Memory and cognition Flashcards
What is cognition
Cognition describes the integration of all sensory information to make sense of a situation.
Thought processing - making sense of something requires an ability to remember events and learn from them
Most of the cerebrum is Association areas. What does this mean?
association areas make sense of things - they integrate information from multiple sources rather than being concerned with one specific function.
Example - when you put your hand in to your pocket to find your keys - you can’t see them but you can feel the shape, temperature, size of them and compare this with other things in the pocket in order to pull out your keys correctly etc and all this info is assessed (association)
this processing is required for cognition and relies on an ability to learn and remember
what are 3 key components/ parts of the brain associated with learning and memory?
Hippocampus
Cortex
Thalamus
we require all 3 for normal memory to take place
What is the purpose of the hippocampus
formation of memories
What is the purpose of the cortex
storage of memories
Almost all sensory information goes through the hippocampus, which in turn relays information to other limbic system structures
What is the purpose of the thalamus
searches and accesses memories
Which system is involved in forming memories?
Limbic system - this gives events emotional significance - essential for memory
What is the limbic system
Most primitive part of the cortex
Consists of four distinct areas – hypothalamus (assoc. with ANS responses), hippocampus (assoc. with memory), cingulate gyrus and the amygdala (assoc. with emotion). These areas are also responsible for instinctive behaviour - thirst, sex, hunger etc
It seems as though the limbic system is responsible for selecting what experiences are stored in memory, with a small number of significant experiences being stored but most experiences being ignored and never remembered.
Electrical stimulation of certain areas in the limbic system in conscious patients causes what?
intense feelings of well being, euphoria and sexual arousal = reward areas
What feelings do punishment areas near limbic system elicit?
fear/terror, anger or pain
What gives a task significance? ie what motivates you to study for an exam?
reward and punishment - drives almost every conscious thing we do
Motivation to learn comes from gaining a reward (passing an exam) or avoiding a “punishment” (resitting an exam).
Bilateral hippocampal damage
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 4 categories can memory be divided into?
Immediate or Sensory memory
short-term memory
Intermediate long-term memory
Long-term memory
Describe Immediate or Sensory memory
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).
Describe Short-term memory
seconds - hours. Often called Working Memory.
Used for short term tasks such as dialling a phone number, mental arithmetic, reading a sentence.
Associated with maintained excitation from reverberating circuits (ie continue to excite all the neurons in the pathway from A-B - keep memory alive) It is an electrical phenomenon. If deemed significant eventually results in consolidation into long term storage
if insignificant - reverberation fades - no consolidation
Describe Intermediate long-term memory
hours to weeks e.g. what you did last weekend.
Associated with chemical adaptation at the presynaptic terminal. Increasing Ca2+ entry to presynaptic terminals increases neurotransmitter release
Describe long-term memory
can be lifelong. e.g. where you grew up and your childhood friends.
Associated with structural changes in synaptic connections
LTM is basically a well established, well rehearsed pattern of neuronal firing unique to that particular memory.
What is anterograde amnesia
cannot form new memories after the event that caused amnesia, leading to a partial or complete inability to recall the recent past, while long-term memories from before the event remain intact.
Depending on the severity of the injury this can be short lived or permanent
what is retrograde amnesia
A loss of memory-access to events that occurred, or information that was learned in the past. It is caused by an injury or the onset of a disease.
Amnesia often presents with anterograde amnesia. However, interestingly, if only the thalamus is damaged, and the hippocampus spared, only retrograde amnesia is seen
Illustrates that memory requires ability to form (hippocampus), store (cerebrum) AND search (thalamus) our memories.
Name 3 structural changes at synpases that can occur with 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
Two main types of long term memory
Declarative or Explicit Memory
Procedural/ Reflexive/Implicit Memory
What is Procedural/ Reflexive/Implicit Memory?
Acquired and used unconsciously, and can affect thoughts and behaviours
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.
Helps people performing certain tasks without conscious awareness of these previous experiences
Is based mainly in the cerebellum.
Is independent of hippocampus
What is Declarative or Explicit Memory?
The conscious, intentional recollection of factual information, previous experiences, and concepts
Episodic - specific personal experiences
Semantic - Factual information
Relies heavily on the hippocampus
How is short-term memory converted to long-term memory?
through consolidation - involves selective strengthening of synaptic connections through repetition (for minutes to hours)
Consolidation 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.
What assesses the significance of events?
The frontal cortex and its association with the reward/punishment centres in the limbic system assess the significance of an event in STM
What is the Papez circuit
neural circuit for the control of emotional expression
hippocampus - mamillary bodies - anterior thalamus - cingulate gyrus - hippocampus
What is Korsakoff’s syndrome
(chronic alcoholism)
There is Vitamin B1 deficiency which leads to damage of limbic system structures.
The ability to consolidate memory is impaired.
Alzheimer’s disease
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.
Have greatly reduced REM sleep
Why is sleep important for memory?
REM sleep is 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.
