PSYC 310 Lecture Notes - Lecture 13: Synaptic Tagging, Habituation, Rodent
7 May 2018
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PSYC 318 Lecture 17/24: Cellular memory consolidation
Monday, Mar 19th
• Wayne Sossin, new prof for the next 6 lectures
• Talking about memory
• Learning objectives:
o Molecular memory trace – understanding of it is a goal for all 6 lectures
o Protein phosphorylation
o Transcription factors
o Synaptic strength
▪ How neurons control the size and strength of connections between other
neurons
▪ Synaptic strength: P, how is the probability of release regulated?
o Cellular and molecule understanding of facilitation
o Sensitization
o Cellular depression underlying behavioral habituation
o Role of transcription in determining the differences between short and long-
term memory
• Memory at the molecular level
o For an experience to have impact on future behavior, something has to change
o Physical change inside the brain
o Coputes hae eo like ou ais do: log te s. shot te saig o
computers
• Diffeet ioheial taes a e gaded thei olatilit
o Has to do with how long the memory lasts for
o Memories last for different periods of time and have fundamentally different
biological underpinnings
o Today: changes in phosphorylation state, whether a protein is phosphorylated or
not
o Insertion and removal of memory proteins:
▪ If phosphorylation of proteins can regulate synaptic strength then turning
those kinases on for longer periods of time can lead to a longer lasting
change in synaptic strength.
• Aplysia model system
o Marine mollusk Aplysia Californica
o This model system is justifiable because it is very simple, has simple neuronal
circuits
o Allows you to ask questions in a reductivist way
o Much of what we know about molecular biology was done using approach where
people tried understanding how bacteria coded for information.
o In aplysia
▪ Neurons are very large
▪ Identifiable between preparations
find more resources at oneclass.com
find more resources at oneclass.com
▪ Rodent systems are more difficult because each neuron is doing 10
different things
▪ Aplysia neurons only do one thing each, allows for easier tracing
o Invertebrate system: neurons do very well when you take them outside of the
animal
• Aplysia has non-associative memories
o Simple
o They have associative memories as well, which is when you connect a
conditioned and unconditioned stimulus
▪ Like Palos dogs
o Aplysia defensive reflex where animal is touched then moves
o If you touch animal repeatedly then this behavior disappears
o If ou shok aial it ieases the defesie efle, doest euie paiig of
shock to touch of animal
▪ Shock itself sufficient to increase defensive reflex even in absence of
touching
o Alpysia breathes with its siphon and gills
▪ Siphon-induced gill withdrawal
▪ Touch siphon of animal, withdraws gill in defensive reflex
▪ Very sensitive, no protective shield like snails have
• Plays movie on Sensitization
o Erik Kendell, Nobel prize winner 2000 for understanding how synaptic changes
underlie behavioral memory in aplysia system
o Behavior = sensitization
▪ Noxious stimulus to tail causes increase in time and extent of gill
withdrawal to touch to siphon
o After shock the animal changed its behavior
• Schematic diagram of the abdominal ganglion showing identified neurons
o The easily identifiable (large) neurons with fixed circuitry allowed for easy
identification of the circuit
o Motor, sensory neurons in here.
o Very large R2 is a millimeter
o Drosophila is another good model system for learning and memory
o Big difference in size makes it easier to study these neurons
• How to measure synaptic strength
o EPSP excitatory
o IPSP inhibitory
o APs cause presynaptic cell to release neurotransmitter
▪ Neurotransmitter acts as a ligand to open channels in the postsynaptic
cell
▪ Measure flow of ions by change in voltage
▪ In postsynaptic neuron thees a change of voltage
▪ More depolarized excitatory and less depolarized inhibitory
find more resources at oneclass.com
find more resources at oneclass.com
o Measure strength of synapse between two cells, using electrodes in postsynaptic
cell.
• Evidence that in aplysia a synaptic change underlies behavior?
o Cellular analogue of sensitization
o Motor neuron of withdraw of siphon and sensory neuron receding to touch
▪ Neurons have direct connection between them
▪ You can mimic touch of siphon by stimulating siphon nerve
▪ Mimic shock of animal if you stimulate connective
o In invertebrates, neurons do well when you take them outside of the animal
• Non-associative memories
• Depression and Facilitation
o Changed synaptic strength between sensory and motor neurons
o Depression decreased the size of the EPSP and cellular depression underlies
habituation
o Increase in EPSP between sensory and motor neuron partially underlies increase
in defensive reflex
▪ Sensitization behavior is underlying cellular facilitation
• Serotonin is the facilitation transmitter
o 5-HT stands for 5 hydroxytryptamine
o Acronyms are important to know
o If you remove serotonergic neurons with toxin you decrease amount of
sensitization animal saw after shock
o Neurons encoding serotonin after shock showed increased firing
o Evidence that shock could be replaced by serotonin
• Sensory to motor neuron synapses and facilitation
o Touch siphon, activate siphon sensory neuron
o Connects to motor neuron and causes gill withdrawal
o Firing synapse repetitively leads to depression
o Serotonin is necessary and sufficient to cause the increase of synaptic strengths
which underlie sensitization.
• Reductionist culture system
o you apply serotonin once you get a short-term memory and if you apply it in a
spae ae oe ties just like ou do i the aial oull get a log-term
memory
• Links behind behaviors and cellular properties
o Behavioral habituation: the repeated touches leads to the decrease of withdrawal
o Cellular depression: leads to less release and the decrease of the EPSP to motor
neuron
o Behavioral sensitization: leads to the increase of the withdrawal
o Cellular facilitation: leads to an increase in transmitter release, and an increase of the
EPSP to the motor neuron.
• The point of this
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Identifiable between preparations: rodent systems are more difficult because each neuron is doing 10 different things, aplysia neurons only do one thing each, allows for easier tracing. If you touch animal repeatedly then this behavior disappears. Ipsp inhibitory: aps cause presynaptic cell to release neurotransmitter, neurotransmitter acts as a ligand to open channels in the postsynaptic cell, measure flow of ions by change in voltage, more depolarized excitatory and less depolarized inhibitory. In invertebrates, neurons do well when you take them outside of the animal: non-associative memories, depression and facilitation, changed synaptic strength between sensory and motor neurons, depression decreased the size of the epsp and cellular depression underlies habituation. Increase in epsp between sensory and motor neuron partially underlies increase in defensive reflex: sensitization behavior is underlying cellular facilitation, serotonin is the facilitation transmitter, 5-ht stands for 5 hydroxytryptamine, acronyms are important to know.
