W6 - Techniques in Animals

Question 1

Do both optogenetics and chemogenetics have good spatial resolution?

Answer 1

Yes.

Question 2

Do both optogenetics and chemogenetics have good temporal resolution?

Answer 2

No, excellent for optogenetics but extremely arbitrary for chemogenetics

Question 3

How is it possible to activate different channelrhodopsins with the same optic fiber?

Answer 3

Shine light of different wavelengths.

Question 4

True or false: Chemogenetics regulates excitability to exogenous stimulation over hours

Answer 4

False: Chemogenetics regulates excitability to endogenous stimulation over hours

Question 5

What can be used to target genetic modifications with regional and cell-type specificity?

Answer 5

Viral expression with a specific promoter

Question 6

Is chemogenetics relying the insertion of transmembrane channels or the injection of ligands?

Answer 6

Both.
First, synthetic receptors derived from targeted mutagenesis of endogenous G-protein coupled receptor DNA, DREADDs (Designer Receptors Exclusively Activated by Designer Drugs), are selectively expressed in the neural regions of interest.
Then, their respective ligands are injected, activating the DREADDs.

Question 7

What is an important limitation of optogenetics?

Answer 7

Excitability is exogenously controlled, so it probably does not match the “natural” activity of of the neurobiological pathways modulated.

Question 8

What is GCaMP?

Answer 8

GCaMP is a modified green fluorescent protein that activates upon calcium binding

Question 9

Name two imaging techniques that can visualize activity of neurons in real-time.

Answer 9

Fibre photometry and 1P miniscope imaging.

Question 10

What is the main difference between fibre photometry and 1P miniscope imaging?

Answer 10

Fibre photometry: record activity on the population level.
1P miniscope imaging: can record activity on the single-cell level.

Question 11

What is the incentive of using an headfixed set up when doing imaging?

Answer 11

Reduces noise due to movements.

Question 12

What is the main advantage of 2P imaging?

Answer 12

Great depth resolution = provides good layer specificity.

Question 13

What is widefield imaging used for?

Answer 13

Activity across whole cortex, more useful for network study

Question 14

What is the advantage of coupling optogenetics with imaging methods?

Answer 14

Imaging methods can provide a read-out of “natural” activity, which then can be used to tuned optogenetic parameters and try to simulate “natural” activity as close as possible.

Question 15

True or false: all optical methods rely on fluorescence.

Answer 15

True.