Behavioural and Cognitive Neuroscience - Memory & Cognition

Question 1

what does cognition describe?

Answer 1

describes the integration of all sensory information to make sense of a situation.

Question 2

what does cognition relate to?

Answer 2

highest order of brain function and relates to behaviour that deals with thought processing

Question 3

what is neuronal plasticity?

Answer 3

the ability of central neurons to adapt their neuronal connections in responses to “learning” experiences.

Question 4

what is most of the cerebrum?

Answer 4

Most of the cerebrum is Association areas which 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 5

what are the 3 key components of learning and memory?

Answer 5

hippocampus
cortex
thalamus

Question 6

what is the role of hippocampus?

Answer 6

formation of memories

Question 7

what is the role of the cortex?

Answer 7

storage of memories

Question 8

what is the role of the thalamus?

Answer 8

searches and accesses memories

Question 9

what does the limbic system represent?

Answer 9

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.

Limbic system gives events emotional significance – essential for memory.

Question 10

what is the limbic system?

Answer 10

Most primitive part of the cortex.

Question 11

what four distinct areas does the limbic system represent?

Answer 11

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

Question 12

what are the areas of the limbic system responsible for?

Answer 12

instinctive behaviour, e.g. thirst, sex, hunger etc. and emotive behaviour are driven by seeking reward or avoiding punishment.

Question 13

what does electrical stimulation of certain areas in the limbic system in conscious patients result in?

Answer 13

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

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

Question 14

what forms the affective components of sensory experiences?

Answer 14

reward and punishment

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 15

how is the frontal cortex associated with reward / punishment centres?

Answer 15

limbic system assess the significance of an event.

If deemed insignificant, forgotten.

Question 16

what do people with bilateral hippocampal damage suffer from?

Answer 16

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.

Question 17

what can memory be divided into?

Answer 17

Immediate or Sensory memory
Short-term memory
Intermediate long-term memory
Long-term memory

Question 18

what is immediate or sensory memory?

Answer 18

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 19

what is short term memory?

Answer 19

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 20

what is immediate long term memory?

Answer 20

hours to weeks e.g. what you did last weekend. Associated with chemical adaptation at the presynaptic terminal.

Question 21

what is long-term memory?

Answer 21

can be lifelong. e.g. where you grew up and your childhood friends. Associated with structural changes in synaptic connections.

Question 22

what is short term memory dependent on?

Answer 22

electrical phenomenon. It depends on maintained excitation from reverberating circuits i.e. they need to be constantly refreshed.

Question 23

what is each synapse in a reverberating circuit?

Answer 23

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 24

The reverberating circuit keeps the brief short term memory alive. If it is deemed significant what happens?

Answer 24

eventually this reverberation results in consolidation of the memory into long-term memory storage.

Question 25

The reverberating circuit keeps the brief short term memory alive. If it is deemed insignificant what happens?

Answer 25

if it is deemed insignificant then the reverberation fades and no consolidation occurs

Question 26

If reverberation is disrupted e.g. following a head injury or infection, especially if it involves the hippocampus and/or thalamus what ussually results?

Answer 26

memory loss normally results – amnesia

Question 27

what are two types of amnesia?

Answer 27

Anterograde – cannot form new memories

Retrograde – cannot access (more recent) old memories

Question 28

what is anterograde amnesia?

Answer 28

inability to recall events that happen after the injury.

Depending on the severity of the injury this can be short lived or permanent.

Question 29

what results in permanent inability to form new memories?

Answer 29

Destruction of the hippocampus (as with Clive Wearing)

Question 30

what is retrograde amnesia?

Answer 30

can’t remember events leading up to the injury, although recall of events that happened a long time ago is usually unaffected, probably because they are better rehearsed and more deeply imbedded.

Question 31

what dooes retrograde amnesia often present with?

Answer 31

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 32

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

Question 33

what does intermediate long term memory involve?

Answer 33

Involves chemical changes in presynaptic neurons:

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

Question 34

what does long term memory involve?

Answer 34

Involves 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.

LTM is basically a well established, well rehearsed pattern of neuronal firing unique to that particular memory.

Question 35

what types does long term memory come in?

Answer 35

Declarative or Explicit Memory

Procedural/ Reflexive/Implicit Memory

Question 36

what is Declarative or Explicit Memory?

Answer 36

Abstract memory for events (episodic memory) and for words, rules and language (semantic memory).
Relies heavily on the hippocampus.

Question 37

what is Procedural/ Reflexive/Implicit Memory?

Answer 37

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).

Question 38

how is short term memory converted into long term memory?

Answer 38

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

Question 39

what does memory recall depend on?

Answer 39

significance of an event.
Your brain naturally gives attention to experiences it deems 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.
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 40

Korsakoff’s syndrome

Answer 40

(chronic alcoholism), there is Vitamin B1 deficiency which leads to damage of limbic system structures. The ability to consolidate memory is impaired.

Question 41

Alzheimer’s disease

Answer 41

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.

Question 42

REM sleep

Answer 42

mportant 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. (Cholinergic neurones responsible for REM).

Answer 43

lofactory 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.