Chapter 14 - Perception
population code
________ is a consistent difference in the patterning of the relative responses of a population of differently tuned neurons; used in olfaction
10,000, 100,000
although it is unsure how many different odors human can actually discriminate, some estimates claim that its somewhere between _______ and _______
narrowly
anterior piriform cortex (APC) neurons tend to be (narrowly/broadly) tuned
figure-ground organization
A phenomenon analogous to _______ organization of the visual system is seen in pyriform cortex activity; when new odor arrives in the nose against an unchanged olfactory scene, it evokes a distinct pattern of responses though to reflect the representation of the odor as an "object" for potential identification and evaluation
familiarity, context
the memory for odors is influenced by ______ and _____
10
the mucus produced by bowman's glad regenerates every _____ minutes
true
true/false: when people are presented with an odor out of context (without info identifying the kind of odor) their ability to identify even familiar odors is quite poor
1, 4
typical dogs have a TOTAL of about _____ billion olfactory receptor neurons (ORN), while bloodhounds can have as many as ______
molecules
________ consists of two or more atoms bound together by electromagnetic forces
3
According to the American Medical Association, a total loss of smell is equivalent to a _____% impairment of the whole person (compared to a 35% impairment for loss of hearing and 85% impairment for loss of vision)
5
Although early studies indicated that the Centration of an odorant must change substantially in order for people to notice a difference in intensity more recent research suggests that some odorants have a difference threshold of as little as _______%
olfactory bulb
Congenital anosmia is associated with the absence or deformity of the _________ (first brain area that receives olfactory signals from the nose)
OLFACTORY RECEPTOR NEURONS (ORN): Neurons that transduce odorant molecules into neural signals (embedded in olfactory epithelium, with cilia protruding into mucus layer) ORN NUMBER: 350 types (10,000 - 20,000 receptors of each type in humans, total of 3-7 million) RECEPTORS = OLFACTORY RECEPTORS: G-protein coupled receptors located on the surface of olfactory receptor neuron cilia (odorant molecules come in contact with these receptors after dissolving into and crossing the mucus) - G-PROTEIN COUPLED RECEPTORS (GPCRs): a large family of proteins that function as receptors; they provide a mechanism for molecules outside a cell to influence the inner workings of the cell - DEPOLARIZATION: Occurs when Ca+ and Na+ flow into the cell after a cascade of internal events (action potential sent if odorant molecules bind to a sufficient number of receptors on the cilia) - LIFESPAN: Few weeks (replaced by new ones after) - NUMBER: About 350 different receptors (each ORN has just one type) AXONS = OLFACTORY NERVE: Term used for the axons of ORNs, carrying neural signals from ORNs to the glomeruli of olfactory bulb via tiny holes in the cribriform plate - CRIBRIFORM PLATE: Part of the skull immediately above the nasal cavity; the axons of ORNs pass through a grid of tiny holes in the plate - SYNAPSE SITES: mitral cells + tufted cell (in glomeruli of olfactory bulb; their axons form the olfactory tract which carries info to higher areas of the brain)
Describe olfactory receptor neurons (ORN) and related components
MRI STUDY OF 4 OLFACTORY REGIONS AND ACTIVITY PATTERNS (Howard et al., 2009) DESCRIPTION: In this fMRI study, the brain activity in the anterior piriform cortex (APC), posterior piriform cortex (PPC), amygdala, and and orbitofrontal cortex (OFC) was measured as participants sniffed three odorants belonging to three different odor categories (minty, woody, and citrus). The odorants within each category had very different molecular structures despite their perceptual similarity. RESULTS: - PPC ACTIVITY: Patterns of activity were very similar for for odorants within a given category and different for odorants in different categories (activities in other areas did not show this difference - AMYGDALA AND OFC: Patterns of activity did not reflect differences in the quality of minty, woody, and citrus odorants (all of which are pretty pleasant) IMPLICATIONS: - PPC: PPC represents odor quality (not merely the chemical structure of odorants) - AMYGDALA AND OFC: Amygdala and involved in representing the emotional dimension of odor perception, and not the identity of odors (activity did not differ because all smells were pretty pleasant)
