Learning and memory

Question 1

Brain damage

Answer 1

1. often causes memory loss for earlier events - retrograde amnesia
2. within a limited time period of hours, days, years
3. HM - bilateral medial temporal lobotomy, also suffered from anterograde amnesia

Question 2

Different brain areas involved in memory formation

Answer 2

1. HM’s cognitive abilities were largely persevered, as was short-term memory and episodic memories for past events and information learned before the operation
2. he could acquire new motoric skills such as tracing a shape seen in the mirror but could not recall performing this task the day before
3. Scoville and Milner - provided first evidence of involvement of the hippocampus in memory formation

Question 3

Cortical engrams

Answer 3

1. Karl Lashley - unsuccessful in his attempts to find a memory engram, a localised trace of memory in the cortex
2. Concluded that learning and memory is not located in a single area of the cortex but is distributed widely across the brain
3. slice downwards through the cortex causes less disruption

Question 4

Comparative research in neuropsychology and psychiatry

Answer 4

1. only weak causal inferences can be drawn regarding the role played by substrates in psychological functioning
2. it is unethical to manipulate the human brain
3. patients with accidental or surgical lesions are small in number, have diverse patterns of damage across multiple functional units and may differ from uninjured people to begin with, limiting generalisability of findings
4. following damage there may be compensation
5. brain imaging techniques can demonstrate correlations

Question 5

surgical lesions vary in precision

Answer 5

1. traditional method in experimental animal neuroscience to causally infer function of brain areas by abated neurons or pharmalogical methods
2. with these techniques, the loss of neurons is permanent, and it is hard to avoid significant damage of non-target tissues in surrounding areas, even with animal methods
3. even with animal studies, brain-behaviour causal inferences are uncertain

Question 6

optogenetics - precise temporary activation of neurons

Answer 6

1. functional control of targeted cell types using light of a specific wavelength
2. microstimulations during behavioural tests with high spatial and temporal precision
3. reversible, temporary manipulations allowing within-subject comparisons
4. light-sensitive molecules are inserted in membrane using genetic tools
5. animals are selectively bred to generate transgenic lines to investigate specific circuits in the brain
6. genetically tractable models, mainly mice, drosophila flies

Question 7

targeted lesions in medial temporal lobe

Answer 7

extended hippocampal region involved in episodic memory in the delayed non-matching to sample task

Question 8

non associative learning - habituation

Answer 8

1. response weakens with repeated stimulus presentation due to repetition not adaptation
2. repeated tactile stimulation of the siphon in a giant squid mollusc, reduced gill withdrawal response

Question 9

LTM in habituation

Answer 9

1. training sessions over 4 days
2. memory recall test on next day
3. test a week later
4. memory had partically decayed by 3 weeks

Question 10

Pavlov’s dog

Answer 10

1. when a dog receives food it starts to salivate
2. pavlov noticed that his experimental dogs were already salivating before being given food
3. if a sound always precedes food then the dog learns that the sound precedes food
4. contingency - the CS predicts the occurrence of the UCS meaning it is contingent on the prior occurrence of the CS

Question 11

eye blink conditioning

Answer 11

1. neuronal circuit involves cranial nerves and nuclei, connecting interneurons and the cerebellum
2. sensory input UCS - trigeminal nerve, CS input - auditory nuclei, motor output in facial and eye muscles

Question 12

contextual and cued fear conditioning

Answer 12

1. mild foot shock elicits freezing, increased blood pressure and heartbeat
2. cued conditioning - tone predicts punishment
3. contextual conditioning - box alone predicts punishment

Question 13

operant or instrumental learning

Answer 13

1. thorndike proposed that animals learn based on the outcomes of their actions
2. according to his law of effect, when a response is followed by a reinforcer then a stimulus response connection is strengthened
3. John watson and BF skinner influenced ideas that lead to the emergence of behaviourism in the 1920s as research field dedicated to the study of operant conditioning
4. reinforcement learning - if a behaviour is reinforced, it will be repeated

Question 14

spatial learning

Answer 14

learning about places, how to get from A-B

Question 15

memories differ in their durability

Answer 15

1. different types of memory processes occur at different timepoints after encoding
2. shortest memories in sensory buffers
3. STM is few seconds
4. Intermediate memory is longer lasting but not as long as LTM

Question 16

memory processes: encoding, consolidation and retrieval

Answer 16

1. inaccurate recalling of memorised event can be due to inadequate encoding and consolidation at the time of the event (consolidation theory)
2. or absence of cues that can trigger retrieval of a memory (retrieval theory)

Question 17

behavioural models of system consolidation in rodents

Answer 17

contextual fear conditioning - single trial training can generate life lasting memory in the same context

Question 18

Standard LTM consolidation model

Answer 18

1. connections between the hippocampus and various cortical modules are critical for encoding and consolidation
2. as time progresses the hippocampus is less involved in encoding the memory, which has transferred fully to the cortex by the end of the period

