Learning and Memory Flashcards
Learning
Acquisition of new information
Memory
Retention of learned information
Declarative memory (explicit)
Facts and events
- can be verbalised
Hippocampus is important
Nondeclarative memory (implicit)
Procedural memory - motor skills, habits
Utilised the straitum (
Areas of the brain important in declarative memory
Medial temporal lobe
Dinecephalon
Hippocampus
Areas of the brain important in nondeclarative memory
Procedural memory: skills and habits in the Striatum
Cerebellum
Amygdala
Forms of condition that fall under nondeclarative memory
Classical conditioning
- Skeletal musculature (cerebellum)
- Emotional responses (amygdala)
What are the types of declarative memory?
- Working memory
- Short-term memories
- Long-term memories
Working memory
Temporary storage, lasting seconds
Short-term memories
Vulnerable to disruption
Facts and events stored in short-term memory
Subsets are converted to long-term memories
Long-term memories
Recalled months or years later
Describe the process of converting short- to long-term memories
- Sensory information passes into the working memory and the short-term memory
- Consolidation over time means the memories can pass into the long-term memory
What is parallel memory working?
Things can go to short-term and immediate working memory
Information can flow between working memory and short-term memory easily
Where is the long-term memory located?
There is no single site for long-term memory. It can diffuse throughout the cerebral cortex.
Function of the pre-frontal cortex
Self- awareness, capacity for planning and problem solving.
Why do primates have a large frontal lobe?
Capability for the high-level decision making and the use of the working memory. Also able to make more coherent decisions
Delayed response task
A brief visual or auditory stimulus that is then withdrawn, and after a delay of several seconds attempts to identify the location where the stimulus appeared, and is rewarded if correct.
Cue period in testing for working memory
Tests show that there was a reasonable level of activity in the pre-frontal cortical neurons when remember information that has been seen to record later.
Delay period in the working memory task
In some regions of the pre-frontal cortex, increase in spike activity but decrease in others. Assummed that this period is active for remembering when the stimuli has been hidden.
Conclusions of the working memory task
Some evidence suggesting that there is a population of neurons that increase firing and associated with retaining information in the working memory
Other brain regions involved in working memory
Lateral intraparietal cortex neurons located towards the posterior part of the brain.
Describe the delayed saccadic task used to detect the use of lateral intraparietal cortex neurons in memory
- An animal is trained to sit infront of a VDU screen and to fixate on a central point (fixation point).
- At that time, a target will flash off to the periphery.
- There is a delayed period of which the fixation point remains and the animal is trained to remain fixated on the point. It is also trained that when the fixation point is removed, they will look at where the target was. This is a saccade.
- During the fixation delay period, this is assuming the working memory is at play for the animal to retain where the target flashed.
Recording neuronal activity in the lateral intraparietal cortex neurons, during the delay period, there is an increase in neuronal firing compared to the quiescent period before the start of the experiment.
Saccadic eye movements
Rather than, slow tracking movements, quick movement off to the periphery.
What is another concept based on neurons in terms of where memories are stored?
The engram
Who postulated the Engram Theory?
Donald Hebb in the 40s, which has now been proven to be correct.
What is Hebb’s Cell Assembly and Memory Storage Model?
- All neurons in the brain are interconnected not just with single neurons but other neurons in neural networks.
- With an external stimulus, for example the presentation of a circle in the visual field, this activated the cell assembly (a group of interconnected neurons firing together).
- With collective firing, there was reverberating electrical circuits within the neurons continuing to show increased activity even after removal of the stimulus.
- This leads to Hebbian modification. A modification of these circuits will cause strengthen of connection between the neurons. This will cause a strengthened group of neuronal connections responding to a particular stimulus.
- After a learning process, even if there is only a partial presentation of the original stimulus, it is possible that the series of circuits will be activated. Such that there is sufficient activation, that the brain will interpret what it is seeing as the full original stimulus.
Consolidation of Memory
The movement of memories from the working memory or short-term memory into the long-term memory.
What is the function of the medial temporal lobes
- Involved in consilidation.
- Language and speech. - - Home of the hippocampus
Position of the Hippocampus
Shown a coronal section it is located near:
- The entorhinal cortex
- The perirhinal cortex
- The parahippocampal cortex
Information flow through the medial temporal lobe
- Sensory information enters the cortical association areas throughout the brain.
- Then funnelled through the parahippocampal and rhinal cortical areas
- Allow the funnelling of neurons and information transmitted by the neurons into the hippocampus.
- Memories may not stay here, they pass through the pathway known as the fornix to the thalamus and hypothalamus.
- The thalamus is the sorting region of the brain where information (memories) are distributed across the cortex or other brain regions.
- Can also go from the hippocampus through pathways directly to other cortical areas.