Describe the MRI study that focused on the activity patterns in the anterior piriform cortex (APC), posterior piriform cortex (PPC), amygdala, and orbitofrontal cortex (OFC) (Howard et al., 2009)
PET STUDY OF AMYGDALA + OFC AND THEIR REPRESENTATION OF EMOTIONALLY-CHARGED ODORS (Zald & Pardo, 1997) DESCRIPTION: Responses of amygdala and OFC were recorded using PET while participant sniffed odors that varied along the emotional dimension of aversiveness (mildly to extremely unpleasant) RESULTS: Magnitude of activation in both amygdala and OFC correlated with participants' subjective ratings of the odor's aversiveness (more aversive = more activation) IMPLICATIONS: Amygdala and OFC are involved in representing the emotional dimension of odor
Describe the PET study which focused on the responses of amygdala and OFC to emotional dimensions of stimuli (Zald & Pardo, 1997)
AMYGDALA: A structure that receives input from the olfactory bulb (among other regions); plays a critical role in emotional responses and can be activated by emotional stimuli across various sensory modalities (like visual, auditory, olfactory, and gustatory stimuli) ROLE: Plays a critical role in emotional responses ACTIVATED BY: Emotional stimuli across various sensory modalities (like visual, auditory, olfactory, and gustatory stimuli) PROJECTS TO: Hypothalamus + Orbitofrontal cortex - HYPOTHALAMUS: Almond-shaped region below the front of the thalamus; involved in a wide range of functions (through the release of hormones and through neural activity) such as regulation of thirst, hunger, and sexual behavior - ORBITOFRONTAL CORTEX: A a region of the brain which, among other things, plays a role in evaluating incoming stimuli as positive and negative (rewarding or unpleasant)
Describe the amygdala
BOWMAN'S GLAND: A structure that continuously secretes the mucus which covers the olfactory epithelium GLAND LOCATION: olfactory epithelium MUCUS FLOW: Bowman's gland --> back of nasal cavity --> pharynx --> swallowed MUCUS REGENERATION: Regenerates every 10 minutes MUCUS FUNCTIONS: - 1. WASHING OUT ODORANTS: Elimination of mucus from the olfactory epithelium serves to wash out the odorant molecules so that they do not continue to stimulate odor perception after odors are no longer present in environment - 2. PROTECTIVE BARRIER: Mucus serves as a protective layer against irritants and harmful organisms that could otherwise penetrate into the central nervous system
Describe the bowman's gland and its functions
ELEMENTS OF THE OLFACTORY SYSTEM 1. NOSE - Exterior portion of the olfactory system 2. NOSTRILS - Either of two openings in the nose 3. NASAL SEPTUM - A wall of cartilage that separates the nostrils 4. NASAL CAVITIES: Hollow cavities located posterior to the nose whose posterior region joins with the pharynx (upper part of threat) 5. TURBINATES - bony convolutions of tissue protruding into the nasal cavities, functioning to disperse air evenly throughout the nasal cavities (covered with epithelial tissue 6. OLFACTORY EPITHELIUM: A patch of tissue (about 2 cm^2) in the upper reaches of each nasal cavity; the epithelium contains ORNs, supporting cells, basal cells, Bowman's gland and is covered by layers of olfactory mucus - OLFACTORY RECEPTOR NEURONS (ORN): Neurons that transduce odorant molecules into neural signals (embedded in olfactory epithelium, hairlike cilia protrude into olfactory mucus) - SUPPORTING CELLS: Provide structural matrix for the olfactory receptor neurons (ORN) - BOWMAN'S GLAND: Continuously secretes the mucus which covers the olfactory epithelium 7. OLFACTORY NERVE: term used for the axons of ORNs, carrying neural signals from ORNs to the olfactory bulb via tiny holes in the cribriform plate - CRIBFORM PLATE: Part of the skull immediately above the nasal cavity; the axons of ORNs pass through a grid of tiny holes in the plate 8. GLOMERULI (GLOMERULUS): Small, more or less sphericsl structures in the olfactory bulb; within the glomeruli, the axons of ORNs make synapses with the dendrites of mitral cells and tufted cells - MITRAL CELLS - Cells that relay neurons within the glomeruli in the olfactory bulb; the axons of these cells and tufted cells form the olfactory tract - TUFTED CELLS: Cells that relay neurons within the glomeruli in the olfactory bulb; the axons of these cells and mitral form the olfactory tract 9. OLFACTORY TRACT: The axons of mitral cells and tufted cells, carrying neural signals from olfactory bulb to higher areas of the brain 10. PIRIFORM CORTEX AMYGDALA, ENTORHINAL CORTEX
