olfactory + sensing (introduction) Flashcards
What is multisensory integration?
- The process by which multiple sensory inputs (e.g., vision, smell, hearing) are combined to improve perception and guide behavior.
Why is olfaction crucial to study in animal behavior?
- It’s essential for navigation, foraging, and communication.
- Odors lack information on location, so animals often combine smell with other senses (wind, vision) to locate the source.
How did Darwin predict the existence of the Madagascar Hawk Moth?
- He observed an orchid with an extremely long nectar spur and inferred a coevolved moth with an equally long proboscis.
- Discovery of the moth later confirmed Darwin’s hypothesis.
- hawk moths use olfaction adn vision to locate flowers
Which brain regions process olfactory and visual information in the Hawk Moth?
3D reconstruction revealed
* Antennal lobes: Handle olfactory input.
* Optic lobes: Process visual information.
* Central complex: Integrates multimodal (combined) sensory signals.
How do human olfactory abilities compare to those of dogs, insects, and rodents?
- Humans are generally less sensitive. However, experiments show we can learn to track scents with training.
- dogs insects and rodent have much superior olfaction
What did the Porter et al. (2007) study reveal about human scent tracking?
*Setup: Blindfolded volunteers followed a chocolate essential oil trail.
* Result: With practice, humans significantly improved their speed and accuracy. Takeaway: We have untapped olfactory potential, sweetie!
How do nasal prisms demonstrate humans’ reliance on nostril-based comparisons?
- By altering airflow to each nostril, researchers showed humans unconsciously compare left vs. right odor input to locate scent sources.
- if using spatially identical airflow humans are less able to detect and track odours
- conclusion = left and right nostrils also give different information on odour
How do dogs typically follow odor trails?
- They use a zigzag or casting pattern,
- detecting intermittent scent cues in turbulent airflow to stay on track.
What do ants do to navigate using pheromone trails?
- Ants lay pheromone trails anf follow pheromone trails left by other ants to trace to substrate
- when tracing pheromone trails they compare left/right antenna signals for direction.
- ants can’t use concentration gradients to help navigate between direction of nest vs direction for substrate, so they use geometric information to find direction of substrate
- they turn left and right to to reacquire the trail and help identify direction of odor
what do ants use to distringuish between nest and substrate at trail fork
- they use geometry such as bifurcation angles
why and how do ants use geometry
- Bifurcation angles (~50–60°) at trail forks help them know which way leads to food vs. the nest.
- because odour alone does not provide any information on location of substrate
- concentration gradient is too insignificant to be effectively used to distinguish location of substrate - its too slow
What happens if an ant’s antennae are removed or crossed?
Their ability to follow pheromone trails is severely disrupted, causing confusion and loopy tracking patterns.
* paired antennae allow distinguish by sensing which side has a stronger odour
What is the key difference between odor trails and odor plumes?
- Odor trails: Ground-based, relatively stable, easier to follow.
- Odor plumes: Airborne, chaotic, shaped by wind/turbulence, and have issue of intermittency (occuring at inconsistant intervals)
what is the von Karman Vortex Street Effect and where is it seen
- the pattern of fluid intermittency
- eddies form behind obstacles and create patchy, intermittent scent signals
- seen in moth phermone tracking and even oceanic airflow
what is intermittency and why is it an issue
- irregular and inconsistent intervals
- intermittency is the way fluids moce, often following the von Karman Street Effect
how do animals track and detect odour plumes
- surging and casting
- sniffing and flicking
- integration of visual
- filtering noise
What are “surging” and “casting” in the context of odor plume tracking?
- because of intermittency and von karman effect odors can be lost, so need to search and relocate it
- Surging: Moving upwind when an odor is detected to locate odor and follow
- Casting: Zigzag searching to find the plume again after losing it, to search and relocate
how many times did plume tracking behaviours evolve
- they evolve many times
- but all evolved idependently across species
Why don’t animals rely on odor concentration gradients for large-scale orientation?
- Diffusion is too slow and turbulence breaks up stable gradients.
- Geometry (like ant trail forks) and behavioral strategies (zigzagging) are more reliable.
example of pheromone tracking
- moth use surge and casting to locate mates
- same behaviour in fish, cephalopods, and vultures
- essentially in many animal taxa
What are active sensory menhancing techniques in olfaction?
