Lecture 10 - Memory Flashcards
What are the two types of learning
1- Non associative= when a person learns to/not to react to a stimulus
(habituation and sensitization)
2- Associate learning = relation of one stimulus to another.
(classical and operant conditioning)
Habituation
Stop reacting to a stimulus after frequent exposure, ability to be able to ignore irrelevant and repetitive stimuli so we are not overwhelmed.
- Sea slug has gills which are sensitive and needed to breath so they are protective over these.
When the siphon is stimulated these gills will be withdrawn to keep them safe. If continuously stimulated, they will no longer with draw.
- This short term habituation is caused by change in the synapse between sensory and motor nerves as less neurotransmitters will be released resulting in less motion at motor neuron.
- In long-term there may be structural changes such as decrease in density of receptors and less synapses.
Sensitization
Having a heightened reaction. More generalised and targets as whole class of stimuli.
- In sea slug, shock to tail results to sensitization of gill withdrawal. The modulatory neuron increase synaptic transmission of sensory neuron to motor, creating an amplified response.
- Transmission is strengthened by releasing of serotonin from modulatory neurons.
- In long-term PKA enzyme lead to growth of new synaptic contacts between sensory and motor neurons making response stronger.
Classical conditioning
Learning to associate 2 stimuli with each other- a conditioned response.
Leads to a conditioned reflex:
- Unconditioned stimulus: naturally and automatically triggers a certain response even without learning
- Conditioned stimulus: when paired causes a response but not on its own- then it is a neutral stimulus and requires associative learning for a response
Operant conditioning
Subject taught to perform voluntary action in response to stimulus for either a reward or punishment
The alerting signal = conditioned stimulus
Pleasant/unpleasant event = unconditioned
Operant means that the behaviour is voluntary depending on consequence where as classical the behaviour will occur regardless.
Reward ties in with dopamine pathways
- In short term there are changes in synaptic efficiency such as increase in density or transmitter release.
- Long term there can be increased activity of intermodulatory neurons such as synaptic genesis (forming new synapses) and synaptic plasticity (re arranging formation to be more efficient)
Short term, long term and consolidation memory
SHORT: immediate memory for events which may or may not be considered for long term. Rehearsal can help keep memories here
CONSOLIDATION: process by which memories are converted from short to long
LONG: stable memory of events which happened in the distant past.
Types of short term memory
1- Digit span: examiner reads out 1 per second a series of digits and patient repeats them back in the same order. Most people can reply 7 and in reverse 5. Involves frontal cortex.
2- Working memory: Contents are used to solve a problem by manipulating it to solve a problem
The Baddeley - hitch multicomponent model (short term)
Visuo-spatial sketch pad (store visual and spatial information)
Central executive (maintenance decides if memory should be stored and if so, where should they go)
Phonological loop (verbal information)
Those who have to remember objects and names there is less interference than objects and spatial location as the first can be held in either store but second they must be in the same.
There will always be interference as the central executive must decide.
Types of long term memory
1- Explicit: declarative and can be verbalised
Semantic: facts and information (date and capital cities) in temporal cortex
Episodic: recalling of instances in life in the hippocampus
2- Implicit: non-declarative (motor skills) cannot be demonstrated verbally.
Procedural: Motor skills
Priming: exposure to stimuli influences behaviour
Delayed match to sample task
Monkey given object to explore then presented with same object and novel one after delay.
Rewarded for reaching novel object as it shows recalling of previous object,
Neurons are most active when presented with new object and there is still some activity during the delay.
Long term memory
To make information long term, connections between brain areas must become stronger
- Connections get stronger every time the information is recalled and then because they are often together they create an engram for the stimulus.
- When memory is recalled as engram is already stored, only part of the stimulus is required. Some neurons will be stimulated but as they are so strongly connected the others will automatically activate
Clive wearing
- Correlation of brain areas with symptoms.
Anterograde amnesia: unable to recall recent episodic memories and create new ones. - Clive thought he was 30-40 years younger and terrified by old face as he had no concept of time passing.
Caused bilateral damage
Patient H.M
Epilepsy began when he was 10 multiple seizures a day and EG recording found seizures occured in medial tempoal lobe.
So removed temporal lobes in both hemispheres. Led to anterograde amnesia.
He was able to converse and recall events from childhood and facts before surgery but unable to recognise new faces.
Medial temporal lobe contains hippocampus for forming new episodic memories encoding memories with support of surrounding areas.
He was asked to complete a tracing task and performed as normal meaning procedural memory was still intact.
He remembered his parents passing after surgery.
Dissociation between declarative (impaired) and non-declarative memory
Patient NA
Fencing coil went up nose and damaged hypothalamus and thalamus significantly.
Damaging a circuit which is important for episodic memories
Amnesia can be caused by damage to other structures not only hippocampus.
Damage to left hemisphere meaning struggled more with verbal memories.
Other wise intellectually intact
What is Korsakoff’s syndrome
Memory deficiency caused by thiamine deficiency (chronic alcoholism) leading to severe episodic memory impairment
Patients often made up fake facts to fill gaps in knowledge and believed them to be true known as confabulating
Patient KC
Cannot retrieve personal episodic memory due to motorcycle accident where there was damage to media temporal lobe including hippocampus.
Remembered facts but lost some episodic memory with greatest impairment in creating new episodic memories despite non-declarative memory being fully functional.
Good knowledge and chess player, relying on implicit memory
What does the hippocampus do
Spatial navigation
Episodic memory
Significantly larger in London taxi drivers and degenerates in Alzheimer’s disease
Implicit memory preservation (procedural learning)
Consolidation
Developmental amnesia is from birth where hippocampus is damaged as a result of a hypoxic episode from birth where there is a lack of oxygen leading to life long damage to spatial navigation and episodic memory.
What do different areas contribute
Hippocampus forms cognitive map.
PLACE CELLS in hippocampus activated when moving towards particular location
GRID CELLS fire at regular intervals when crossing intersection points of a grid.
BORDER CELLS respond to the perimeters
Together they create an internal system
