Memory and Cognition Flashcards
What does cognition relate to?
The highest order of brain function and the behaviour that deals with thought processing.
What does cognition describe?
The integration of all sensory information to make sense of a situation.
What does making sense of something require?
An ability to remember events and learn from them
What does learning and remembering require?
Motivation
Neuronal plasticity
The ability of central neurons to adapt their neuronal connections in responses to learning experiences
What is most of the cerebrum formed from?
Association areas
What do association areas 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
What are the 3 key components of learning and memory?
- Hippocampus
- Cortex
- Thalamus
What role does the hippocampus play in learning and memory?
Formation of memories
What role does the cortex play in learning and memory?
Storage of memories
What role does the thalamus play in learning and memory?
Searches and accesses memories
What does the limbic system do?
Gives events emotional significance which is essential for memory
What are the 4 distinct areas of the limbic system?
-Cingulate gyrus: plays a role in emotion
-Hippocampus: associated with memory
-Amygdala: associated with emotion
Hypothalamus: associated with AMS responses
What does the limbic system represent?
The old cortex
What does the limbic system have connections with?
The neo cortex in particular the temporal and frontal lobes which allow us to make sense of situations through learning.
What is the most primitive part of the cortex?
Limbic system
Collectively, what are the 4 areas of the limbic system responsible for?
- Instinctive behaviour like thirst, hunger and sex
- Emotion behaviour driven by seeking reward or avoiding punishment
What are reward areas?
Electrical stimulation in these areas of the brain in conscious patients will elicit intense feelings of well being, euphoria and sexual arousal
What are punishment areas?
Electrical stimulation in these areas of the brain in conscious patients will elicit feelings of terror, anger or pain
What do reward and punishment areas form?
Affective components of sensory experiences
Where does motivation to learn come from?
Gaining a reward or avoiding a punishment which gives the task significance
What drives almost every conscious thing we do?
Reward and punishment
What is barely remembered?
Experiences that are neither rewarding or punishing
What does your brain naturally five attention to?
Experiences it deems significant
What assesses the significance of an event?
The frontal cortex and its association with the reward/punishment centres in the limbic system
If something is deemed insignificant what happens to it?
It is forgotten
Where does nearly all sensory information go through?
Hippocampus
What does the hippocampus do to sensory information it receives?
Relays information to other limbic system structures
What do 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 (motor skills) remain intact
Immediate or Sensory memory
- 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 slowest (<4s)
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
Long-term memory
- Can be lifelong
- Where you grew up and your childhood friends
- Associated with structural changes in synaptic connections
Intermediate long-term memory
- Hours to weeks
- What you did last weekend
- Associated with chemical adaption at presynaptic terminal
Which type of memory is associated with electrical phenomenon?
Short-term
What does short-term memory depend on?
Maintained excitation from reverberating circuits
-They constantly need to refreshed
What is each synapse in a reverberating circuit?
-Excitatory hence a brief excitatory stimulus will cause a long lasting neuronal activity as the reverberating circuit neurons continue to excite all neurons in the pathway
What happens if a short-term memory is deemed significant?
Eventually the reverberation will result in consolidation of the memory in long term memory storage
What happens if a short-term memory is deemed insignificant?
The reverberation fades and no consolidation occurs
What may disrupt reverberation?
- Head injury
- Infection
What happens if reverberation is disrupted?
Memory loss normally results especially if it involves the hippocampus and/or the thalamus
Amnesia
Memory loss
Anterograde amnesia
- Inability to form new memories
- Inability to recall events that happen after the injury
- Depending on the severity of the injury it can be short lived or permanent
Retrograde amnesia
- Inability to access (more recent) old memories
- Can’t remember events leading up to the injury although recall of vents that happened a long time ago is usually unaffected, probably because they are better rehearsed and more deeply ingrained
What will destruction of the hippocampus result in?
Inability to form new memories
What does retrograde amnesia often present with?
Anterograde
What occurs if the thalamus is damaged but not the hippocampus?
Retrograde amnesia
What does memory require?
The ability to form, store and search for our memories
How is intermediate long-term memory established?
- Involves chemical changes in presynaptic neurons
- Increasing Ca entry to presynaptic terminals, increases neurotransmitter release
What structural changes at synapses are involved in long-term memory?
- Increase in NT release sites in presynaptic membrane
- Increase in number of NT vesicles stored and released
- Increase in number of presynaptic terminals
- Increase in number of presynaptic terminals
What is long term potentiation?
- Basically a well established, well rehearse pattern of neuronal firing unique to that particular memory
- Increased amplitude in graded membrane potential in the post-synaptic cell
- Strengthens the synapse
- Forms the basis of much learning and memory
What are the 2 main types of long term memory?
- Declarative or explicit memory
- Procedural/reflexive/implicit memory
Declarative or explicit memory
- Abstract memory for events (episodic memory) and for words, rules and language (semantic memory)
- Is based mainly in the hippocampus
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 driving on the left in the UK
- Thinking about these skills (memories) often impairs performance
- Is based mainly in the cerebellum
- Is independent of hippocampus
How is short-term memory converted to long-term memory?
Through consolidation
What does consolidation involve?
Selective strengthening of synaptic connections through repetition (for minutes to hours)
Where do similar process to consolidation for motor learning take place?
Cerebellum
How does memory exist during consolidation?
It exists as electrical activity and is vulnerable to being wiped out
What does consolidation require to be effective?
Attention
Why doe you sometimes see something that isn’t really there like faces on cars or fruit?
- 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 an experience is considered useful what does the frontal cortex do?
It gates the Papez circuit
What are the 4 components of the Papez circuit?
- Hippocampus
- Mammillary bodies
- Anterior thalamus
- Cingulate gyrus
Where does reverberation take place until consolidation is established?
Between the Papez circuit, the frontal cortex, the sensory and association areas
How are different components of the memory laid down?
In different parts of the cortex
- Visual component in the visual cortex
- Auditory component in the auditory cortex
Why are smells especially powerful in evoking long term memories?
- Olfactory stimuli are relayed from the olfactory tract through the amygdala and hippocampus to the prefrontal cortex where they can be acknowledges.
- The route through the limbic system and hippocampus helps in evoking long term memories.
Korsakoff’s syndrome
- Chronic alcoholism
- Vitamin B1 deficiency which leads to damage of limbic system structures
- The ability to consolidate memory is impaired
Alzheimer’s disease
- 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-cholinesterase’s but underlying degeneration continues
- Cause unknown
REM Sleep
- Important for memory
- Subjects deprived of REM sleep show significant impairment of memory consolidation for complex cognitive tasks.
- Dreaming may enable memory consolidation, reinforce weak circuits
- Patients with Korsakoff’s syndrome or Alzheimer’s have greatly reduced REM sleep
What type of memories are we born with?
Inherited memories essential for survival
