Learning And Memory Flashcards
Define the term “Learning”
Acquisition of new information
Define the term “memory”
Retention of learned information
What are the 2 types of memory?
- Declarative memory (explicit): Facts and events - Hippocampus
- Non-declarative memory (implicit): Procedural memory, motor skills, skills - Stratium
List some types of declarative memories
- Working memory: Temporary storage, lasting seconds
- Short term memories: Facts and events in STM, Subset are converted to LTM
- Long term memories: Recalled months or years later
List some non declarative memories
- Procedural memory: Skills & habits
- Skeletal musculature (Classical conditioning)
- Emotional response (Classical conditioning)
Describe the process of memory being converted from the STM to the LTM
Sensory information -> either working memory or STM -> LTM via consolidation and with time
Where is the prefrontal cortex found?
What is special about this area of the brain in regards to humans?
- Found in the frontal lobe
- Primates have a large frontal lobe
- Meaning they’ve got a large/well developed prefrontal cortex
What is the function of the prefrontal cortex?
- Self awareness
- Capacity for planning and problem solving
- Higher order thinking
- Rational thinking
How does the working memory activity in the monkey prefrontal cortex work?
- Produces a delayed response
- First there is a cue period
- This is then followed by a 10 second delayed response
- Finally the monkey undergoes a choice period
What other brain regions are involved in the delayed response saccade task?
- Anterior intraparietal area
- Lateral intraparietal area
- Parietal region reach
How does these areas affect and cause the delayed response?
- First the target is flashed whilst the monkey is staring at the fixation point
- The target then moves whilst the monkey is still staring at the fixation point (delay stage)
- The monkey then finally started to look at the target (Saccade stage)
Where are memories stored?
- In general, they can be stored throughout the brain
- In neurons, they can be stored in the engram
Describe Hebb’s cell assembly and memory storage model (PART 1)
- Came up with the idea neurons don’t exist in isolation but instead in a network
- As a consequence, he presented an external stimulus (circle)
- This resulted in the activation of the cell assembly by a stimulus
Describe Hebb’s cell assembly and memory storage model (PART 2)
- revertibrating activity continues activation after the stimulus is removed
- The hebbian modification then strengthens the reciprocal connections between neurons that are active at the same time
- The strengthened connections of the cell assembly contain the engram for the stimulus
Describe Hebb’s cell assembly and memory storage model (PART 3)
- After learning, partial information activation of the assembly leads to activation of the entire representation of the stimulus
- Producing a circle in the end
What occurs in the consolidation stage of memory?
Memory is moved to different parts of the brain so they can be retrieved for long term memory
What does the consolidation stage involve?
Involvement of the temporal medial lobe
How does information flow from the cortex to the hippocampus?
There is a flow of information into the hippocampus via
- Parahippocampal cortex
- Perirhinal cortex
- Entorhinal cortex
These structures flow into the hippocampus
How does information flow through the medial temporal lobe?
Sensory information -> Cortical association areas -> Parahippocampal and rhinal cortical areas -> Hippocampus -> Thalamus, hippocampus via fornix
Describe amnesia
A serious loss of memory or ability to learn
- Causes: Concussion, chronic alcoholism, encephalitis, brain tumours, stroke
What are the 2 types of amnesia?
- Retrograde amnesia: No memory before the time of trauma
- Anterograde amnesia: No new memories after the time of trauma
Who was Henry Molaison (HM)?
- Had a bicycle accident at age
- Developed epilepsy
- In 1953 was referred to William Scoville at Hartford hospital
- Scoville localised the epilepsy to the right and left medial temporal lobes of HM’s brain and removed both LTMs
What was the result of the surgery?
- The surgery was effective in reducing occurrence of seizures
- However it had a devastating side effect
- HM lost the ability to form new long term memories but remembered events before the surgery
- However he was able to learn new motor skills but didn’t remember learning them
What was the impact of HM on memory research?
- Findings from HM shaped subsequent memory research
- Established the memories separateness from other cognitive functions
- No overall intellectual loss or perceptual disorders in HM
How has the role of the hippocampus in spatial memory been established?
Through the Morris water maze
What is the Morris water maze?
- A large pool of water which is opaque
- Has a hidden platform in the water
- When you place a rodent in the water, it’s natural reaction is to get out
- In the morris water maze, it will swim around once it finds the platform then will climb onto it and get out
- After repeated exposure, the rat remembers the platform and gets out asap
What does learning the morris water maze require?
A hippocampus
What happens if you block neuronal activity in the hippocampus?
- By using a molecule such as glutamate, you can block the learning process in the hippocampus
- Therefore the rat will continue to swim around before finding the platform
What are place cells?
- Fire when an animal is in a specific place
- Place fields dynamic
What happens when a place cell is activated?
- Once the rat is placed in a specific environment, there is activity in the place cells
- That is specific for the subject being in a specific place
What happens if the subject moves to a different part of the environment?
- There will be increased activity in the other place cells
- There is just a differential firing pattern between the cells in different locations of the cell
What are the two models of memory consolidation?
- Standard model of memory consolidation
- Multiple trace model of consolidation
- Both dependent upon synaptic plasticity: the biological process by which specific patterns of synaptic activity result in changes in synaptic strength
Describe the standard model of memory consolidation
- Information from neocortex areas associated with sensory systems sent to medial temporal lobe for processing
- Synaptic consolidation, system consolidation
- Post consolidation, hippocampus not necessary
Describe the multiple trace model of consolidation
- Hippocampal involvement is continued
- Multiple memory traces
Describe the model of distributed memory
- Instead of one specific neuron in the brain holding specific information for one memory
- It distributed memories across neuronal populations
How does the model of distributed memory work
- Depending on when the individual is exposed to the memory
- Before learning, each cell has the same base line firing
- After learning, each cell has a corresponding change in activity between neurons
How does the change in activity occur across multiple neurons?
- Changes in the neuronal response can be explained by synaptic plasticity
- The trisynaptic circuit of the hippocampus is often used in studies of this phenomenon
Describe what happens in the trisynaptic circuit
- Information flows from entorhinal cortex via performant path to the dentate gyrus
- Mossy fibres originate from dentate gyrus and synapse upon pyramidal neurons in CA3 Hippocampal regions
- Axons from CA3 synapse upon pyramidal neurons in CA1 Hippocampal region
Describe the long term potentiation
- They essentially stimulated the shape of collaterals and recorded the CA1 neurons via a record EPSP electrode
- They found depending on the frequency of stimulation, you got a change in the excitatory post synaptic potential
Describe the long term potentiation (PART 2)
- If you recorded post synaptically, there wasn’t really a change in respect to what’s happening in this point of view
-If you changed the frequency of stimulation, you find the magnitude of the excitatory synaptic potential, frequency of stimulation greatly increased - This is a potentiation of the excitatory post synaptic potentially recording since it can be maintained over a period of time
In short, What is synaptic plasticity?
If you continue to stimulate neurons at a very high frequency, you will get increased responsivity
What underlies the long term potentiation response?
- Glutamate receptors mediate excitatory synaptic transmission via NMDA and AMPA receptors
- Normally when Glutamate binds to AMPA receptors, you get activation of NMDA receptors
- This then causes calcium to flood in through NMDA receptors
What happens if excess calcium enters into the cell?
- Causes activation of Calcium calmodulin kinases which has a few affects
- Increases phosphorylation of AMPA receptors in the membrane increasing their responsivity which magnifies the size of the post synaptic response
- This also causes a second effect of increased expression of receptors in the post synaptic membrane
What are the structural changes following Long term potentiation?
Spine growth
