Chapter 14 - Perception Psychology
What is the lock and key theory/ shape pattern theory
Combinations of chemical features of molecules are thought to play a role in their capacity to bind to the olfactory receptor neurons.
How do humans ID odors
Concentration, • The structure of the odorant molecule, • Context, • Experience.
How does each odorant produce a pattern and whats done with this pattern
Each odorant produces a characteristic pattern of responses within a subset of glomeruli in the olfactory bulb. • This pattern is sent to higher areas of the brain via the tufted and mitral cell axons, which together form the olfactory tract. • The distribution of glomeruli in the olfactory bulb takes place according to a chemotopic arrangement --The axons of olfactory receptor neurons activated by odorants with similar molecular structures tend to travel to glomeruli in the same part of the olfactory bulb. • Glomeruli in different parts of the bulb tend to receive the axons of olfactory receptor neurons activated by odorants with different molecular structures.
What are olfactory receptors
G-protein couples receptors in the cilia of ORNs
Why is human cross-adaptation more difficult
Human participants develop cross-adaptation for some perceptually similar odorants, but not for others. • This inconsistency is seen regardless of how similar or dissimilar are the molecular structure of different odors. • In addition, there are many situations in which two perceptually dissimilar odors nevertheless produce crossadaptation. • Exposure to a first odor sometimes enhances sensitivity to a second odor. -Cross-adaptation effects usually go away after a few minutes
What the olfactory nerve
the axons of ORNs carrying neural signals from ORNs to the olfactory bulb via tiny holes in the cribform plate
Olfaction in different species
Molecule detection tends to be species specific, although there are molecule detection overlaps across species. • Just as we cannot see the whole color spectrum of wavelengths or hear the entire sound spectrum of frequencies, we cannot smell all odorant molecules.
Orothonasal pathway vs retronasal pathway
Odorant molecules from the air enter the nasal cavities by the nostrils, also known as the orthonasal pathway. • Odorant molecules or other substances in the oral cavity are carried into the nasal cavities via the pharynx, also known as the retronasal pathway. • This is the pathway that helps us to perceive flavor.
Why humans have olfaction
Olfaction: • Facilitates survival: • Recognition of poisonous smells, • Seeking out healthy food. • Enriches life. -Evolutionary advantages of odors: • Food: Survival through nutrition. • Species/Potential Mates: Reproduction. • Putrid smells: Toxic bacteria in decomposing substances.
Is good/bad smell innate?
Researchers on the innate side of the debate claim that we are born with a predisposition to view various smells as pleasant or unpleasant. • It is difficult to design studies that demonstrate any biological responses to smells. Research results thus may be biased in favor of the experiential dimension . • Researchers found that the molecular structure of odorants accounts for 30% of the variance in participants' responses related to pleasantness versus unpleasantness of odors . • These data support the thesis that a portion of odor pleasantness or unpleasantess perception maybe innate.
What is the entorhinal cortex
The entorhinal cortex: • The gateway to the hippocampus. • Long-term memories are stored & retrieved.
simple vs complex odors
Simple odor: resulting from the presence of just one type of odorant molecule. • Complex odor: reflecting the presence of many different types of odorant molecules.
What does the olfactory epithelium contain
The olfactory epithelium contains: • Supporting cells. • The structural matrix for the olfactory receptor neurons. • Basal cells. • Precursors to new olfactory receptor neurons. • Bowman's glands. • Mucus secreting glands. • The mucus covers the olfactory epithelium. ---- This process washes out odorant molecules from the epithelium, otherwise we would continue to perceive the odor even after it left the air in the immediate environment.
Does the olfactory system use the thalamus
The olfactory system is the only sensory system in which pathways from the sensory receptors to the cortex do not pass through a nucleus within the thalamus. • This difference is thought to be related to the early development of the olfactory system in comparison to the other senses.
More about transduction
When an odorant molecule binds to an olfactory G-protein coupled receptor, ion channels in the olfactory receptor neurons cell membrane open, positively charged calcium and sodium ions enter the cell, and the cell membrane slightly depolarizes. --Odorant molecules in sufficient concentrations are transduced into neural signals.
How does the olfactory system 'self heal'
When receptors are damaged due to injury, the olfactory system is remarkably self-healing. Stem cells in the nose become new receptor neurons that reconnect the nose to the brain.