Question 19

Synaptic plasticity

Answer 19

1. the brain translates inputs into appropriate outputs through modifiable synapses
2. although the brain is often characterised as a stimulus-response machine, it is more complex
3. memories and consciousness accumulated over our lifetime play a role in how we respond to situations
4. the brain changes synaptic weights so that circuits are configured so stimulus events produce the appropriate response output adapting the agent to its circumstances to maximise survival

Question 20

cell theory

Answer 20

1. the idea that the body is made up of single specialised cells which interact with one another to create the overall functioning
2. emerged alongside the development of techniques of microscopy

Question 21

neuron theory

Answer 21

1. another key technical advance was cell staining, developed by golgi
2. his technique fixed silver chromate particles to the neuron membrane resulting in a stark black deposit contrasted against a yellow background
3. traced to create a library of different neurons
4. led to acceptance that psychology is governed by the operation of single neurons interacting with each other

Question 22

hebb synapse

Answer 22

1. Santiago Cajal - first proposed the idea that the site of contact between neurons could play a role in memory formation
2. Foster and Sherrington - named the sites synapses
3. Hebb - proposed a theory that some connections in neural networks could be strengthened if frequently activated or weakened if used less
4. concept of Hebb synapse implies that the strength of synaptic transmission can increase if the presynaptic cell repeatedly and persistently activates the postsynaptic cell

Question 23

synaptic plasticity in learning and memory

Answer 23

1. synaptic plasticity - biological processes at the synapse by which patterns of synaptic activity change
2. hebb - when an axon of cell a is near enough to excite cell b and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A’s efficiency as one of the cells firing B is increased
3. “takes part” assumes that other cells not shown in the figure must also be activating B
4. it is this proposal that cells only strengthen if their activity is contingent, that makes the cellular process such an excellent fit for associative learning

Question 24

studying aplysia

Answer 24

1. much of what is known about synaptic plasticity comes from the aplysia model
2. small number of neurons, with large soma and axons
3. makes it possible to measure and manipulate neural signals in single sensory and motor neurons
4. signals transmitted at few, individually identified sensorimotor synapses, control the gill withdrawal response

Question 25

non associative learning - habituation

Answer 25

gill withdrawal response to siphon tap weakens with repetition reflecting synaptic weight change in the sensory motor circuit

Question 26

Short term habituation

Answer 26

1. repeated siphon tap causes the defensive withdrawal of the gill to decrease 2. this 3-stimulation habituation effects last under 30 minutes and recovers in about 1 hour 3. this can be considered a form of short term memory, as repeated exposure leaves a memory trace which quickly decays 4. the cellular changes underpinning this effect occur in the two synapses between the siphon and the gill

Question 27

long term habituation

Answer 27

1. with more extensive training of repeated siphon tap exposure, the decrease in the gill withdrawal can last weeks 2. this is a longer term form of memory 3. figure shows that 4 days of habituation training was retained for 7 days and partially decayed at 21 days 4. different cellular processes must underpin these forms of short and long term habituation

Question 28

short and long term sensitisation

Answer 28

1. if the tail is electrocuted causing mild pain, this enhances the subsequent sensitivity to the siphon tap producing a gill withdrawal response 2. a small amount of sensitisation training produces a sensitised response that lasts for 3 days (short term) 3. but repeated sensitisation training, 16 shocks a day for 4 days, produced a longer lasting sensitised response to the siphon tap, still strong at day 7

Question 29

classical (differential) conditioning

Answer 29

1. conditioning is like sensitisation in that tail shock enhances sensitivity to siphon tap, but this sensitivity becomes selectice to siphon tap as opposed to stimuli 2. if the siphon is tapped and this predicts tail shock, the tap become a conditioned stimulus capable of eliciting a gill withdrawal reflex on its own, compared to a tap to a different part of the body which does not predict tail shock 3. classical conditioning of the gill withdrawal reflex is like long term sensitisation in that it can last for many days and duration depends on the amount of training, shock intensity, force of the tap

Question 30

Cellular mechanisms which play a role

Answer 30

4 main cellular adaptations underpin the weight change between the siphon sensory and the gill motor neurons 1. synaptic facilitation 2. long term potentiation 3. long term depression 4. synaptogenesis

Question 31

synaptic facilitation

Answer 31

1. changes is neurotransmitter availability and release in the presynaptic sensory neuron play a role in short term habituation and sensitisation 2. short term habituation = reduced neurotransmitter in the presynaptic syphon sensory neurons reduces the action potential to the gill withdrawal motor neuron 3. short term sensitisation = due to tail shock, the interneurons in presynaptic siphon sensory synapse via the axo-axonic synapse into the gill withrawal motor neuron

