lecture 5- Olfactory and gustatory Flashcards
What is the difference between the labelled line code and a combinatorial code
labeled line- dedicated channel for each neuron
combinatorial- stimulus coded by multiple neurons, lots of different combinations
how many receptor types does a mature neuron express
1
describe info transfer in drosophila at neurons
olfactory receptor neurons
glomeruli
projection neurons (2nd order)
brain
describe info transfer in mammals at neurons
olfactory sensory neurons
glomeruli
mitral cells (2nd order)
brain
what is the purpose of local neurons/granule cells
very sensitive to all odours so make the responses very different
use lateral inhibition to do so
what is the purpose of the 2nd order neurons extending from the glomerulus to the brain
strengthens the weak stimulus
what does the first relay synapse do
transforms the odour code
what are the learned behaviour areas in the brain
piriform centre (human)
mushroom body (insect)
what are the innate behaviour areas of the brain
amygdala (human)
lateral horn (insect)
which experiment shows the innate areas of the brain
silencing certain brain areas and observing the effects
what are the key differences between innate and learning circuitry
innate- categorises
dense activity
has certain prefered odours
stereotyped to sense key behaviours
learning- discriminates
sparse activity
arbitrary odours
random connections
describe olfactory searching in bacteria
swim straight or turn due to flagella movement.
if things are getting better they will swim more
describe c. elegans olfactory searching
as odour increases, circuit is active so they swim
as odour decreases, circuit silent so they turn
describe mice olfactory searching
coordinate sniff cycle with how they move their head
this means signals are constantly changed so the brain responds better
describe drosophila olfactory searching
smell something good= fly upwind
lose odour= wait before turning around
when they reach the source= use other sensory cues to reach the target
Which tastes are related to G proteins
sweet
bitter
umami
which taste is related to proton channels
sour
which taste is related to ENaC channels
salty
describe the taste circuit in the brain
taste buds
solitary nucleus of brain
VPM of thalamus
Insula+ parietal cortex
describe lateral inhibition in the gustatory system
when you have sweet and bitter at the same time, the bitter sensory neuron activates a GABA interneuron to sweet sensory neurons to inhibit them