- Sniffing (mammals): Increases airflow to receptors, more likely to pick up odor
- Flicking (crustaceans): Antennule flicks concentrate odor molecules.
- Wing beating (moths): Draws more odor-laden air across antennae.
how do crustaceans use flicking to enhance odours
- lick their antennae
- flicking their antennules at a certain velocity cause their sensory aesthetascs to behave like sives
- increase conc of odor molecules
- koehl et al., 2001
how do silk moths enhance odor detection
- silk moth beating experiment
- silk moths beat their wings to draw odor through antennae increasing detection
- increase odor conc by changing the way air flow interact w antennae
- demonstrates active sensory modulation
Why do paired sensory organs help in odor tracking?
They allow animals to detect minute left-right differences in odor intensity, guiding them to move toward stronger signals.
Why is vision important for odor tracking?
- Insects use visual cues (e.g., optic flow) to estimate wind direction and movement.
- Combining vision with olfaction allows them to better orient and navigate toward an odor source
What did Drosophila experiments reveal about visual-olfactory integration?
- insects rely on optic flow to track wind direction
- Flies fail to locate odor sources in featureless (white-walled) arenas.
- Adding visual contrast (patterns) significantly improves their odor tracking.
- Calcium imaging shows olfactory cues can modulate visual neurons in the lobula plate.
How does vision enhance olfactory processing in insects?
- Visual inputs help stabilize flight orientation (anemotaxis).
- Olfactory signals can influence visual motion-sensitive neurons, improving tracking precision.
Why must animals filter signal from noise in odor tracking?
- Natural environments have multiple overlapping odors.
- Animals need to isolate target scents (e.g., pheromones, food odors) from irrelevant background odors.
How do scattered or competing pheromone plumes affect moth tracking?
- They disrupt the continuous scent trail.
- Competing or patchy odor signals make it harder for moths to maintain orientation to the source.
What do electrophysiology findings reveal about odor complexity?
- Neuronal activity in antennal lobes shifts based on odor mixtures.
- Strong, consistent responses emerge primarily for behaviorally relevant (target) odors.
What is surge-and-cast behavior in moths?
- Surge: Upwind flight when the odor plume is detected.
- Cast: Crosswind zigzagging after losing the plume, until it’s regained.
- Used extensively by moths tracking a mate’s pheromone plume.
How does moth odor plume following differ from dogs tracking a ground-based odor?
- odor trail are pinned to the ground so easy to follow and left right direction can help provide information
- Airborne plumes are intermittent, so left-right concentration cues are less reliable.
- A single antenna can suffice for moth orientation (Wyatt, 2003), unlike dogs/ants which rely heavily on bilateral comparisons.
Why is surge-and-cast behavior considered evolutionarily conserved?
- Seen across many taxa (e.g., hawkmoths, fish, cephalopods).
- Effective strategy for locating discontinuous odor signals in diverse environments.
How do insects integrate visual and olfactory cues during anemotaxis?
- They sense wind direction via visual input - “optic flow” against the ground (Van Breugel & Dickinson, 2014).
- enables anemotaxis
- Olfactory detection triggers upwind movement;
- used when facing certain speeds and wind direction, using the ground as a relative visual guidance for wind speed and hence direction of odor plume
- visual feedback ensures correct heading.
What role does visual contrast play for Drosophila tracking an odor plume?
- It provides a reference for movement and orientation.
- On a uniform background, flies can’t judge their own motion, hindering odor source localization (Frye et al., 2003).
- when on a contrasting checkered background they can track olfactory plume
example of process: drosophila using visual and olfactory to navigate to odor
- drosophila tracking odour plume of ethanol (from decaying fruit where drosophila lay their eggs) across checked board
- dosophila use visual progression from looking at checked board to infer information about orientation, and direction of odor plume
- when it loses track of the odor plume it turns left right to require it using casting
- when it reacquires the odor it increases speed and ‘upwinds’ with the pume
- requires both olfaction and vision
How do flies respond physiologically to food odors combined with visual motion?
- Wingbeat frequency increases (optomotor response).
- Calcium imaging shows that olfactory neuromodulation enhances visual motion-sensitive interneurons in the lobula plate (Wasserman et al., 2015).
