Memory & Cognition Flashcards
Define Cognition?
Describes the integration of all sensory information to make sense of a situation
What is neuronal plasticity?
The ability of central neurons to adapt their connections in response to learning experiences
What parts of the brain are involved in memory?
- Hippocampus forms memories
- Cortex stores them
- Thalamus searches/accesses them
The rest of the limbic system (hypothalamus, hippocampus, cingulate gyrus, amygdala) applies emotional significance to events
How does the limbic system decide what events are Significant?
It contains Reward and Punishment Areas.
If an event has any long term reward or punishment it will be picked up by these areas and marked for committing to memory
What is the effect of bilateral hippocampal destruction?
The patient loses the ability to make anything more than immediate new memories.
They still have their long term memories from before but wont remember more than the last 30 seconds of anything after the damage
What are the different types of memory?
- Immediate/Sensory ~a few seconds
- Short Term (working) Memory ~seconds to hours
- Immediate Long Term Memory ~hours to weeks
- Long Term Memory ~can be lifelong
What type of sensory memory decays fastest?
Visual memory decays in <1s
Auditory memory lasts longest (~4seconds)
What method controls short term memory?
Reverberating circuits
What process controls immediate long-term memory?
Chemical adaptations occur at the pre-synaptic terminal
- Such as increasing calcium at the terminal leading to increased neurotransmitters released
What process controls long term memories?
Structural changes at neuron synaptic connections
What is a reverberating circuit?
an electrical phenomenon where a neuronal circuit maintains a memory.
Basically neuron A fires which activates Neuron B.
Simultaneously Neuron A activates a circuit which keeps B activated
How is a reverberating circuit converted to long term memory?
If a short term memory is deemed significant by the limbic system then the reverberating circuit undergoes Consolidation
What do we call it if the reverberating circuit is disrupted? e.g. by a head injury or an infection
Amnesia
Define Anterograde amnesia?
Inability to form new memories. It can be short lived or permanent.
Most associated with hippocampal injury
Define Retrograde Amnesia?
Lose memories prior to the injury, often further back ones are ok. Perhaps because they’re better ingrained.
Most associated with thalamus damage
What structural changes occur to form long term memories?
- Increase in the no. of neurotransmitter release sites at a presynaptic membrane
- Increase in numbers of NT vesicles released
- Increase in number of presynaptic terminals
Also long term potentiation
Basically a long term memory is a unique pattern of neuronal firing that becomes strong & well-established
Define long-term potentiation?
Increased amplitude in the EPSP following high-frequency stimulation.
What are the different types of long term memory?
- Declarative/Explicit
Further split into episodic (abstract memory of events) & Semantic (words,rules,language)
Mainly in the hippocampus - Procedural
Includes motor memories such as cycling
Mainly based in Cerebellum
How are memories consolidated?
Selective strengthening of the synaptic connections that are part of a memory considered Significant.
This is done through repetition
What does it mean to say new memories are ‘coded’?
It means they are stored with memories the brain considers similar
Which part of the cerebrum is a memory stored in?
Different components of a memory are stored in different parts of the cortex
e.g. visual in the visual cortex or auditory in auditory cortex
Because of this a memory can be evoked by more than one association
Which is the most effective sense for evoking a memory?
Smell, possibly becuase the olfactory nerve passes through the hippocampus on its way to the prefrontal cortex
How does sleep relate to memory?
REM sleep is vital for memory
People deprived of REM sleep show significant impairment of consolidation, possibly dreaming enables consolidation
Are we born with any memories?
Evidence suggests yes
E.g. new born monkeys fear snakes despite never seeing one before
What is Korsakoff’s syndrome?
Chronic Alcoholism leading to Vitamin B1 deficiency.
One consequence is damage to the limbic system, impairing the ability to consolidate memories
How does Alzheimer’s affect memory?
It causes a severe loss of cholinergic neurons in the brain, incl the hippocampus so you lose memories and cant properly form new ones.
Summary of how memories are formed:
1) Sensory input reaches sensory & association areas
2) A reverberating circuit is set up by the hippocampus to maintain a short term memory
3) The frontal cortex & limbic system reward/punishment areas assess an events “significance” [The Papez Circuit]
4) If significant the memory is consolidated into long term memory by structural/chemical changes to the neuronal synapses
5) Returns to Papez circuit
6) if still significant its written into LTM again
