The+Paper

(At the top is the link to my final paper - the actual exciting stuff! Underneath, this includes, in order: my proposal, lit review, outline, source notes, and working draft. The working draft started out as a rougly draft - for a definition see the SYP link at the bottom of the home page - and I'm editing it on this wiki. It's going to stay as the second-to-last draft, my final being posted at the top. Previous drafts are visible in old edits of this wiki.)


 * Final Paper**

media type="custom" key="17526364" (available as a google doc)


 * Proposal**

My first idea was to make a scrapbook of overheard conversations. I thought this would be interesting because I had just recently overheard some interesting things while waiting for a college interview, but as I thought more about it, I realized how passive this project was. It involves a lot of waiting and luck and is probably something that I can do on my own time and doesn't even require that much effort. Also, I couldn't think of something I wanted to write an essay about. So then in my psych class, Joel gave us a book review project. I realized that I am really interested in sensory information and the brain. Also, I wanted to find a project that involved active work, like experimentation. Then, on Christmas, my little sister bought me basil perfume, which actually smelled like licorice, and I had the idea to learn how to distill the scents of plants that we grow in my garden at home. In order to do this, I'd have to build a still - the machine in which you can distill scents - and then experiment with different plants and techniques. I'm not a big perfume person, but I really love the smells of the garden; I imagine my final project being a collection of various garden smells with a description of the complicated process about how they were made. I'd either use plants from our own garden at home or buy them from farmer's markets. That project really excites me because I don't know anything about how the process works and because the experimentation means that I would actually get to work on something rather than hang around and wait to overhear things. Also, I'm excited to write a paper about either the history of distillery or the role of scent in the brain. I've looked online, and there's a lot of resources about how to distill scents. There are books on the process itself as well as multiple books and studies on olfactory sensory information. I don't think that a lack of reliable information will be a problem, or the lack of actual stuff to do (and that is what I worried about/what made me less interested in my old project).

**Lit Review**
For centuries, people have recognized and revered the intensely strong connection between the sense of smell and memory. Getting a whiff of a familiar scent seems to bring back such monumental things as people and entire periods of time. However, even though we are continuously perceiving the scents that surround us, people are rarely aware of using their sense of olfaction. Perhaps for this reason, the small amount of scientific research on the sense of smell pales in comparison to the plethora of books published on the other senses. Very little is understood about the nose and its connection to the brain; from how the nose smells to the reason that scent is so closely related to memory, much remains undiscovered. In fact, scientists and perfumists are still debating theories of smell that deal with the most basic processes - how the nose smells smells - to the most complex - how the brain encodes memories.

The physiology of the nose is well-documented. Biology textbooks detail the structure of the nasal cavity; the olfactory membrane is on top of the cavity, covered by mucus, and has cilia protruding from it to which odorants bond ( Woronczuk). Most of this is agreed upon by scientists, but there is still debate over the function of the vomeronasal organ in humans, which may detect pheromones and is located near the nostrils (Meredith). From the olfactory membrane, action potentials are sent up the olfactory nerve towards the brain, synapsing from the olfactory bulb on the cribiform plate - a thin layer of bone - to glomeruli, then onto the brain (Woronczuk). The exact process of synapsing onto glomeruli is also a topic of research; scientist P.-G. de Gennes believes that the synapses help categorize the information in its process to the brain. From here, the synapses travel to the hippocampus and amygdala, near the limbic system of the brain, and are converted to memory (Woronczuk).

There are two predominant theories of how the nose processes smell. The predominant theory is the syllabic theory of olfaction, which explains that odorants fit into a specific protein on the olfactory membrane, using a lock-and-key mechanism (Doty). The way that this process works is well-documented because it is universal in biology, and seems to be applicable to this same case, although there are also technical complications that seem to refute the theory (Turin). Less popular is the vibrational theory, most recently detailed by Luca Turin in his novel //The Secret of Scent//, which claims that the electrical impulses fired from the olfactory membrane actually result from each molecule's specific vibrational energy (Turin).

Although the entire sense of olfaction is a source of mystery, olfactory memories are possibly the most enigmatic piece. It is known that olfactory information is transferred directly to the hippocampus and amygdala without passing through the thalamus, as most information does - pheromones, being a slight exception, go directly to the hypothalamus where it is postulated that they affect the distribution of hormones (Craver, Meredith). The hippocampus and amygdala are very old parts of the brain that deal with memory and emotion, so it seems logical that scent would feel intangibly connected to these two processes (Heuberger). However, what happens to the data here is a source of confusion. Once the information has reached these places, the next process that occurs is writing it into memory, most likely, a process on which many psychologists have published theories (Gray). Psychologists are still researching both the mechanics of memory and how memory is experienced as a part of consciousness. Joseph Ledoux, a leading psychologist and researcher, argues in his book // Synaptic Self // that both explicit and implicit memories are integral parts of who we are. Other researchers study the processes of how our sensory information helps creates our continuous sense of mind, looking at theories like the computational theory of mind, which explains that the mind works like a multi-functional computer, working on many different problems at once by using lateral processing (Pinker).

In order to fully understand olfaction, much research needs to be performed o n every aspect of the process, from our basic sense of smell to how episodic memories become attached by scent. Although scientists have filled in a basic picture of the journey from odorant to memory, many details remain to be fleshed out. As researchers continue to experiment in this rapidly changing field, they are constantly finding new, interesting facets of our sense of smell and how it relates to memory.

