Neuro: Learning and Memory Flashcards
What is learning?
Acquisition of new information
What is memory?
Retention of new information
What are the different types of memory?
- Declarative memory - Facts and events (hippocampus)
- Non-declarative memory - motor skills and habits (striatum)
What are the different types of non-declarative memory?
- Procedural memory (motor skils)
- Emotional responses
- Skeletal musculature - e.g. salavating in response to a stimulus becuase you remember that stimulus is associated with food
What are the different types of declarative memory?
- Working memory - Temporary, lasts seconds
- Short term memories - Facts and events initially stored in short term memory and can be converted to long-term memory
- Long-term memory - Can be recalled months/years later
What is memory consolidation?
Process in which short-term memories are converted into long-term memories
How is the prefrontal cortex involved in working memory?
- Memories that form working memory are stored in prefrontal cortex
- Area of prefrontal cortex that deals with working memories works with areas of pre-frontal cortex involved in self-awareness and problem-solving
- This means working memory has an affect on these higher level processes
Explain how a delayed response task experiment in monkeys proved that the prefrontal cortex has a role in working memories
- Monkeys placed in front of table with 2 wells - one with food and one without
- They are able to see in which well food is placed (this is cue period of experiment)
- Then shutter placed between monkey and table and wells covered up (Delay period)
- Screen then comes up and monkey makes choice on which one of the 2 covered wells contains food (choice period)
- Monkeys doing task were subjected to neuronal recording of their prefrontal cortex
- Recording showed during delay period there was a massive increase in prefrontal cortex activity in some areas but no increase in others
- Monkey had to remember where food was during delay period so increase in prefrontal cortex activity shows it’s involved with working memory
Explain how a delayed-saccade task experiment proved that other areas of brain apart from prefrontal cortex are involved in working memory
- Animal placed in front of screen and looks at fixation point
- A target is then flashed on screen at different location to fixation point
- Target then stops flashing on screen but fixation point still tehre so animal still looks at fixation point (delay period)
- Fixation point then removed from screen so animal instinctively looks at where they thought target was on screen
- During this task neuronal recordings taken of lateral intraparietal area of brain
- Recording showed increase in activity during delay period
- Because working memory needed for animal to remember where target was on screen during delay period increase in activity shows lateral intraparietal area involved in working memory
Explain the concept of an engram
- An engram is a memory represented in a group of closely interconnected neurons
- Presentation of an external stimulus causes group of interconnected neurons to fire simultaneously
- When stimulus is removed there’s continued activity of those interconnected neurons which makes their connections even stronger
- This makes the memory of that external stimulus within those interconnected neurons stronger
What parts of the brain are thought to play a role in memory consolidation?
- Hippocampus
- Parahippocampal cortex
- Rhinal cortexes
Explain the flow of information through the brain during memory consolidation
- Sensory information comes into cortical association areas of brain
- Info is then funneled into parahippocampal and rhinal cortical areas
- Info then transfered from those areas into hippocampus which provide long term storage
- From hippocampus info can pass into thalamus/hypothalamus via fornix
- Can also be transferred from hippocampus to cortical asociation areas
What is Amnesia?
Serious loss of memory and/or the ability to learn
What are the different types of amnesia?
- Retrograde amnesia - After trauma you’re able to form new memories but can’t recall old memories
- Anterograde amnesia - After trauma you’re able to recall old memories but are unable to form new ones
Apart from long-term memory what other type of memory is the hippocampus important in?
Spatial memory
Explain how subjecting mice to the Morris water maze provided evidence for the hippocampus being important in spatial memory
- Water maze involves filling small pool up with cloudy water
- Pool has a maze in it that leads to a platform that allows mouse to get out of water but both are hidden due to cloudy water
- When mouse first goes into maze it tries variety of different paths through maze until it eventually makes it to platform
- Mouse taken out of pool and then there’s a delay period between then and when same mice is placed in same water maze again
- If info about maze retained then mouse will swim straight to platform
- If you repeat this experiment with a mouse that has a lesioned hippocampus then second time it goes into maze it has difficulty remebering it
What role do place cells within the hippocampus play in spatial memory?
- Different place cells fire when an animal is in a specific location within an environment
- Place cells are dynamic - when animal is placed in environment it’s never been before as it gets familiar within that environment particular place cells will start to fire
Explain the model of distributed memory
- Model shows that when presented with a particular learned stimulus, e.g. recognising a face of someone you know, there’s firing of different parts of neurons within a group
- This differential firing in different parts of the group all contribute to the memory of that particular stimulus
Recall the pathway of the trisynaptic circuit in the hippocampus
- Info flows from entorhinal cortex to dentate gyrus via perforant path (synapses with dentate gyrus)
- Mossy fibres that originate from dentate gyrus then synapse with pyramidal neurons in CA3 region of hippocampus
- Axons of pyradmidal neurons in CA3 region then synapse with pyradmidal cells in CA1 region of hippocampus
Explain the experiment that showed that long-term potentiation occurs in CA1 neurons within trisynaptic circuit of hippocampus
- Repeated stimulation of one of the inputs to the CA1 neuron (input 1) lead to increase in excitatory post-synaptic potential in CA1 neuron
- This means repeated stimulation has strengthend the connection between the input neuron of CA1 and the CA1 neuron itself
- If you stimulate another input to CA1 neuron (input 2) because there hasn’t been repeated stimulation the connection hasn’t been strengthed
- This means you don’t get an increase in excitatory post-syanptic potential of CA1 neuron
Explain the mechanism of long-term potentiation within the CA1 neurons
- Repeated stimulation of input neuron of CA1 leads to increased release of glutamate from pre-synaptic terminal via exocytosis
- Increased glutamate release will cause increased activation of AMPA receptors via increased binding to them
- This leads to increased influx of Na+ leading to depolarisation
- Depolarisation removes Mg2+ block on NMDA receptors leading to influx of Ca2+ and Na+
- Ca2+ forms complex with calmodulin which activates kinases
- Kinases phosphorylate AMPA receptors making them more sensitive
- Kinases also cause recruitment of more AMPA receptors to post-synaptic membrane
- These changes lead to increased excitatory post-synaptic potential
