Memory and Cognition Flashcards
What are the three key components of learning and memory?
- Hippocampus – formation of memories
- Cortex – storage of memories
- Thalamus – searches and accesses memories
What does cognition describe?
All sensory info to make sense of a situation
What does the ability to make sense require?
An ability to remember events and learn from them, and learning and remembering requires motivation
Require all three for normal memory to take place
Describe the processing required for cognition
Most of the cerebrum is Association areas which integrate information from multiple sources, rather than being concerned with one specific function. The brain can therefore be thought of as parallel processing units.
What is the limbic system?
Memories are formed in the limbic system and it gives events emotional significance which is essential for memory
What does the limbic system have connections with and what is the importance of this?
The limbic system represents the ‘old cortex’, but has important connections with the ‘neo’ cortex, in particular the temporal and frontal lobes, which allows us to make sense of situations through learning.
What are the four distinct areas of the limbic system?
- Hypothalamus (associated with ANS responses)
- Hippocampus (associated with memory)
- Cingulate gyrus
- Amydala (associated with emotion)
What are the distinct areas of the limbic system responsible for?
Instinctive behaviour i.e. thirst, sex, hunger, and emotive behaviour which is drive by seeking reward or avoiding punishment
What are the reward areas?
Electrical stimulation of certain areas in the limbic system in conscious patient intense feelings of well-being, euphoria and sexual arousal
What are the punishment areas?
Nearby areas to reward areas elicit terror, anger or pain when electrically stimulated
Why are reward and punishment are central aspects to learning?
They form the ‘affective components’ if sensory experiences. Motivation to learn comes from gaining a reward (passing an exam) or avoiding ‘punishment’ (resitting an exam) – gives a task significance.
Experiences that are neither rewarding or punishing (insignificant experiences) are barely remembered.
What areas of the brain assess the significance of an event?
The frontal cortex and its association with the reward/punishment centres in the limbic system assess the significance of an event. If deemed insignificant, forgotten.
What is the significance of the hippocampus?
Almost all sensory information goes through the hippocampus, which in turn relays information to other limbic system structures
Essential for the learning and formation of memories
What is the effect of bilateral hippocampal damage?
Still 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
What are the four different types of memory?
- Immediate or sensory memory
- Short-term memory
- Intermediate long-term memory
- Long-term memory
Describe immediate or sensory memory
- A few seconds
- Ability to hold experiences in the mind for a few seconds
- Based on different sensory modalities
- Visual memory decays fastest and auditory ones slowest
Describe short-term memory
- Seconds - hours
- Used for short term tasks such as dialling a phone number, mental arithmetic, reading a sentence
- Associated with reverberating circuits.
Describe intermediate long-term memory
- Hours to weeks i.e. what you did last weekend
* Associated with chemical adaptation at the presynaptic terminal
Describe long-term memory
- Can be lifelong i.e. where you grew up and your childhood friends
- Associated with structural changes in synaptic connections
What does short-term memory depend on?
Reverberating circuits i.e. they need to be constantly refreshed
How does a reverberating circuit work?
Each synapse in a reverberating circuit is excitatory and hence a brief excitatory stimulus at A will cause a long lasting neuronal activity in B, as the reverberating circuit neurone continue to excite all neurons in the pathway.
How does the reverberating circuit in short-term memory work to store memories?
Keeps the evanescent short-term memory alive. If deemed significant eventually this reverberation results in consolidation of the memory in long term memory storage.
If it is deemed insignificant then the reverberation fades and no consolidation occurs.
How does amnesia occur?
If reverberation is disrupted i.e. following a head injury or infection, especially if it involves the hippocampus and/or thalamus, memory loss normally occurs
What are the two types of amnesia?
- Anterograde - cannot form new memories
2. Retrograde - cannot access old memories
Describe anterograde amnesia
Inability to recall events that happen after the injury. Depending on the severity of the injury, this can be short liver or permanent.
What is the effect of the destruction of the hippocampus?
Permanent inability to form new memories (anterograde amnesia)
Describe 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.
What does retrograde amnesia often present with?
Anterograde amnesia.
However, if only the thalamus is damaged, and the hippocampus spared, only retrograde amnesia is seen.
- Suggests thalamus is required for ‘searching’ our existing memory bank
What is the role of the hippocampus, cerebrum and thalamus in memory?
Memory requires ability to form (hippocampus)), store (cerebrum) AND search (thalamus) our memories.
What is the physiology behind immediate long-term memory?
Involves chemical changes in presynaptic neurons:
Increasing Ca+ entry to presynaptic terminals, which increases neurotransmitter release.
What is the physiology of long-term memory?
Involves structural changes at synapses:
- Increases in NT release sites on presynaptic membrane
- Increase in number of NT vesicles stores and released
- Increase in number of presynaptic terminals
Also increased amplitude in graded membrane potential (EPSP) in post-synaptic cell occurs, strengthening synapse.
What is long term potentiation?
Occurs in long-term memory - increased amplitude in graded membrane potential (EPSP) in the post-synaptic cell occurs. This strengthens the synapse.
What are the two types of long-term memory?
- Declarative or Explicit Memory
* Procedural/Reflective/Implicit memory
What is declarative or explicit memory?
- Abstract memory for events (episodic memory) and for words, rules and language (semantic memory).
- Relies heavily on the hippocampus
What is Procedural/Reflective/Implicit Memory?
- Acquired slowly through repetition
- Include motor memory for acquired motor skills such as playing sport, and rules based learning i.e. driving rules.
- Based mainly in the cerebellum
- Independent of hippocampus
How is STM converted to LTM?
Through consolidation
What is consolidation?
Selective strengthening of synaptic connections through repetition (for minutes to hours).
What is memory before consolidation?
Memory exists as electrical activity and is vulnerable to being wiped out
What happens to new memories one the frontal cortex and its association areas deem that it’s significant?
New memories are ‘coded’ then stored in the sensory and association areas of the cortex. Coding results in new memories being stored alongside other existing memories the brain deems similar.
What is the papez circuit?
Fundamental component of the limbic system. It is a closed neural circuitry that starts and ends in the hippocampus.
Hippocampus -> mammillary bodies -> anterior thalamus -> cingulate gyrus (repeat)
What does consolidation involve?
Reverberating activity continues between the Papez circuit, the frontal cortex, the sensory and association areas until the consolidation process is complete.
Is the a system to how memories are stored?
Different components of the memory are laid down in different parts of the cortex, i.e. visual component in the visual cortex, auditory in auditory cortex etc.
