Memory & Cognition

Question 1

Define Cognition?

Answer 1

Describes the integration of all sensory information to make sense of a situation

Question 2

What is neuronal plasticity?

Answer 2

The ability of central neurons to adapt their connections in response to learning experiences

Question 3

What parts of the brain are involved in memory?

Answer 3

• Hippocampus forms memories
• Cortex stores them
• Thalamus searches/accesses them

The rest of the limbic system (hypothalamus, hippocampus, cingulate gyrus, amygdala) applies emotional significance to events

Question 4

How does the limbic system decide what events are Significant?

Answer 4

It contains Reward and Punishment Areas.
If an event has any long term reward or punishment it will be picked up by these areas and marked for committing to memory

Question 5

What is the effect of bilateral hippocampal destruction?

Answer 5

The patient loses the ability to make anything more than immediate new memories.

They still have their long term memories from before but wont remember more than the last 30 seconds of anything after the damage

Question 6

What are the different types of memory?

Answer 6

• Immediate/Sensory ~a few seconds
• Short Term (working) Memory ~seconds to hours
• Intermediate Long Term Memory ~hours to weeks
• Long Term Memory ~can be lifelong

Question 7

What type of sensory memory decays fastest?

Answer 7

Visual memory decays in <1s

Auditory memory lasts longest (~4seconds)

Question 8

What method controls short term memory?

Answer 8

Reverberating circuits

Question 9

What process controls immediate long-term memory?

Answer 9

Chemical adaptations occur at the pre-synaptic terminal

- Such as increasing calcium at the terminal leading to increased neurotransmitters released

Question 10

What process controls long term memories?

Answer 10

Structural changes at neuron synaptic connections:

1- Increased neurotransmitters sites in pre-synaptic membrane
2- Increased number of neurotransmitter vesicles stored and released
3- Increased number of presynaptic terminals

Question 11

What is a reverberating circuit?

Answer 11

an electrical phenomenon where a neuronal circuit maintains a memory.
Basically neuron A fires which activates Neuron B.
Simultaneously Neuron A activates a circuit which keeps B activated

Question 12

How is a reverberating circuit converted to long term memory?

Answer 12

If a short term memory is deemed significant by the limbic system then the reverberating circuit undergoes Consolidation

Question 13

What do we call it if the reverberating circuit is disrupted? e.g. by a head injury or an infection

Answer 13

Amnesia

Question 14

Define Anterograde amnesia?

Answer 14

Inability to form new memories. It can be short lived or permanent.

Most associated with hippocampal injury

Question 15

Define Retrograde Amnesia?

Answer 15

Lose memories prior to the injury, often further back ones are ok. Perhaps because they’re better ingrained.

Most associated with thalamus damage

Question 16

What structural changes occur to form long term memories?

Answer 16

• Increase in the no. of neurotransmitter release sites at a presynaptic membrane
• Increase in numbers of NT vesicles released
• Increase in number of presynaptic terminals

Leading to long term potentiation

Basically a long term memory is a unique pattern of neuronal firing that becomes strong & well-established

Question 17

Define long-term potentiation?

Answer 17

Increased amplitude in the EPSP following high-frequency stimulation.

Question 18

What are the different types of long term memory?

Answer 18

• Declarative/Explicit
  Further split into episodic (abstract memory of events) & Semantic (words,rules,language)
  Mainly in the hippocampus
• Procedural
  Includes motor memories such as cycling
  Mainly based in Cerebellum

Question 19

How are memories consolidated?

Answer 19

Selective strengthening of the synaptic connections that are part of a memory considered Significant.
This is done through repetition

Question 20

What does it mean to say new memories are ‘coded’?

Answer 20

It means they are stored with memories the brain considers similar

Question 21

Which part of the cerebrum is a memory stored in?

Answer 21

Different components of a memory are stored in different parts of the cortex
e.g. visual in the visual cortex or auditory in auditory cortex

Because of this a memory can be evoked by more than one association

Question 22

Which is the most effective sense for evoking a memory?

Answer 22

Smell, possibly becuase the olfactory nerve passes through the hippocampus on its way to the prefrontal cortex

Question 23

How does sleep relate to memory?

Answer 23

REM sleep is vital for memory

People deprived of REM sleep show significant impairment of consolidation, possibly dreaming enables consolidation

Question 24

Are we born with any memories?

Answer 24

Evidence suggests yes

E.g. new born monkeys fear snakes despite never seeing one before

Question 25

What is Korsakoff’s syndrome?

Answer 25

Chronic Alcoholism leading to Vitamin B1 deficiency.

One consequence is damage to the limbic system, impairing the ability to consolidate memories

Question 26

How does Alzheimer’s affect memory?

Answer 26

It causes a severe loss of cholinergic neurons in the brain, incl the hippocampus so you lose memories and cant properly form new ones.

Question 27

Summary of how memories are formed:

Answer 27

1) Sensory input reaches sensory & association areas
2) A reverberating circuit is set up by the hippocampus to maintain a short term memory
3) The frontal cortex & limbic system reward/punishment areas assess an events “significance” [The Papez Circuit]
4) If significant the memory is consolidated into long term memory by structural/chemical changes to the neuronal synapses
5) Returns to Papez circuit
6) if still significant its written into LTM again