NEUROBIOLOGICAL BASIS OF MEMORY Flashcards
What did Karl Lashley do?
Explored the problem about 100 years ago of memory by making lesions in the brain of animals such as rats and monkeys
What was lashley searching for?
Evidence of the engram = the group fo neurons that serve as the physical representation of memory
Whats the law of mass action?
The severity of the memory impartment for maze performance correlated with the size of the cortical area removed and not with specific location
What did modern study of the brain basis start with?
Famous report of scoville and Milner in patient HM
Explain the background behind patient H.M?
- sustained a head injury at age 7
- experienced his first major seizure at age 10
- experienced his first generalised convulsion at 16
- experimental surgery performed in 1953 was 27 years old
Where was the tissue removed for patient H.M?
Had tissue removed from the temporal lobes - hippocampus
What kind of memory was still intact for patient H.M?
Short term memory
What was patient h.m not able to remember?
Uable to remember events that happened several years before the surgery - retrograde memory impairment
- unable to form new memories / learn new information = anterograde memory impairment
- unable to navigate a new neighbourhood
Whats it know as when you are unable to remember events that happend several years before?
Retrograde memory impairment
Whats its know as when you are unable to form new memories/ learn new information?
Anterograde memory impairment
What was spared for patient H.M?
Procedural memory - ability to learn and remember skills
Who designed the experiment for HM?
Miller
What was the experiment by Milner accessed to do.
Learning and long term rendition abilities on task requiring viso- moto coordination in HM
What was the main results for HM ?
Performance was initially poor but improved over days
What are the two types of long term memory?
Declarative memory
Non declarative memory
What kinds of memory are under declarative memory ?
Episodic memory
Semantic memory
What kind of memory is under non- declarative memory?
Procedural memory
Priming
Simple classical conditioning
Habituation sensitisation
Where is declaritve memory found in?
Medial temporal lobe, dienceophalon
Where’s procedural memory skills found in?
Basal ganglia
Where’s priming memory found in?
Neocortex
Where’s habituation sensitisation found in ?
Reflex pathways
What’s the hebbian theory ?
Hebbs theory that neurophysiological change underlying learning and memory is is three stages
- Synaptic changes
- Formation of a cell assembly
- Formation of a phase sequence
What does long term memory require for activation and strengthening?
Pre and post synaptic neuron
Who worked to uncover the neural mechanism of learning and memory
Psychiatrist Eric kandel and colleagues arvid Carlsson and Paul greengard
For habituation what did they study?
Gill- withdrawal reflex A defensive motor response behaviour
Explain the gill withdrawal reflex circuit
Heavily tried on 2 different population of neurons
- the glutamatergic sensory neurons that receive somatosensory information from the skin of 5e siphon
- the motor neurons that control th emuscles of the gill
What is habituation?
A decreased response to a stimulus after repeated presentation
What happens when there’s an immediate change for habituation?
Immediate change - less neurotransmitters released in the synapse - results in less retraction
What happens in short term habituation?
Stimulus
Siphon
Sensory neurons
Motor neuron
Gill withdrawal
Hat happens in long term habituation?
Stimulus
Siphon
Sensory neurons
Motor neuron
No response
What happens in sensitisation?
- when they pair the mild siphon touch with a painful electric shock to the tail
- ## the palisade began responding with a strong motor reaction which withdraws the gill very intensely indicating that the inhibited response disappeared
What did they observe in the electrophysiological studies?
They observed that the EPSP at the motor neuron was much larger following the tail shock
Define dishabituation.
Restoration of response amplitude after habituation
Define sensitisation?
Prior strong stimulation increases response to most stimuli
Explain the discovery of long term potentiation?
Discovered in rabbit hippocampus by bliss and lomo
Strengthening of synaptic efficacy between neurons in the brain
LTP is found to be essential for declarative memory
What is LTP defined as?
A long lasting increase in the magnitude of then synaptic response of a neuron following. A short train of high frequency afferent stimulation or simialr induction protocols
What kind of physiological changes at synapse may store information?
Presynaptic
Postsynaptic
Both
What could be some changes example?
Increased neurotransmitter release
Effectiveness of receptors
What’s LTP.
Strength in of synaptic efficiency between neurons in the brain
What’s LTD?
Long lasting decrease win the efficient of synaptic transmission
What can synaptic plasticity change?
The amount of neurotransmitter released
The number of postsynaptic receptors avaliable
Or both
What can structural changes at the synapse provide?
Long term storage
And new synapses could form or some could be elimate with training
Training or experience might also lead to synaptic reorganisation
What is long term depression expressed by?
Decrease in efficiency of synaptic transmission
Can also encode information