Works Cited

Craver, Carl F. "The Making of a Memory Mechanism." //Journal of the History of Biology //36.1 (2003): 153-95. //Jstor //. Kluwer Academic Publishers. Web. 9 Feb. 2012.

Doty, Richard L. //Olfaction //. //Questia //. Web. 9 Feb. 2012.

Gennes, P-C De. "Organization of a Primitive Memory: Olfaction." //Proceedings of the National Academy of Sciences of the United States of America // 44 (2004): 15778-5781. //Chemical Senses //. Web. 2 Mar. 2012.\

Gray, Peter. //<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">Psychology //<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">. New York: Worth, 1999. Print.

<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">Meredith, Michael. "Human Vomeronasal Organ Function: A Critical Review of Best and Worst Cases." //<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">Chemical Senses //<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;"> 26.4 (2001): 433-45. Print.

<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">Pinker, Steven. //<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">How the Mind Works //<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">. New York: Norton, 1997. Print.

<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">Turin, Luca. //<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">The Secret of Scent: Adventures in Perfume and the Science of Smell //<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">. New York: Ecco, 2006. Print

<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">Weber, Sandra T., and Eva Heuberger. "The Impact of Natural Odors on Affective States in Humans." //<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">Chemical Senses //<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;"> 33.5 (2008): 441-47. //<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">Chemse.oxfordjournals.org //<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">. Oxford Journals. Web. 9 Feb. 2012.

<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">Woronczuk, Julia, Stephanie Medwid, Laura Neumann, and Sarah Eshelman. "The Olfactory System: Anatomy and Physiology." //<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">Macalester College: Private Liberal Arts College //<span style="background-color: #ffffff; font-family: 'Times New Roman',Times,serif;">. Macalester College. Web. 02 Mar. 2012. <http://www.macalester.edu/academics/psychology/whathap/ubnrp/smell/nasal.html>.


 * Source Notes**

__(__note: These typed lab notes mostly exclude my notes on methods/results and are taken from the abstracts/introductions/ conclusions. Links to the labs and websites as well as citations for book can be found on the Artifact List page.)

__Organization of a Primitive Memory: Olfaction__ ("olfaction storage in primitive mammals") (incomplete notes)

1) pathways leaving from olfactory bulb (on cribiform plate) excite only a certain number of cells in the piriform cortex (also called olfactory cortex, located in neocortex of mammals) 2) these cells give info to storage areas (in vertebrates), w/ 2 different types of systems (a) simple recognition of smell (b) connection of smell to image = more complicated

-300 types of detectors on nasal epithelium -from here, info goes to glomeruli in specific path -then info goes to lateral olfactory tract, pyramidal cells in P.C. (piriform cortex) analyze info

-hypothesis: specific types of phyramidal cells fire in specific responses/patterns, mainly for specific pathways 1) info leaves glomeruli goes to targeted areas of PC (assumption made here that is disproved: bc there is a certain # of emitter cells on PC, and every type sends a certain # of signals to the storage area, (which is a large #), then each neuron in the storage area is reached only once, by one pathway (the number of cells in the storage area matches up to the number of signals sent)

attractor networks: groups of coupled neurons, 80% excitatory, 20% (ish) inhibitory, get hit by external signals, certain neurons fire and others don't based on how they are coupled -then, long-term plasticity occurs here, becomes part of memory (look at LTP in //Synaptic Self//) -issue:

__The Impact of Natural Odors on Affective States in Humans__ -olfaction/"affective memory processing" (essentially, emotion) closely related, odors can change mood --- long term -good odors make ppl happy/improve mood, bad odors do opposite, unsure about intensity's effect on mood -examining natural fragrances, effect on mood, alertness, calmness, rated pleasantness/intensity of spaces w/ fragrant blooming plants and non-fragrant blooming plants -performed 1 experiment at night to account for differences in visual stimuli -performed in "Duftgarten" (Fragrance Garden) in vienna

-blooming plants - complex natural odor - improves all 3 in duftgarten, rated more intense/pleasant -possible that effect of experience lasts long time (look at experiment #3, in which control comes after experiment and there is no significant difference in mood/alertness/calmness) -averse odor have averse effects, last shorter -some odors increase alertness while subject is awake -complex natural odors improve mood/alertness/calmness in outdoor setting regardless of visual input

__Laterality of the Olfactory Event-Related Potential Response__ -use electroencephalographic (EEG) recordings to look at amplitude of brain waves while odor applied to 1 nostril -amplitude = amount of energy going into process, latency = speed of process -these are affected by stimulus' intensity/length -possibly, handedness affects laterality of OERPs -when vanillin (pleasant odor) applied to left nostril, higher amplitudes than right nostril

