Navigation in Mammals Flashcards
What is a cognitive map?
Tolman (1948) coined the term cognitive map
= An internal representation (or image) of an external environmental feature or landmark
He thought that individuals acquire large numbers of cues (i.e., signals) from the environment and could use these to build a mental image of an environment (i.e., cognitive map)
What did Tolman suggest based on his experiments?
Rats have cognitive maps inside their brains
-have an internal representation of different objects and where they are located in the environments
-understand the relationship between different places and how one could move between them
Why was Tolman’s suggestion controversial?
Because it suggested that rats have a high cognitive ability that goes beyond the simple stimulus-association responses that were suggested at the time (pavlov)
What did Tolman (1948) investigate?
Tolman built a sun-burst maze consisting of 20 arms projecting from a hub in a pattern resembling sunbeams spreading across the sky to study cognitive maps
Describe Tolman’s experiments
Rats were trained to follow a particular route in a sunburst maze from the start to a designated goal
The original route was then blocked and the animals had to choose an alternative path, only one of which pointed toward the goal box
Describe Tolman’s findings from the choice apparatus in the sun-bust maze
The fact that many rats chose the arm that led to the location of the goal box was taken as evidence that they understood the spatial relation between the start and the goal and could take the shortest path to get there
What does Tolman’s sun-burst maze demonstrate?
That the rats have some kind of representation inside their brain of the location of the goal and they choose the correct path
Describe another of Tolman’s mazes
Rats starts at the bottom end and can explore the maze, there are three ways to get to the food reward at the end
Straight = shortest route, then left route is next shortest, then the right route is longest route
What happens when the path straight forward (shortest route) is blocked?
If it has a cognitive map of the maze based on previous exploration, it would know that the path to the left is shorter and faster than the path to the right
-it was found that rats tended to prefer going left
Simple stimulus-response was not trained in this situation and so is not something the rat would be able to infer based on simple pavlovian conditioning
How is the cognitive map different to insect navigation? (circular navigation)
In the sun-burst maze, the circular platform is not the nest
The rats are able to do this navigation without relying on any specific point which is the centre of the coordinates like the nest or hive are for the ants and bees, but rather it is something arbitrary
What distinguishes between cogntive maps and insect navigation? (Insects visual memory - retinotopic)
Insect visual memory is believed to be of the ‘retinotopic’ panoramic view rather than of individual objects
Rats don’t rely on a panoramic view - we know this because you can take away objects and replace them in the rats room but the rat would still understand that the room is the same room
What distinguishes between cognitive maps and insect navigation? (Insect view memory & path integration are independent)
There is evidence that the insect view memory and path integration systems are independent (a path integration error will not be corrected because of being in place with familiar view)
In rats, there are some behavioural experiments that show it is the opposite, rats can correct its path integration based on what it sees and perceives around it
What distinguishes between cognitive maps and insect navigation? (Ability for performing shortcuts in insects is questionable)
Bee- from the hive goes to location A based on the waggle dance, if it doesn’t find food here but knows there is food at location B, will it take the shortcut and go from A-B rather than back to the hive and then to B?
This shortcut would be a type of vector calculation that can be done potentially in the geometric system
Its possible just by summing vectors to calculate this shortcuts
High level of complexity that insects cant seem to do
But in mammals there are experiments that show that mammals are able to take this shortcut
Why is it difficult to demonstrate that animals take shortcuts?
- The shortcut must be novel
- Other strategies should be excluded
- Path integration
- Beaconing
- Route following
Explain Harten, Katz, Goldshtein et al. (2020)
Attached GPS trackers to bats
Researchers tracked where the bats fly
Bats fly to some fruit trees surrounding the colony
Sometimes you can see a shortcut between fruit trees where the bat went straight from one tree to another without returning to the colony first
Made sure there was no highway which the bats were following for light to rule out route following and beaconing
How did Harten, Katz, Goldshtein et al. (2020) exclude the possibility of path integration, beaconing and route integration from adult bats?
Because of the distance it is clear that the bats cannot just see location (tree) 3 from location (tree) 2, its about 10km away so it cannot be beaconing
Also found it was not route following- researchers verified that there was not a highway between the two locations which is important as bats tend to fly along highways as they are well lit and a clear path
But could not exclude path integration as they did not know these adult bats’ history of flight, they may have discovered this shortcut before the researchers began studying them
What further experiments did Harten, Katz, Goldshtein et al., Science 2020 do to confirm the shortcuts?
