Learning and Memory

What happened to HM?

he had an increasing number of seizures and to stop it from spreading to the other part of his brain where he would go unconscious he had surgery

What surgery did HM have?

He had a bilateral removal of his temporal lobe which included the hippocampus

What did HM treatment result in

memory impairments and anterograde amnesia

What could HM remember

things that happened before his operation, could repeat 7 numbers back to experimenters, as long as he kept repeating the numbers

Types of memory

Sensory, short-term, long-term

HM - motor learning

mirror drawing so it shows it the opposite way round to what you normally see it so it is difficult to do. So on day 1 your really bad at it but gradually get better over the trials. He thought he had never done it before on day 3 as he had forgotten it. But he got better at it by day 3

HM - perceptual learning

broken drawings so they start off showing you a drawing with just a few lines and gradually as you go through it gets more detailed until you can guess it. On the next day he was able to identify what the images were earlier on when the drawings were more broken but he wasn’t able to remember when he saw them 

Human eyelid conditioning

• In this preparation the unconditioned stimulus is the airpuff

• The tone is the CS

• The CR is eyeblink

Human eyelid conditioning in HM

would blink because they put air when he heard a tone and he wouldn’t know why he was blinking

Classical conditioning in the real world chronic use of drugs (Crowell et al, 1981)

• They would always give injections of saline in a blue room

• And they would always give injections of alcohol in a purple room which causes the body to cool down. But if you do it over and over they are able to predict the hypothermia is going to happen when they are in the purple room

Classical conditioning in the real world chronic use of drugs (Crowell et al, 1981) - What did they do after they could predict which room they were going to get hypothermia in?

So in the test session they gave the alcohol in the blue room so the body is not expecting the hypothermia so instead of getting the tolerance to it they get the hypothermia

HM couldn’t remember in LTM

Declarative memories - includes episodic memories, spatial memories and semantic memories

HM could remember in LTM

nondeclarative memory - includes memories that we aren’t conscious of

Anterograde Amnesia

Declarative and nondeclarative memories

 can learn to perform tasks, they do not remember learning them. unable to form declarative memories but can form nondeclarative memories

Maguire et al (1998)

showed activity in the right hippocampus in participants navigating around a virtual town

Feigenbaum and Morris (2004) - spatial

damage limited to the right hippocampus cause spatial impairment

Luzzi et al (2000) - find rooms

reported patients with damage to the right Parahippocampal gyrus could only find his room by counting the doors from the end of the hal

Barkas et al (2012) - rats

reported both rats and epilepsy patients with scarring caused by seizures in the right hippocampus couldn't use spatial cues to locate objects

Morris water maze (Morrris et al, 1982) - procedure

 underneath the water is a platform and the rats would swim around the water until they find the platform so intially you are wondering all around.

Morris water maze (Morrris et al, 1982) - results

Next time they would have an idea of where the platform would be. After a while able to swim straight towards it

• But the animals with damage to the hippocampus were not able to find the plaform even after multiple times

Not all spatial ability is controlled by hippocampus - Mcdonald and White (1995)

Entorhinal cortex controls egocentric guidance (knowing where something is in comparison to yourself)

Role of the hippocampus formation in consolidation of declarative memories

• Hippocampus recieves information about what is going on from the sensory and motor associations cortex and processes this information

• The hippocampus tells you where you are

The efferent connections of the hippocampus tie together…

the memories that are consolidated in other brain regions

Entrohinal cortex can tell us… but we need hippocampus…

where we need to go, to work out where we are in the first place

Hebbs rule - evidence of long term potentiation

• If both A and B stimulate it will trigger the excitatory synapse. You want the threshold to decrease and that is what is meant by strengthening a synapse

• Over time it is strengthened

Hobbs rule by strengthening it

the synapse is more sensitive so when you hear than tone you will now blink due to long term potentiation

Glutamate neurones

 neurones within the hippocampi

LTP among glutamate synapses

help establish conditioned responses

Glutamate bonds with 2 types of receptors

NDMA and AMPA receptors in the post synaptic membrane. So opens these receptors

When postsynaptic membrane is at resting potential (-70mV) the NMDA receptors are blocked by

magnesium

Synaptic strengthening

• When the conditions for long-term potentiation are met…

Ca2+ ions enter the dendritic spine through NMDA recpetors. The calcium ions activate enzymes in the spine

The activated enzymes cause..

AMPA receptors to move into the spine

An increased number of AMPA receptors in the postysnaptic membrane…

strengthens the synapse