Memory and Cognition Flashcards
What is cognition?
Cognition relates to the highest order of brain function and relates to behaviour that deals with thought processing. It is extremely complex but in very brief summary Cognition describes the integration of all sensory information to make sense of a situation.
What do you need in order to make sense of a situation?
Making sense requires an ability to remember events and learn from them
Learning and remembering requires motivation
How can memory and cognition be explained in the brain?
All of this can be explained by changes in “neuronal plasticity” or the ability of central neurons to adapt their neuronal connections in responses to “learning” experiences
Most of the cerebrum is a made up oif what type of areas?
association areas
What do the association areas of the cerebrum do?
integrate information from multiple sources, rather than being concerned with one specific function
The brain can therefore be thought of as multiple parallel processing units
Such processing is required for cognition and relies on an ability to learn and remember
What are the 3 key components of learning and memory that are required (all 3) for normal memory to take place?
Hippocampus
Cortex
Thalamus
What is the function of the hippocampus?
formation of memories
What is the function of the cortex?
storage of memories
What is the function of the thalamus?
searches and accesses memories
Where are memories formed?
in the limbic system
What forms the limbic system?
What is the limbic system in connection with and what doe this allow to happen?
The limbic system represents the “old” cortex, but has important connections with the “neo” cortex, in particular the temporal and frontal lobes, which allow us to make sense of situations through learning
The limbic system gives events emotional significance and this is essential for what?
essential for memory
What are the 4 areas of the limbic system?
hypothalamus (assoc. with ANS responses), hippocampus (assoc. with memory), cingulate gyrus and the amygdala (assoc. with emotion)
WHat is the limbic system responsible for?
Collectively these areas are responsible for instinctive behaviour, e.g. thirst, sex, hunger etc. and emotive behaviour are driven by seeking reward or avoiding punishment.
What does electrical stimulation of certain areas in the limbic system in conscious patients lead to?
intense feelings of well being, euphoria and sexual arousal = reward areas
other nearby areas elicit fear/terror, anger or pain = punishment areas
Why is reward and punishment important?
Reward and punishment are central aspects to learning. They form the “affective components” of sensory experiences. Motivation to learn comes from gaining a reward (passing an exam) or avoiding a “punishment” (resitting an exam). Gives a task significance.
Reward and punishment drive almost every (conscious) thing we do.
What happens to Experiences that are neither rewarding or punishing?
(insignificant experiences) are barely remembered
Your brain naturally gives attention to experiences it deems significant, what is responsible for this?
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 responsible for selecting experiences that should be stored in memory?
limbic system
with a small number of significant experiences being stored but most experiences (neither rewarding or punishing) being ignored and never remembered
What is the function of the hippocampcus?
Almost all sensory information goes through the hippocampus, which in turn relays information to other limbic system structures
Hippocampus is essential for the formation of memories
central to learning and the formation of memories
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
The effect is totally devastating
What is memory divided into?
Immediate or Sensory memory
Short-term memory
Intermediate long-term memory
Long-term memory
What is Immediate or Sensory memory?
a few seconds
Describes the ability to hold experiences in the mind for a few seconds
Based on different sensory modalities. Visual memories decay fastest (<1s), auditory ones slowest (<4s).
What is short-term memory?
seconds - hours
Often called Working Memory
Brain’s “post-it note”
Used for short term tasks such as dialling a phone number, mental arithmetic, reading a sentence
Associated with reverberating circuits
What is intermediate long-term memory?
hours to weeks e.g. what you did last weekend
Associated 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
How does short-term memory worl by reverberating circuits?
Short-term memory is an electrical phenomenon. It depends on maintained excitation from reverberating circuits i.e. they need to be constantly refreshed
Each synapse in a reverberating circuit is excitatory and hence a brief excitatory stimulus at A can cause a long lasting neuronal activity in B as the reverberating circuit neurons continue to excite all neurons in the pathway
What keeps the brief short term memory alive?
reverberating circuit
What happens to the reverberation if something is deemed significant or insignificant?
If it is deemed significant eventually this reverberation results in consolidation of the memory into long-term memory storage
If it is deemed insignificant then the reverberation fades and no consolidation occurs
What happens if reverberation is disrupted e.g. following a head injury or infection, especially if it involves the hippocampus and/or thalamus?
memory loss normally results – amnesia
What are the 2 types of amnesia?
Anterograde
Retrograde
What is anterograde amnesia?
Anterograde – cannot form new memories
inability to recall events that happen after the injury. Depending on the severity of the injury this can be short lived or permanent. Destruction of the hippocampus (as with Clive Wearing) results in permanent inability to form new memories
What is retrograde amnesia?
Retrograde – cannot access (more recent) old memories
can’t remember events leading up to the injury, but recall of events that happened a long time ago is usually unaffected, probably because they are better rehearsed and more deeply imbedded
What does Retrograde amnesia often present with?
often presents with anterograde amnesia
However, interestingly, 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 does memory require?
memory requires ability to form (hippocampus), store (cerebrum) AND search (thalamus) our memories
What does intermediate long-term memory involve?
Involves chemical changes in presynaptic neurons:
Increasing Ca++ entry to presynaptic terminals, increases neurotransmitter release
Long-term memory required what structural changes at synapses?
- Increase in NT release sites on presynaptic membrane
- Increase in number of NT vesicles stored and released
- Increase in number of presynaptic terminals
At the same time increased amplitude in graded membrane potential (EPSP) in the post-synaptic cell is often observed. This “strengthens the synapse”, is called Long Term Potentiation and forms the basis of much learning and memory
What are the 2 types of long term memory?
Declarative or Explicit Memory
Procedural/Reflexive/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
a memory that can be intentionally and consciously recalled
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)
memory that cannot be recalled consciously
Short-term memory is converted to long-term memory through __________
consolidation
What is consolidation?
Consolidation involves selective strengthening of synaptic connections through repetition (for minutes to hours). Reason why you need to keep challenging your brain to perform repeated recall when studying!
Similar process occurs in the cerebellum during motor learning
Consolidation involves all the processes just discussed so takes time (hours/days). During the consolidation process, memory simply exists as electrical activity and is vulnerable to being wiped out
Consolidation requires attention, hence learning is harder when you are tired
Memory recall depends on _________________
the significance of an event
Your brain naturally gives attention to experiences it deems significant
What decides if an experience is significant?
The frontal cortex and its association with the reward/punishment centres in the limbic system assess the significance of an event in STM
If not deemed significant, forgotten
How are new memories stored?
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
If experience is considered useful, what happens?
the frontal cortex “gates” the so-called Papez circuit
Reverberating activity then continues between the Papez circuit, the frontal cortex, the sensory and association areas until the consolidation process is complete.
Different components of the memory are laid down in different parts of the cortex, eg visual component in the visual cortex, auditory in auditory cortex, etc.
As such, recall can be evoked by multiple associations. Many memories have strong emotional components to them, ie pleasant or unpleasant.
Where is each component of memory stored in the cortex?
Each component of the memory is stored in different relevant parts of the cortex
How do the limbic and olfactory systems work together?
Olfactory stimuli are relayed via the olfactory tract to the primary olfactory cortex where substantial connections to the amygdala and hippocampus are found. This association with the limbic system, and hippocampus in particular, explains why smells are especially powerful in evoking long term memories