Describe the elements of the olfactory system
ENTORHINAL CORTEX: A structure that receives input from the olfactory bulb; it is the gateway to the hippocampus (where long-term memories are stored and retrieved) PROJECTS TO: hippocampus, prefrontal cortex - HIPPOCAMPUS: Structure involved in the storage and retrieval of long-term memories - ORBITOFRONTAL CORTEX: A a region of the brain which, among other things, plays a role in evaluating incoming stimuli as positive and negative (rewarding or unpleasant)
Describe the entorhinal cortex
fMRI SWEAT AND ANDROSTADIENONE STUDY (Zhou & Chen, 2008) DESCRIPTION: The fMRI study compared the brain responses of women exposed to androstadienone, male sweat produced when watching arousing videos, and male sweat produced when watching neutral videos. The women were unaware of what they were smelling RESULTS: The brain responses varied in the female orbitofrontal cortex (OFC) - SEXUAL SWEAT: Produced highest level of activation in right orbitofrontal cortex (OFC) - ANDROSTADIENONE: Produced slightly but not statistically higher level of activity in right orbitofrontal cortex (OFC) compared to neutral sweat - NEUTRAL SWEAT: Produced least OFC activity (but still above baseline CONCLUSION: Because the orbitofrontal cortex (OFC) hasn't been implicated in sexual motivation or behavior, the results can't be used to indicate that women registered the sexual nature of the sweat (although it is clear that their brains responded differently)
Describe the fMRI study focused on comparing women's brain responses to the smell of male sweat compared to androstadienone
DETECTION THRESHOLD METHOD 1. SNIFF COMPARISON: a participant is instructed to sniff two equal volumes of air delivered by an olfactometer one containing an odorless substance (vapor given off by distilled water) and the other containing target odorant at a given concentration 2. ODOR IDENTIFICATION: Participant is asked to choose which of the two samples contains the odorant (This is repeated 10 to 20 times using odorants of different concentrations) 3. DETECTION tHRESHOLD ESTABLISHMENT: The concentration that leads to a predetermined performance level (e. g. 75% correct) is determined as the participants detection threshold
Describe the method used to establish the detection threshold
OLFACTORY RECEPTOR ADAPTATION STUDY (TAKEUCHI ET AL., 2003) DESCRIPTION: An ORN's response to a brief pulse of odorant molecules was measured using the voltage clamping technique. In this technique, electrical current is applied to the ORN to hold the membrane potential at a fixed valve. Researchers measured the ion flow / ORN transduction in response to odorant presentation by quantifying the amount of electricity that was required to keep the membrane potential constant following the presentation RESULTS: 1. FAST ADAPTATION: Second odorant pulse presented 1 second after the initial pulse was characterized by a significantly lower rate of transduction 2. FAST RECOVERY: Second odorant pulse presented 5 seconds after the initial pulse produced almost the same rate of transduction
Describe the olfactory receptor adaptation study (Takeuchi et al., 2003)
PIRIFORM CORTEX: the brain region considered to be the primary olfactory cortex because it's the only region that both receives signals directly from the olfactory bulb and is known to be dedicated solely to olfaction PROJECTS TO: Orbitofrontal cortex MAPPING: no chemotropic mapping RESPONSIBLE FOR: adaptation to odors (such as when you stop smelling the bread of the bakery you entered) - ORBITOFRONTAL CORTEX: A a region of the brain which, among other things, plays a role in evaluating incoming stimuli as positive and negative (rewarding or unpleasant) SUBDIVISIONS: anterior piriform cortex (APC) and posterior piriform cortex (PPC) 1. ANTERIOR PIRIFORM CORTEX (APC): the anterior (front) portion of the piriform cortex; it produces representations of features of the chemical structure of odorant molecules (like carbon chain length, which affects detection threshold, cross adaptation, and the perceptual similarity of odorants) - NEURONAL TUNING: Narrow tuning (meaning that odorant features are represented in fine enough detail to support odorant identification) - ANALOGOUS TO: V1 in vision 2. POSTERIOR PIRIFORM CORTEX (PPC): 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 (represents odors as "olfactory objects" that can be names and that have associated representations in long-term memory) - ANALOGOUS TO: Lateral occipital cortex (LOC) in vision
