chapter 16 part 2

Question 1

what does it mean for an animal to be macrosmatic?

Answer 1

it means that they have a keen sense of smell that is necessary to survival

Question 2

what does it means for an animal to be microsmatic?

Answer 2

it means they have a less keen sense of smell that is not crucial to survival

Question 3

how do we measure the detection threshold for odors?

Answer 3

yes no procedure:
- ps presented with odors and blanks
- indicated yes or no to whether they can detect them

forced choice:
- two trials are given, one with odorant and one without
- ps indicate which smells the strongest
- theshold: concentration that results in a correct response on 75 percent of trials

Question 4

what is the difference between the sense of smell in human and rats? humans and dogs?

Answer 4

rats are 8 to 50 times more sensitive to odors than us

dogs are 300 to 10,000 times more sensitive to odors than us

the difference lies in the number of receptors (not the sensitivity of individual receptors)
- dogs have one billion receptors and humans have ten million

Question 5

how good are humans at detecting odors?

Answer 5

we can discriminate more than one trillion different odors
- but find it difficult to identify odors
- tend only to be successful half the time

Question 6

why is the perceptual experience of smelling something difficult to map onto the physical attributes of odorants

Answer 6

• there isn’t a specific language for odor quality
• some molecules that have a similar structure smell different, and some molecules that have a different structure smell different

Question 7

olfactory mucosa

Answer 7

area at the top of the nasal cavity just below the olfactory bulb which contains olfactory receptor neurons. these neurons contain olfactory receptors

odorants are carried along the mucosa so that they can come into contact with these neurons

Question 8

how many olfactory receptors do humans have?

Answer 8

350 types of receptors - each have a protein that crosses the membrane seven times

Question 9

what are the two stages of olfactory processing that happen when we perceive odors

Answer 9

1. analyzing: takes place at the beginning of the olfactory system in the olfactory mucosa and olfactory bulb. the olfactory system analyzes the different chemical components of odors and transforms these components into neural activity at specific places in the olfactory bulb
2. synthesizing - takes place in the olfactory cortex and beyond. the olfactory system synthesizes information about chemical components received from the olfactory bulb into representations of odor objects

Question 10

where does the olfactory bulb send its signals

Answer 10

to the primary olfactory (piriform) cortex in the temporal lobe and amygdala (plays a role in emotional reactions to odors)

then to the secondary olfactory (orbitofrontal) cortex in the frontal lobe

Question 11

rennaker experiment

Answer 11

used multiple electrodes to measure neural responding in the piriform cortex, and found that isoamyl acetate causes activation across the cortex

Question 12

how are odors represented

Answer 12

1. odorant molecules come off the odor object
2. a chemotopic map is activated in the olfactory bulb
3. scattered activation in the piriform cortex
4. after learning piriform cortex forms a patter for the odor object

Question 13

wilson experiment

Answer 13

study that provides support for the idea that learning plays and important role in perceiving odors

• measured response of neurons in the rats piriform to two odorants
  1. a mixture: isoamyl acetate and peppermint
  2. a compound: isoamyl acetate alone

with enough exposure, the piriform cortex could discriminate between the mixture and the compound

Question 14

recent measures of human odor sensitivity

Answer 14

humans are more sensitive to many odors than a wide range of animals, including mice, monkeys, rabbits, and seals

Question 15

anosmia

Answer 15

no sense of smell

Question 16

what is a possible explanation for why COVID-19 causes people to lose their sense of smell

Answer 16

covid molecules attach to an enzyme called ACE2 that is found in the intestines, lungs, arteries, heart, and nose. In the nose, it is found on the surface of sustentacular cells, which provide metabolic and structural support to the olfactory sensory neurons

because of this, it has been proposed that COVID-19 causes loss of smell by attacking the supporting cells of sensory neurons

Question 17

sustentacular cells

Answer 17

cells which provide metabolic and structural support to the olfactory sensory neurons

