3. Learning and memory

Question 1

Engrams?

Answer 1

The link between memory’s and remembering is presumed

biochemical in nature

Question 2

memory and learning is performed using _____ processing systems and not serial processing systems

Answer 2

memory and learning is performed using PARALLEL processing systems and not serial processing systems

Question 3

What is the synaptic premises of Hebbian learning?

Answer 3

As cells fire simultaneously they increase the synaptic associations. This results in networks of cells which are synaptically linked - associative learning

I.e. Hebbian Learning

Question 4

What is habituation?

Answer 4

decrease in response (& NT release ) with repeated stimulus
e.g. Driving with constant background noise, repeating siphon stroke

Question 5

What is sensitisation?

Answer 5

Increase in response with repeated stimulation – mediated by an interneuron

e.g. sitting in lecture with someone poking you ==> rage

Question 6

How is the difference between stimulus to siphon at skin and at the tail?

Answer 6

Repeated Siphon stroke on SKIN causes habituation as the sensory neuron EPSP reduces

Concurrent TAIL stimulation causes Sensitisation. The tail shock causes release of 5HT onto the pre-synaptic membrane of the siphon skin sensory neurons from interneurons. This prolongs the NT release and causes sensitisation

Question 7

What is the mechanism of long term potentiation (LTP)?

Answer 7

1. Stimulate pathway 1 with a single spike
2. Stimulate pathway 1 with a train of spikes
3. re-stimulate with a single spike and measure EPSP
4. Stimulate pathway B with a single spike and measure the EPSP
5. Enhanced response in Path 1 is long-lived and specific to that pathway
   Long term synaptic changes requires genetic involvement

So…
AFTER STIMULATION WITH TRAIN OF SPIKES, SECOND SINGLE STIMULUS LEADS TO UPREGULATED EPSP

Question 8

To prevent ‘whole brain potentiation’ there is a reverse effect (recall habituation)….

Answer 8

Long term depression (LTD)

Question 9

How is long term depression achieved?

Answer 9

LTD is initiated by a slower train of stimulatory impulses over a longer period
LTD can modulate LTP or even reverse it

Question 10

How are memory’s classified?

Answer 10

By duration!

Memory duration is used to define memory types and processes:
Short term memory, Long term memory, & Working memory

Question 11

A short term memory is?

Answer 11

1) a very brief memory (seconds) either from an external
stimulus or retrieval from a long term memory
**2) easily displaced by another stimulus **
3) Can be extended into working memory by:
a) repetition in a phonic loop (temporal extension) or
b) chunking which links familiar chunks together to extend the size of chunk

Question 12

example of phonic loop?

Answer 12

“MUST REMEMBER MY KEYS” REPEATING OVER AND OVER

Question 13

Common clinical test for short term memory?

Answer 13

Digit span.
Subject reads an increasing series of numbers which they immediately repeat
The number of digits that can be repeated back immediately is the digital span. - Usually around 6-7 digits is normal

Question 14

Technique to improve short term memeory?

Answer 14

Chunking

Grouping list logically to lessen number of individual items to remember

Question 15

What is working memory?

Answer 15

The maintenance and integration of information in an active state for a relatively
brief time in order to achieve a short term task or goal

Made up of: s comprised of a mixture of short and/or retrieved long term memory

Question 16

How do short term memories become working memories?

What happens when task is over?

Answer 16

As Short term memory only lasts a few seconds it must be repeatedly re-activated, its reactivation and subsequent duration is working memory (this is known as an executive function).

When the task is over, the working memory either is encoded into long term memory or is left to lapse

Question 17

Note that it is also possible for LTM to be formed directly from ______ input under control of executive functions (pre-frontal cortex)

Answer 17

Note that it is also possible for LTM to be formed directly from sensory input under control of executive functions (pre-frontal cortex)

Question 18

Subdivisions of logn term memory?

Answer 18

Declarative memory (explicit)
\+
Non-declarative memory (automatic)

Question 19

Classification of declarative long term memory…

Answer 19

(Conscious memory)

1. Semantics (language/facts)
2. Epispodic (events and experiences)
   - Familiarity
   - Recollection

1+2 Form the autobiographical memory

IN THE MEDIAL TEMPORAL LOBE STRUCTURES AND ASSOCIATION AREAS

Question 20

What is the classification of non-declarative long term memory?