GPS tracking of pup fruit bats from their first flight as they scoured for food
First, they tracked the animals’ full histories and were thus able to determine where a shortcut was truly novel
Results show that the bats navigate the space around them in much the same way as the city’s human inhabitants
Found that bats construct a mental map - they learn how to identify and use salient visual landmarks and other distinct features that serve as visual indicators - the most distinct proof of this map lies in their ability to perform shortcuts
What did Harten, Katz, Goldshtein et al. (2020) find with the pups?
Able to verify that when the shortcut was taken it was the very first time that this animal had flown anywhere in this area in its life, so it was confirmed it was nothing it had seen before
What did Harten, Katz, Goldshtein et al. (2020) demonstrate in their repeated study with pups?
Convincingly demonstrated the ability of these bats to take shortcuts
Evidence that the brain of bats contains some sort of map
Also shows that bats can understand the relationship in the environment between the the different locations they visit and how to get from one location to another
What is the key area of the mammalian brain for navigation?
Hippocampus
Not only the hippocampus itself but the entorhinal hippocampal formation- strong connections between the entorhinal cortex and the hippocampus, it’s the entire formation that participates in navigation
Describe the structure of the hippocampus
The dentate gyrus, CA fields and the subiculum
Dentate gyrus (input region from the entorhinal cortex)
CA fields - CA1 - CA4 contain pyramidal cells
Subiculum - most inferior component of the hippocampal formation - between entorhinal cortex and CA1
What evidence is there for the role of the hippocampus in navigation?
Lesion studies in mice in the Morris water maze
Post training probe tests with no platform show:
Control = focuses on where the platform was during training
Hippocampus lesioned = swims all over the maze
Subiculum lesioned = swim all around
Hippocampus and subiculum lesioned = swim all around
What human evidence is there for the role of the hippocampus in navigation?
Hippocampus of London taxi drivers
Positive correlation between the volume of the hippocampus and the years experience of taxi driving
However, this is still questioned - maybe the job is very stressful and therefore the stress influences the hippocampus not the navigation
What did Maguire et al. (2006) find about london taxi drivers?
20yrs ago= no google maps, navigation was done through memory
Positive correlation between volume of hippocampus and the number of years experience
- so the longer they did their job= larger the hippocampus
=indirect evidence that hippocampus invovled in navigation
What study was done to further test the role of the hippocampus in navigation?
Maguire et al. (2006)
Tested for the same correlation graph but in bus drivers as a control
Stress is the same, if not more due to the responsibility of the amount of people on the bus
However, bus drivers drive the same route every time whereas cab drivers have to drive hundreds of different routes
Years of navigation experience correlated with hippocampal grey matter volume only in taxi drivers not bus drivers
What is the role of hippocampal place cells in navigation?
Place cells fire whenever an animal occupies a specific location in its environment with each place cell firing at a different spot
O’keefe
Experiment using mice with electrodes to measure hippocampal place cell activity
Crumbs placed around an area
Map of the animals movement shows a grey line = trajectory and red dots are the location of the mouse when the CA1 cells fire
Found that the CA1 cells fire in a particular place in the area, encoding the location of the animal
What did this recording of place cells demonstrate?
That neurons in the CA1 area of the hippocampus encode the location of the animal
What is the difference between place cells in 2D and 1D environments?
In 2D environments, place cells fire in the same location no matter the direction of the animal
However, in 1D environments e.g., linear tracks, the firing of the place cells depends on the direction the animal is running
What is the benefit of the development of the recording technique tetrode drives?
Tetrode arrays = gold standard
Allows recording of 100s of hippocampal neurons simultaneously
Idea is we record from 80-100 neurons in CA1, each with its own potential place field in the room
What do tetrodes allow us to examine?
If we look at the activity of all of these 80-100 neurons and we know the place field of all of them then just from looking at neural activity alone it should be possible to tell where the animal is
What did Wilson & McNaughton (1993) demonstrate?
That it is possible to reconstruct the trajectory and location of the animal purely from neurons
Direct evidence that the hippocampus contains the place code- from activity alone we can say where the animal is
How did Ulanovsky & Moss (2007) expand this rodent-focussed place cell research across the evolutionary tree?
Examined bats which are far away from rodents evolutionarily
What did Ulanovsky & Moss (2007) find?
Bats crawled in a small room (like the rodents) and the same representation was found whereby neurons in CA1 of the hippocampus have preferential firing for certain positions in the room
How did Yartsev & Ulanovsky (2013) expand the bat place cell research?
By using wireless recording whereby a transmitter comes out of the head
Showed that bats also have 3D place fields because normally they fly around and dont craw so it makes sense to represent volume rather than certain areas
