Week 6: Recap of Place cells Flashcards
Across species (humans and rodents), we can identify different portions of the hippocampus (4)
- DG
- CA3
- CA2
- CA1
Hippocampus receives main input from
EC (Enthorine cortex) which last stage of cortical processing prior to the hippocampus
Remindar what we found in hippocampus diagram:
Typical experiment to record neurons from hippocampal formation is from
single-cell recordings
Reminder of single-cell recordings (3)
- Microdrives with electrodes are chronically implanted
- Once the animal has recovered from surgrey it performs a task or simple runs around a box to collect food pellets around the box to cover the entire space of maze
- Electrodes are moved until they record spikes
Diagram of single-cell recordings
Neurons found in hippocampal formation (4)
- Place cells
- Head direction (HD) cells
- Grid cells
- Boudary cells
The single-cell recordings allow us to have direct recordings from
rodent brain in behaving animal
There is a visual cue (e.g., white card) in the box from single-cell recordings that help animal to
orientate itself in this box
Remindar: Place cells
Place cells fire whenever an animal occupies a specific location in its environment, with each place cell firing at a different spot.
Remindar: Grid cells (2)
A grid cell is a type of neuron within the entorhinal cortex that fires at regular intervals as an animal navigates an open area,
Grid cells generate virtual maps of the surroundings that resemble grids of repeating triangles.
Location of place cells
Hippocampus
Location of grid cells:
EC
Diagram of place and grid cells:
Remindar: HD cells
Head direction cells fire selectively when the rat’s head is pointed in a particular direction in allocentric space, regardless of its location (Ranck, 1985)
Diagram of HD cells graph
Boundary cells are measured the same way
as place cells (recording intensity of firing of a neuron, red = highest)
Boundary cells have receptive fields and whenever the boundary cells is in that receptive field
that boundary cells fires an action potential
Boundary cells respond to a specific
environmental boundary/objects at a particular distance and direction from an animal
As an animal moves away from receptive field, that boundary cells
stops firing action potentials
Boundary’s cells firing is
independent of the rat’s heading direction.
Most of the neurons in hippocampal formation has been recorded in
humans as well
Place fields are receptive fields for
space
HD cells have receptive fields for
heading
Place cell property 1
Location of a place field can not be predicted based on anatomical vicnity
Location of the place field can not be predicted based on anatomical vincity means
Anatomically close place cells can have place fields far from each other (rather than close to each other) or one cell can be silent while other is active in different enviroments
Place cell property 2 (3)
- Firing is independent of the rat’s orientation in open field
- Firing is directional in narrow-armed mazes
- Firing is robust to the removal of sensory cues
Firing of PC is independent of rat’s orientation in open field = how? (2)
- Separated data according to movement direction
- The activity of the place cell is still in the same location if the animal direction is west to east or east to west
Firing of PC is directional in a narrow-armed maze (linear track = animal runs back and forth)
Meaning the animal only fires in one direction
Firing of PC is robust to the removal of sensory cues (2) Nakazawa (2002)
If you have 4 sensory cues in enviroment, you can remove 3/4 and the PC cells still fire
If you block the NMDA receptor, this is not the case, meaning formation of PC fields is important for plasicity by NMDA-receptor for these PC cells
Place cell property 3 = Global remapping
Individual PC cells at given enviroment fire at different locations or are silent and together all active PC cells
likely to cover the entire enviroment with their place fields
Place cell property 3
Some PC cells are silent in one enviroment but
active in another
Place cell property 3
If a PC cell is active in both enviroment it is so at
different locations
Place cell property 3 what is global remapping?
The process of changing firing locaiton or turning on/off between enviroments
Place property 3 (after def of glob remap) we can think of the set of active PC across an enviroment akin to
extended attractor network (current context recruits a given set)
We can think that the set of active PC cells across enviroment akin to an extended attractor network but be careful… - (2)
If the set of active PC is bounded together by CA3 recurrence, it can’t be via CA3 place cell with small receptive place fields
Must be via CA3 cells that are active throughout the enviroment (i.e., not CA3 place cells)
Place cell propertities (3)
- Property 1 = location of place fields can not be predicted by anatomical vicinity
- Property 2 = Firing is directional , independent or orientation and robust to removal of sensory cues
- Property 3 = Global remapping
Similar to Nakazawa paper,
you need synaptic plasticity of the NMDA-receptor to have stable place fields
(Kentros et al., 1998) - (2)
Inject saline , place field is stable
Place field stability falls when NMDA receptors are blocked (i.e.,NMDAR anatgonist is injected in rat
There is slow, experience-dependent changes to PC fields showing global remapping (Lever et al., 2002) is not the whole story (3)
- global remapping is akin to change between attractor
- But the attractor ‘is slowly deformed over time’
- We need to keep these caveats in mind when building a model
- Recall: question determines level of detial in model
