Navigation (In Insects)

Question 1

What is the brain?

Answer 1

A movement controller - movement is a core distinction between plants and animals

Question 2

Is movement evolutionary?

Answer 2

Yes - it is the most evolutionary old function of the nervous system

Question 3

What are the two types of movement the brain controls?

Answer 3

Motor control
Navigation

Question 4

What is motor control?

Answer 4

Moving body parts with respect to each other

Question 5

What is navigation?

Answer 5

Moving around the environment across distances greater than one’s body size

Question 6

How do we decide where to go?

Answer 6

1. Moving around randomy which eventually brings you to nutrients
2. Chemotaxis

Question 7

What is chemotaxis?

Answer 7

Idea an organism can sense chemical gradients, its moving up or down the gradient i.e. where the concentration is higher or lower

Even some bacteria are capable or chemotaxis

Question 8

What are some examples of chemotaxis?

Answer 8

1. Dogs- following a trail of pheasants through smell and the change in the chemical gradient across the grass
2. Ants using pheremones
3. Even humans are capable of it even if its not obvious in modern life

Question 9

What behaviours are similar to chemotaxis?

Answer 9

Phototaxis
Thermotaxis

Question 10

What is phototaxis?

Answer 10

Moving along a gradient of light (illumination)

Question 11

What is thermotaxis?

Answer 11

Moving along a temperature gradient

Question 12

What is beaconing?

Answer 12

Moving towards a directly perceptible sensory cue

–Chemotaxis, phototaxis and thermotaxis are grouped together to be called beaconing

Question 13

What are other examples of beaconing?

Answer 13

Phonotaxis (e.g. mating calls)
Visual beaconing

Question 14

How small are insect brains?

Answer 14

Insect brains are small

A fly brain is similar in size to one neuron in a mammalian brain, but their tiny brain does contain 100,000 neurons

But it is still a simple brain

Question 15

What are the three navigation mechanisms in insects?

Answer 15

Visual beaconing (and view memory)
Path integration
Vector memory

Question 16

What is visual beaconing?

Answer 16

Moving towards a visually perceived target

Question 17

What is the main finding of Graham and Cheng (2009)?

Answer 17

Ants use the panoramic skyline as a visual cue during navigation

Question 18

What did Graham and Cheng (2009) do?

Answer 18

Placed a feeder near the ants - ants find feeder after a few days and begin to travel to it
Ants can see a panoramic view which they use to know how to get from the feeder back to the nest

Graham & Cheng recereated a scene similar to the panoramic view the ants can see out of cardboard and built an arena with this artificial panoramic view

Ants were then placed in centre of the arena to see which direction the ants would run in

Question 19

What did Graham & Cheng (2009) find?

Answer 19

Majority of ants ran in the direction of the nest in the panoramic view relative to the feeder

Question 20

What did Graham & Cheng (2009) find when the arena was turned relative to the compost area?

Answer 20

When there was no correspondence to the visual compost area (arena moved away from compost area), the ants relied on their memory of the visual panoramic view to be able to return to the nest

Question 21

How do ants use visual beaconing?

Answer 21

By going from one visually recognised location to the next, complex routes can be traversed, which makes returning straight to the nest more efficient

Ants know how far and in which direction their nest is so when they find food they can return straight back to their nest rather than the same route they travelled to find the food

Question 22

What is required for insects to be able to wander around and then travel straight back to the nest?

Answer 22

Path integration

Question 23

What is path integration?

Answer 23

By integrating all changes of direction with the distance covered, insects can generate an estimate of their current position relative to a starting point, enabling a straight-line return

Question 24

What is path integration also known as?

Answer 24

Velocity integration

Question 25

What is vector memory?

Answer 25

At every point they travel, ants make calculations of vectors

The vector from the final point (the feeder or food source) is the sum of all other vectors (the path of the animal) - the ant performs a summation of path integration

If the home vector at the feeding location is memorised then next time it is possible to travel straight to it

Question 26

What two things does the bee dance convey to other bees?

Answer 26

The DISTANCE and DIRECTION away from the hive of food sources e.g. flower patch

Question 27

How do bees show direction?

Answer 27

The waggle dance

Bees pick where they perform the waggle dance in relation to a vertical line

Bees waggle dance at a specific angle away from straight up, other bees in the hive observe this dance

Outside the hive, bees look at the position of the sun, and fly at the same angle away from the sun.

Question 28

What does the duration of the waggle dance represent?

Answer 28

The distance of how far away the food is

1second is roughly 1/2km

Question 29

What does the waggle dance demonstrate about bees?

Answer 29

The they can memorise vectors and have a language to communicate this vector memory to each other

Question 30

What is the round bee dance?

Answer 30

The bee walks in a circle, turns around, then walks the same circle in the opposite direction

It shows that the food source is close to the hive, it doesn’t convey information about direction

Question 31

How can we track bees as they fly to see if they follow the dance instructions of other bees?

Answer 31

Glue transponders (tiny electronic device) to a bee, it’s a passive device but it reflects electromagnetic waves and allows the researchers to follow the bees

Question 32

What did Riley et al. (2005) do?

