Learning and Memory

Question 1

Cognition

Answer 1

Cognitive states such as motivation, learning and memory were once considered in the realm of psychology rather than physiology

However, cellular events that influence plasticity underlie these cognitive functions

Changes in neuronal connections as a response to experiences is fundamental to learning and memory

Question 2

Learning definition

Answer 2

the acquisition of knowledge about our environment.

Any relative permanent change in behaviour brought about by past experience.

Question 3

Memory definition

Answer 3

the process by which that knowledge is encoded, stored and later retrieved.

Question 4

Associative learning

Answer 4

Forming new association between two events

Includes classical and operant learning

Question 5

Cognitive (non-associative) learning

Answer 5

Interpretation of present information in light of past experience
Includes habituation and sensitisation

Question 6

Pavlov,classical conditioning

Answer 6

learning a simple behavioural response in the presence of a given stimulus.
concerned with reflex behaviour: an unconditional stimulus (US) eg. food leads to an unconditioned response (salivation)
If a novel stimulus (eg. light/bell) is paired with the US, the novel stimulus alone soon elicits the response ie. it becomes a conditioned stimulus and the response becomes a conditioned response

Question 7

Steps in classical conditioning

Answer 7

Neutral stimulus (NS) has no effect on the subject 
Unconditioned stimulus (US) elicits an unconditioned response (UR)

NS is paired repeatedly with
the US; UR occurs

NS is presented alone, UR occurs
Neutral stimulus is now the conditioned stimulus (CS)

Question 8

Associative learning-operant conditioning

Answer 8

Skinner, 1938

Operant conditioning increases the likelihood of a response by following its occurrence with a reinforcer

Involves a voluntary response (behaviour), with which an organism ‘operates’ on its environment;

Initially happens by chance, consequences determine likelihood of doing it again.

Question 9

Classical conditioning

Answer 9

organism is passive, simply responds to stimuli

Question 10

operant conditioning

Answer 10

organism is active, own behaviour brings on reinforcement (e.g. foot pedal causes food to be released).

Question 11

reinforcement

Answer 11

Any event which increases the likelihood of a response
May be positive (reward training) or negative (escape/avoidance training- not punishment)
Primary reinforcer: satisfies a basic drive e.g. food, pain avoidance
Secondary reinforcer: conditioned e.g. money

Question 12

Structural changes in learning

Answer 12

In humans, disruption of brain activity within 10 minutes of learning abolishes the memory, but if greater than 1 hour, it does not.

Structural changes do occur during learning
e.g. rats reared in a visually enriched environment have much thicker visual cortices
Disuse atrophy of neurons occurs.

Inhibition of protein synthesis within 30 minutes of learning disrupts learning.

Question 13

Habituation-cognitive learning

Answer 13

repeated exposure to a stimulus results in reduced responding to that stimulus
generally neutral, non-noxious stimuli

Question 14

Sensitisation

Answer 14

repeated exposure to a stimulus results in increased responding to that stimulus
generally biologically relevant
also refers to augmentation of responding following exposure to a second stimulus

Question 15

Research on neural mechanism has focused on non-associative learning and classical conditioning.

Answer 15

Eric Kandel and his collaborators used Aplysia to unravel synaptic mechanisms for
Short- and long-term habituation
Short- and long-term sensitization
Classical conditioning.

Eric Kandel won the Nobel Prize for Physiology and Medicine 2000 for this work.

Question 16

Gill withdrawal reflex in Aplysia Californica

Answer 16

The gill is used for breathing
The gill can be covered with the mantle shelf
Waste and seawater are released through the siphon
The gill-withdrawal reflex occurs when touching the siphon produces a retraction of the gill

Question 17

Mechanism for habituation:

Answer 17

↑ K+ conductance → hyperpolarisation → ↓Ca2+ influx → ↓NT release

Question 18

Mechanism for sensitisation:

Answer 18

5-HT → ↑cAMP → ↓K+ conductance → prolonged depolarisation → ↑ Ca2+ influx → ↑ NT release

Question 19

Habituation in aplysia

Answer 19

short term and long term aplysia-refer to notes

Question 20

Sensitisation in aplysia

Answer 20

Kandel termed the neural mechanisms that underlie behavioural sensitisation,
“heterosynaptic facilitation,” which is produced by a second (usually stronger) stimulus

