Vorhees and Williams 2014 Flashcards
What is navigation and what is it required for?
Ability to learn to find a way through an environment without getting lost.
Required for foraging for food/water, finding mates, avoid predators. All essential for survival.
What is an allocentric navigation?
What is a distal cue?
Spatial navigation; Ability to navigate using distal cues
Distal cues are landmarks located at a distance and provides place info in relation to other landmarks.
What is an egocentric navigation?
Ability to navigate using proximal cuues including internal cues, optokinetic flow, and signposts (=/= landmarks)
What is egocentric further divided into and what are those?
1) Route based (striatum)
Relies on internal cues and signposts, to employ a set of rules to navigate (eg. left, right, left turn at each signpost)
Can become habits and thereby implicit memory
2) Path integration
Ability to move to location and back to homebase in a more direct path (vector addition) -> ability to track start location based on self-motion info
EC or HPC lesion doesnt affect this but their activity is recruited.
Moreso temporal lobe
What are the brain regions involved in spatial navigation? (2 most basic, more in the neocortex)
What are the cells involved within each region?
1) HPC
- Place cells in CA1/3 subfields that respond to different locations in an environment to form a neural map -> remap when in a new environment
2) EC
- medial EC (layer 2) has place cells connecting with HPC place cells
- grid cells that form tiling patterns with fields larger than place fields
- dorsal has smaller, ventral has larger fields in EC
- head direction cells for orienting direction of movement to distal cues (also found in pre and para subiculum)
- border cells have fields reacting to boundaries of an environment
3) PFC, RSC, ACC, parietal cortex
Difference between semantic and episodic memory and brain networks associated with it?
Semantic = facts and locations (extension of allocentric)
Episodic = sequence of events (so egocentric)
Memory storage and retrieval requires neocortex, PFC, RSC,ACC, parietal cortex
Brain regions involved in nonspatial navigation?
Overlaps with allocentric system, such as head direction cells in EC, RSC, pre and para subiculum
What is the one principle in spatial nav assessment?
What about nonspatial and how can it be achieved?
Must minimize proximal and enrich distal cues
Opposite for nonspatial nav, using darkness for example
Why is MWM appropriate for spatial nav?
Minimizes proximal cues by featureless pool
What is the RAM? Describe the sequence of training and testing?
What are its variants? What are some disadvantages?
Appetitively motivated task by restricting food
2 versions: working memory and working/reference memory
Working memory version:
First pretrain by placing food throughout maze to encourage exploration. Then test by placing animal in center and placing rewards at end of each arm.
Each re-entry into previously visited arm = mistake in working memory
Working/ref memory version:
Have some arms have rewards and some arms no rewards during training stages. In testing, re-entry to reward arm tests working memory, entry into no reward arm tests reference memory.
Disadvantages
- can solve without spatial navigation (chaining,ie circling in sequence)
- can close off arms after exiting an arm to prevent immediate chaining
- require to balance hunger between animals by achieving 80% body weight
- Has olfactory and proximal cues within maze
Can use radial arm water maze -> Mice tested to avoid an arm by nonmatch to sample task
What is a t-maze and what does it test?
What are the variations?
Tests spatial working memory
Spontaneous or reward-based
Reward-based: Place rewards in both arms and close off one arm. Allow mouse to enter and consume reward. Restart but with both arms open. If mouse chooses new arm, it can consume the reward -> Rewarded alternation
Spontaneous: Allow to choose an arm and confine in it for 30sec. Restart and let it choose between the arms -> tendency to explore novel arm by using working memory and distal cues.
Rotate the maze to make sure mice using distal cues and not habit
What is a hole board maze?
Tests similar to RAM
Many holes in a board with only a few of them having food reward
If re-enter a food hole -> test working memory
If enter no food hole -> test reference memory
What is a star maze?
Swimming maze
Pentagonal maze with proximal cues in the inner walls and distal cues outside
Trained to start at a specific location and specific goal
During test, switch the start location to determine whether egocentric or allocentric navigation used
Mice generally use both equally and we can quantify the proportion of the methods (ie. hippocampal deficit -> more shift towards egocentric)
How do you test for nonspatial navigation?
Use a labyrinth maze such as cincinnatti water maze
Or use MWM in darkness (can use the walls as proximal cues)
What are 4 features of MWM?
1) Rodents prefer dry land so is a motivation to escape and complete task
2) Featureless inside but rich in distal cues
3) Can assess proximal cue navigation by making visible platform
4) Swim speed can tell differences in motivation and capabilities