Describe the piriform cortex
POPULATION CODE MOUSE STUDY DESCRIPTION: Olfactory receptor neurons (ORNs) were exposed to two different odorant molecules in each of four different chemical families. Responses of olfactory receptor neurons were measured to determine which ORNs responded to which odorants RESULTS: - RESPONSE SELECTIVITY: Any given odorant molecule evoked a response from some olfactory receptor neurons (ORNs) but not other - RESPONSE STRENGTH DIFFERENCE: Any given olfactory receptor neuron (ORN) may respond strongly to some odorant, weakly to others, or none at all - RESPONSE PATTER DIFFERENCE FOR SIMILAR STRUCTURE: Patterns of olfactory receptor neuron (ORN) responses can be different for odorant molecules with similar molecular structures IMPLICATION: The pattern of olfactory receptor neuron (ORN) responses that determines how an odorant smells (and patterns can be different for odorants with similar molecular structures)
Describe the population code mouse study (Malnic et al., 1999)
CONTEXT AND OLFACTORY MEMORIES STUDY (Stevenson, 2001) DESCRIPTION: Participants first smelled and described odors that were presented alone. Next, they smelled pairs of these same odors mixed in different combinations. Lastly, they again smelled the same individual odors RESULTS: Original odors, when smelled again, tended to acquire the characteristics of odors they were combined with (and could even be confused for the odors they were combined with) IMPLICATIONS: Mixing of odors influences later perception of odors and produces a sort of perceptual grouping (where distinct odors get grouped into one single olfactory object) <-- "olfactory scene"
Describe the study focused on how context affects olfactory memory (Stevenson, 2001)
WINE EXPERT AND NOVICE STUDY (Parr et al., 2002) DESCRIPTION: Researchers measure the absolute detection threshold as well as the ability to discriminate remember and identify wine-related odors among nervous and experts winetasters - NOVICES: people who regularly drink wine but had no specialized training - EXPERTS: people who were established winemakers, wine researchers, and or wine professionals RESULTS: - DETECTION THRESHOLD: no difference in absolute detection threshold between two groups - DISCRIMINATING, REMEMBERING, IDENTIFYING, WINE-ODORS: performance significantly better among experts
Describe the study focused on the differences in abilities to discriminate,remember, and identify whineand related odors among why novices and wine experts (Parr et al., 2002)
OLFACTORY MEMORIES AND EMOTIONS STUDY (Willander & Larrson, 2006) DESCRIPTION: In the experimental group, people age 65-80 smelled 20 different substances (whiskey, tobacco, chlorine, snuff, tar, anise, clove, etc.). For each odor that evoked an autobiographical memory, the participants provided a brief written description of the memory and supplied its date when possible to indicate the age decade of the memory. The two control groups were presented with either pictures or words describing the odors and were asked to complete the same task RESULTS: In addition to demonstrating the recency effect, the odor group differed in the decade from which most memories stemmed - ODOR GROUP: Nearly half of the memories came from from the first decade of life (age 0 to 10), and participants most strongly indicated as if they've been "brought back in time" - PICTURE GROUP: Highest percentage of memories came from the second decade of life (11-20) - WORDS GROUP: Highest percentage of memories came from the second decade of life (11-20)
Describe the study focused on the emotional aspect of odor memory (Willander & Larrson, 2006)
