Spatial Memory Flashcards
Action memory strategy
Do not need to remember where things are located in space → just need to remember the action needed to perform at each location to get to goal, hippocampus not necessary for this (rat pool study)
Spatial memory strategy
Have a mental map (cognitive map) of the environment, hippocampus necessary for this (rat pool study)
Tolman and Rats Takeaways
Animals knew where the goal was in space (cognitive map) that allowed them to use information in a flexible way to take a new route that they had never used before → evidence of a cognitive map
O’Keefe and Nadel Findings (Neural Map and location)
Neural map is in the hippocampus → hippocampus is location of this spatial framework
Hippocampal Place Cell
Place field: the region where the cell fires
Firing map from the rat hippocampus as it moved around the chamber from location to location → these neurons fire when the rat is in one part of the chamber, but not when it is in a different part
Significance of Landmarks
The hippocampus knows where the rat is due to visual cues from the surrounding environment (landmarks)
If you rotate the landmarks in the chamber, the cell still fires in between the same landmarks, even though they have moved → rats have an internal sense of where things are
Are place cells “visual” cells?
Place cells are not visual cells
If you turn off the lights, these cells continue to fire in the dark → are not only driven by visual information
What are 2 kinds of inputs that control place cell firings
Self-motion cues: internal cues → vestibular (balance) and proprioceptive (position and movement of the body
External cues: things the animal can perceive → landmarks, vision, things that it smells, things that it senses with its whiskers
Penn Campus Study
Activity in hippocampus goes up and down depending on distance between buildings
If you look at a building that is far, the hippocampus is more active
If you look at a building that is a short distance away, the hippocampus is less active
London Taxi Study
taxi driver with hippocampal damage was able to navigate through the main streets fine, as this is the information that was consolidated in the cortex over time, however, they were not able to go through side roads as this required fine detail.
Patient EP
Extensive bilateral damage to the MTL, including the hippocampus → was profoundly amnesic like HM
Spatial memory for the town that he grew up in and longer lived in (prior to his injury) were totally normal
Shows that the memory must eventually come out of the hippocampus that goes into the cortex
Over time, memories are re-encoded and consolidated in cortex → become immune to hippocampal damage
Many cortical regions are active during spatial navigation in addition to the hippocampus
Retrospenial Cortex
Cortical region that is important for long-term, consolidated spatial memory
When this area of the brain gets damaged, general memory is not damaged → problem specific to spatial memory
Ex. taxi driver that could look at buildings and understand where he was → but the landmarks that he recognized did not provoke directional information about any other places with respect to those landmarks → could not determine which direction to proceed to go home
fMRI activity in retrosplenial cortex increases from session to session as participants learn the spatial layout of a fake town → stores the spatial information
When is the hippocampus necessary in spatial memory?
There are some types of spatial memories that always require the hippocampus
Ex. Patient TT: London taxi driver that could navigate on main streets, but he got lost when route requires navigation of smaller side-streets
Only the broad outline of the cognitive map gets consolidated to cortex → recall of the fine spatial details requires the hippocampus
