Lecture 7

Question 1

Figure 5.7: Brain of a human cadaver.
(a) Dorsal view looking down on the top of the brain. Note that the deep longitudinal fissure divides the cerebrum into the right and left cerebral hemispheres. (b) Sagittal view of the right half of the brain. All major brain regions are visible from this midline interior view. The corpus callosum serves as a neural bridge between the two cerebral hemispheres.

Question 2

Question 3

Cerebral cortex organization

Answer 3

Highly developed, 80% of total brain weight
2 hemispheres connected by corpus callosum, 300 mio axons
Outer shell grey matter, central core white matter
Tracts and nuclei –> integration between different regions, and initiation of neural output at synapses

Question 4

Question 5

Question 6

Question 7

4 lobes, 4 functional areas

Answer 7

• No part functions in isolation
  Occipital lobes
  Temporal lobes
  Parietal lobes
  Frontal lobes

Question 8

Occipital lobes:

Answer 8

posteriorly, initial processing of visual input

Question 9

Temporal lobes:

Answer 9

laterally, auditory perception

Question 10

Parietal and frontal lobes separated by

Answer 10

the central sulcus

Question 11

Parietal lobes:

Answer 11

receiving and processing sensory input

Question 12

Frontal lobes:

Answer 12

1. voluntary motor activity
2. speaking ability
3. elaboration of thought

Question 13

Question 14

Figure 5.8: Cortical lobes.
Each half of the cerebral cortex is divided into the occipital, temporal, parietal, and frontal lobes, as depicted in this lateral view of the brain.

Question 15

Figure 5.9: Functional areas of the cerebral cortex.
(a) Various regions of the cerebral cortex are primarily responsible for various aspects of neural processing, as indicated in this lateral view of the brain. (b) Different areas of the brain “light up” on positron-emission tomography (PET) scans as a person performs different tasks. PET scans detect the magnitude of blood flow in various regions of the brain. Because more blood flows into a particular region of the brain when it is more active, neuroscientists can use PET scans to “take pictures” of the brain at work on various tasks.

Question 16

Figure 5.10: Somatotopic maps of the somatosensory cortex and primary motor cortex.
(a) Top view of cerebral hemispheres showing somatosensory cortex and primary motor cortex. (b) Sensory homunculus showing the distribution of sensory input to the somatosensory cortex from different parts of the body. The distorted graphic representation of the body parts indicates the relative proportion of the somatosensory cortex devoted to reception of sensory input from each area. (c) Motor homunculus showing the distribution of motor output from the primary motor cortex to different parts of the body. The distorted graphic representation of the body parts indicates the relative proportion of the primary motor cortex devoted to controlling skeletal muscles in each area.

Question 17

Parietal lobes:
What type of processing occurs here?

Answer 17

• somatosensory processing
  Somatosensory cortex: somesthetic (touch, pressure, heat, cold, pain etc) and proprioceptive (position of body) input

Projected into specific region: sensory homunculus: relative proportion of cortex dedicated to specific area

Question 18

Figure 5.10: Somatotopic maps of the somatosensory cortex and primary motor cortex.
(a) Top view of cerebral hemispheres showing somatosensory cortex and primary motor cortex. (b) Sensory homunculus showing the distribution of sensory input to the somatosensory cortex from different parts of the body. The distorted graphic representation of the body parts indicates the relative proportion of the somatosensory cortex devoted to reception of sensory input from each area. (c) Motor homunculus showing the distribution of motor output from the primary motor cortex to different parts of the body. The distorted graphic representation of the body parts indicates the relative proportion of the primary motor cortex devoted to controlling skeletal muscles in each area.

