Memory and Cognition

Question 1

What is cognition?

Answer 1

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.

Question 2

What do you need in order to make sense of a situation?

Answer 2

Making sense requires an ability to remember events and learn from them

Learning and remembering requires motivation

Question 3

How can memory and cognition be explained in the brain?

Answer 3

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

Question 4

Most of the cerebrum is a made up oif what type of areas?

Answer 4

association areas

Question 5

What do the association areas of the cerebrum do?

Answer 5

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

Question 6

What are the 3 key components of learning and memory that are required (all 3) for normal memory to take place?

Answer 6

Hippocampus

Cortex

Thalamus

Question 7

What is the function of the hippocampus?

Answer 7

formation of memories

Question 8

What is the function of the cortex?

Answer 8

storage of memories

Question 9

What is the function of the thalamus?

Answer 9

searches and accesses memories

Question 10

Where are memories formed?

Answer 10

in the limbic system

Question 11

What forms the limbic system?

Answer 11

Question 12

What is the limbic system in connection with and what doe this allow to happen?

Answer 12

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

Question 13

The limbic system gives events emotional significance and this is essential for what?

Answer 13

essential for memory

Question 14

What are the 4 areas of the limbic system?

Answer 14

hypothalamus (assoc. with ANS responses), hippocampus (assoc. with memory), cingulate gyrus and the amygdala (assoc. with emotion)

Question 15

WHat is the limbic system responsible for?

Answer 15

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.

Question 16

What does electrical stimulation of certain areas in the limbic system in conscious patients lead to?

Answer 16

intense feelings of well being, euphoria and sexual arousal = reward areas

other nearby areas elicit fear/terror, anger or pain = punishment areas

Question 17

Why is reward and punishment important?

Answer 17

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.

Question 18

What happens to Experiences that are neither rewarding or punishing?

Answer 18

(insignificant experiences) are barely remembered

Question 19

Your brain naturally gives attention to experiences it deems significant, what is responsible for this?

Answer 19

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

Question 20

What is responsible for selecting experiences that should be stored in memory?

Answer 20

limbic system

with a small number of significant experiences being stored but most experiences (neither rewarding or punishing) being ignored and never remembered

Question 21

What is the function of the hippocampcus?

Answer 21

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

Question 22

People with bilateral hippocampal damage have?

Answer 22

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

Question 23

What is memory divided into?

Answer 23

Immediate or Sensory memory

Short-term memory

Intermediate long-term memory

Long-term memory

Question 24

What is Immediate or Sensory memory?

Answer 24

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).

Question 25

What is short-term memory?

Answer 25

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

Question 26

What is intermediate long-term memory?

Answer 26

hours to weeks e.g. what you did last weekend

Associated with chemical adaptation at the presynaptic terminal

Question 27

What is long-term memory?

Answer 27

can be lifelong e.g. where you grew up and your childhood friends

Associated with structural changes in synaptic connections

Question 28

How does short-term memory worl by reverberating circuits?

Answer 28

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

Question 29

What keeps the brief short term memory alive?

Answer 29

reverberating circuit

Question 30

What happens to the reverberation if something is deemed significant or insignificant?

Answer 30

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

Question 31

What happens if reverberation is disrupted e.g. following a head injury or infection, especially if it involves the hippocampus and/or thalamus?

Answer 31

memory loss normally results – amnesia

Question 32

What are the 2 types of amnesia?

Answer 32

Anterograde

Retrograde

Question 33

What is anterograde amnesia?

Answer 33

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

Question 34

What is retrograde amnesia?

Answer 34

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

Question 35

What does Retrograde amnesia often present with?

Answer 35

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

Question 36

What does memory require?

Answer 36

memory requires ability to form (hippocampus), store (cerebrum) AND search (thalamus) our memories

Question 37

What does intermediate long-term memory involve?

Answer 37

Involves chemical changes in presynaptic neurons:

Increasing Ca++ entry to presynaptic terminals, increases neurotransmitter release

Question 38

Long-term memory required what structural changes at synapses?

Answer 38

1. Increase in NT release sites on presynaptic membrane
2. Increase in number of NT vesicles stored and released
3. 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

Question 39

What are the 2 types of long term memory?

Answer 39

Declarative or Explicit Memory

Procedural/Reflexive/Implicit Memory

Question 40

What is Declarative or Explicit Memory?

Answer 40

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

Question 41

What is Procedural/Reflexive/Implicit Memory?

Answer 41

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

Question 42

Short-term memory is converted to long-term memory through __________

Answer 42

consolidation

Question 43

What is consolidation?

Answer 43

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

Question 44

Memory recall depends on _________________

Answer 44

the significance of an event

Question 45

Your brain naturally gives attention to experiences it deems significant

What decides if an experience is significant?

Answer 45

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

Question 46

How are new memories stored?

Answer 46

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

Question 47

If experience is considered useful, what happens?

Answer 47

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.

Question 48

Where is each component of memory stored in the cortex?

Answer 48

Each component of the memory is stored in different relevant parts of the cortex

Question 49

How do the limbic and olfactory systems work together?

Answer 49

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