11 - Learning And Memory Flashcards
Learning vs memory
Learning: acquiring new information
Memory: store and retrieve information
Learning and memory are closely related; cannot be sure learning has occurred without memory
Classical conditioning
Associative learning
Ivan Pavlov
Pairing two stimuli changes the response to one of them
Conditioned and unconditioned stimuli
Operant conditioning
Individuals response followed by reinforcer or punishment
Reinforcer: events that increase the probability that the response will occur again
Punishment: events that decrease the probability that the response will occur again
Engram
Physical representation of learning
Engram - Descartes
Descartes is suggested as the first to consider the physical representation of learning
Considered the pineal glands as the master controller
Animal spirits move through the brain through pores and tubes
Easier for the spirits to move through pores which have previously been opened
Engram - Lashley
Karl Lashley proposed that severing connections between brain regions should abolish learning
Based on the assumption that learning depends on connections between brain regions
Cuts through cortical regions produced no consistent impairments in learning in rats
Never found the engram
Lashley’s principles about the nervous system
Equipotentiality: all parts of the cortex contribute equally to complex functioning behaviours (eg learning)
Mass action: the cortex works as a whole, and more cortex is better
Engram - Thompson
Thompson and colleagues proposed that the classical conditioning engram is located in the cerebellum
Lateral interpositus nucleus (sub-section of cerebellum) identified as central for learning
Responses increase as learning proceeds
Temporary inactivation resulted in no learning
Types of memory - Donald Hebb
Donald Hebb supported the assumption that memory and learning relies on a physical change
Differentiated between two types of memory:
Short-term memory: memory of recent events
Long-term memory: memory of distant events
Consolidation of memory
Consolidation from short-term to long-term memory is suggested to rely on protein synthesis
Inhibition of transcription/translation results in amnesia
However, consolidation is likely a complex process
Significant variability in the time taken for consolidation - e.g. Emotional events
Working memory components
Proposed by Baddeley and Hitch as an alternative to short-term memory
Consists of:
Phonological loop
Visuospatial sketchpad
Episodic buffer (brings all parts together)
Executive control
Working memory assessed and damage
Assessed using the delayed response task
Requires responding to something you heard or saw a short while ago
Damage to the prefrontal cortex produced impairments in performance on the delayed response task
Hippocampus and amnesia
H.M. suffered from severe epilepsy
The hippocampus, amygdala, and parts of the temporal lobe were removed from both hemispheres
H.M. suffered significant memory impairment
But impairment was not consistent across all memory domains
H.M.’s memory
Severe anterograde amnesia and some retrograde amnesia Unimpaired working (short term) memory Severe loss of episodic memories Better implicit memory Largely intact procedural memory
Anterograde amnesia
Loss of ability to form new memory after the brain damage
Retrograde amnesia
Loss of memory of events prior to the occurrence of the brain damage
Semantic memory
Memories of factual information - general knowledge
H.M. showed impaired semantic memory, but was able to form some weak semantic memories
Episodic memory
Memories of single personal events
H.M. could not describe any event since his surgery
Explicit memory
Deliberate recall of information that one recognises as a memory
Most impaired in H.M.
Implicit memory
The influence of experience on behaviour even if one does not recognise that influence
Assessed using priming tasks
Procedural memory
Korsakoff’s syndrome
Memory disorder typically resulting from Wernicke’s encephalopathy
Causes by brain damage in response to prolonged thiamine deficiency
Impedes brain’s ability to use glucose
Leads to neural damage in regions surrounding the ventricles
Symptoms:
Confabulation (taking guesses to fill in gaps in memory), confusion, memory loss
Alzheimers Disease
Is a type of dementia characterised by a gradual decline in memory
Neural degeneration seen throughout both cortical and subcortical regions
Associated with changes at a cellular level:
Beta-amyloid
Tau protein
Accumulation of the beta-amyloid and tau protein results in:
Plaques: structures formed from damaged axons and dendrites (beta-amyloid)
Tangles: structures formed from degeneration within neurons (tau protein)
Basal ganglia & memory
Gradual learning realise on the basal ganglia
Damage to the basal ganglia prevents gradual learning
Weather prediction game
Amygdala & memory
Associated with fear learning
Inhibition of protein formation in the amygdala interrupts consolidation
Parietal lobe & memory
Associated with piecing together aspects of episodic memory
Free recall impairments
Anterior temporal cortex & memory
Damage to the anterior temporal cortex results in loss of semantic memory
Semantic dementia
Prefrontal cortex & memory
Involved in learned behaviour and decision-making
Initiates top-down influence for working memory
Neuronal changes and learning
Patterns of activity in the brain leave a path of physical changes
Physical changes can take place at many different sites to cause a change in the size of the postsynaptic potential
Presynaptic, postsynaptic or both
Can result in greater neurotransmitter release
More receptors or receptors become more sensitive
Learning and the Hebbian synapse
“Neurons that fire together wire together”
A synapse that increases in effectiveness because of simultaneous activity in the presynaptic and postsynaptic neurons
Such synapses may be critical for many kinds of associative learning
Long-Term Potentiation in Vertebrates
LTP occurs when one or more axons bombard a dendrite with stimulation
Leave the synapse ‘potentiated’ for a period of time and the neuron is more responsive
Long-Term Depression (LTD)
A prolonged decrease in response at a synapse that occurs when axons have been less active than others
Compensatory process: (can’t have brain constantly strengthening) as one synapse strengthens, another weakens
Lack of activity within a network causes weakening of synaptic connection
Biochemical mechanisms
Studies most in the hippocampus LTP depends on changes at glutamate synapses Two types of glutamate receptions: AMPA receptors NMDA receptors
The LTP process in hippocampal neurons
See book and slides
LTP and memory
LTP is proposed as one of the many neuronal mechanisms likely to underlie memory construction and storage
LTP process has similar time course to short term and long term memory
Blocking LTP impairs learning
Genetic manipulation in mice to increase number of NMDA receptors results in enhanced learning capacity
Performing learning tasks activates LTP-like processes
