Memory and Cognition Flashcards
What is cognition?
HIghest order of brain function, involves thought processing.
It describes the integration of all sensory information to make sense of a situation
How does changes in neoronal plasticity reflect learning?
Central neurones adapt their neuronal connections in response to learning experiences
Most of the cerebrum is Association areas, what do these do?
Integrate information from multiple sources, rather than being concerned with one specific function
Give examples of association areas
Motor association area
Sensory association area
Prefrontal association area
Visual association area
Auditory association area
What are the three components of learning and memory and what are their functions?
Hippocampus – formation of memories
Cortex – storage of memories
Thalamus – searches and accesses memories
Which brain system is involved with memory formation and emotional significance?
Responsible for istinctive behaviour - thirst, sex, hunger etc. and emotive behaviour are driven by seeking reward or avoiding punishment.
Limbic system
What portions of the brain are included in the limbic system?
Limbic – cingulate gyrus, amygdala – particulary involved in emotion, hippocampus, hypothalamus
How does emotion evoke an ANS response?
Hypothalamus links emotion to autonomic response
Where does the limbic system make connections to in the brain?
The limbic system is part of the ‘old’ cortex and is described as the most primitive part of the cortex. It has important connections with the “neo” cortex, in particular the temporal and frontal lobes, which allow us to make sense of situations through learning.
Where does the motivation to learn come from?
Comes from gaining a reward or avoiding a punishment - gives task significance
Which memories are often forgotten?
Experiences that are neither rewarding or punishing (insignificant experiences)
How is the significance of an event determined?
The forntal cortex and its association with the reward/punishment centres located in the limbic system are responsible for assessing the significance of an event
Which part of the limbic system does almost all sensory information travel through?
The hippocampus, which in turn relays information to other limbic system structures
What is the effect of bilateral hippocampal damage?
People with bilateral hippocampal damage have immediate (sensory) memory (seconds in length) and intact long-term memory (from time before damage), but are unable to form new long-term memories.
Their reflexive memory (motor skills) remains intact.
What are the categories of memory?
Immediate or sensory memory
Short - term memory
Immediate long-term memory
Long-term memory
What is immediate or sensory memory?
A few seconds
The ability to hold experiences in the mind for a few seconds
Different sensory modalitites have different rates of decay
Visual memories decay fastest (<1s), auditory ones slowest (<4s).
What is short term memory?
Seconds - hours
Used for short term tasks such as dialling a phone number, mental arithmetic and reading a senstence
Associated with reverberating circuits
What is intermediate long-term memory?
Hours to weeks - what you did last weekend -
Association with chemical adaptation at the presynaptic terminal
What is long term memory?
Can be lifelong. e.g. where you grew up and your childhood friends. Associated with structural changes in synaptic connections.
What is short term memory dependant on?
Maintained excitation from reverberating circuits - they need to be constantly refreshed
Describe how a brief stimulus at A will cause a long lasting neuronal activity in B?
Each synapse in a reverbating circuit is excitatory. Therefore in a reverberating circuit the neurones continue to excite all neurones in the pathway.
What is the effect of the reverberaing circuit?
Keeps evanescent short term memory alive
What happens if the memory is deemed significant?
Reverberation results in consolidation of the memory in long term memory storage
Consolidation involves selective strengthening of synaptic connections through repetition (for minutes to hours).
What happens if a memory is deemed insignificant?
Reverberation fades and no consolidation occurs
What is the result of disruption of reverberation?
Disruption can be the result of head injury, infection - especially if it involves the hippocampus and/or thalamus.
Memory loss normally results - amnesia
What is enterograde and retrograde amnesia?
- Anterograde – cannot form new memories - may be short lived or permanent depending on the severity of the injury
- Retrograde – cannot access (more recent) old memories
Which memories are often spared in the case of retrograde amnesia?
Retrograde amnesia, can’t remember events leading up to the injury, although recall of events that happened a long time ago is usually unaffected, probably because they are better rehearsed and more deeply ingrained
How does retrograde amnesia often present?
Anterograde amnesia
If only the thalamus is damaged and the hippocampus is spared then only retrograde amnesia is seen
Suggests that the thalamus is reponsible for searching our existing memory banks
What are the chemical changes in presynaptic terminals that occur in the intermediate long-term memory?
Increasing Ca++ entry to presynaptic terminals, increases neurotransmitter release.
What are the structural changes at synapses that occur in long term memory?
- Increase in NT release sites on presynaptic membrane.
- Increase in number of NT vesicles stored and released.
- Increase in number of presynaptic terminals
What is meant by long term potentiation?
Increase in graded membrane potential (EPSP) in post - synaptic cell
Strengthens the synapse
LTM is basically a well established, well rehearsed pattern of neuronal firing unique to that particular memory.
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What is declarative or explicit memory?
Abstract memory for events (episodic memory) and for words, rules and language (semantic memory).
Is based mainly in the hippocampus.
What is Procedural/ Reflexive/Implicit Memory?
Acquired slowly through repetition. Includes motor memory for acquired motor skills such as playing tennis, and rules based learning such as, in the UK, always driving on the left.
Thinking about these skills (“memories”) often impairs performance!
Is based mainly in the cerebellum.
Is independent of hippocampus (remember Clive Wearing).
Where else does consolidation occur?
Similar process occurs in the cerebellum during motor learning.
Why is learning harder when you are tired?
Consolidation requires attention
Where are coded memories stored?
Sensory association areas of the cortex alongside existing memories the brain deems similar
When is entry to the papez circuit made possible?
When the frontal cortex and its association with the reward/punishment centres in the limbic system consider an experience significant or useful
Frontal cortex gates the papez circuit
What does the papez circuit consist of?
Which parts of the brain does reverberation occur?
Reverberation continues between the Papez circuit, the frontal cortex, the sensory and association areas until the consolidation process is complete.
Where are visual components of memory and auditory components of memory laid down in the cortex?
Visual cortex and the auditory cortex respectively
Why does chronic alcoholism lead to impairment in the consolidation of memory?
There is Vitamin B1 deficiency which leads to damage of limbic system structures. The ability to consolidate memory is impaired.
What causes the impairment of memory in alzheimers?
There is a severe loss of cholinergic neurons throughout the brain, including the hippocampus. Gross impairment of memory.
Some improvement in Alzheimer’s may be seen with anti-cholinesterases, but underlying degeneration continues. Cause unknown.
What is REM sleep like in korsakoff’s syndrome (alcoholism) or alzheimers?
Patients with Korsakoff’s syndrome or Alzheimer’s have greatly reduced REM sleep.
How does REM sleep contribute to memory?
Subjects deprived of REM sleep show significant impairment of memory consolidation for complex cognitive tasks. Dreaming may enable memory consolidation, reinforce weak circuits.
