Rat Spatial Navigation

Question 1

Ideothetic cues

Answer 1

Internal cues
Vestibular, propioception, corollary discharge, optic flow
Provide PATH INTEGRATION, continuous movement/distance estimate

Question 2

Allothetic cues

Answer 2

External cues
5 senses

Question 3

3 tasks for spatial learning

Answer 3

Radial arm maze, learn to visit each arm once (hippo damage = repeat visited arms, perseveration)
Morris water maze, learn to swim to platform (hippo damage = swim randomly)
Circular platform maze, learn which hole had tunnel
morris/circle require external cue

Question 4

Types of memory

Answer 4

Declarative explicit -spatial memory!/facts
Procedural implicit - skills/habit

Consolidate working memory into long term, prefrontal cortex does working memory

Question 5

Amnesia types and H.M.

Answer 5

Retrograde - memory loss before trauma
Anterograde - no new memories (H.M./Dory)
H.M. bilateral temporal lesion - caused anterograde amnesia, unable to form new delcarative, PROCEDURAL AND WORKING INTACT (stored elsewhere)

Question 6

Hippocampus Pathways

Answer 6

Perforant Pathway - Entorhinal cortex -> Dentate Gyrus
Mossy fiber - Dentate -> CA3
Schaffer collateral - CA3 -> CA1 (CA1 has pyramidal PLACE CELLS)

Hippo grew for taxi drivers, used in spatial!

Question 7

Place cells

Answer 7

CA1 region hippo
have place field influnced by external and internal cues
spike at specific points, create COGNITIVE MAP

Question 8

Time Cells

Answer 8

hippo Fire at successive moments in a temporal structure
at least one cell fire at each moment

Question 9

Head Direction Cells

Answer 9

Postsubiciculum
compass for direction
same preference in any environment, intenral/external cues

Question 10

Grid Cells

Answer 10

Entorhinal Cortex
Positioning system
different cells have grids of diff sizes and orientation, all stacked on top each other allow for a POPULATION CODE of location, grids scaled to each other at possibly sqrt of e

Question 11

Speed cells

Answer 11

Medial entorhinal cortex
Linear firing rate to speed
updates position rep with head direction and grid cells

Question 12

Border Cells

Answer 12

Fire at proximity to boundaries
important to anchor grid cells and create geometric reference frame

Question 13

All cells working together

Answer 13

Each place in local enviro has unique combo of cells firing (grid cell overlap), hippo place cells
Medial entorhinal cortex MAJOR INPUT TO HIPPO, allow modifiable place cell synapses

Question 14

Where does synaptic plasticity occur in hippo

Answer 14

Schaffer collateral, LTP between CA3/1

Question 15

Inducing LTP

Answer 15

Induce axons with tetanus stimulus, allows EPSPs of post axon to heighten
input specific, diff input wont actiavte
BOTH ACTIVE WHEN POST STRONGLY DEPOL

2 required things for LTP (PRE/POST ACTIVE TOGETHER FIRE TOGETHER WIRE TOGETHER)
High freq stim causes temporal summation
Spatial summation across synapses needs to happen

Question 16

LTP Mediated by what

Answer 16

NMDA receptors
Ligand and voltage gated
AMPA binds with glutamate, depols the post cell
NMDA receptor voltage unlocked (Mg blokc removed)
Channel opens, Ca enters
NMDA IS COINCIDENCE DETECTOR FOR PRE/POST BEING ACTIVE

Question 17

LTP Mechanisms

Answer 17

Ca entering NMDA activates protein kinases
Kinases phosphorylate AMPA, more efficient
Insert new AMPA receptors

Question 18

Inducing LTD

Answer 18

Long term depression
give tetanus of LOW freq stim
input specific, diff input wont activate
BOTH ACTIVE WHEN POST WEAKLY DEPOL

Question 19

Bidirectional Plasticity

Answer 19

Ca can induce LTP or LTD, synapses can change both ways
Protein kinases = high Ca, LTP
Protein phosphatases = DEPHOSPHORYLATE PROTEINS, low Ca, LTD. AMPA dephosphorylated = LTD

Question 20

AMPA receptor balance

Answer 20

LTP creates need for more room on emmbrane for synapses,
Newly formed AMPA receptors have GLuR1 subunit to allow to fit into membrane
LTD leads to need for smaller membrane

Question 21

Knockout Mice types

Answer 21

NMDA Blocker = never learn, NMDA needed for memory, swim randomly. Impair LTP, less precise

CAMK11 Knockout = lack Ca-dependent kinases = IMPAIR LTP, fewer place cells/less precise/less stable, impaired spatial learning