Question 21

Memory

Answer 21

Refers to the processes of

Acquiring information
Storing it in the brain
Subsequent retrieval and use

Question 22

Declarative (explicit)

Answer 22

conscious, expressed by language
Episodic – associated with a time
Semantic – factual knowledge

Question 23

non-declarative (implicit)

Answer 23

a memory recalled unconsciously
Procedural or skill learning
Priming: resistant to brain injury, aging and dementia
Conditioning

Question 24

Acquisition and storage of declarative information

Answer 24

Short term storage (hippocampus and related structures)->
long term storage ( a variety of cortical sites: Wernickes area for the meaning of words, temporal cortex for the memories of objects and faces etc,

Question 25

Acquisition and storage of nondeclarative information

Answer 25

short term memory (sites unknown but presumably widespread)-> long term storage ( cerebellum,basal ganglia, premoter cortex, other sites related to motor behaviour)

Question 26

Short term memory

Answer 26

a cognitive system that is used for holding sensory events, movements, and cognitive information, such as digits, words, names, or other items for a brief period of time Maintenance

Question 27

working memory

Answer 27

the maintenance and controlled manipulation of a limited amount of information before recall

Question 28

sensory traces

Answer 28

e.g. iconic (visual) and echoic (auditory) ‘after images’ E.g. brief glance at a setting sun At most a few seconds in duration (example on next slide – negative after image) Allows an initial evaluation of physical characteristics or psychological meaning, and a decision as to whether to send the info to short term memory i.e. to attend to it (decided by the limbic system)

Question 29

Selective attention

Answer 29

Voluntary e.g. studying Involuntary e.g. we attend to loud noises, moving objects, psychologically-significant words i.e. potentially threatening / rewarding

Question 30

Short term/working memory

Answer 30

Information attended to passes into STM Encoding: mainly acoustic (sound) Storage: if unrehearsed memory span 7 ± 2 items, for ~30 seconds (Miller, 1956). Modern estimates are lower: 4 - 5 items. Forgetting: a) decay over time b) displacement of new information Maintenance rehearsal (repetition) keeps information in ST store Capacity of short term memory digit / item span (aka working memory load) is ~7 ± 2 items. However, an “item” can be a single letter or digit, or a CHUNK of several letters or numbers. Chunking makes more efficient use of short-term memory by recoding information. Various kinds of memory training systems and mnemonics include training and drill in specially-designed recoding or chunking schemes.

Question 31

Functions of STM

Answer 31

Working Memory: what we are ‘thinking’ about Important for cognitive processes - facilitates conversation, reading, computation, problem solving. Evaluation of information and a decision as to whether to send it to Long term memory (selected by the limbic system)

Question 32

Characterisation of mechanisms of memory formation

Answer 32

Sensory traces persistent activity in sensory pathways – changes at the level of the synapses Short-term memory (STM) or working memory Reverberating circuits Electrical basis Limited capacity Can be disrupted by intrusion of other activity E.g. Stroop test – example of interference

Question 33

Neural basis of short-term memory

Answer 33

Due to reverberating circuits: self-exciting chains of neurons (e.g. wind-up, see lecture on cortical function) in the relevant sensory, association and motor areas (neural networks). Medial temporal lobe and mammillary bodies form and consolidate verbal memories (Papez circuit) which are stored in the appropriate areas of the cortex. STM is very susceptible to disruption of the electrical activity of the brain, e.g. during concussion, epileptic fits or general anaesthetics, leading to amnesia for the immediate preceding events.

Question 34

Long term memory

Answer 34

Small amount of information in STM transferred to LTM Ability to store very large amounts of information for very long periods of time Encoding: mainly semantic (meaning), also visual (faces), auditory (voices), olfactory (scents). Transfer requires elaborative rehearsal i.e. coding, relating to stored information, devising associations, organizing. Storage: probably unlimited capacity, for very long periods of time Retrieval ‘cues’ ‘unlock’ correct ‘box’ for memories (recognition is easier than recall). ‘Forgetting’ is usually due to retrieval failure from LTM . Retrieval is increased by elaboration and organisation (information in many ‘boxes’). Increased if recalled in context “recall” indicates the ability to retrieve information related to an item in absence of the item The thalamus is key to memory recall – damage to this area (e.g. Kluver-Bucy syndrome) can result in retrograde amnesia (recalling memories from the past). Recall is decreased by interference e.g. anxiety Influence of emotional factors: Rehearsal of emotionally-charged items leads to increased storage Negative emotions can interfere with retrieval Freud: retrieval of traumatic experiences blocked

