems.
• Right hemisphere:
–Most adept at visuospatial tasks.
–Damage:
• Difficulty finding way around house.
Figure 8-14

17. Cerebral lateralization

18. Lateralization of Function: anatomical
variation
• 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.
• MRI studies indicate that the a big difference
in the ratio of left to right planum temporale is
related to increased language performance.

20. Lateralization of Function-language
areas
• 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.

21. Lateralization of Function: language
• Damage to left hemisphere often results in
language deficiencies.
• Left side seems to be specialized for language
from the very beginning in most people.
• Recovery of language after damage to the brain
varies.
• Age of the patient affects the extent of brain
recovery.
– Brain is more plastic at an early age.
• Right hemisphere reorganizes to serve some of
the left-hemisphere function.
.

22. Lateralization of Function
• Rasmussen’s encephalopathy is a rare condition
in which the immune system initially attacks the
glia and then the neurons of one hemispheres of
the brain.
– Usually begins in childhood or adole-scence.
• Treatment-Surgeons remove or disconnect the
damaged brain side.
• Language recovers slowly but substantially.
– Slow deterioration allows the other side of the
brain to compensate and reorganize.

23. Lateralization of Function-Axonal
connections
• The left and right hemisphere exchange information
primarily through a set of axons called the corpus
callosum.
• The corpus callosum allows each hemisphere of the
brain access to information from both sides.
• 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

26. Other axonal commissural
connections
• Other areas that exchange information in the
absence of corpus callosum include:
– The anterior commissure.
– The hippocampal commissure.
– A few other small commissures.
• Information crosses to the other hemisphere
with only a brief delay.

27. Lateralization of Function-axonal
connection
• 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 performance on some tasks that
differs from split-brain people.

28. Fig. 14-5, p. 422

29. Lateralization of Function-Epilepsy
• 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 have in the past cut the corpus
callosum to prevent the seizure from spreading to
the opposite side of the body.

30. Lateralization of Function-Split-brain
condition
• 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.

31. Lateralization of Function: spli-brain
• 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.

33. Lateralization of Function-axonal
connection
• 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 to use the other smaller
connections such as hippocampal and anterior
commissural fibres.
• However, difficulty in integrating information
between both remains.

34. Fig. 14-5, p. 422

37. Lateralization of Function-vision
• 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.

39. Lateralization of Function-vision and
auditory
• 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.

41. Lateralization of Function-Spatial
relationship and vision
• The right hemisphere is also better at
comprehending spatial relationships.
• In general, the left hemisphere seems to
focus more on visual details,
• While, the right hemisphere focuses more on
visual patterns.

42. Lateralization of Function-Emotion
• Right hemisphere is better at perceiving emotions.
• Damage to parts of the right hemisphere causes
difficulty perceiving other’s emotions,
• Aso include 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.

43. Lateralization of Function: Speech
• The left hemisphere is dominant for speech in
95% of right-handed people.
• Most left-handers have left-hemisphere or
mixed-dominance for speech.
– Few people have strong right hemisphere
dominance.

44. Evolution and Physiology of
Language-definition
• 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.
• Human language is most likely a modification
of a behavior also found in other species.

45. Evolution and Physiology of
Language-II
• 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.

46. Evolution and Physiology of
Language-comprehension
• Bonobos or pygmy chimpanzees show an
increased comprehension of human language:
– Understand more than they can produce.
– Use symbols and names to describe objects.
– Request items not seen.
– Use symbols to describe past events.
– Make original, creative requests.

47. Evolution and Physiology of
Language-spoken language
• Non-primates also display some aspects of
spoken language.
• Elephants imitate sounds they hear, including
the vocalizations of other elephants.
• Dolphins respond to gestures and sounds.
• The African gray parrot show a great ability
for imitating sounds and also using sounds
meaningfully.
– Example: Alex the gray parrot.

48. Evolution and Physiology of
Language-teaching
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.
• Illustrate the ambiguity of our concept of
language.
– Allows for more precise definition.

49. Evolution and Physiology of
Language- I.Q
• 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.

50. Fig. 14-14, p. 433

51. Evolution and Physiology of
Language-acquisition
• 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.

52. Evolution and Physiology of
Language-Learning
• Two categories of theories attempt to
explain the human ability to learn language
more easily than other species.
1. “Language evolved as a by-product of
overall brain development.”
2. “Language evolved as an extra part of the
brain.”

53. Evolution and Physiology of
Language-research
• 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.

54. Evolution and Physiology of
Language-learning
• Research suggests a critical period exists for
the learning of language.
• Learning of a second language differs as a
function of age:
– Children are better at learning
pronunciation and unfamiliar aspects of
grammar.
• No sharp cutoff exist for second language
learning.
– Adults learn a second-language vocabulary
better.

55. Evolution and Physiology of
Language-language deficits
• 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.

56. Evolution and Physiology of
Language-Brain damage conditions
• 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.

57. Evolution and Physiology of
Language-Broca`s asphasia
• Broca’s aphasia/nonfluent aphasia refers to
serious impairment in language production,
usually due to brain damage.
• Broca’s area thus seems to be critical for the
understanding of some, but not all, aspects of
grammar.
• Omission of most pronouns, prepositions,
conjunctions, auxiliary verbs, tense and number
endings during speech production.