__Lateralization of Olfactory Processes__ -lots of centrifugal fibres lead from piriform cortex to olfactory bulb -EEG is quick (few milliseconds) but doesn't go deep into skull (few centimeters), can't study olfactory events deep in brain -PET/fMRI better for olfactory study: study regional cerebral blood flow (rCBF), shows neural activity. fMRI measures changes in oxygen levels in blood (these are haemodynamic techniques, haemodynamic = blood circulation resolution)) -distribution of processes/activities is not symmetrical -left hemisphere deals with language, right hemisphere deals with music, faces, visual stimuli like that -except, when healthy subject smells very bad odor, left hemisphere increases rCBF activity -neutral, passively smelled odors first used to study olfaction, diff. tasks look at diff parts of neurological processes -judging pleasantness/familiarity vs. naming scent, w/ 1 singular name -to detect odor, superficial judgement that doesn't need stored memories of odor, perceptions/semantic memories of odors stored in different areas, semantic memories are activated by questions of edibility -assessing familiarity = rCBF inc. in right hemisphere, not w/ detection -primary olfactory cortex activated in non-olfactory processes of sniffing and smelling -left hemisphere = hedonic judgements, right = familiarity judgements -passively smelled odor still (probably) activates implicit semantic processing -3 main aspects of olfaction: 1) semantics (analytical processing) 2) emotional processing 3) familiarity processing -left = semantics + hedonic value -right = familiary + holisitic, not analytical -separation of familiarity/ability to judge unpleasant odor makes evolutionary sense, bc it's faster to react to dangerous situations -emotional processing happens before other judgements -look at rxn times in response to different odors - averse vs. pleasant, etc

-parallel processing in right and left (as detailed) -serial processing in primary and secondary olfactory areas -piriform/amygdala deal with emotional rxn, (intense vs not intense), OFC assesses odor -then, superior frontal cortex integrates rxn to odor into decision making -hard for humans to speak about/identify odors bc the pathway from nose to brain is so short -perceptions of odors are (possibly) created by ourselves, as units (Gestalt-y)

__Olfactory Memory: the Long and Short of it__

__Demystifying Wine Expertise: Olfactory Threshold, Perceptual Skill and Semantic Memory in Expert and Novice Wine Judges__

__Odor-Evoked Autobiographical Memories: Age and Gender Differences Along the Life Span__ -odors can evoke both autobiographical and referential memories (name and objects) -investigating RTs for identifying scents that are tied to triplets of words, looking at gender/age -and the ratio of autobiographical/referential memories that are thought of for each scent

-olfaction = good for studying autobiographical memories bc it evokes them -supposed to judge pleasantness/vividness

-autobiographical memory studied w/ verbal cues ("describe 1st experience to come to mind...) -shows childhood amnesia, reminiscence "bump", recency (can't remember childhood until 3 yrs old, adults over 50 remember ages 10-30 best, easier to remember more recent events, respectively) (look at gray) -with olfaction, reminiscence bump is 1st 10 years (so maybe olfactory memory is older/lasts longer than other sensory memories, also more emotional, thought of/retrieved less than visual/auditory memories. more prone to semantic processing) -capability of evoking emotions leads to evoking memory? -naming odors reduces feeling of being brought back (look at other labs) -identifying/naming odors makes it harder to tie them to specific situations -looked at tying them to triplets of words

-in adolescence, females better at verbal memory (difference changes as subjects age) -fewer autobiographical than semantic memories at adolescence (also haven't lived long)

-in adulthood, autobiographical memories have faster reaction times (naming of word in triplet) than semantic memories, also faster in females (possibly, these memories more emotionally vivid in women)

-elderly ppl=same RT trend, more autobiographical than referential memories (but have lived longer) -also, in old age smell and memory retrieval worsens

-females have faster RTs, are better at identification/discriminating b/w odors, semantic memory, odor memiory, have different ideas of what smells good than men, and increases drastically during puberty -impt to use odors known to both genders (shoe polish vs. hair spray ... ?) -b/w adolescence and adulthood, memory/odor memory improves -b/w adulthood/old age, memory/odor memory declines

-some studies: women more anxious when exposed to bad smells, more distressed w/ conditioned visual stimuli and public speaking -maybe women are more prone to autobiographically encoded odors provoking 1st, memory of experience, and 2nd, responses to experience -esp during years leading up to puberty

-if odor is encoded referentially or autobiographically has difference on retrieval, but both improve retrieval of thing that was learned with smell (Loci mnemonic, word triplet)

-possibly odors connect more to implicit memories than other stimuli do, more base emotion than just odor name/cue -when odor is named, subject has fewer autobiographical memories -when not noticed, an unidentified odor is remembered better than an identified odor by unaware subject

__Odor Localization and Sniffing__ -to localize an odor (tell which nostril you're sniffing it from), odor has to stimulate trigeminal nerve (connects to brain) -should be easier to localize a scent when you sniff -pure odorants are difficult to localize, maybe not even localize-able (mixed odorants are easier) with air stream -pure odorants include phenyl ethyl alcohol, lavender, n-butane -sniffing makes it easier to smell, by making the brain pay more attention -don't understand why olfaction is bilateral (has two separate halves, like 2 nostrils and a left olfactory lobe and a right olfactory lobe)

-deliver odorants either by blowing air into nose or having subject sniff -when sniffing, difficult to identify nostril of pure odorant, but easier (sometimes) with sniff -sniffing makes it easier to identify/detect smells

-find that: some (mixed trigeminal-olfactory) stimuli easier to localize with passive sniff -possibly sniffing is useful bc it requires attention -important to perform lots of trials with localization test -if an odorant is localizable, it probably does stimulate trigeminal nerve -some pure odorants can be sometimes "localized", but this might mean that occasionally they stimulate trigeminal nerve but are still pure

-harder to localize pure odorants given to left nostril (subjects perform worse than chance, at chance with right nostril) -independent of handedness -auditory localization has the same right bias, vision too (when dividing horizontal lines, divide closer to the left like center moved right) -maybe because right hemisphere controls spatial attention

__Odor Recognition Memory as a Function of Odor-Naming Performance__ -subjects better at recognizing smells when given alternative scent names -but, most likely only helpful if these names are available when odor is encoded and when name is being retreived -also experiment with # of labels given (4-16) -if given feedback when identification is correct, memory improves significantly -conclude that perceptual processes of matching odorant to learned odor representations is impt to naming odorants/episodic memory

