Lecture 6: Central Olfactory Processing

Question 1

What do KCs of mushroom body exhibit?

Answer 1

broad excitation by PNs, but sparse spiking

Question 2

What is sparse coding in the olfactory system?

Answer 2

any odour activates only small % of neurons in the mushroom body

Question 3

Compare olfactory coding in the fly mushroom body to olfactory coding in the mammalian piriform cortex.

Answer 3

fly and vertebrate peripheral circuitry is similar
OSNs → glomeruli → PNs

single glomerulus projects to several downstream brain regions

Question 4

Are most odours complex blends?

Answer 4

yes, most odours are complex chemical blends that take on their own identity – elicit a single odour percept

two different blends that share components smell completely different

Question 5

Model for Odour Processing Between Mitral Cells and Piriform Cortex

Answer 5

very similar to PN > KC connections, but with more inhibition

Question 6

What is optogenetics?

Answer 6

activation or inhibition of neurons with light (and genetically-encoded light-gated channels)

Question 7

What is channelrhodopsin?

Answer 7

cation channel that responds to blue light

• depolarizes the neuron

Question 8

What is halorhodopsin?

Answer 8

anion (Cl-) channel that responds to yellow light
- hyperpolarizes the neuron
- suppresses firing

Question 9

What does activating subsets of cortical amygdala neurons in absence of odours lead to?

Answer 9

leads to innate behaviours
- negative response in negative area of CoA
- positive response in positive area of CoA