Learning and memory Flashcards
Learning
Strengthening or formation of responses to stimuli due to repetition or practice
Memory
Storage and retrieval of knowledge gained through learning
Declarative/explicit memory
knowledge about facts and their meaning (recalled consciously)
Non-declarative/implicit memory
Knowledge about how to perform something (recalled unconsciously)
Can be associative or non-associative
Non-associative memory
Habituation is decrease in response to a benign stimulus through repeated presentation
Sensitisation is an enhanced response to multiple different stimuli after presentation of an intense stimulus
Associative memory
Association between two stimuli
Pavlov’s dog food is unconditioned stimulus (US) and bell is conditioned stimulus (CS)
bell is repeatedly paired with food and can elicit salivation (conditioned response)
Short term memory
Lasts minutes and involves covalent modifications of pre-existing proteins at synapse by kinases
Intermediate term memory
Lasts hours and involves new protein synthesis (but not mRNA synthesis)
Long term memory
Lasts days and weeks
Requires CREB-mediated gene expression, new mRNA and protein synthesis
Neuromodulation in Aplysia
sea snails close gills and syphon and eject a cloud of ink in response to spiny lobster
Sea snail is sensitised to future attacks
Short/intermediate memory formation in Aplysia
Serotonin released and binds receptors on sensory neurons
Activates adenyl cyclase which promotes cAMP production
Increased cAMP increases synaptic connection (short term sensitisation/facilitation)
Also enhanced release of glutamate by sensory neuron
Increase in excitability
Classical olfactory learning in Drosophila
Learning contingency between odor (cs) and appetitive stimulus (us)
adenyl cyclase intergrates these stimuli in the mushroom body neurons of the brain
Dopaminergic neurons transmit aversive stimuli to MB
Octopaminergic neurons transmit appetitive stimuli
Long term memory formation in Aplysia
Equilibrium between kinase and phosphatase activity at synapse
Retrograde transport from synapse to nucleus
Activation of nuclear TFs
Chromatin alteration and epigenetic changes
Local protein synthesis at active synapses
Synaptic growth, activation of silent synapses and formation of new synapses
Aversive olfactory conditioning
CS information presented to mushroom body neurons by PNs
PNs release Ach, causing influx of calcium in MB cells
Adenylate cyclase activates, increasing cAMP concentration
US information presented by PPL1/PPL2ab neurons which release dopamine onto MB neurons. Increase in cAMP
Coincident CS and US pathway activation leads to synergistic cAMP increase
Appetitive olfactory conditioning
Same CS pathway to mushroom body
US information may cause octopamine or dopamine release
Coincident application produces sub-additive increase in cAMP
