lecture 1

Question 1

lesion studies
- how they do this more recently?
5 uncertainties involved in lesion studies

Answer 1

recently: microinjections, activate small ensembles of neurons, micro-ablation with electicity, cooling probes.
- 5 uncertainy
lesion of correct area; en passant axons; lesion of facilitating area; reduction of blood supply; lesion of inhibiting area

Question 2

electrical stimulation of NS

• revealed 3 aspects of CNS function
• few clinical examples
• 3 problems
• uncertanties in interpretation

Answer 2

• nerve conduction velocity; spinal cord reflexes; brain associating senses
• DBS, cochlear, vagus, phrenic nerve
• en passant, lesion facilitating or inhibiting area.
• e- stim doesnt activate natural firing patter. activate en passant or neuronal networks that facilitate/inhibit other networks. implanted electrodes are invasice.

Question 3

TMS
- quick mechanism
advantages
disadvantages

Answer 3

• strong magnetic field pulse, induce electrical current = activate or inhibit neurons and brain function
  + Non-invasice; test spine during surgery; stundy interaction of spinal cord and corticospinal commands
• spatial resolution is poor; low repitition rate; stimulates brain surface.

Question 4

recording electrical activity of large numbers of neurons. = EEG

• advantages
• disadvantages

Answer 4

non-invasive; detect normal and abnormal activity; high temporal resoltuion, diagnose epilepsy, tumors stroke.

• low spatieal resolution
• monitors surface activity

Question 5

recording small ensembles of neurons

• implants
• representation of area

Answer 5

• implant array is more stable

- array is more representative than single neuron

Question 6

recording single neurons in slices

• method:
• advantage
• disadvantage

Answer 6

• electrical/optical recording from neuron in brain slice
  (+): record identified neurons, net, or neural networks. visualize and patch clamp single neuron. high spatial and temporal; apply drugs, NT, blocker
  (-): invasive, damage surrounding tissue, abolish normal inputs/outputs

Question 7

fundamental discoveries- intracellular second messengers; minute quantity of drug causes change = major change in bodily function.
(+)
(-)

Answer 7

characterize neurons in neurotransmitter properties.
visualize neurons.
manipulate specific functions.
drug discover

may not reveal mechanism.
may affect many parts of CNS

Question 8

neurogenetics - how genes = neural function
mechanism: 
method
advantages
disadvantages

Answer 8

specific neuronal types turned on after neuron is born. specific genes turned on by transcription facts or factors/signals secretes
- specific genes knocked out. = developmental or behavioural change
(+): highly conserved from invertebrates to humans. genetic testing can confirm
(-): absence from birth = other CNS neurons take over function. behaviour - complex and variable.

Question 9

optogenetics: insert genes that sensitize neurons to light
method:
(+):
(-)

Answer 9

gene codes for production of membrane channels sensitive to specific wavelengths of light
\+: popln of specific types of neurons may be turned on or off. = sudden change in behaviour. clinical applications.
-: induced neuronal firing could be abnormal, sub-class of targeted neurons may have conflicting functions

Question 10

PET

• mechanism
• +
• -

Answer 10

activate neurons metabolize glucose.
FDG - radioactive glucose. taken in by active neuron, photon emission detected
+: noninvasice, detect deep brain activity, human research
-: isotope injection, low temporal & spatial, doesnt differentiate btw inhibitory & excitatory.

Question 11

fMRI
mechanism
method
BOLD
\+
-

Answer 11

brain areas with active neurons have higher blood flow.
- line up to magnetic field. relaxing back to orginical state detected.
Blood oxygenation level dependent (BOLD)
+: noninvasive, detects local blood flow, better temporal resolution
-: blood flow =/= neuronal activity. neurons not primarily responsible for function, no distinction btw excite/inhibit. thresholding can be misleading

Question 12

tensor diffusion MRI
-water
+
-

Answer 12

water along axons. allows white matter to be visualized
+: non-invasive, functional connectivity (w fmRI pair)
-: smae as fMRI, new technique

Question 13

fluorescence of active neurons
mechanism
method
\+
-

Answer 13

voltage and Ca fluctuate.
changes in reflectance of active neurons are detected through hole in skull - add sensitive dyes.
+: detect large area of brain. very good temporal, good spatial
-: invasive, surface layers only

Question 14

mathematical modeling - neurocomputation
method:
+
-

Answer 14

set up computer model w software.
+: experiments impossible on live animals. desvribe system in precise math terms. predictions of behaviour
-: difficult to mathematically model, difficult to see where are correct, take lots of computing time.