-some studies say: no relationship b/w odor naming and memory, others say yes -this study looks at both semantic + episodic memory -when not given labels, odor identification = 50%. given labels, 85% -used 18 familiar odors with distinct names

-when given label options while trying to recognize/name an odor, accuracy/recognition memory improve -(consistency of naming strongly correlates to accuracy of memory) -but also, look at Brearton: actually naming odor (when recognizing it) doesn't help memory, but giving name at encoding does -maybe bc processes of recalling remembered odor is different than encoding new one

-2nd experiment shows strong improvement w/ labels given at both times, not either -maybe labels give brain context to search with (general idea? linked to each other?) -becomes matching one list w/ another, instead of generating idea -"meaningfulness of an olfactory experience is closely tied to its categorization as an odor object" (odor object = representation in brain, movie-in-the-brain kind of) -so, labels help match input w/ encoded experience -73% of trials naming scents = "new", when name was incorrect or inconsistent (subject thought odor was new, but had already been exposed to it)

-expertise may also help identification -consistently/correct naming = well remembered, inconsistently/incorrectly named = not well remembered -connects semantic info w/ episodic memory

-possible to identify new smell out of new/old pairing even if old is inconsistenly/incorrectly named -Olsson et al: inc. odor memory disappears after week, con/corr. remains -for working memory, naming may not be necessary but helps -labels don't actually improve processes of memory but identification of odor object -when retrieving, remember only name and not actual sensation? (self-generated odor labels)

-flat odor recognition memory forgetting curve: odors encoded/kept as single units/perceptions -dual-coding theory: 2 different memory systems, one for odor label and one for olfactory pattern (perception) and there is learned relationship. (supported by good connections, poor connection doesn't support it.. b/c a strong olfactory memory in general would make up for a bad connection/weak semantic memory there)

__Olfactory Hypersensitivity in Migraneurs__ -olfactory hypersensitivity = frequent w/ migraines, unique -greater blood flow in left piriform cortex in migraineurs -during migraine, more activity in left temporal lobe, lower in right parts of the brain (frontal/temporo-parietal) -maybe indicative of malfunctioning top-down processing (olfaction is bottom-up mostly)

__Fragrance: Beverly Plummer__ - Plants are best harvested at their peak; flowers when they are first blooming, leaves when they're almost mature. This is when the essential oils are most accessible and will come out most easily in the distillation process. - Also, plants should be harvested right after the dew has dried but before the sun has dehydrated them.

//leaves//: cut stalks when leaves are newly formed //roots//: gathered in the fall for best results, but roots harvested in the springtime will also work //flowers//: cut when mature

- Materials should be dried/stored quickly and naturally (They shouldn't be heated) - They should be cleaned before they are stored

//leaves//: can be stored either on or off the stalk - should be dried in the open air/warmth, between layers of window screens or cheesecloth - drying time is between four days to three weeks (material is done when it's dry and crumbly) - if the leaves are left on the stems, they should be tied into bundles and left to hang upside-down (attics are good, and if they're dusty the plants can be stored in grocery bags with holes) - when the material is dry, it should be stored in a light-tight glass container and labelled

//roots//: should be washed and then cut into 1/4 to 1/2 inch pieces - roots can be treated the same way as leaves OR they can be treated in the overn - when the oven is at 175 degrees, put the roots in with the door open until the roots are brittle - they should be stored in light-tight glass containers and labelled

//flowers//: should be treated the same way as leaves - after a few days, check the container for evaporated moisture; if there is any, the flowers should be re-dried - Extracting oils without using a still (for more notes, see the Basic Overview pages) - List of fragrant plants:

//leaves//: lavender, lemon, hyssop, rosemary, thyme, lemon balm, orange mint, strawberry, //roots/seeds//: ambrette seeds, khuskhus roots, lovage roots, sandalwood roots, corianderseeds, aniseed //flowers:// lilac, lily of the valley, magnolia, oleander, tuberose, acacia, lavender, pinks - per/fumum = through/smoke

__The Secret of Scent__ - Every molecule has a different scent - A perfumist's job: - The shape theory of smell: scent is based on the shape of the molecule, like so much else in biology is based on shape. (The basic idea: "smooth" scents are rose-like, "sharp" scents are mustard-like, for example.) - Scent works with a lock and key mechanism; different molecules unlock different enzymes (they bind to specifically shaped binding sites that will only bind to one molecule)

- odotope theory: there are specific components in scent molecules that, when combined, form a unique smell, like twenty-six different letters form different words (components like: earthy, woody, harsh, etc) -issues with the odotope theory: - the magnet issue: it's hard to smell low concentrations - if each molecule that can be smelled has many different components, they must all be really large; the binding sties for those molecules would also have to be large and very complex, and there would have to be a huge amount of them

-1916, philosopher Hans Henring develops primary smell theory: a triangular prism, and each vertex represents a primary smell (floral, putrid, fruity, burnt, resinous, spicy). - each smell is made of these six primary smells - issue = "smell illusions": in scent, you can't mix two smells to smell like a pure smell, like you can in additive color mixing (red+blue=purple).

