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1

terms

Distal (long range) vs proximal (short range) cues

Egocentric (relative to the individual) vs allocentric (relative to the environment) frames of reference

Beacons (Pavlovian approach – automatic reflexive behaviour – becomes attractive due to conditioning) vs landmarks (used as a reference)

2

spatial learning in lab rat

If there is any way of solving a learning task by treating it as a spatial problem, that’s what a rat will do (“position effects”)

Rats can learn complex mazes, e.g. Hampton Court replica (Small, 1900)

Tolman et al’s (1946) “sunburst” maze seemed to show that rats have a sense of direction and can take a shortcut

…though only if there’s a “beacon” available

Train until able to do it quickly

Route used to take blocked off in test

Learnt where goal was relative to starting position – take shortcut

Confound – bright light above the goal – every time close to bright light = food  conditioning = beacon

see notes

3

T-mazes

see notes

4

possible reasons for behaviour in the t-maze

SMELL

Glands brush against floor – mark where they have been

PAVLOVIAN CONDITIONED APPROACH

INSTRUMENTAL RESPONSE

MAP

All possibilities are right – rats does whatever it takes to get the food

5

odour as a reason

Test in extinction

“+” = trained side but no food there

Swap the arms of the T-maze

If it’s following an odour trail it will go to the “wrong” side.

Still goes the the left side – not following odour trail

see notes

Enclosed = learns to go left

Not enclosed – goes to correct side – can see landmarks

6

landmarks as a reason

If we’ve established that the rat is heading for a certain point in space, the question then arises of how it is doing that. Is it using a map - or just approaching a specific landmark (beacon)?

see slides

A - closest – associated – beacon

By taking the landmark away (deletion) we can assess the effect on the rats performance. We can also try altering the configuration (spatial arrangement) of the landmarks

If using configuration – should still go to right location

7

the radial arm maze

Radial Arm Maze experiments with rats.

There is now abundant evidence that rats typically solve this maze by using the external (extra-maze) landmarks.

Rotation tests and landmark deletion / re-arrangement studies all point to this conclusion.

8

rotation test

The animals are forced to the 4 arms shown in blue, then the maze is rotated through 45º (or the landmarks are rotated relative to the maze.

Control = before rotation test them on which arms they go down

Now the rats are offered a choice between an unvisited arm U (animal has not been down it, there is food at the end, but it’s now at the location that was visited) or a visited arm V (animal has just been down it, no food at end, but is at an unvisited location.)

see notes

The result is that rats tend to choose the visited arm. In my studies a typical result was that on 32 trials 20 were revisits to previously visited arms. A control test where the maze was not rotated gave only 2 visits to previously visited arms, a highly reliable difference.

Not using intra-maze cues

Going to unvisited place

9

Suzuki, Augerinos and Black (1980)

used a cylindrical testing chamber with discrete landmarks at each arm of the radial maze.

They found that rats ‘followed” rotation of the landmarks with respect to the maze, but a re-arrangement of the landmarks relative to one another (i.e. transposition) dramatically worsened performance between study and test.

These data suggest that rats use configurations of landmarks to define locations in the radial maze, rather than using them as beacons to mark specific locations close by.

10

O'Keefe and Nadel (1978)

claimed that animals use a map to navigate, and that the mechanisms for constructing and using this map were located in the hippocampus.

11

the hippocampus as a cognitive map

There is good evidence that the hippocampus is involved in spatial learning, e.g.

O’Keefe and Nadel: single cell recording in the hippocampus shows “place cells” which fire when a rat is in a particular place in a maze

Hippocampal lesions disrupt performance in the Morris water maze

see slides

12

O'Keefe and Conway (1978)

see notes

Some cues may not have been adequately controlled

13

the Morris water maze

see notes

The rat is put in the pool at a random location along the side (S).

It then swims to the platform, at first in a roundabout fashion, later more directly.

