Animals are able to detect chemical signals because they have Important evolutionary job – keep genes in gene pool
Emotional reaction happen firstSmell has a direct link to the amgdyla
Dogs are better at smelling, It’s because they have a lot more olfactory receptors, not because theirs are better
Olfactory neuron will only carry one olfactory kind of receptor
Olfactory receptor neurons are located in nose, send axons to glomerulus in olfactory bulb (right under the brain)Receptors distributed all over
Similar patterns of activity, then we perceive similar odorsDon’t need to memorize the acids
Highly organized further organized by the size of the molecules
Red means lots of activityCool colors = less activityblack Arrows show that the activity is the sameWhite arrows show differences in activityRats can tell the different kind of carvone depending on the different activity of the neurons
Neuron enters the olfactory bulb, goes to the piriform cortex, then gets bounced to the orbitofrontal cortex, then straight to the prefrontal areaThe olfactory senses are the only ones that don’t stop at the thalamus
This is why it takes a little longer for us to realize the emotional responseUsually, the olfactory was take the longer route
Expectation alters perception of how favorable the smell was
Subjects were told that it was either cheddar cheese or sweat, but it was actually both togetherChemical caused the exact same pattern of activity, the pattern of activity downstream was different depending on what they thought they were smelling
Umami, sour, bitter, salt, sugar
Know filiform, know that there are 4 forms of papillae
TASTE budshave receptors that bind together and at the tips, transduce
Area in the brain stem, first area information synapses
Olfaction and taste are linked downstream such that perception of taste is heavily dependent on olfactory Smell influences taste
There is a difference between the two group
Taste and Smell
detect airborne chemicals detect chemicals dissolved in salivaChemosenses provide survival value for animals
Some molecules can have same structures, but different “smells”Others can have different structures and be id’d as same smell
350 types ofolfactory receptors,each sensitive to aparticular group ofodors.Each olfactoryreceptor neuroncontains only 1type of olfactoryreceptor.
The functional grpasocc. w/ a compound (COOH for acids;OH for alcohols) determines the general area of theolfactory bulb that is activated, and the compounds lengthdetermines the position of the area.
Rats can distinguish betwn the 2 forms of Carvone, butnot Limoene.
Others are more complex due to downstream processing.
Now add other odors, w/ their 100’s ofmolecules. We will not experience ajumble…here we’ll smell coffee, bacon eggs!!!
Onion smell labeled pizza perceived more positively than one labeled body odor
Activity pattern in olfactory receptors the same. The label changedperception & this was reflected in different activity of secondary ctx.
– All over, no taste buds – Tip & sides fungiform – Folds along back & sidesfolaite
• Site of transduction• Each receptor cell responds to a ltd # of molecule types.• Receptors synapse w/ 3 cranial nerves – These also carry non- taste info such as pain &tmp
• Rat studies indicate some taste perception is based on distributed coding.• Chemicals that produced similar firing patterns were perceived as the same (red & green lines)
• Involves taste & olfaction• Orbitofrontalctx combines taste, olfaction, primary somatosensory &what pathway• Has neurons that respond to both taste & smell; others taste & vision• Often respond to similar qualities (smell of sweet & taste of sweet)
• A.L. Fox (worked for DuPont) prepped some PTC., co-worker c/o bitter taste from dust….Fox tasted nothing.• A.F Blaheslee ( a geneticist) dispensed PTC to 2500 Ss at a conference. – 28%: “tasteless” – 66% “bitter”
Why? – Different # of receptors – Some have specialized neurons