AQUISITION OF OLFACTORY MEMORIES STUDY (Rabin & Cain, 1984) DESCRIPTION: People were first asked to smell and name 20 different substances (baby powder, bananas, coffee, etc.). After an interval of either 10 minutes, 1 day, or 7 days, they were asked to smell a randomly ordered mix of the 20 original substances and 20 new substances. For each presented odor, the participants had to decide whether it was new or old RESULTS: Performance at 7 days was only slightly worse than performance after 10 minutes IMPLICATION: Memories for specific smells are formed quickly and decline slowly ISSUE: Substances more accurately named in first stage were more accurately identified in second stage (indicating that participants may be relying not only on smell, but also on the name attached to it) FOLLOW UP STUDY (Murphy et al., 1991) DESCRIPTION: Study compared memory for odors that varied in familiarity (how "nameable" they were). After 6 months, the memory of the odors was tested RESULTS: Easily names odors were remembered a little better than unfamiliar odors (but even unfamiliar odors were remembered above chance) IMPLICATIONS: Naming plays some role in odor memory, but "pure" odor memory is nevertheless quite good
Describe the study focused on the fast acquisition of olfactory memories (Rabin & Cain, 1984) and the follow up study (Murphy et al., 1991)
AGE AND OLFACTORY PERFORMANCE STUDY (Doty et al., 1984) DESCRIPTION: 2,000 participants of different ages were tested for their ability to identify a wide range of 40 odors using the University of Pennsylvania Smell Identification Test (UPSIT). Each odorant was embedded in a scratch-and-sniff pad. After sniffing the odorant, the participant had to select from four written choices to identify the odor SCORING: - 40: Perfect score - 35+: Normal - 18 or lower: Diagnostic criteria for anosmia - 10: Random guessing RESULTS: - Age 20-60: Average performance was normal, with a small decrease in performance beginning to appear at age 60 - Age 70+: Dramatic decrease in performance
Describe the study focusing on how a factory performance declines with age
USES OF OLFACTION 1. DETECTION OF HAZARDOUS CONDITIONS: Helps detect things like bad air or spoiled food 2. IDENTIFICATION OF FOOD: Allows us to identify bread, wine, meat, etc. by smell 3. MATE SELECTION: Allows organisms (possibly also humans) to smell and recognize
Describe the uses of olfaction
VOMERONASAL OLFACTORY SYSTEM: An olfactory system that senses pheromones; it is distinct from the main olfactory system used to smell most substances (found in bony capsule near nostrils in mice) NEURONS: receptor neurons, support cells, basal cells (like main olfactory epithelium) SIGNAL PATHWAY: 1. VOMERONASAL RECEPTOR NEURONS: Neurons possessing pheromone-activated receptors whose axons travel to the accessory olfactory bulb 2. ACCESSORY OLFACTORY BULB: Structure that's distinct from the main olfactory bulb; site of synapse for axons of vomeronasal receptor neurons 3. AMYGDALA + HYPOTHALAMUS: Structures involved in emotional processing and the release of hormones
Describe the vomeronasal olfactory system
105, 5
If an odorant with a difference threshold of 5% was presented at a concentration of 100 ppm then a concentration increase to at least ___________ ppm would be required for the individual to perceive a change in the smell's intensity. In this case the just noticeable difference value would equal ________ ppm
supporting cells, basal cells, Bowman's gland
In addition to olfactory receptor neurons (ORN), the olfactory epithelium contains _______, ________, and _________
10, 20
In humans each type of ORN travels to ______ to _______ glomeruli in each olfactory bulb
1, 2
In mice each type of ORN travels to ______ to _______ glomeruli in each olfactory bulb
cognitive decline
In older adults olfactory performance (ability to identify smells) can predict _______ more accurately than scores on cognitive tests
cross-adaptation
In olfaction, _______ refers to a reduced sensitivity to odorants that are chemically or perceptually similar to odorants which the person has been continuously or repeatedly expose
Intensity, quality
Increasing the concentration of odorant molecules can lead to perceptual changes in the ________ and _______ of the odor
CAUSES OF OLFACTORY IMPAIRMENTS 1. AGE: olfactory performance declines with age 2. SMOKING: Smokers suffer a decile in olfactory performance that increases with the number of pack-years, but recovers over time after smoking cessation 3. DEFORMED / ABSENT OLFACTORY BULB: Associated with congenital anosmia 4. DISEASES (MENTAL): Olfactory performance is often impaired in individuals with Schizophrenia, Alzheimer's disease, Parkinson's disease, Down's syndrome, and others 5. BRAIN INJURY: Injury to anatomical structures supporting olfaction can produce olfactory impairments 6. GENETIC MUTATION: The same mutation that leads to the inability to experience pain also leads to anosmia in humans and mice
List the factors that contribute to a decreased olfactory performance
