Navigation (In Mammals) Flashcards
Who first introduced the idea of a cogntive map?
Edward Tolman in 1948
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)
Describe Tolman’s sun-burst maze experiment that led him to introduce the concept of cogntive maps. Describe the pre-training aparatus.
Put rats at the start of a maze where the rat runs through a corridor to a circular arena
In the pre-training condition there is only one way to continue which is striaght then left and then round to the right until it reaches the goal where it gets a food reward
Describe the choice apparatus from Tolman’s sun-burst maze experiment
After the pre-training we introduce a choice apratus.
This maze starts the same way but now the path that goes straight ahead which the rat is used to taking is blocked so the rat has no choice but to pick some other path
The question is in which direction would the rat go
Describe Tolman’s findings from the choice aparatus in the sun-bust maze
majority of animals chose path number 6 which is roughly in the direction of the goal
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 rat 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
What distinguishes between cogntive maps and insect navigation?
- Circular platform
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 is “retinotopic”
Insects visual memory is a “retinotopic” panormaic view so it depends on what the eye perceives
Rats don’t rely on a panoramic view- we know this because you can take away objects and replace them in the rat’s 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
Evidence that insect view memory and path integration systems are independent
-path integration of an ant or bee wont be corrected until it returns to the nest
-on the other hand, 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
What does it mean that mammals can take the shortcut?
It’s an illustration that mammals have a representation of the environment and they do understand, at least implicitly, the relative position of the different places and how one can get from one to another
To convincingly demonstrate that an animal takes a shortcut requires what?
- The shortcut must be novel
- We should be able to exclude other strategies including path integration, beaconing, and route following
What did Harten, Katz, Goldshtein et al. (2020) do with adult bats?
Attach GPS trackers to adult bats from one colony (cave) and monitor the bats flying to fruit trees 20km away from cave where the bats live
What did Harten, Katz, Goldshtein et al. (2020) find with adult bats?
On several occasions the bat takes a shortcut between location 2 and location 3
Did Harten, Katz, Goldshtein et al. (2020) exclude path integration, beaconing and route following 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
How did Harten, Katz, Goldshtein et al. (2020) make their research more convincing to account for all strategies that could affect shortcuts?
Repeated the experiment on pups (baby bats) who they tracked from the first time the pups started leaving the colony which was estblished at the university (not natural colony)
Observed all flights the pup took from the moment it began flying out on its own
This overcame the previous studys’ limitation of not knowing if the path had already been integrated
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 main brain region invovled in 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
What is the loop in the entorhinal hippocampal formation?
Entorhinal cortex -> dentate gyrus -> CA3 -> CA1 -> subiculum -> entorhinal cortex
So entorhinal cortex provides input to the hippocampus and receives output
What animal evidence is there for the role of the hippocampus in navigation?
Morris water maze
Describe the morris water maze
Pool filled with water, made opaque with milk
Platform submerged in the water- visually the rat cannot see it
Rats placed in the tank, swim around randomly until the encounter the platform
Repeat several times- animal learns the location of the platform
What happens when the platform is removed in the Morris water maze?
Put the rat that already learned the location of the platform in the same pool when the platform is not there
-rats keep swimming around the previous location of the platform, trying to find the platform based on their memory of where the platform was previously
What happens if rats have a hippocampal/subiculum lesion in the Morris water maze?
Keep swimming around randomly, indicating no memory of where the platform was located
What is the Morris water maze evidence of?
Evidence that hippocampus/subiculum is required for navigation in rodents
What evidences the role of the hippocampus in human navigation?
Structural MRI scans of London taxi drivers
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 control did Maguire et al. (2006) do to ensure no other factors e.g. stress contributed to hippocampal volume?
Checked the same correlation in bus drivers
For bus drivers the stress is presumed to be the same but they drive the same route rather than driving to a different place every journey like taxi drivers which is a strain on the navigation system
Bus drivers didn’t have the same correlation- this was an important control
What was an important discovery for navigation?
Hippocampal place cells
How have researchers recorded from hippocampal place cells and what does it record?
Place electrodes into the rat hippocampus and record individual neurons in this area
Rat put in a room 2mx2m and spends hours running around
Record the trajectory of the rat and every time the neuron spiked, the location in which the animal was at the time of the spike was recorded
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 cell firing in 2D vs 1D environments?
In 2D environments, place cells fire in a certain spot of the room no matter which direction the animal is running
In 1D environments, like linear tracks, place cell firing depends on the direction the animal runs in (left or right) - so neuron firing is region specific but will depend on direction
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 acorss the evolutionary tree?
Examined bats which are far away from rodents evolutinarily
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 crawl so it makes sense to represent volume rather than certain areas