- syllabic theory of smell: similar to the component theory of smell, but involves chunks of components (like syllables, in an alphabet) that form functional groups, the parts that actually bind to/determine binding sites - issue = mirror-image (chiral) molecules that have the same construction, smell the same, but can't bind to the same binding sites (chiral molecules = molecules that display "handedness", that are different viewed from the left and the right side) - it would make sense if enzymes could be mirror-images and bind the two different molecules, but the amino acids in enzymes also display "handedness" (also, sometimes a left-handed molecule will had adverse health effects, while the right-handed molecule will have health benefits; they're different, basically) -an agonist: when an agonist molecule binds to an enzyme, it turns it on -an antagonist: when an antagonist molecule binds to an enzyme, it turns it off - but, perfumists have never made a molecule that can block the receptor. So, is there even a lock-and-key mechanism for smell? - smell is hard to study bc most of the data involves self-report, and so much of it is taken as fact that little research is done into all of it -a functional group: a group of atoms that determine the chemical behavior of a substance (for instance, its smell) - thiols (-SH) smell like rotten eggs - so, functional groups could be like primaries

__Luca Turin's Ted Talk__ - vibrational wavelengths created by molecules translate to sound - ex: borane and sulfur smell similar, and they have the same wavelength (found by Turin) - spectroscopes: people are trying to make them - Ford now makes nano-spectroscopes (so maybe, there could be a spectroscope small enough to fit in the nose) - electron tunneling (direct, indirect, assisted) creates wavelengths - coumarin = expensive, hard to produce scent that everyone wants (Turin finds a molecule with the same wavelength, called tonkin. It smells the same, big success !)

__Macalester College Olfaction Website__ A) Structure of the Nasal Cavity - olfactory membrane at the top of nasal cavity, covered by mucus-covered cilia - these cilia are heads of dendrites that are one end of bipolar olfactory receptor neurons - dust, bacteria, etc is caught in the mucus, denatures in stomach when mucus is swallowed - airflow through nostril = 250 mL/sec (not much air reaches olfactory cleft b/c it moves so quickly and is turbulent; when you breath in or sniff, more air crosses the membrane and more smell is processed) - in females, the exit space at the back of the nasal cavity is larger than in men - the color of the olfactory membrane matters (albinos can't smell) -olfactory membrane is made of three layers: 1) supporting cells that make mucus 2) basal cells that produce receptors (which are replaced every 4-8 weeks) 3) olfactory receptor cells (neurons where transduction takes places) - odorants in mucus bind to proteins in the cilia, stimulates G-proteins that activate adenylyl cydase, which catalyzes the ATP->cAMP (cyclic adenosine monophosphate) reaction. cAMP acts as a messenger, binds to membrane proteins inside the cilia, open CA++ channels, CA++ floods in and opens CL- channels. CL- flows out (following concentration gradient), membrane potential depolarizes, action potential fires down axon to the olfactory nerve (bundle of axons). Then, to cross the cribiform plate (thin layer of bone) synapses to glomeruli (cluster of neurons in olfactory bulb), each of which has two sets of outputs; one goes directly to the brain, the other crosses to the 2nd olfactory lobe

- from olfactory bulb, info sent to primary olfactory cortex, near the amygdala and hippocampus - 2 synapses away from amygdala, which deals with emotional memory/emotions, 3 synapses away from hippocampus, which deals with short-term/working memory - very close to limbic system (oldest part of brain, emotion, memory) - olfactory neurons = unmyelinated, so they're slow (maybe this is why they are connected to memory; longer sensation, lasts longer than visual/auditory) - directly connected to env't: (maybe it's simple to code memories for a sense which can directly deal with physical stimuli) - don't yet understand olfactory memory storage or decay - no evidence for olfactory primary (1st scent smelled in a series = easiest to remember) but familiarity and recognizability improve memory of smell (maybe no primary bc, unlike w/ visual or auditory stimuli, can't rehearse it in working memory) - keep smell in verbal memory?

- after 1 or 2 exposures, rats learn to avoid drinking liquid w/ odorant + quinine hydrochloride: so, probably there is olfactory memory - normal hamsters (not raised on liquid diet) learn spatial memories of odors in allocentric tasks - yellow chipmunks can find stores of wet (not dry) seeds: olfactory memory? - Mexican fur-tail bats nurse in same spots frequently: olfactory memory?

- Korsakoff's Syndrome: chronic alcoholism causes loss of memory + smell, apathy - hypsomia = less sensitive to smell, sometimes reversible or improvable. anosmia = complete loss of smell, usually irreversible. 1) less air gets to olfactory cleft b/c of nasal polyps/deviated septum/chronic sinusitis (infection) 2) epithelial problems: viral infections, sensory epithelium destroyed by solvents/gases (heavy metals, benzene, industrial dust) - 5-10% of head trauma involves loss of smell, more when trauma = more intense or if there's amnesia - loss of smell can be early symptom of Parkinson's/Alzheimer's - pregnant women sensitive to smell (look to notes in //How the Mind Works// on pregnant women and taste; similar hypothesis, maybe?) - epileptic seizures are sometimes preluded by a scent hallucination; sometimes scents can stop a seizure