Question 35

Locating the memory trace (engram)

Answer 35

Engram: physical representation or location of a memory Karl Lashley (1930s) observed the effects of lesions on rats’learning in a maze The larger the amount of cortex damaged, the more errors the rats made Lashley believed that the engram was distributed across the cortex However, the lesions were so large they damaged several cortical regions. Moreover, the rats might solve the maze using sight, smell and feel in addition to memory. Lashley was incorrect. All cortical regions don’t contribute equally to memory but they are distributed through the cortex.

Question 36

Scoville and Milner,1957

Answer 36

Patient H.M. (Henry Molaison) Sustained a head injury at age 7 Experienced his first major seizure aged 10 Experimental surgery carried out in 1953, (H.M aged 27) where both hippocampus and amygdala removed as a treatment for the seizures Epilepsy much improved, controlled by medication However, H.M had great difficulty forming new long-term memories. STM and working memory remained intact. Suggested that the hippocampus/amygdala is vital for the formation of new long-term memories. Memory could be impaired selectively without loss of other cognitive functions Memory functions localised to the medial temporal lobe The hippocampus is thought to be a key structure for memory, but impairment may be due to combined damage of the hippocampus and the amygdala- localisation of memory not completely clear. Impaired ability to form new memories after surgical removal of hippocampi & amygdala - anteretrograde amnesia. Partially spared: memories formed before onset of amnesia - retrograde amnesia. ** This means that the medial temporal lobe is critical for the initial formation/encoding of new memory but not the place where well established, long-term memories are stored *

Question 37

Neural basis of LTM

Answer 37

Depends on permanent structural changes in the relevant sensorimotor and association areas: Disruption of the brain’s electrical activity does not abolish LTM Highly specific cortical activation occurs during recall, and retrograde amnesia is specific for cortical area damaged. Consolidation: process of transfer of information from STM to LTM, when structural changes occur; corresponds to period of elaborate rehearsal, ~1 hr Interneural hypothesis: changes in synaptic activity in a neural circuit lead to facilitation of that circuit- a ‘memory engram’. E.g. increased number of presynaptic terminals, vesicle-release sites and transmitter vesicles. Altered post synaptic dendritic spines Long Term Potentiation (LTP): well documented mechanism of learning in hippocampus, cerebellum. Long Term Depression (LTD): long-lasting activity-dependent reduction in the efficacy of synaptic transmission

Question 38

Two common types of brain damage

Answer 38

Korsakoff's syndrome and alzheimer's disease

Question 39

Korsakoff's syndrome

Answer 39

Prolonged thiamine (vitamin B1) deficiency. Often due to chronic alcoholism Impedes the ability of the brain to metabolize glucose. Leads to a loss of or shrinkage of neurons in the brain (mammillary body). Symptoms include apathy, confusion, and forgetting and confabulation (taking guesses to fill in gaps in memory).

Question 40

Alzheimer's disease

Answer 40

Associated with a gradually progressive loss of memory often occurring in old age. Affects 50% of people over 85. Early onset seems to be influenced by genes, but 99% of cases are late onset. About half of all patients with late onset have no known relative with the disease. Alzheimer’s disease is associated with an accumulation and clumping of the following brain proteins: Amyloid beta protein 42 which produces widespread atrophy of the cerebral cortex, hippocampus and other areas. An abnormal form of the tau protein, part of the intracellular support system of neurons. Accumulation of the tau protein results in: Plaques – structures formed from degenerating neurons. Tangles – structures formed from degenerating structures within a neuronal body.

Question 41

Lessons from studying amnesiac patients

Answer 41

There can be deficiencies of very different aspects of memory. There are independent kinds of memory. Various kinds of memory depend on different brain areas.

Question 42

Improving declarative memory

Answer 42

Chunking: Grouping items in STM may be recoded, using information from LTM, into larger more meaningful units (chunks) – memory span is still 7±2 items Elaboration, organisation – hierarchical most efficient Context: recreating learning situation in imagination Imagery: meaningful connection between two words e.g. method of loci – mind palace, key-word system, mnemonics PQ4R (Preview, Question, Read, Reflect, Recite, Review) Practicing retrieval as one learns ↑↑ retrieval later