Dean NMR 1

Question 1

Whats the issue with attempting to understand the neural bases of learning?

Answer 1

It’s difficult to know where to look due to the trillions of synapses in the brain which underlie various complex processes. To solve this issue can look at a form of learning that is as simple as possible - with the hope that only a relatively small number of synapses are involved, giving us a chance of identifying them

Question 2

What is this simple form of conditioning?

Answer 2

Classical Conditioning - first investigated in Pavlov’s dogs.
Probably involves changes in synapses e.g. LTP

Question 3

Outline the Pavlov’s dogs experiment

Answer 3

Before training the US (food) produced an UCR (salivation). When the bell was rang it produced no response
But pairing the bell with US it lead to salivation - allowing for conditioning.
After conditioning the bell (CS) on its own produced salivation (CR)

Question 4

What are the different types of conditioning?

Answer 4

Is the US bad or good?
The salivation CR is ‘appetitive conditioning’ to the food US and a limb withdrawal CR to a painful US would be ‘aversive/defensive conditioning’
Can condition autonomic responses such as anxious body responses like increased heart rate to exams

Question 5

What is the chosen method of studying conditioning?

Answer 5

Eye blink conditioning has proved the easiest to study as oppose to limb withdrawal.
The US is usually a puff of air to the eye or a peri-orbital shock
The CS is usually a tone
And the CR and UR is movements of the eyelid

Question 6

How can we use eye blink conditioning in animals?

Answer 6

Some animals such as birds, cats and rabbits have a third eyelid (the nictitating membrane) which can also be classically conditioned as it doesn’t appear to be under voluntary control so there’s no apparent interference.
The rabbit is the animal of choice in these studies as they can easily be trained to sit quietly

Question 7

What can be seen in nictitating membrane conditioning studies?

Answer 7

After just 3 days (typically 100 trials per day) the NM starts to move before the somatosensory stimulus; indicating the anticipation of US
On day 5 the NM moves way before the CS

Question 8

What are the 2 types of classical conditioning?

Answer 8

Delayed conditioning = where the US overlaps with the CS

Trace conditioning = when there’s a gap between the US and CS which involves more neural structures so is less simple

Question 9

What is the US used in these animal studies of NMR?

Answer 9

Usually a brief mild peri-orbital shock (skin around the eye) which doesn’t cause distress - it means that closing the eye has no effect on the US, if it did it would be a form of avoidance learning not instrumental learning

Question 10

Is the hippocampus involved?

Answer 10

Through patient H.M it was theorised that maybe it could be involved.
But a study by Weiskrantz and Warrington (1979) demonstrated clear evidence of learning after damage to the hippocampus despite the subject having no memory of the apparatus

Question 11

How were Weiskrantz and Warrington’s (1979) findings developed?

Answer 11

Gabrieli et al., (1995) added more subjects and a control group, verifying that although there was damage to the medial temporal lobe, the rates of conditioning were the same in both groups.

Question 12

How is LTM divided?

Answer 12

Split into:

• Conscious memory (explicit) e.g. facts and events
• Non-conscious memory (implicit) e.g. skill and habit learning, simple CC and priming

Question 13

Where does CC possibly occur in the brain? What have studies found?

Answer 13

Studies found that it doesn’t occur in the forebrain as delayed conditioning was still present in rabbits lacking a hippocampus, cerebral cortex or when the forebrain was separated from the brain stem and cerebellum (decerebrate preparation)
Needed further exploration

Question 14

What was the first technique that Thompson (1983) used?

Answer 14

Electrophysiological mapping during conditioning to systematically record from multiple units in the cerebellar cortex and the deep cerebellar nuclei

Question 15

How did Thompson (1983) use the electrophysiological mapping?

Answer 15

Had a control condition in which the CS and US were presented as frequently as in the training condition but they were unrelated so the CS produced no neuronal response
In the training condition they were paired and even on day 1 could see a clear response
The recording was from the deep cerebellar nuclei close to the cerebellum, almost all cerebellar goes through these nuclei

Question 16

What was the second technique that Thompson (1983) used?

Answer 16

Lesions because the recordings do not establish a causal role

Question 17

What did Thompson (1983) find from the lesions?

Answer 17

Large lesions of the entire cerebellum plus the deep cerebellar nuclei found that if the animal had been trained, the CR was then abolished and could not be relearned
A similar effect is seen with smaller lesions confined to the deep cerebellar nuclei
Lesions confined to the anterior portion of the middle (interpositus) nucleus are effective (Yeo et al., 1985)
There was a selective loss of the CR, the UCR was unaffected

Question 18

Why is it important that the UCR was unaffected after anterior lesions of the interpositus nucleus?

Answer 18

As it shows that the lesion does not produce a simple motor deficit, and that it doesn’t cause deafness to the response because unilateral lesions only affected the conditioning of the ipsilateral eye.
Appears to be a genuine loss of the memory trace (the ‘engram’)