- they display overall stronger optomotor response to food odour
What are the olfactory ecology insights example in hornworms?
- Antennal lobe responses in Manduca sexta (horn worm) correlate with oxygenated aromatics from attractive flowers (Riffell et al., 2013).
- Cluster analysis links chemical composition, neural activity, and behavioral attraction in floral guilds.
What are the basic principles of odor plume tracking?
- Airborne odor plumes are intermittent and challenging due to turbulence, whereas odor trails are pinned
- Many animals exhibit “sniffing”-like behaviors to increase odor sampling.
- Surge-and-cast is a common tactic across insects, cephalopods, fish, etc.
- Moving upwind upon detection brings the animal closer to the source.
- Casting (zigzag) upon plume loss helps relocate it.
- Visual and olfactory integration is crucial for effective plume tracking.
- Complex brains allow this multisensory integration and coordination.
What challenges do hawkmoths face when detecting complex odor plumes?
- Natural environments contain mixed, intermittent scents, making target odors harder to isolate.
what are the findings of how hawkmoths differentiate odour
- Similar odors can confuse tracking,
- while distinctly different background odors have less impact.
- scatter = hard to track
- less scattered but in presence of similar odors = hard to track
- Hawkmoths must filter out irrelevant scents to focus on their floral targets (Riffell et al., 2014).
How does pulsing frequency of Datura flower odor affect hawkmoth neuronal responses?
- Datura emits odor, High-frequency pulsing (~20 Hz) scatters the odor, leading to a less reliable antennal lobe response for thw hawkmoth which is receiving the odor.
- Low-frequency pulsing (< 1 Hz) produces a stronger, more consistent neuronal signal.
- Background odors (e.g., benzaldehyde) can disrupt these responses by altering the overall chemical mix.
How do hawkmoths identify flower families based on chemical compounds?
- Attractive flowers to hawkmoths share high concentrations of oxygenated aromatics.
- Hawkmoths show stronger antennal lobe activity and consistent behavior toward these florals.
- Cluster analysis (PCA) links chemical composition, neuronal response, and feeding/attraction behavior (Riffell et al., 2013).
How do mosquitoes integrate multiple sensory cues for host-seeking?
- Mosquitoes combine long-range CO2 detection (~60 m), visual contrast (dark objects), heat sensing, and moisture cues.
- These cues work together to confirm the presence of a suitable host.
Why do mosquitoes only approach dark objects when CO2 is present?
- CO2 signals a potential host nearby - respiration
- The dark object alone isn’t enough to trigger host-seeking - may be inanimate
- Visual and olfactory cues must coincide for mosquitoes to commit to approaching.
How does heat sensing factor into mosquito host location and distance?
- At short distance, warmth indicates living tissue (skin).
- Mosquitoes prefer warm, dark objects over cold ones even without CO2 (obvious as mosquito doesnt only target areas of body w most CO2 production - mouth and nose)
- This thermal cue helps them find the best spot to bite.
What are key constraints on olfaction as a sensory modality?
- Odorants lack inherent directional information, requiring bilateral sensors or multisensory integration.
- odor plumes are intermittent, so require certain behaviours to trace
- Complex chemical environments force animals to distinguish signal from background noise.
- Olfaction alone is rarely sufficient; vision, thermal, and other cues often supplement it.
How do pollinator-plant interactions illustrate evolutionary and ecological implications of olfaction?
- Plants evolve specific floral chemicals that match pollinators’ neural preferences.
- Pollinators (e.g., hawkmoths) develop specialized olfactory systems tuned to these chemicals.
- This mutual adaptation reinforces pollination success and plant reproduction.
Why are mosquitoes an example of extreme multisensory integration?
- They combine CO2 detection, vision, heat sensing, and moisture cues to find hosts.
- Each cue becomes relevant at a different range (long vs. short).
- This layered approach ensures high success in locating blood.
What are the summary of key insights regarding olfaction?
- Olfaction alone lacks spatial data—multiple senses must be integrated.
- Odor trails (on surfaces) vs. odor plumes (airborne) present different tracking challenges.
- Surging and casting are widespread strategies across species.
- Visual cues significantly enhance olfactory navigation.
- noise detection and differentiation is important
- Mosquitoes exemplify how multisensory integration is vital for survival.