58. 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.
– Sentence structure is complicated.
– Thus, people with Broca's aphasia have trouble
understanding the same kinds of words they omit
(prepositions and conjunctions).

59. Fig. 14-15, p. 435

60. Fig. 14-16, p. 436

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

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

63. Table 14-1, p. 438

64. Dyslexia
• Dyslexia is a specific impairment of reading in
a person with adequate vision and adequate
skills in other academic areas.
– More common in boys.
– Research suggests a genetic influence.

65. Dyslexia
• In some cases, dyslexia is associated with
mild abnormality in the structures of various
brain areas.
– More likely to have a bilateral symmetrical
cerebral cortex.
– Language–related areas in the right
hemisphere are larger in some.
– Weak connections exist among other
areas.

66. Dyslexia-hypothesis
• One hypothesis to explain dyslexia
emphasizes a hearing impairment rather than
visual impairment.
– Less than normal response to speech
sounds in the brain.
– Lack of ability to pay close attention to
sounds.

67. Dyslexia-hypothesis II
• Another hypothesis to explain dyslexia is
connecting vision to sound.
• Brain scans indicate that reading strongly
activates areas of the left temporal and
parietal cortex for most people.
– Areas are associated with connecting
visual and auditory information.
• Only weakly activated for people with
dyslexia.

68. Dyslexia-hypothesis III
• 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.

69. Kinds of dyslexia
• Different kinds of dyslexics have different reading
problems.
• “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.

70. Evolution and Physiology of
Language- dyseidetic dyslexia
• 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.

71. Fig. 14-17, p. 440

72. Attention
• Attention is a multi-dimensional process and
related to consciousness.
• Attention relates to increased brain activity in
the areas responsive to a stimulus.
• Stimuli destined to become conscious or
unconscious produce about the same brain
activity in the first 200-250 milliseconds.
• In the next few milliseconds, the brain
enhances activity for stimuli that become
conscious.

73. Attention
• Enhancement of activity can be due to
intensity of the stimulus, similarity to past
important stimuli, or other features of the
stimulus itself.
• Enhancement of activity can also be due to
shifting of attention.
• Research suggests that attention pertains
more to the enhancing of relevant activity
than inhibiting irrelevant activity.

74. INATTENTION/NEGLECT
• “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. Fig. 14-19, p. 444

77. Neglect-problem
• 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.

78. Attention-motivators
• 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. Fig. 14-20, p. 444

80. 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.

81. Attention-Deficit Hyperactivity
Disorder
• Attention-Deficit Hyperactivity Disorder
(ADHD) is characterized by the following:
– Attention deficits (distractibility).
– Hyperactivity (fidgetiness).
– Impulsiveness.
– Mood swings.
– Short temper.
– High sensitivity to stress.
– Impaired ability to make and follow plans.

82. Attention-Deficit Hyperactivity
Disorder-prevalence
• ADHD affects social behavior and school
performance.
• Some have occupational problems and
antisocial behaviors in adulthood.
• Estimates range from 3%-10% of children
• Twice or three times as likely in males.
• Research is complicated by the ability to
make reliable diagnoses.

83. Attention tasks
• Three example of tasks which people with
ADHD differ:
1. “The choice delay task” - more likely than
others to choose a smaller but quicker
reward (impulsiveness).
2. “The stop signal task” - difficulty inhibiting
behaviors.
3. “The attentional blink task” - indicates
trouble controlling attention and difficulty
shifting it when needed.

84. Attention deficits-causes
• Twin studies suggest fairly high heritability
(Thapar et al., 2003).
– Several genes have been identified which
influence performance on tests of attention.
• ADHD probably depends on multiple genes
as well as environmental influences.
• Probability of ADHD is elevated among
children of women who smoked cigarettes
during pregnancy.

85. Attention
• Structural brain differences include a smaller
than average prefrontal cortex and
cerebellum.
– Cerebellar dysfunction is known to be
associated with difficulty switching
attention.
• Structural differences in the brain are small
and inconsistent between cases.
– Brain scans do not provide reliable results
for diagnoses.

86. Attention-treatment
• The most common treatment for ADHD is
stimulant drugs or amphetamines.
– Example: methylphenidate/Ritalin.
• Stimulant drugs increase attentiveness,
improve school performance and social
relationships, and decrease impulsiveness.
• Also improve scores on laboratory tests, such
as the “stop signal task”.
• Justifying the benefits derived from taking the
drugs is a complex and controversial issue.

87. Attention
• Amphetamines and methylphenidate increase
the availability of dopamine to the
postsynaptic receptors.
• Maximum benefit occurs 1 hour after
ingestion and benefits last for a few hours.
• Several studies have found that stimulant
drugs enhance certain aspects of learning
and attention for all people, not just those
with ADHD.

88. Attention
• Behavioral techniques are available as
supplements or substitutes for stimulant
drugs:
– Reduce distractions.
– Use lists, calendars, and other
organizational techniques.
– Practice strategies to pace yourself.
– Learn to relax; tension and stress can
magnify attention deficits.