-pheromones detected by vomeronasal organ. present in humans? maybe. Some scientists think it's only present in fetuses, some have done tests to show that pheromones can be detected in adults and info goes directly to brain - if the VNO is present in humans, the accessory olfactory bulb is either not present or has been flattened by human's large frontal lobe (accessory olfactory bulb = integral in processing pheromones) - researchers believe that VNO sends signals to hypothalamus, on which hormones to release/not release (affects neuroendocrine system, which deals with behavior like reproduction/sleep.) maybe also linked to limbic system. - MHC genes: major histocompatability genes, code for special protein markers that tell body if cell is intruder. Women/female animals prefer mates with different MHC genes; children will have wide variety of MHC genes, be better protected. These are also smell-able; asked men to wear shirts for two days, no deodorant, women choosing shirts to wear chose different MHC genes from their own. Possibly, MHC or other pheromones have hand in instant attraction; also, with memory, if women choose men who smell like past boyfriend (who presumably smelled good, had different MHC genes than her)


 * Outline**

Part 1 (introduction) the history of scents/humans (perfume, etc) -scent has been important for a long time, ancient part of the brain (close to limbic system, oldest part that deals with emotions/memories) -evolution-arily important sense: smelling rotten food, etc (pregnancy morning sickness theory) -development of perfume (emergence from alchemy), spiritual/erotic symbol -development of synthetics in early 1900s, chanel no. 5 -modern perfume industry, (a few sentences...)

Part 2 (background) how the nose works -syllabic vs vibrational theory (scent of odorant determined by shape or vibrational energy?) -odorant attaches to cilia in olfactory membrane at top of olfactory cavity, covered by mucus, causes action potential to be sent down olfactory nerve, through cribiform plate, (maybe is categorized here?) goes to olfactory cortex in the brain (brief explanation of different sections) -depending on what nostril odorant is breathed through, activates different parts of the olfactory lobe (right vs left, look for distinction in the lab) -encoded into long-term memory by plasticity of synapses, brief description of synapses/memory storage (long/short/working term) -is there an olfactory short-term? or working-term? debate, look at lab -close to amygdala/hippocampus, two of the oldest parts of the brain that deal with emotion/memory, theory is that this is why scent is so visceral

Part 3 (question) are there certain scents, or categories of scents, that are more prone to evoking autobiographical memories than other scents are? -field work (survey: most evocative scent, either autobiographical or semantic) -then divide them into categories, make observations -(this will, and can only, be fleshed out by the actual field work)

-"and now, to look at what sort of lab might investigate this further..."

Part 4 (lab proposal) -includes introduction (research on scent, not much is understood, explanation of EEG and other brain scans, different scents activate different parts of the olfactory lobe) aaaaaand -> -methods: collect a list of 20 common scents introduce people to the scents that find most evocative of autobiographical memories and record the EEG levels (there might be a better indicator) have people sniff the scents through both nostrils -results: different EEG levels for different scents? (maybe test autonomic body responses? do those even happen?)

Part 5 (proposed answer) brief discussion of other labs -mention: older people have more autobiographical memories, sniffing changing how scent is processed, discuss some scents are more frequent, women better at earlier age -but: if there are definite differences, then maybe it speaks to either vibrational/syllabic theories (more energy = stronger reaction... that's kind of silly, but maybe there could be a correlation like that) -maybe food-related scents are more evocative, b/c they are related to another chemical sense discussion: maybe this could have something to do with evolutionary importance of smells, maybe speaks to why some people like certain smells while other people don't

Part 6: scent is the smell that never sleeps, is closely connected to memory: and implicit and explicit memories are both very important in determining our self.

That is mainly my conclusion, but I'll also add a few sentences on how neurology=a rapidly evolving field, and the study of olfaction is definitely part of that.


 * Rougly Draft** (or part of it, at least; by no means is this a finished product! In word, double-spaced, this is 10 pages. I am going to add citations when I edit.)

For centuries, people have recognized and revered the intensely strong connection between the sense of smell and memory. Getting a whiff of a familiar scent seems to bring us back to specific times in our lives or evoke memories of people, similar to Marcel Proust’s famous madeleine scene in //In Search of Lost Time//.

Now, often the scent that reminds us of a person will be a perfume that they frequently wear, usually created out of synthetic odorants. After the discovery of the first synthetics in the late 19th century, the business of perfumery rapidly expanded. Synthetic molecules – molecules that are fabricated in a lab – smelled almost identical to natural odorants in addition to having low-cost and fast production. With the innovation of the iconic Chanel No. 5, the first perfume to boldly flaunt its harshly synthetic smell, synthetics began to dominate the perfumist market and few true essential oils were used. There still remained natural odorants for which a synthetic substitute was not found, like lavender, civet, or sandalwood, that scientists struggled with for decades after the initial rush.

Now, most natural scents can be recreated nearly identically in the lab, and new scents are discovered daily. The job of the modern-day perfumist is to sort through tens of samples of new scents then rate, match, and label them. These scents are now everywhere around us, not only in romantic little bottles, but also in most cleaning products as well as several department stores. Most body and health products also have artificial scent.

However, the art of perfumery dates back to a time before the invention of synthetic odorants and mass-production of scent. Perfumery began as a subcategory of alchemy; while experimenting with turning base metals into gold, alchemists discovered certain materials that they believed held magical essences. Those alchemists who tried to extract the essences from these materials soon moved on to the study of odor, believing scent to have a connection to the spiritual world. Soon. they extracted the first essential oils from fragrant plants and became the first perfumists. They believed that the scents connected to the soul and could transport the sniffer into a spiritual realm, and perfumes became wildly popular for aristocrats who could afford them.

Stories and legends about our ancestor’s use of scent are still told. In ancient Egypt, Cleopatra allegedly soaked the sails of Mark Antony’s barge in her singular perfume so that he would be reminded of her as he sailed away. Nero covered Lake Lucinia with fragrant rose petals during a particularly extravagant feast, and Romans would send scented doves into the air during feasts to cover the room with scent. The use of perfumes as powerful erotic and spiritual tools has been widespread across the entire globe and throughout history.