Wine experts = SCAM
When the labels are removed (or when they are reversed without the knowledge of the expert), experts can be fooled. • Some academics, based on blinded wine tastings, have cast doubt on the ability of professional tasters to judge wines consistently.
What is pheromone
a chemical substance emitted by individual organisms that evokes behavioral or hormonal responses in other individuals of the same species
What are G-protein coupled receptors (GPCRs)
a large family of proteins that function as receptros, they provide mechanisms for molecules outside a cell to influence the inner workings of the cell
What is olfactory epithelium
a patch of tissue in the upper reaches of each nasal cavity the epithelium contains ORNs and is covered by a later of olfactory mucus
What is the neural code for odor
a population code -- diff odorants activate diff populations of ORN types to diff degrees enabling the olfactory system to discriminate an enormous number of odorants
How many types of ORNs do humans have
about 350 diff types each of which can be activated by a restricted set of odorant molecules -Humans have an estimated 10,000-20,000 of each type of olfactory receptor neuron, for a total of about 3,000,000 to 7,000,000 olfactory receptor neurons which send their axons to about 5,000 glomeruli in the olfactory bulb -About 1,000 genes are devoted to the genetic code for our approximately 350 different receptor types. • The array of odorants encoded by the approximately 350 different receptor types is unknown, estimates range from 10,000-100,000. • Because of the volume of odorants, it is clear there is no 1:1 relationship between one molecule binding to one receptor type
What is eNose
an electronic nose currently able to detect and identify odorants , localizing their source and tracking odor plumes -consists of an array of sensors that change their electrical resistance whne exposed to diff typeos of odorant molecules -pattern of resistance changes across all the sensors is a pop code that can be used to detect and id particular odorants -enoses mounted on mobile robots can detect locate and discriminate odorants at difff locations and track odor plumes at their source
What is the olfactory tract
axons of mitral and tufted cells carrying neural signals from the olfactory bulb to higher areas of the brain
What are turbinates
bony convolutions of tissue protruding into the nasal cavities functioning to disperse air evenly throughout the nasal cavities
What are pheromones
chemicals that evoke hormonal or behavioral responses in other individuals of the same species (many animals emit them) -these may be perceived by vomeronasal olfactory system, distinct from the main olfactroy system
Can odors be perceptually grouped
combinations of odors undergo a kind of perceptual grouping, where distinct odors are bound together into a single olfactory object analogous to the groupings in the perceptual organization of vision and audition. -The piriform cortex performs a sort of figureground activation in response to new odors that are presented against a background of mixed odors. • When a new odor arrives against an unchanging the background, it evokes a distinct pattern of responses in the piriform cortex.
How does odor ID ability change w age
declines
What to do orbitofrontal cortex and amygdala represent
emotional dimensions of odor perception (pleasantness and unpleasantness)
What does the anterior piriform cortex represent
features of chemical structure of odorants
Does linguistic pairing effect memory of perceived smell
human memory for specific odors are formed quickly and decline slowly . • Study participants can recall after a delay of one week which odors were presented in a study and which were not. • The effect is enhanced when the odors are named and thus there may be a linguistic memory component to recall -Studies that have controlled for the linguistic effect, by presenting odors that are unfamiliar and therefore lacking in a name in the person's existing memory bank, have illustrated that: • linguistic pairing aids in the detection of familiar odors, • even without linguistic pairing, memory for odors is quite strong, even after a delayed recall gap of 6 months.
What is the vomeronasal olfactory system
in many species an olfactory system that senses pheromones it is distinct from the main olfactory sysyem used to smell most substances
Do humans emit pheromones
inconclusive data.. but humans are sensitive to differences in the odors that other ppl emit -there is evidence that human sexual behvior (choice of mates) can be influenced by olfactory detection of human leukocyte antigens (genes that regulate the immune system)
What is anosmia
loss of the ability to perceive odors
What is the difference threshold
min amount by which the concentration must change for a person to notice the difference
What are odorants
molecules that olfactory receptors 'recognize' and respond to by producing neural signals that the brain represents as perceptions of different odors
What are olfactory receptor neurons (ORNs)
neurons that transduce odorant molecules into neural signals -• It is likely that each olfactory receptor neuron is tuned to a fairly narrow range of different odorant molecules.