Question 32

long term potentiation and long term depression

Answer 32

1. longer training on the procedures evokes long term potentiation (increase) or long term depression (decrease) post synaptic receptors density 2. long term habitation = decreased receptor density in the postsynaptic membrane of the gill withdrawal motor neuron, decreases sensitivity to activation by the siphon sensory neuron 3. long term sensitisation - increased receptor density in the postsynaptic membrane of the gill withdrawal motor neuron due to the axo-axonic input from the tail interneuron, increases sensitivity to activation by the siphon sensory neuron 4. conditioning - similar to sensitisation but whereas sensitisation reflects a generalised increase in sensitivity to all stimuli, in differential conditioning, LTP is more pronounced 5. in conditioning, it is the contingent activation of the siphon CS and the tail UCS which instantiates substantial LTP between the siphon and gill withdrawal motor neuron

Question 33

synaptogenesis

Answer 33

1. refers to the formation of more synapses of removal of existing synapses 2. long term habituation = decreased number of synapses from the siphon sensory neuron to gill motor neuron 3. long term sensitisation = increased number of synapses from the siphon sensory neuron to gill motor neuron 4. conditioning = increased number of synapses from the siphon sensory neuron, but due to signalling from tail interneuron carrying the contingent signal from the tail shock

Question 34

long term potentiation

Answer 34

1. LTP is a lab model used to demonstrate change in synaptic strength due to increase in postsynaptic receptor density first shown in the hippocampus 2. hippocampus is a specialised extension of the fornix 3. fornix is the white fibre bundle connecting subcortical nuclei 4. fornix damage produces wide ranging abnormality in memory, navigation, motion and voluntary motor control 5. hippocampus receives input from all major nuclei of the limbic system therefore part of an integrative system 6. hippocampus is layered and rolled and slices are collected for the procedure in vitro 7. associative LTP - a weak test stimulus produces a weak activation at a recording site 8. but if the weak stimulus is paired with the stronger stimulus it comes to elicit a larger activation at the recording site showing strengthening of synapses 9. the weak and strong stimulation must be contingent for LTP to be produced

Question 35

NMDA receptor

Answer 35

1. glutamate pyramidal neurons mediate LTP 2. the membrane of these neurons express AMPA receptors which conduct the action potential from pre synaptic neurons in response to glutamate neurotransmitter release opening the sodium ion channel 3. the NMDA receptor is special, in that it can increase the number of AMPA receptors underlies LTP and LTM 4. the NMDA receptor is a contingency detector, being both voltage and ion gated 5. the magnesium plug will only release if the neuron is activated by other cells nearby simultaneously with glutamate release on the receptors 6. removal of the magnesium ion plug allows calcium into the cell engaging the second messenger system which drives the increase in AMPA receptors 7. LTP is controlled by a specialised ionotropic glutamate receptors that control calcium channels which are blocked by magnesium ions 8. magnesium ion blocking the calcium channel can only be pushed out by depolarisation of the postsynaptic membrane plus NMDA binding to the receptor allowing calcium to enter the cell 9. NMDA receptors engage calcium dependent second messenger system which increases the number of AMPA receptors strengthening the synaptic connection to produce learning 10. greater AMPA receptors transmit stronger action potential = LTP

Question 36

role of hippcampal NMDA receptors in navigation

Answer 36

1. morris water maze used to study navigation in rats 2. the rats must find platform from a random starting position 3. landmarks outside the pool guide path to platform 4. hippocampal lesioned rats cannot learn to find the platform 5. its not that hippocampal lesions are just damaging the ability of the rat to control its movement 6. hippocampal lesioned rats placed in the pool consistently in one location can learn a simple instrumental response to the platform 7. suggests its use of landmarks to guide navigation memory is impaired in lesioned rats 8. injection of AP5, a selective NMDA receptor antagonist, into the hippocampus to suppress LTP abolishes navigation memory similar to lesions

Question 37

place cells

Answer 37

1. different place cells are active in different parts of a maze, suggesting they collectively encode different areas 2. suggests that the hippocampus is mapping the spatial layout of the animals environment 3. different place cells encode different locations suggesting they collectively map the spatial layout of the animal's environment

Question 38

targeted lesions in the medial temporal lobe

Answer 38

1. the hippocampus is extensively connected within the wider area, especially the entorhinal cortex 2. the greater damage to the wider hippocampal regions produced greater impairment in delayed nonmatching to sample performance in monkeys 3. suggested that the hippocampus was not the single site of memory but memory relied in the integrity of the network between regions

Question 39

hippocampal formation encodes locations in space

Answer 39

1. some have attempted to apply knowledge of GPS technology to try and understand how these cells are integrated to map out and enable navigation in space 2. neuroinformatics - research field devoted to the links between neuroscience and computational science

Question 40

other spatially sensitive neurons in the brain

Answer 40

1. to understand how the brain as a whole represents space it is also important to understand these neurons 2. egocentric boundary cells respond to boundaries but only if they are on one side or other of the animal's body