Olfaction has also long been a symbol of eroticism. Although odors like civet and musk are popularly described as the most erotic scents, pheromones may play a large role in sexual attraction for humans. Although most scientists agree on this basic layout of the nose, there is still debate over the function of the vomeronasal organ in humans, which may detect pheromones and is located near the nostrils (Meredith). This organ is clearly present in many mammals and plays an instrumental role in their mating season and pairing, but its exact role in humans has yet to be determined. Some studies suggest that the vomeronasal organ strongly influences human sexual desires; studies have shown that when a woman is given two shirts to wear, one coated with major histocompatability genes - a smell-able pheromone abbreviated as “MHC gene” - similar to hers and one coated with a different MHC genes, the woman is likely to prefer the shirt (macalester website.) This suggests that MHC genes, which seem to be codes for different types of antibodies present in a body, help a woman choose to reproduce with somebody possessing antibodies different from her own in order to have a child with diverse antibodies.

Many scientists believe that olfaction has played another important role in human evolution. Humans with acute senses of smell and strong connections between olfaction and memory learn the smells of rotten food and can thus learn to avoid food-related illnesses. This connection between olfaction and memory seems to be explained, in a very basic way, by the fact that the olfactory cortex - the place where olfactory information is processed - is located next to the limbic system, the oldest part of the brain that processes memory and emotion. Because they are literally close to each other in the brain and developed around the same time, the olfactory cortex is more closely connected by electrical bridges called synapses than the other somatosensory cortexes are to the limbic system. In addition, the asymmetry of the left and right hemispheres of the olfactory cortex grant humans with a fast response to dangerous situations; while the left hemisphere processes the hedonic value of the odor, the right is simultaneously processing its familiarity. These two conclusions inform the fight or flight reaction that may occur after a human smells an averse odor.

Although we constantly perceive scents around us that affect our behavior, people are rarely aware of using their sense of olfaction. Perhaps for this reason, the amount of scientific research on the sense of smell pales in comparison to the plethora of books published on the other senses. Very little is understood about the nose and its connection to the brain; from how the nose smells to the close relationship between olfaction and memory, much remains undiscovered. In fact, scientists and perfumists still debate theories of smell that deal with the most basic processes, like how the nose processes odorants, to the most complex, how the brain encodes memories. In this paper I will examine the neurological journey from odorant to memory and focus on the question of whether or not there are specific categories of odorants that are more prone to being encoded with episodic memories than others.

The physiology of the nose is well-documented. Each nostril, lined with hairs that prevent dirt and dust from touching the sensitive skin on the inside of the nose, creates a passage for air into the nasal cavity. The olfactory membrane is located at the top of the nasal cavity and is covered by a layer of mucus that protects the membrane from dust and harmful molecules, which are caught in the mucus and denature in the stomach when swallowed. The olfactory membrane is covered by cilia, little hair-like protrusions that are the only part of the central nervous system that touches the outside environment. Odorants, when inhaled through the nose, bond to these cilia and send a chemical signal to the brain: this is called the firing of an action potential. For this reason, olfaction is considered one of the two chemical senses, along with taste (Woronczuk).

When an odorant bonds to a membrane protein, channels in the membrane open and allow other molecules to flow in and out of the cilia. When these channels are not open, there is an established membrane potential and the inside of the cilia, which is also the dendrite of an olfactory neuron, is very negative compared to the outside. So, when an odorant binds to a membrane protein, it catalyzes a series of complex chemical steps that lead to the opening of channels that allow CA++ molecules to flow into the cilia, moving down their concentration gradient and depolarizing the membrane potential. At the same time, Cl- flows out of another newly opened channel, also following its concentration gradient and depolarizing the membrane potential.

This reaction occurs simultaneously in multiple cilia, which are all connected to the nucleus of the olfactory neuron. When the membrane potential of the entire nucleus head reaches a certain level of depolarization, an action potential fires down the axon. The area of depolarization travels through the axon, which is like a very long cell divided into sections by Schwann cells that cover the axon and prevent the molecules involved in the reaction from escaping the reaction area. At the end of the axon, another chemical signal is sent out into the extracellular fluid that is received by dendrites of a receiving neuron.

There are two predominant theories of how the nose processes smell. Scientists predominantly accept the syllabic theory of olfaction, which explains that odorants fit into specific proteins on the olfactory membrane using a lock-and-key mechanism (Doty). The lock-and-key theory functions on the principle that molecules act like keys by because they can only bind to a unique lock, or membrane protein. In order to bond on to a protein, a molecule has to fit into a binding site on that protein. Each binding site and molecule is uniquely shaped, so it follows that each molecule could fit into one binding site, very simply. The theory also suggests that each protein, having only one molecule for which it will open channels, has a unique reaction that follows. Perhaps the signal is sent repeatedly for a basil odorant and only once for a thyme odorant, although this is very oversimplified. This reaction is then sent down the olfactory nerve to the olfactory bulb and limbic system, where it evokes memories, is perhaps named, and elicits an emotional reaction. Although the lock-and-key mechanism is prevalent in biology – for example, with antibodies and hormones and most other chemical signaling in the body – there are several complications that seem to refute its application to olfaction (Turin).