How does odor effect memory
odor that evoke autobiographical memories tend to relate to emotionally charged experiences from the first decade of life -feel more transported back to the original time and place of the event than when memories are triggered by cues in any other modality -The centers of emotion lie on and adjacent to the olfactory pathways, as does the hippocampus (the memory center). • Olfactory information travels to these brain structures more directly then does information from any other sensory modality --Binocular rivalry studies have illustrated that people stare preferentially at an image evoking a pleasant odor when presented with that odor. • They stare preferentially at an image evoking an unpleasant odor when presented with that odor
Cycle of olfactory adaptation
olfaction is especially sensitive to change. • We rapidly detect the presence of something new, • We orient to the new thing, • We adapat -• Adaptation occurs rapidly, with each successive olfactory neuronal pulse weakening in response to an odorant molecule. • Recovery from adaptation also occurs relatively quickly -After that process, continued detection, identification, and evaluation serve no further evolutionary advantage. • By adapting to the smell, so that it is no longer perceived, the organism is better prepared to detect new smells.
What does the mucus layer do
provides a barrier against irritants and harmful microorganisms that might otherwise penetrate into the central nervous system.
What is cross-adaptation
reduced sensitivity to odorants that are chemically or perceptually similar to odorants to which the person has been continuously or repeatedly exposed
What are tufted cells
relay neurons within the glomeruli in the olfactory bulb, the axons of tufted cells and mitral cells form the olfactory tract
What are mitral cells
relay neurons within the glomeruli in the olfactroy bulb, the axons of the mitral cells and tufted cells form the olfactroy tract
When do humans adapt to odors
repeated or continuous exposure to an odorant causes adaption to that odorant, cross-adaptation to similar odorants can also occur
What does the posterior piriform cortex represent
represents the quality of an odor as whole
How does signal travel in higher parts of the brain
signals travel along the olfactory tract to the piriform cortex (considered the primary olfactory cortex) as well as to the amygdala and the entorhinal cortex --> orbitofrontal cortex, hypothalmus and the hippocampus
What injures the anatomical structures that support olfaction
smoking- Cigarette smokers on average suffer from a decline in olfactory performance that increases with the number of pack-years. • Once people quit smoking, olfactory performance tends to recover, with the degree of recovery increasing over time. - genetic mutations, gender - Women retain their sense of smell better than men. -age • Full anosmia typically is not seen until age 90—and more often for men than women.
Is olfactory preference learned?
taking the learned view posit that we are born merely with a predisposition to learn to view certain smells as pleasant or unpleasant. • Whether a smell is liked or not is determined by the emotional value (pleasant or unpleasant) of the experiences that have been associated with it • In other words, associative learning explains most of the statistical variance concerning odor pleasantness versus unpleasantness. --A great deal of evidence suggests that odor hedonics are almost exclusively learned. • Infants and young children do not share the same aversions to unpleasant odors as adults. • (Children with in utero exposure to distinctive smelling odors such as garlic, alcohol, and cigarette smoke during pregnancy and breast-feeding demonstrate greater preferences for those smells than infants not exposed to those smells. & inability to make stink bombs)
What is the anterior piriform cortex (APC)
the anterior (front) portion of the piriform cortex, it produces representations of features of the chemical structure of odorant molecules -It is narrowly tuned; odorant features must represented in fine enough detail to support odorant identification to activate this region
What is the piriform cortex
the brain region considered to be the primary olfactory cortex bc its the only region that both receives signals directly from the olfactory bulb and is known to be dedicated solely to olfaction -• Results from this region allow us to name odor quality (e.g., oily, citrus) and form associated representations in long-term memory. • There is no obvious chemotopic mapping in the piriform cortex -is activated in a way that explains cortical adaptations to odors that can last for several minutes.
