Neuro 44: Cerebral Hemispheres

Question 1

2 methods of functional brain imaging

Answer 1

1. PET
2. fMRI
   - both based on the fat that neuronal activity causes an increase in metabolic demands and a localized increase in cerebral blood flow
   - both require image averaging and statistical comparisons b/c the brain is always active!

Question 2

PET

Answer 2

• = positron emission tomography

- meausres the changes in cerebral blood flow or metabolism via short lived isotopes that are injected

Question 3

fMRI

Answer 3

• = functional magnetic resonance imaging

- measures changes in cerebral blood flow based on how Hb/O2 affects protons

Question 4

Two types of cortical areas

Answer 4

1. primary areas - ex. sensory and motor

2. association areas - assist nearby primary areas, help modulate and integrate info

Question 5

Functional variability in the cortex

Answer 5

• the pattern of cortical folding differs from one brain to another
• neurosurgeons use electrophysiology to map the cortex

Question 6

Association fibers

Answer 6

• aid in communication by interconnecting cortical areas in one hemisphere
• short fibers = interconnect adjacent gyri –> important for communication in one area
• long fibers = interconnect more distant areas –> important for distance communication
• cant see these tracts grossly, but can use some MRI technology to map them out
• conditions that damage the white matter of hemispheres can interrupt the association fibers and cause cognitive deficits (ex. MS)

Question 7

Projection fibers

Answer 7

• play a role in communication
• these are the input and output fibers of the cortex that go to other areas of the CNS
• damage to these fibers = mjr sensory or motor deficits

Question 8

Commissural fibers

Answer 8

• play a role in communication
• interconnect the cortex of the right and left hemispheres
• developmental agenesis or damage to the corpus callosum does not cause any obvious functional deficits!

Question 9

3 cerebral commissures

Answer 9

1. corpus callosum
2. anterior commissure
3. hippocampal commisure

Question 10

Neocortex

Answer 10

• has 6 lyrs
• organization of these lyrs is essential for info processing
• dev probs can cause siezures, mental retardation, or cognitive deficits

Question 11

Two mjr classes of cortical neurons

Answer 11

1. long axon projection neurons = pyramidal neuron
2. short axon interneurons = golgi neurons
   - both allow for integration of info across the lyrs
   - the brain changes from moment to moment, the dendrites expand and retract in response to activity –> connections are made and broken