The main objection to this theory stems from the sheer number of odorants that humans can smell and distinguish. There are so many odorants that the olfactory membrane would have to be significantly larger than it is in order to have a separate protein for each odorant. To address this issue, several variations on the basic lock-and-key theory have been developed. In 1916, philosopher Hans Henring developed the theory of primary smell which establishes six primary smells on the vertexes of a triangular prism: floral, putrid, fruity, burnt, resinous, and spicy. All odorants are a combination of these six primaries, in varying proportions. Although this solves the multitude of membrane protein problem, it raises the issue of smell illusions. Two odorants cannot be combined to make the same smell as a pure odorant, but the primary theory makes this a possibility.

A slightly more complex theory is the odotope theory, for example, suggests the existence of different components of scent like woodiness, earthiness, or harshness that form a new smell when combined, similar to how the combination of letters form words. Although this solves the issue of having a plethora of membrane proteins, odorants formed by various multiple components like this would have to be huge and fit into incredibly complex binding sites.

The syllabic theory of smell addresses this next issue by suggesting the combination of components into groups called functional groups, comparable to syllables in a word. Functional groups are the parts of molecules that actually bind to binding sites in proteins, so this simplifies the complicated-binding site issue. The new problem with this theory is that chiral – mirror-image – molecules with the same construction, that have been shown to smell identical, cannot bind to the same binding sites even though they have the same functional groups. The same enzyme cannot bind a molecule and its mirror-image molecule because the amino acids that make up enzymes display handedness.

Another objection to the lock-and-key theory, which encompasses all these variations, is that a lock-and-key mechanism implies that the channels in a membrane protein can be turned off by an odorant as well as turned on. However, scientists have not yet found an odorant that closes channels in the olfactory membrane.

Less accepted is the vibrational theory, most recently detailed by Luca Turin in his novel //The Secret of Scent//. Turin refurbishes an old and largely disclaimed theory that suggests that the electrical impulses fired from the olfactory membrane actually result from each molecule's specific vibrational energy rather than its shape (Turin). Every molecule has a unique vibrational energy that depends on the periodic movement of atoms, especially of electrons. Turin adopted this theory after he found that sulfur and borane, which have very similar smells, also have very similar wavelengths. After this discovery, Turin experimented with other molecules sharing similar wavelengths and found more scent pairs.

In olfaction, the axons are connected into a bundle called the olfactory nerve. This nerve leads directly to the brain, although it crosses a thin layer of bone called the cribiform plate which supports the olfactory bulb. From there, the axons synapse onto glomeruli, which are clusters of neurons in the olfactory bulb (Woronczuk). The olfactory bulb is located in the front most part of the brain and processes olfactory input. From the glomeruli, neurons also send information to the nearby hippocampus and amygdala, two parts of the limbic system that process memory and emotion, respectively. The exact process of synapsing onto glomeruli is also a topic of research; scientist P.-G. de Gennes believes that the synapses help categorize the information in its process to the brain. Olfactory information does not pass through the thalamus, the relay center for information coming into or leaving the brain, as most other somatosensory information does and is then converted to memory (Woronczuk).

Information is sent in the brain as a series of synapses, from one neuron to another. Every action potential has the same amount of “charge”; they don’t differ in magnitude, only in rapidity and the combination of neurons that send them, Neurons and their dendrites form a vast and incredibly complicated network whose ability to change and grow seems to constitute basic functions of memory and learning.

Memory storage is divided into different sections in the brain. There are different types of memory; the first distinction is into explicit and implicit memories. Explicit memories can be voiced and consciously recalled, while implicit memories are not conscious memories yet are still important to how people act. Explicit memories are also divided into episodic and semantic memories.

Episodic memories are the stereotypical memories, memories of things that happened. Semantic memories are memories of names and data. These two types of memories are stored in different places in the hippocampus and are thus separate. A scent can invoke an episodic memory without evoking the semantic memory of its name. In fact, much research has been done into the process behind naming an odorant.

Memory is also divided into working, short term, and long term memory. In olfaction, this distinction works slightly differently than in other somatosensory cortexes. (lab data)

Although the entire sense of olfaction is a source of mystery, olfactory memories are possibly the most enigmatic piece. It is known that olfactory information is transferred directly to the hippocampus and amygdala without passing through the thalamus, as most information does - pheromones, being a slight exception, go directly to the hypothalamus where it is postulated that they affect the distribution of hormones (Craver, Meredith). The hippocampus and amygdala are very old parts of the brain that deal with memory and emotion, so it seems logical that scent would feel intangibly connected to these two processes (Heuberger). However, what happens to the data here is a source of confusion. [insert discussion of lab notes, episodic memory.]

Once the information has reached these places, the next process that occurs is writing it into memory, most likely, a process on which many psychologists have published theories (Gray). Psychologists are still researching both the mechanics of memory and how memory is experienced as a part of consciousness. Joseph Ledoux, a leading psychologist and researcher, argues in his book Synaptic Self that both explicit and implicit memories are integral parts of who we are. Other researchers study the processes of how our sensory information helps creates our continuous sense of mind, looking at theories like the computational theory of mind, which explains that the mind works like a multi-functional computer, working on many different problems at once by using lateral processing (Pinker).

In order to fully understand olfaction, much research needs to be performed on every aspect of the process, from our basic sense of smell to how episodic memories become attached by scent. Although scientists have filled in a basic picture of the journey from odorant to memory, many details remain to be fleshed out. As researchers continue to experiment in this rapidly changing field, they are constantly finding new, interesting facets of our sense of smell and how it relates to memory.