Answer 20

(Does not require conscious effort to form or access)
1. Procedural (habits and skills)
@ basal gangia and cerebellum
2. Priming
-Habituation e.g. traffic noise
-Sensitisation e.g. paper cut pain
3. Associative learning
-Classical conditioning e.g.  @ hypothalamus
-Emotional responses e.g. @ amygdala

Question 21

Despite all subdivisions of long term memory, what are the 4 stages in the process of learning?

Answer 21

1. Encoding (memory creation)
2. Storage (persistence of memory traces)
3. Retrieval (memory recovery)
4. Consolidation (strengthening of memory traces)

Question 22

Describe the events and structures involved in memory formation?

Answer 22

A) A series of events are encoded by the hippocampus, and a reference is made to their memory location – hippocampal index (File Allocation Table)
B) If this information is recalled prior to consolidation, the hippocampus performs the retrieval from its index of the events
C) After consolidation of the memory retrieval can be initiated directly from the sensory cortices

Question 23

How is Plasticity in LTM is used ?

Answer 23

Treating post traumatic stress disorder.

Patients are asked to re-live the events leading to PTSD then given an adrenergic beta receptor blocker (propranolol) which blocks re-consolidation of the memory

Question 24

Where does consolidating declarative memory take place?

Answer 24

Medial temporal lobe

Question 25

How does consolidating declarative memories work?

Answer 25

‘fire together wire together”
So frequent firing leads to physical changes at the synapse to strengthen the connection
LTM memory is associated with changes in connectivity in networks of neurons
predominantly in the cortex

Question 26

Four changes in morphology on dendritic spines when consolidating declarative memory, what are they?

Answer 26

1. Increase in number of presynaptic vesicles, post synaptic recepors and ribosomes
2. Separate synaptic zones developed which are divided by a wall/cleft in the spine
3. Single spine divides in two
4. New dendritic spine appear

Question 27

How are non-declarative long term memories consolidated?

Answer 27

Amygdala
Caudate nucleus
Putamen
Cerebellum

Corpus striatum (part of Basal ganglia):
Made up of: caudate nucleus + putamen
Role: Influences memories involving movement & procedural memory e.g. Olympic diving

Cerebellum:
Role: influences fine motor learning including speech movements

Question 28

Case of HM, suffered from frequent severe epileptic seizures from age 9.
Source was assumed to be the medial temporal lobe.
8cm removed bilaterally (including enterohinal cortex, amygdala and the anterior 2/3 of hippocampus)
What was the result?

Answer 28

Source was assumed to be the medial temporal lobe.
8cm removed bilaterally (including enterohinal cortex, amygdala and the anterior 2/3 of hippocampus)
Result:
-Alleviated symptoms. No effect on perception, inteliegence and personality.

• Working memory was normal but he has two forms of amnesia:
  1. Some retrograde amnesia (loss of memory of some year pre operation)
  2. Extreme anterograde i.e. unable to identify people just met, or certain events

-Was able to learn a skill which is non-declarative

Therefore: Unable to consolidate new DECLARATIVE long term memories. But able to learn NON-DECLARATIVE skill. So shows that declarative, non-declarative, short term and long term memory are not processed in the same place or by the same mechanisms

Question 29

Difference between retrograde and anterograde amnesia?

Answer 29

Retrograde: Loss of non-consolidated memories immediately before trauma. All else in full capacity

Anterograde amnesia: No memory following trauma

Question 30

Types of amnesia?

Answer 30

Retrograde
Anterograde
Dissociated amnesia: Amnesia occurring without any other deficits

Question 31

Brain structures other than the temporal lobes can cause amnesia when damaged and are involved in memory consolidation. Which structures?

Answer 31

Lesions in the following can cause anterograde amnesia:

• the anterior or dorsomedial nuclei of the thalamus
• in the Mammillary bodies
• Dorsomedial nucleus of the thalamus (receives input from temporal lobe and output to frontal cortex)

Question 32

Case of NA:
Trauma to the left dorsomedial thalamic nucleus and bilateral damage to mammiliary bodies. No damage to hippocampus.
What did the patient suffer from as a result?

Answer 32

Some retrograde amnesia and profound anterograde amnesia

Cause NA and NM findings support the idea of a functional link between the dorsomedial thalamus and the medial temporal lobe in memory consolidation

Question 33

How does loss of the non-declarative memory occur?

Answer 33

Damage to the striatum of the basal nuclei

As seen in huntington’s disease in humans leading to a loss of procedural learning