What is the detection threshold
the concentration of an odorant necessary for a person to detect it -The detection threshold typically is the concentration necessary for a person to detect the odor 75% of the time. Studies may set different thresholds. -Different odors have different detection thresholds, as averaged across participants. (ex. t-butyl, toxic gas, super low threshold so humans can detect it)
What is human leukocyte antigens (HLAs)
the genes responsible for regulating the immune system; women can detect HLA differences in odors of men possibly influencing their selection of a mate
What is the cribriform plate
the part of the skull immediately above the nasal cavity, axons of ORNs pass through a gride of tiny holes in the plate
What is the posterior piriform cortex (PPC)
the posterior (rear) portion of the piriform cortex, it produces representations of the quality of an odor as a whole regardless of whether the odor is simple or complex
Is there any olfaction consensus
they are quite consistent (within cultural groupings) at determining the pleasant versus unpleasant quality of odors. • Nutrition leads to survival. • Aversion toward poison or bacteria leads to survival.
What is a molecule
two + atoms bound together by electromagnetic forces -The 3-D shapes of molecules are equally varied, depending on how the electromagnetic forces interact.
What effect could variability in receptor genes have
variability in the receptor genes that are expressed across individuals may influence odor intensity and perceived pleasantness or unpleasantness of odors. • People who like a smell that most people find unpleasant may exhibit this response in part because they are missing receptors for detecting some of the more pungent volatiles.
How does recognition affect how we perceive a smell
we tend to give pleasant (versus unpleasant) ratings to odors that we have smelled many times before. • When we smell an unfamiliar but pleasant odor, we tend to perceive it as familiar even though we have not smelled it before.
When does olfactory transduction occur
when odorant molecules bind to G-protein coupled receptors on the cilia of olfactory receptor neurons (ORNs) embedded in the olfactroy epithelium -ORNs axons form the olfactory nerve carrying signals into the glomeruli within the olfactory bulb -ORN axons make synapses w/ mitral cells and tufted ells and their axons form the olfactory tract --transmitting the singals to higher areas of the brain
When do we perceive odors
when odorants evoke responses in our olfactory receptors -a crucial factor in detecting odorants is in their concentration -People have no difficulty detecting odors when given multiple choice options especially when they all fall under the same category (food)
Why is concentration of same odorant important
• Different concentrations of the same odorant may evoke different patterns of mitral cell and tufted cell activation. • This explains why some odorants smell different at different concentrations
Are olfactory neurons permanent
• Each olfactory receptor neuron dies after a few weeks and is replaced by a new one. • Each olfactory receptor neuron has numerous hairlike cilia which project into the mucus layer. • The surface of each cilium is studded with olfactory receptors. • Odorant molecules contact these receptors when they dissolve into and flow through the mucus.
How is info carried to the olfactory bulb
• Information is carried olfactory bulb through the olfactory tract. • It enters a number of brain regions: • Piriform cortex, • the amygdala, • the entorhinal cortex.
How do we measure odor concentration
• Odor concentration is measured by the number of odorant molecules present in 1 million molecules of air, or parts per million (ppm). • Concentration depends on: • The source (some sources give off a greater number of odorant molecules than others), • How far away it is (odorant molecules disperse as they travel away from a source), • Whether the molecules are confined to a small enclosed space or are floating in open air (and thus dispersed by the wind).
How are taste and olfaction related
• Odors play a key role in detecting flavor. • Much of what we attribute to the "taste" of food is actually due to odor molecules entering the nose as we consume the food. • People who report taste deficiencies typically have only an olfactory deficit
When are people bad at detecting odors
• People are not very good at identifying odors without some context or some expectation about the identification of the odor -easily influenced by factors such as visual or verbal cues. • (ex. Adding red food coloring to white wine changes the adjectives people use)
How does the state of the smeller effect the smell
• Some odors may be experienced as pleasant or unpleasant depending on the state of the smeller: (• The smell of dinner when hungry, • The smell of dinner when full. ) • Some odors are experienced in the same way regardless of the state of the smeller, but there nonetheless appears to be some learning involved (infants and young children show less aversion than adults). The outcome likely is a combined function of innate and experiential factors. • The smell of a prey animal, • bodily waste, • decomposing life forms, • spoiled food
What is the role of the amygdala and hypothalamus
• The amygdala is activated by the combination of emotional material with other sensory material (from all senses). • Pleasant and unpleasant smells are more effective at activating this emotional center of the brain than are sights and sounds. • The amygdala sends signals to the hypothalamus. • The hypothalamus is involved in a wide range of functions through the release of hormones and through neural activity related to hunger, thirst & sexual behavior.