gustation
Olfaction is a critical component in the sensory domain of __________
Context, training, experience
The ability to identify odors and discriminate between odors depends on ________, _______, and ________
Weber's Law
The difference threshold for odor concentration follows the law known as ___________ ( because at low concentrations of very small difference in concentration is detectable very high concentrations a large change is required to make a detectable difference)
False
True/falls: the enhanced ability to identify and discriminate odors witnessed among winetasters is domain specific (applies only to wine)
true
True/false: the ability to accurately identify tastes is significantly reduced in people who have impaired olfactory sensitivity
less
When an individual is full from eating, they are (less/more) likely to describe the odor of food as pleasant
more
When an individual is hungry, they are (less/more) likely to describe the odor of food as pleasant
anosmia
_____ is a condition characterized by the loss of a sense of smell
olfactory nerve
_____ is a term used for the axons of ORNs, carrying neural signals from ORNs to the olfactory bulb via tiny holes in the cribriform plate
turbinates
______ are bony convolutions of tissue protruding into the nasal cavities, functioning to disperse air evenly throughout the nasal cavities
cribriform plate
______ is the part of the skull immediately above the nasal cavity; the axons of ORNs pass through a grid of tiny holes in the plate
Olfactometer
_______ Is a device used in olfactory detection threshold testing. It delivers samples of clear, humidified air containing either calibrated amounts of odorant or no odorant at all
orthonasal pathway
_______ is the pathway in which odorants in the outside air enter the nasal cavity via the nostril
retronasal pathway
_______ is the pathway that odorant molecules released from food or other substances in the oral cavity use to enter the nasal cavity via the pharynx
posterior piriform cortex (PPC)
_______ is 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 (represents odors as "olfactory objects" that can be names and that have associated representations in long-term memory)
96
_______% of patients who report taste deficits actually only have factory deficits
tufted cells
________ are cells that relay neurons within the glomeruli in the olfactory bulb; the axons of mitral cells and these cells form the olfactory tract
mitral cells
________ are cells that relay neurons within the glomeruli in the olfactory bulb; the axons of these cells and tufted cells form the olfactory tract
olfactory receptor neurons (ORN)
________ are neurons that transduce odorant molecules into neural signals (embedded in olfactory epithelium)
glomeruli
________ are small, more or less spherical structures in the olfactory bulb; within the glomeruli, the axons of ORNs make synapses with the dendrites of mitral cells and tufted cells
Human Leukocyte Antigen (HLA)
________ are the genes responsible for regulating the immune system; women can detect HLA differences in odors from men, possibly influencing their selection of a mate
G protein-coupled receptors (GPCRs)
________ consist of a large family of proteins that function as receptors; they provide a mechanism for molecules outside a cell to influence the inner workings of the cell
androstadienone
________ is a steroid derived from hormones produced by men which is claimed to have a strong sexual effect on the other sex (by increasing the recipient's sexual receptivity and perception of emitter's sexual attractiveness)
estratetraneol
________ is a steroid derived from hormones produced by women which is claimed to have a strong sexual effect on the other sex (by increasing the recipient's sexual receptivity and perception of emitter's sexual attractiveness)
amygdala
________ is a structure that receives input from the olfactory bulb; it plays a critical role in emotional responses and can be activated by emotional stimuli across various sensory modalities (like visual, auditory, olfactory, and gustatory stimuli)
recency effect
________ is the tendency to remember recent information better than earlier information
anterior piriform cortex (APC), posterior piriform cortex (PPC)
_________ and ___________ are the two subdivisions of the piriform cortex
odorants
_________ are molecules that olfactory receptors "recognize" and respond to by producing neural signals that the brain represents as perceptions of different odora
entorhinal cortex