Question 19

Question 20

Somatosensory cortex

Answer 20

Receives input from opposite side
Damage to eg right cortex: left sensory deficit

Thalamus: awareness for sensation without localization and intensity
Somatosensory cortex: source and level of intensity, spatial discrimination –> shape etc

Sensory input projected to higher sensory areas for further analysis (concomitantly texture, shape, position etc)

Question 21

Sensation processed into perception

Answer 21

Question 22

Primary motorcortex

Answer 22

Voluntary control over skeletal muscle movement (crossing at pyramids)
Motor homunculus: representation ~ precision and complexity of motor skills
Motorunit: 1 motorneuron with its muscle fibers (10-1000 muscle fibers, eye vs back)
However: does not initiate itself voluntary movement (supplementary motor area: complex patterns like opening/closing hand, premotor cortex: orienting body toward specific target, and posterior parietal cortex: movement in spatial context)

Question 23

Cerebral Cortex has three areas:

Answer 23

Supplementary motor area
Premotor cortex
Posterior parietal cortex

Question 24

Supplementary motor area

Answer 24

Plays preparatory role in programming complex sequences of movement

Complex patterns of movement:
- Opening or closing hand

Question 25

Premotor cortex

Answer 25

Important in orienting the body and arms toward a specific target

Question 26

Posterior parietal cortex

Answer 26

• Lies posterior to primary somatosensory cortex
• When either of these areas is damaged, one can’t process complex sensory information to accomplish purposeful movement in spatial context
  ie: manipulating eating utensils

Question 27

Figure 5.9: Functional areas of the cerebral cortex.
(a) Various regions of the cerebral cortex are primarily responsible for various aspects of neural processing, as indicated in this lateral view of the brain. (b) Different areas of the brain “light up” on positron-emission tomography (PET) scans as a person performs different tasks. PET scans detect the magnitude of blood flow in various regions of the brain. Because more blood flows into a particular region of the brain when it is more active, neuroscientists can use PET scans to “take pictures” of the brain at work on various tasks.

Question 28

Somatotopic maps

Answer 28

Not static but dynamic
Precise distribution unique and individual
Genetic, developmental and use-specific
String instrument musician, sms/touch screens

Question 29

Language

Answer 29

In vast majority of people: areas for language in left hemisphere (can be transferred in age <2 if damage occurs)
Written/spoken/heard words
–> symbolism –> ideas/concepts

Involves: speaking ability (expression) and comprehension (understanding meaning)
Broca’s area vs Wernicke’s area

Question 30

Broca’s area VS Wernicke’s area

Answer 30

motorcontrol vs comprehension, choice, sequence

Question 31

Wernicke’s area receives input from:

Answer 31

primary visual cortex, primary auditory cortex

Question 32

Figure 5.11: Cortical pathway for speaking a word seen or heard.
The arrows and numbered steps describe the pathway used to speak about something seen or heard. Similarly, appropriate muscles of the hand can be commanded to write the desired words.

Question 33

Language disorders

Answer 33

Damage Broca’s area: understand spoken and written word, but cannot articulate words

Damage Wernicke’s area: cannot understand spoken or written word, but can speak fluently (without sense)
Damage=aphasias (mainly through stroke)

Speech impediments: weakness/incoordination of vocal apparatus
Dyslexia: inappropriate interpretation of words

Question 34

Association cortex (“silent” areas)

Answer 34

Higher functions: processing in 3 association areas
Prefrontal association cortex
Parietal-temporal-occipital association cortex
Limbic association cortex

Question 35

Prefrontal association cortex:

Answer 35

planning, decision-making, thinking, creativity, personality traits

Question 36

Parietal-temporal-occipital association cortex:

Answer 36

pools somatic, auditory and visual sensations (to get the complete picture)

Question 37

Limbic association cortex:

Answer 37

motivation, emotion, memory

Question 38

Figure 5.12: Linking of various regions of the cortex.
For simplicity, a number of interconnections have been omitted.

Question 39

Cerebral Hemispheres

Answer 39

2 hemispheres complement each other
Left cerebral hemisphere dominance - Associated with “thinkers”
Right hemispheric skills dominate in “creators”

Question 40

Left cerebral hemisphere

Answer 40

• Excels in logical, analytic, sequential, and verbal tasks
  > Math, language forms, philosophy
• Tends to process information in fine-detail way

Question 41

Right cerebral hemisphere

Answer 41

• Excels in nonlanguage skills
  > Spatial perception and artistic and musical talents
• Views the world in a big-picture, holistic way

Question 42

Question 43