Week 6: Boundary vector cell model of place cells

Question 1

What type of neuron does the boundary vector model of place cell use?

Answer 1

standard artifical neurons with no dynamics

Question 2

Boundary vector model based on experiments conducted by which investigated (2)

Answer 2

O’Keefe and Burgess, 1996 investigated:

what are the inputs to place cells?

Question 3

What did O’Keefe and Burgress do (1996)? = Method (2)

Answer 3

• Made a square enviroment where
• Rat forages in a box where the size of the box is varied across dimensions and recorded their PC cells

Question 4

What did O’Keefe and Burgess, 1996 find (2) = PC field did not change

Answer 4

• Data from a single same neuron where they extended box across 1 dimension (e.g., lenght) and in another direction (width) and extended in both directions (length and width)
• Some of the PC they recorded exhibited ‘simple’ place field firing, consistent across box-sizes = place field did not change…

Question 5

What did O’Keefe and Burgess, 1996 = PC field changed (3)

Answer 5

• However, some PC appear to change with firing when the geometry of the box changed
• For example, firing field of PC that was close to east wall
• When the wall was extended on that dimension (towards east) , the firing field of one PC neuron changes and extends so that there is PC spikes all along the east side of the wall of the box

Question 6

These are all for one neuron in which they measured…

Answer 6

Captures its average firing rate

Question 7

Results of O’Keefe and Burgees 1996 when PC field changes shows that (3)

Answer 7

• Other place fields appear to respond at fixed distances from walls …

… with nearer walls more important than further ones.

=> The geometry of a space is an important factor (at least for a subset of PC cells)

Question 8

Subsequently, Hartley et al., (2000) (after O’Keefe and Burgess 1996 study) coined the term boundary vector cells (BVC) to describe the

Answer 8

• cells that respond to presence of a wall

Question 9

Boundary vector cells were not yet found experimentally

Answer 9

around the time of Hartley et al., (2000) research as they did theoretical predictions

Question 10

Hartley et al., (2000) put hypothesised that.. (3)

Answer 10

• Each BVC tuned to respond when a barrier lies at a specific distance from the rat in a particular allocentric direction
• These BVC cells are allocentric cells meaning the direction (of barrier) defined relative to some element of enviroment (like external cue)
• Does not depend on animal’s orientation

Question 11

Allocentric is a fancy term for

Answer 11

world centred

Question 12

BVC cells recorded via

Answer 12

single-cell recordings

Question 13

Hartley et al., (2000) hypothesied that

Answer 13

BVC and may give input to PC and influence their activity

Question 14

Hartley et al., (2000) proposes that the BVC firing is determined by

Answer 14

product of two gaussian functions, defining distance and angle tuning to boundary:

Question 15

Hartley et al., (2000) says sharper tuning for

Answer 15

shorter distances reflecting less unceranity in inputs to BVCs

Question 16

Hartley et al., (2000) if you take set of BVCs with receptive fields in different direction that are active

Answer 16

they together signals the distance to a set of boundaries

Question 17

Hartley put forward that BVC tuned to respond when a barrier lies at a specific distance from a rat in particular allocentric direction meaning that

BVC receptive field at given orientaiton (2)

Answer 17

• in the enviroment relative to the enviroment (not to animal’s orientation)
• As the animal approaches the wall, the wall of a specific barrier/boundary of box, covers more of the receptive field and firing rate of a particulae BVC goes up and is maxiamlly

Question 18

Hartley model of place cell firing is

Answer 18

taking 3/4 BVC and given input weight to PC and simply sum boundary inputs * weight and put through transfer function

Question 19

Hartley hypothesied that We know how far we are from the walls as (BVC)

Answer 19

we know where are are (PC cells)

Question 20

Hartley theoretically predicted that enviromental geometry influences PC (i.e., BVC give inputs to PC)

Answer 20

by having BVC as geometric inputs to PCs in the gaussian functions

Question 21

Diagram of BVC Model of PC Firing

Answer 21

Question 22

Idea of BVC Model is that when I am at a given location where (4)

Answer 22

3 BVC cells are active

These different BVCs will be maximally active and respond to barriers at specific distances and directions

These three different active BVC give input to PC and is then maximally active at this location

Subtract background activity and get place fields at specific locations

Question 23

How do BVC model of place cell firing model experimental data from O’Keefe and Burgess, 1996?

Answer 23

We calculate the activity of PC at all possible positions/locations (x,y) simultaneously since one location does not influence the other

Question 24

In BVC Model of PC Firing we could do it

Answer 24

location by locaiton but nothing stops us at doing all locations

Question 25

Remindar: The BVC Model of Place Firing Hartley et al., (2000) works of producing place field

Answer 25

Sum of 2 or more BVC inputs * its weights and put through transfer function which gives place fields

Question 26

Hartley et al., (2000) modelled O’Keefe and Burgess 1996 using BVC model

2-4 BVC

Answer 26

2-4 BVC oriented at right angles to one another and thresholds are sufficient to fit most (i.e., give best match) of the PC fields in the data by O’Keefe and Burgess 1996

Question 27

After using 2-4 BVC,

Stimulated results of the BVC showed that

Answer 27

• There is a close match of place fields between O’Keefe and Burgess data and Hartley’s model results

Question 28

BVCs predict boundary-referenced firing of PCs across enviroment

Method - (4)

Answer 28

1. Record some place cells in differerent shapes of enviroment (e.g., square, circle)
2. Find BVCs that best fit to those place cells in (e.g., square/circle enviroment)
3. Use the model BVCs to predict firing in other enviroments that have different shapes (e.g., right angle-triangle)
4. Experimentally, then record the same PC cells as found in the step 3 in predicted enviroments (e.g., right-angle triangle)

Question 29

Lever et al., (2009) and Solstad et al., (2008) discovered BVC in an area - (3)

Answer 29

rodent subiculum (area very close to hippocampus)

Rodent has a receptive field for west and everytime rodent is near the west wall of a box, a cell will fire

does not matter if curtain around box, remove the curtain or change shape of the enviroment, the specific BVC will always fire west to the wall

Question 30

Massive achievement for a theoretical model developed of BVC Model of PC firing as they predict BVC cell and this experiment by

Answer 30

Lever et al., 2009 and Solstad et al., 2008 confirms this