_________ is a structure that receives input from the olfactory bulb; it is the gateway to the hippocampus (where long-term memories are stored and retrieved)
accessory olfactory bulb
_________ is a structure that's distinct from the main olfactory bulb; site of synapse for axons of vomeronasal receptor neurons
anterior piriform cortex (APC)
_________ is the anterior (front) portion of the piriform cortex; it produces representations of features of the chemical structure of odorant molecules (like carbon chain length, which affects detection threshold, cross adaptation, and the perceptual similarity of odorants)
detection threshold
_________ refers to the concentration of an odorant necessary for a person to detect it (describes "strength" of an odorant)
carbon, hydrogen, oxygen, nitrogen, sulfur
_________, _________, _________, _________ and _________ are the atoms that make up the odorant molecules detectable by humans
Richard Axel, Linda Buck
__________ and ________ were American scientists that won the 2004 Nobel Prize in Physiology or Medicine for their work on the genetic basis of olfactory transduction; discovered the family of genes that express the G-protein coupled receptors (GPCR) that transduced odorant in the cell membrane of olfactory receptor neurons (ORNs
olfactory receptors
__________ are G-protein coupled receptors located on the surface of olfactory receptor neuron cilia (odorant molecules come in contact with these receptors after dissolving into and crossing the mucus)
pheromone
__________ is a chemical substance emitted by individual organisms that evokes behavioral or hormonal responses in other individuals of the same species (function as means of chemical communication)
piriform cortex
__________ the brain region considered to be the primary olfactory cortex because it's the only region that both receives signals directly from the olfactory bulb and is known to be dedicated solely to olfaction
olfactory epithelium
___________ a patch of tissue (about 2 cm^2) in the upper reaches of each nasal cavity; the epithelium contains ORNs and is covered by layers of olfactory mucus
androstenone
___________ is a pheromone found in pigs that initiates receptive mating behavior in female pig (effect occurs even when it is sprayed and male pig is absent)
hypothalamus
___________ is an almond-shaped region below the front of the thalamus; involved in a wide range of functions (through the release of hormones and through neural activity) such as regulation of thirst, hunger, and sexual behavior
Bowman's gland
___________ is embedded in the olfactory epithelium and continuously secretes the mucus which covers the olfactory epithelium (which then flows to the back of the cavity, into pharynx, and is swallowed)
supporting cells
____________ are cells with the olfactory epithelium that provide a structural matrix for olfactory receptor neurons (ORN)
parts per million (ppm)
____________ is a unit used to measure the concentration of odorant molecules (measured as the number of odorant molecules present in 1 million molecules of air)
memory, quality
context (whether odors are smelled alone or in combination) affects both the _______ and ________ of odors
1
each olfactory receptor neuron (ORN) has ________ receptor type(s) on its cilia
3, 7
humans have a TOTAL of about _____ to ______ million olfactory receptor neurons (ORN)
10,000, 20,000
humans have an estimated _______ to ______ of each olfactory receptor neurons (ORN) type
350
humans have approximately ______ types of olfactory receptor neurons (ORN)
350
humans have approximately _________ different olfactory receptors (each type activated by a restricted set of odorant molecules)
5,000
humans have approximately __________ in the olfactory bulb that receive signals for olfactory receptor neurons (ORNs)
vomeronasal olfactory system
in many species, __________ is an olfactory system that senses pheromones; it is distinct from the main olfactory system used to smell most substances (found in bony capsule near nostrils in mice)
10, 20
mice have a TOTAL of about _____ to ______ million olfactory receptor neurons (ORN)
1,100
mice have approximately ______ types of olfactory receptor neurons (ORN)
1,100
mice have approximately _________ different olfactory receptors (each type activated by a restricted set of odorant molecules)
1,800
mice have approximately __________ in each olfactory bulb