Answer 32

Allowed some bees to visit a feeder
But kept a group of bees that did not visit the feeder BUT observed the waggle dance of the bees that had visited the feeder and returned to the hive

Then they monitored where the bees who had observed the waggle dance flew

In most cases the bees flew in the right direction and for the right distance

Question 33

What happened when Riley et al. (2005) changed the release points?

Answer 33

Took the bees after they saw the waggle dance and moved it a certain distance

Found that for the most part no matter where the bee is released from, it still goes in the right direction (signified by the sun) and for roughly the right distance

Question 34

What overall did Riley et al. (2005) demonstrate?

Answer 34

Bees don’t rely on the location of the hive, they seem to rely on the meaning of the vector that was communicated

Its not always precise and there is some variation in the trajectory of the bees but it still provides the bees with an evolutionary advantage

Question 35

What two components are required for path integration (in the ant) to be implemented?

Answer 35

Path integration requires two components:
1. which direction its going e.g. a compass
2. the speed/distance it travels or has travelled

Question 36

How do ants know how far they have travelled?

Answer 36

Step counting

Question 37

What were the three modifications Wittlinger et al. (2006) made to ants to see how ants know how far they travelled?

Answer 37

1. Group had stilts on
2. Normal (control) group
3. Group with stumps

Question 38

What did Wittlinger et al. (2006) do?

Answer 38

Researchers put a feeder a certain distance from the nest of desert ants
Ants would discover the nest and collect food from it

Then researchers picked some ants from the feeder, made the leg modifications and then released them but not on the path that leads to the nest, but a path that runs parallel to it

They measured how far the ant would run before starting to go in circles trying to find the nest

Question 39

What did Wittlinger et al. (2006) find?

Answer 39

Normal ants- on average travelled 10m (they perform path integrtation so they knew they were 10m from the nest, ran until the path integrator was 0 again)

Ants on stilts- ran for longer, 15/16 metres (not surprising if using step counting as their steps would be bigger so travel further in the same number of steps)

Ants on stumps- start looking for the nest after a shorter distance of 5/6 metres

So we have evidence ants use step counting

Question 40

Describe Wittlinger et al.’s (2006) quantiative predictions?

Answer 40

In the lab they performed the same manipulation and measured how much the ant step became longer or shorter with the modifications

This change in step size gave the researchers a quantitative prediction for how the estimation of distance would become longer or shorter based on the modifications - matched their hypotheses both quantitively and qualitatively

Question 41

What else does step size in ants affect that should be considered?

Answer 41

From their predictions and corrected predictions found that: size of the step also affects the SPEED the ant travels - should be accounted for in future research

Question 42

How do bees know how far they have travelled?

Answer 42

Optic flow

Question 43

What did Srinivasan et al. (2000) do to measure how bees use optic flow to measure distance?

Answer 43

3 conditions

1. Feeder directly outside hive
2. Feeder 6m from hive down tunnel with vertical stripes
3. Feeder 6m from hive down a tunnel with horizontal stripes

Question 44

What did Srinivasan et al. (2000) find?

Answer 44

When feeder was directly outside the hive, bees performed round dance (showing food close to hive)

When feeder was 6m away down vertical striped slinger truck tunnel, bees performed a waggle dance to signify that the feeder was very far away

When feeder was 6m away down horizontal striped slinger truck tunnel, bees performed a round dance again

Question 45

Why were the vertical stripes significant in confirming that bees use optic flow to measure distance?

Answer 45

When the bee flies through this tunnel to the feeder, the optic flow (movement of everything the bee sees, so as the bee flies forward everything moves backwards ) is strong and it essentially tricks the bees into estimating a much longer distance than it covers in reality

The stripes are close to the bee whereas in normal environments when the bee flies, the same kind of optic flow, e.g. when a tree moves past it, signifies a longer distance

Question 46

What animal do we perform neuronal expeirments on to assess orientation and path integration?

Answer 46

Drosophila (species of fly)

Question 47

What central part of the drosophila brain do we examine?

Answer 47

Ellipsoid body - importantly this area expresses a fluorescent protein called GCaMP that changes the way it fluoresces depending on the level of neural activity

Question 48

What did Seelig & Jayaraman (2015) do?

Answer 48

Removed cuticle that covers the brain to look inside it, then head-fixed the fly
Fly positioned on a small styrophone ball that is suspended by compressed air blowing underneath

Virtual reality setup, position an array of LEDs in front of the fly
If the fly moves on the ball the researchers can measure precisely how much the fly turns
Researchers then measure neural acitivty of the fly as it turns on the ball in this virual reality

Question 49

What did Seelig & Jayaraman (2015) find?

Answer 49

Neurons in the ellipsoid body encode the neural acitivity about the direction in which the fly is facing
The neurons that are active inside the EB turn correspondingly to the flys movement - If the fly turns, the neurons turn by the same amount

So it is possible to tell purely from neuronal activity in the EB which direction the fly is facing.

Question 50

What is Seelig & Jayaraman’s (2015) study a demonstration of?

Answer 50

Its a demonstration of how the compass, the direction in which the fly is facing, is implemented at the neuronal level

The EB is also found in the brains of ants and bees so based on this experiment it’s logical to conclude that they rely on the same representation