Function of the Parahippocampal and Rhinal Cortical areas
Closely related to the hippocampus allowing the funneling of neurons and information transmitted by the neurons into the hippocampus.
Amnesia
The serious loss of memory and/or ability of life.
What causes amnesia?
Caused by concussion, chronic alcoholism, encephalitis, brain tumour, stroke
Encephalitis
Inflammation in the brain causing damage to cortical and hippocampal tissue
Retrograde Amnesia
Following trauma, forming new memories, but cannot recall old memories
Anterograde Amnesia
Following trauma, unable or severely limited in capacity to form new memories however, past memory is unaffected
Henry Gustav Molaison
- Had a bicycle accident and started to develop epilepsy and sizures
- Removed parts of his brain including the medial temporal lobes.
- Effective in reducing seizures but he was unable to form new long-term memories but remembered events before his surgery.
- Patient sufference from both types of amnesia
- Findings that memory is a distinct cerebral function, and involves the medial temporal lobe being important in memory.
Clive Wearing
- Piano player
- Suffered from viral encephalitis
- Damage to parts of the brain including the hippocampus
- Little past memory and cannot form new memories so dependent upon his working memory
What is spatial memory?
Ability to navigate around somewhere e.g. A to B
What is the learning morris water maze?
- Large volume of water containing a platform that is not visible from the surface of the water
- Experiment using a rat, its response will be to get out of water and onto dry ground
- Find the dry land, it will swim recording the activity until it finds the platform.
- Delay
- Taking the same animal and putting them into the water maze. If they retain the navigation information, they will make a beeline straight to the platform. It can also use navigational cues
This shows that there is an intact spatial memory.
Lesions in the hippocampus
Using lesions to disrupt regions of the hippocampus, the spatial memory will be disrupted and will take a longer time to get to the platform. Indicating the importance of the hippocampus in spatial memory.
Place cells
Will fire when the animal is in a specific place.
- In spatial memory, these place cells fire when an animal is in a particular location
Adaptation in place fields
If out of the place field, an animal will adapt to the new environment and will start firing from the place cells when there is familiarity with certain areas
What are the two models of memory consolidation?
- Standard model of memory consolidation
- Multiple trace model of memory consolidation
Standard model of memory consolidation
- Information from the neocortex areas assocaited with sensory systems sent to medial temporal lobe for process.
- There is synaptic consolidation and the systems are consolidated.
- Post consolidation, the hippocampus is not necessary as the memories have been distributed throughout the brain.
Multiple trace model of consolidation
- Hippocampal involvement is continued - once the memory is consolidated, they can still be modified or tweaked by involvement of the hippocampus.
- Multiple memory traces
What do both models of memory consolidation depend on?
They are dependent upon synaptic plasticity
What is synaptic plasticity?
The biological process by which specific patterns of synaptic activity result in changes in synaptic strength.
Lazy: what is synaptic plasticity?
The more a neuron fires, the stronger the connection gets
What is the model of distributed memory? How is this detected?
The idea that the memory of a stimulus is spread across multiple neurons. This is detected by looking at the differential firing between stimuli.
How can changes in neuronal responses be explained?
Explained by synaptic plasticity
What is the model used to explain synaptic plasticity?
The Trisynaptic circuit of the hippocampus
Trisynaptic circuit of the hippocampus
- Information flows from entorhinal cortex, via performant path to the dentate gyrus.
- Mossy fibres originate from dentate gyrus (synapse 1) and synapse upon pyramidal neurons in CA3 hippocampal region (synapse 2)
- Axons from CA3 (Schaffer collaterals) synapse upon pyramidal neurons in CA1 hippocampal region (synapse 3)
Bliss and Lomo model of Long-term potentiation in CA1 region of the hippocampus
- Increasing neuronal activity in one input will strengthen the neuronal connections.
- It will increase the excitatory post-synaptic potential for any given stimulus in the post-synaptic target neuron.
- The connection is specific however to that input, as it will not affect the other inputs if there is no increase in neuronal activity there.
Receptors involved in LTP in CA1
NMDA receptors
AMPA receptors
Neurotransmitter involved in LTP in CA1
Glutamate
Mechanism for LTP in CA1
- Increase in tetanic stimulation will increase the release of glutamate
- Activate the AMPA receptors removing the magnesium block and causing depolarisation and the activation of NMDA receptors
- Allows the influx of calcium
- Increase in calcium in the post-synaptic neuron will increase the calcium-calmodulin mechanism
- Kinases are activated that bring effects related to LTP
How does LTP occur in the CA1?
- Increase responsitivity of AMPA receptors
- Movement of additional AMPA receptors and increased expression at the post-synaptic cell surface
- Elevated excitatory post-synaptic potential
Structural changes following LTP
Dendritic spine growth after stimulation to the dendrite, there is an increase in the spine size
Long-term potentiation
a persistent strengthening of synapses based on recent patterns of activity.