350
olfaction is based on the responses of ________ receptor types
visual, verbal
people's judgements of odor quality (either actual identity or just familiarity) can be influenced by ________ and __________ cues
insects
pheromones are particularly important to ______ (animal group)
true
true/false: the state of the individual has an effect on whether some odors are judged as pleasant or unpleasant
sex-related mood, levels of arousal, approach behaviors, hormone levels
research indicates that substances emitted by individuals of one sex can evoke changes in ________, _________, _________ and ________ in the other sex
pattern
research suggests that it is the ________ of olfactory receptor neuron (ORN) responses that determines how an odorant smells
hypothalamus, orbitofrontal cortex
the amygdala sends projections to the _________ and ___________
olfactory tract
the axons of mitral cells and tufted cells, carrying neural signals from olfactory bulb to higher areas of the brain (piriform cortex, amygdala, entorhinal cortex)
chemotopy
the distribution of glomeruli in the olfactory bulb exhibits a coarse ________ in the sense that the axons of ORNs activated by odorants with similar molecular structures tend to travel to glomeruli within the same part of the olfactory bulb
thalamus
the olfactory system is the only sensory system in which the pathways from sensory receptors to the cortex doesn't pass through a nucleus of the _______ (reflects that the olfaction was one of the earliest senses to develop, and that the thalamus did not develop until after olfaction was established)
population code
the olfactory system uses the __________ (neuronal response code type) based on the responses of 350 different olfactory receptor neurons (ORNs) in order to represent the different odorants in neural signals
piriform cortex, amygdala, entorhinal cortex
the olfactory tract from the olfactory bulb sends signals to the ________, _________, and _________
adaptation
the piriform cortex is responsible for the olfactory phenomenon of _______ (of the type that occurs when one enters a bakery and stops smelling the bread after a while)
1,000
there are about ______ genes that are devoted to the genetic code for the 350 different olfactory receptor types (about 4% of human genome)
true (supposedly)
true/false: unpleasant and pleasant smells are more effective at activating the amygdala than sights and sounds
retronasal pathway
transduction of odorants via the (orthonasal pathway/retronasal pathway) is critical for the perception of flavor
true
true/false: Humans are able to rapidly acquire long-lasting memories of odors
true
true/false: Olfaction is fast adapting because once identified, evaluated, and possibly responded to, the organism no longer needs to perceive a smell in order to assess the current situation (allowing it to better prepare for detection of new smells)
true
true/false: The range of molecules that a given organism can detect depends on the conditions under which the organism evolved
true
true/false: cross-adaptations occur between some perceptually similar odors but not others, despite similarity in molecular structure
true
true/false: different concentrations of an odorant produce different patterns of activity in the mitral and tufted cells, and this helps explain why certain odors smell very differently at high and low concentration
false
true/false: humans appear to have a functioning vomeronasal olfactory system
true
true/false: it is possible that the vomeronasal olfactory system is not necessary for sensing pheromones
true
true/false: memories evoked by odor are more emotionally charged than those exiled by words or pictures
false
true/false: odorant molecules with different structures always smell very different
False
true/false: odorant molecules with similar molecular structures always smell the same
false
true/false: once damaged, the olfactory system cannot repair itself
true
true/false: people are better at judging the pleasantness or unpleasantness of odors than the identity of odors
true
true/false: perceptually dissimilar odors can produce a cross-adaptation
false
true/false: research suggests that the disgust reactions to substances like bodily waste are innate (present from birth)
true
true/false: smokers typically experience an improvement of olfactory performance after they stop smoking
false
true/false: the piriform cortex is chemotropically organized (has a chemotropic map)