Question 18

what is the difference between loss of smell ins Alzheimer’s and in COVID

Answer 18

loss of olfaction in Alzheimer’s patients begins occurring decades before the occurrence of clinical symptoms such as memory loss and difficulties in reasoning

attack on the olfactory system also tends to be more widespread than in COVID19

Question 19

differences between the visual system and the olfactory system

Answer 19

there are 400 different types of olfactory receptors, each sensitve to a different group of odorants, compared to only four types of visual pgments

Question 20

olfactory bulb

Answer 20

the structure that receives signals directly from the olfactory receptors - the olfactory bulb contains glomeruli, which receive these signals from receptors

Question 21

calcium imaging to measure receptor response to odorants

Answer 21

when an olfactory receptor responds, the concentration of calcium ions increases inside the receptor. calcium imaging measures this increase by soaking the neurons in a chemical that causes them to fluoresce when exposed to ultraviolet light - increasing Ca++ decreases the glow

measuring decrease in fluorescence indicates how strongly the neuron is activated

Question 22

odorant recognition profile

Answer 22

the pattern of olfactory activation for an odorant, indicating which ORNs (olfactory receptor neurons) are activated by the odorant

can use the profiles to see that each odorant causes a different pattern of firing across ORNs

Question 23

glomeruli

Answer 23

small structures in the olfactory bulb that receive signals from similar olfactory receptor neurons. one function of each glomerulus is to collect information about a small group of odorants

Question 24

chemotopic maps/odor/odotopic maps

Answer 24

the pattern of activation in the olfactory system in which chemicals with different properties create a “map” of activation based on these properties

ex. evidence suggests that chemicals are mapped in the olfactory bulb based on carbon chain length

Question 25

what happens to the chemotopic map in the piriform cortex

Answer 25

it disappears and gets replaced with widespread activation/overlap

Question 26

how are odor objects represented in the piriform cortex?

Answer 26

similar to how memories are formed

• the cortex learns to link together the scattered activations that occur for a particular object - eventually the cortex is able to remember the pattern of activation and forms neural connections between the scattered areas of activation

odor objects become formed when experience with an odor causes neurons in the piriform cortex to become linked

Question 27

proust effect

Answer 27

the elicitation of memories through taste and olfaction

Question 28

odor evoked autobiographical memories

Answer 28

proust effect
- memories about events from a person’s life that are elicited by odors

associated with strong emotions and feelings of being brought back in time

amygdala is involved

Question 29

retronasal route

Answer 29

the opening from the oral cavity, through the nasal pharnyx (connects the mouth cavity and the nasal cavity), into the nasal cavity. This route is the basis for the way smell combines with taste to create flavor

Question 30

retronasal route

Answer 30

the opening from the oral cavity, through the nasal pharnyx (connects the mouth cavity and the nasal cavity), into the nasal cavity. This route is the basis for the way smell combines with taste to create flavor

Question 31

oral capture

Answer 31

the condition in which sensations from both olfaction and taste are perceived as being located in the moth

Question 32

bimodal neurons

Answer 32

neurons that respond to more than one sense - often respond to similar qualities

orbitofrontal cortex contains many of these types of neurons

Question 33

bimodal neurons

Answer 33

neurons that respond to more than one sense - often respond to similar qualities

orbitofrontal cortex contains many of these types of neurons

Question 34

sensory specific satiety

Answer 34

the effect on perception of the odor associated with food eaten to satiety - pleasantness rating of the smell of whatever food we have just eaten will go down after we are full

Question 35

what does the finding that orbitofrontal cortex activity is related to the pleasantness of an odor or flavor suggest?

Answer 35

that the orbitofrontal cortex is involved in determining the reward value of foods

Question 36

multimodal interactions

Answer 36

interactions that involve more than one sense

Question 37

correspondences

Answer 37

refer to how a property of a chemical sense is associated with properties of other senses:
- odors and tastes can be associated with different pitches and instruments
- odors can be associated with different colors
- odors can be associated with different textures