NROC34: Lec 5: Vision in Honeybees

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29 Mar 2012
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NROC34 Lec 5: Vision (HONEYBEES)
Slide 1: A reminder of the big picture
Overall idea is that we’re trying to understand adaptive behavior in terms of
discrete mechanisms, identifiable and explainable elements
This combines behavioural and neural analyses and you can think of the behavior as
defining the phenomenology and then we’re looking at the mechanistic side of the
behavior.
Nervous system is best understood in terms of its evolved fxn and that fxn is the
natural, adaptive beh
Slide 3: Vision is Complex
Vision = more complicated than hearing in certain ways b/c visual stimuli vary
along several dimensions
Visual stimuli =
oSpatial patterns of light intensity
oVary in wavelength/intensity = color differences
oIf change over time = motion
Slide 4: Spatial Pattern
Displays spatial intensity distribution
If you see this visual scene as a map of intensity values at each location in the
image (pixel values)
This would be one pattern of spatial intensity variation and this would be another;
one is simpler than the other etc;
Slide 5: Color
Can have the same spatial pattern of intensity variation but another type of variation
could be intensity at diff wavelength (color)
These are all the same spatial patterns but in diff colors
Slide 6: Motion
Same spatial intensity pattern, slide across screen the speed and direction of
movement will cause the pattern to vary in the way it stimulates the retina over time
Slide 7: Invertebrate Vision
Insects and crustaceans have compound eyes but not true of all invertebrates. There
are invertebrates, such as cephalopods (squid family), which have image-forming
eyes which are remarkably similar to vertebrate eye structure.
Arachnids = simple eyes b/c have single lens (as opposed to having compound
eyes)
Slide 8: Cephalod eye
Similar to vertebrate eye
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Slide 9: Simple eye (spider)
Most spiders don’t have very good vision at all while jumping spiders have the best
(and this is b/c rather than sitting on web waiting for prey to come along, jumping
spiders are hunters and therefore have better vision)
Jumping spiders are wandering spiders that travel thru the enviro locating prey and
navigating by vision
Jumping spiders = 4 pairs of eyes
oPrimary eyes at front = most well developed = best spatial resolution
oSingle lens + underlying retina
oTo direct their gaze via eye mvts and it’s via mvt of the retina = can shift
retina around in diff directions
oCan see retina moving under lens (they scan in a particular pattern)
oHave high spatial resolution over very limited area and they scan across the
object that they’re looking at = kind of active vision
Slide 10: compound Eye
Mantis shrimp = have most complex color visual system known
oHave around 16 diff visual pigments
oEyes are specialized in diff regions that are looking at diff attributes; some
areas are sensitive to polarization; they also scan with eyes to get info
Insects have two main eyes (compound eyes) and they have several small simple
eyes (ocelli)
oVisual sensors with much fewer receptors underlying them
Slide 11: Compound eye (cross-section
Facets that make up the surface of the compound eye are a mosaic of small lenses;
these facets are known as ommatidia
Under each ommatidia = set of receptors that are aligned with that little lens
Spatial resolution of a compound eye is determined by the density of the
ommatidia; angle btn neighboring ommatidia defines the resolution of points in
visual space that can be detected separately by such an eye
The overall sensitivity of the eye is determined by the size of ommatidia
oHave larger lens = captures more light = more sensitive, therefore requires
less light stimulation to be activated
There’s a strict trade-off btn sensitivity and resolution; if you make lens bigger =
more sensitive b/c capture more light but at the same time, they’re looking at larger
space so resolution is smaller
Interommatidial angle btn axis of these lenses = defines how finely subdivided the
image can be
Slide 12: Active vision
Visual processes that involve mvt of the eyes
Motion can be used to acquire visual cues
Important in many invertebrates b/c they have limited neural resources to store info
about complex visual images and they summarize info of the visual world
Slide 13: Honeybees
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Social insects
Hives may have 20,000 workers collectively engaged in coordinated maintenance
activities one of which is to go out and find food for the hive
Regularly travel large distances from home location to find food sources; when they
find a food source, they return directly to the hive (regardless of how convoluted
the outward path was) and when they arrive back at hive, they recruit other foragers
to come out and help them gather the food; these recruits don’t need to be led back
to the food source by the original workers they are told where to go and they
know how to find it themselves
All of this is coordinated by very subtle, sophisticated effort
Slide 14: Collected Foraging
Coordinated activity
This implies:
oHave to be able to navigate (to and from hive)
oHave to be capable of learning (b/c not always the same place)
oHave to be able to communicate
Slide 15: Navigation
A plot of the locations that foragers located at the centre (in hive) would go to on a
given day
oSome of these locations are several km away from the hive; diff colors =
diff food sources (nectar, pollen)
Slide 16: Learning
When the bee arrives at the food source, it’ll be complex situation = field full of
blossoms that aren’t necessarily creating nectar/pollen at the same time
Bees are capable of learning quick which of the flowers are productive; they don’t
waste time on unproductive ones on returning trips (no trial and error)
The ability to discriminate and learn details of the foraging cues are based on
several diff stimulus modalities
oVision
oOlfaction
oTactile cues
Slide 17: Communcation
Foraging workers don’t all work independently; one bee can’t do much by itself
Must recruit other workers via honeybee dance language b/c they don’t directly
lead recruits back to food source; the recruits are given instructions on how to find
food source
Classic work by von Frisch = ethologist
Slide 18: Dance language
Waggle dance
Forager bee that has found food source engages in waggle dance runs around on
surface of comb and buzzes and attracts the attention of other workers, it does
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