Animals with hippocampal lesions are impaired at this task, in that they take longer to find the platform and do not exhibit the ability to swim straight to it in the way that controls can.

works with reversible lesions too

technique can also be applied to humans

14

blocking in the water maze

a problem for the cog map hyp

Two groups are trained in the water maze to find a platform on the basis of different sets of landmarks, either ABC or ABCX.

Landmark X is then added to ABC in the first group, and more training given.

Tests with ABC and ACX reveal how well the animal has learned to use X to find the platform in conjunction with the other landmarks.

see notes

1 = best score

The Blocking Group are worse at using landmark X (see ABX)

Learning is akin to the learning seen in conditioning experiments

15

navigation: what do you need to find your way around?

A map to specify the spatial relations of objects; cf. Tolman (1948), cognitive map to account for rats’ learning of mazes?

A compass to specify directions (orient the map; cf. Kramer (1953), map and compass account of bird navigation

A locator to tell you where you currently are

Redundant systems so that if one is blocked you can still navigate

16

magnetic navigation : the Green Sea Turtle (Chelonia Mydas)

Migrate 2000 km from feeding grounds on the Brazilian coast to nest sites on Ascension island

Thought to use orientation and intensity of earth’s magnetic field – a bearing map

Contributions of instinct and individual learning unclear

17

homing pigeons

Sun compass (requires knowledge of time of day). Clock-shift experiments.
- Shift dark light cycle
- Think midnight is midday – think it’s dawn – think it’s east when you know it’s west – fly in wrong direction

Magnetic compass
- Magnetic field change and grain – no evidence of learning – receive plane/plain? Of polarisation from sun

Infrasound (?) and other beacons

Olfaction (e.g. Guildford et al 1998)

Route marks e.g. motorways (Lipp et al 2004)

Proximal landmarks at start and end of flight (e.g. Biro et al, 2003) – use the way the scene looks when get closer to home – frosted contact lens – cant distinguish parts of scene and can’t find right location

Must all be learned

18

adaptive influence on spatial learning: scatter-hoarders

Scatter-hoarders make numerous (several thousand) caches of food and recover them months later

Often the look of the environment is different at cache time and recovery time (e.g. snow)

Caches cannot be marked (e.g. by scent) or they would be pilfered, so scatter hoarders need exceptional spatial memory

Examples: corvids (scrub jays, Clark’s nutcracker), sciurids (grey squirrel, fox squirrel), parids (marsh tit, coal tit)

Note not all members of same genera/families scatter hoard

19

exps on scatter hoarders

MacDonald (1997)

Krebs et al.

Kamil et al.

Clayton et al.

20

Macdonald (1997)

trained grey squirrels to find nuts she’d buried at random places in a 2m circle

visual signal when nuts would be present

squirrels could still recover nuts accurately 2 months later

decoy nuts buried at different distances from targets… if decoy was more than 2cm away, the squirrels always took the target

21

Krebs et al.

compare storing parids with non-storing species on spatial memory tasks

scatter hoarders do better (e.g. Krebs et al 1990)

22

Kamil et al.

series of experiments on Clark’s Nutcrackers, investigating what cues they use to find caches

e.g. Kamil & Jones (2000) conclude that birds can use both absolute and relative cues, and both distance and direction from landmarks, but direction is more salient

23

Clayton et al.

many experiments on scrub jays showing that they remember what they have stored and when, as well as where (see previous lecture)

24

the hippocampus and spatial memory

The hippocampus is larger, relative to total brain size in:
- Bird families that store food compared with families that don’t, and in scatter hoarding species than non-storing members of the same families (e.g. Krebs et al 1989)
- Individual birds with experience of cache recovery than in inexperienced members of the same species (Clayton & Krebs, 1994)
- Homing pigeons rather than other strains
- London taxi-drivers than control subjects (Maguire et al, 2000).
- The implication is that if you have a lot of stored spatial relations then your hippocampus will be larger.