week 10 - smell Flashcards
What type of stimuli does the vomeronasal organ respond to?
pheromones
phermones
- chemicals detected by VNO
- substance produced by animals/human
What occurred when the VNO was removed from male rats?
- loss of normal sexual behavior
- attempts to mate with males and females
- unable to locate females based on odor
Singh and Bronstad
- showed a relationship between men’s rating of women’s body odors and women’s menstrual cycle
- men preferred scent of women going through ovulation
anosmia
lack the ability to smell
specific anosmia
inability to smell specific chemicals
What procedures have researchers used to measure the detection threshold?
- yes/no procedure
- forced-choice procedure
yes/no procedure
- particpants are given trials with odors along with “blank trials”
- can they smell trial? respond with yes or no
forced-choice procedure
- two trials given (one with odor and one without)
- participant indicates which smells the strongest
What makes humans different from rats and dogs when it comes to odor sensitivity?
individual receptors are equally sensitive but the difference lies in the number of receptors
difference threshold
smallest difference in concentration that can be detected between two samples
recognitions threshold
concentration needed to determine quality of an odorant
Why do researchers have a hard time mapping perceptual experience onto physical attributes of odorants?
- there is no specific language for odor quality
- some molecules can have a similar structure but smell different or have different structures and smell the same
olfactory mucosa
- located on top of nasal cavity
- contains receptors
- odorants are carried along the mucosa coming in contact with the olfactory receptor neurons
What is the pathway of odor information to the glomeruli?
odor information is converged from multiple receptor neurons (same type) and travel through axons in the ethnoid bone and are brought to the glomeruli
Malnic experiment (combinatorial code for odor)
- found that odorants are coded by patterns of activation of olfactory receptors called recognition profiles through calcium imaging
- displayed the amount of receptors used for an odorant as well as their intensities
What type of coding does Malnic’s experiment showcase?
odorant recognition profiles of olfactory mucosa are reminiscent of sparse coding
What occurs when olfactory receptors are damaged?
lose the ability to smell
What type of techniques are used to show how glomeruli respond to different odorants?
optical imaging and 2DG
What has optical imaging research found in regards to the glomeruli?
- displayed activation of olfactory bulb in response to different chemicals
- adding more carbon to each related chemicals -> activation moves left
- related chemicals found in similar areas of olfactory bulb
What has 2DG research found in regards to the glomeruli?
- inject substance to illuminate radioactivity which showcases neural activation
- used different odorant chemicals to showcase different areas of activity
What type of coding does optical imaging and 2DG showcase?
specificity coding
What is the pathway of signals starting from the olfactory bulb?
- signals are sent to primary olfactory (piriform) cortex in the temporal lobe and amygdala
- then sent to secondary olfactory (orbitofrontal) cortex in frontal lobe
What is the role of amygdala in the smell system?
plays a role in emotional reactions to odors
Rennaker experiment (piriform cortex)
- used multiple electrodes to measure neural responding in the piriform cortex
- found that isoamyl acetate causes scattered activation across the cortex
What type of coding does Rennaker’s experiment showcase?
sparse coding
Settler and Axel
- replicated Rennaker’s experiment but with optical imaging
- displayed similar results
Wilson experiment (peppermint)
- measure response of neurons in the rat’s piriform cortex to two odorants
- presented a mixture of two odors (peppermine and isoamyl acetate) and a component (isoamyl acetate)
What were the results of Wilson’s experiment?
with enough exposure, the piriform cortex could discriminate the mixture and the compound
How does odor stimuli reach the olfactory mucosa from the mouth?
through the retronasal route
Clamped nose experiment
- limits taste to only 5 primary tastes
- blocks all info from olfactory bulb from being sent to brain
Plassmann experiment (wine)
- judging taste pleasantness of wine
- same level for bottles not showing a price
- higher rating for more expensive wine despite being the same as cheap wine
O’Doherty experiment
- pleasantness and food-related order are influenced by satiety
- higher rating pre-satiety and lower rates post-satiety for bananas
