0828 - Synaptic Plasticity - Learning and Memory Flashcards
Distinguish nondeclarative and declarative memories
Declarative - Items are available to consciousness and can be expressed by language (phone numbers, images, songs)
Nondeclarative - Not directly available to consciousness (skills, associates, cues). Difficult to express how such procedures are enacted.
Outline key features of neuronal memories
Networked and distributed (not in one spot) and formed via synaptic plasticity and changes in cell excitability.
Structural changes to the neuron - growth and pruning of dendrites/spines.
Consolidation of memory required to achieve storage.
What is the difference between immediate, working, and long-term memory?
Immediate - retention for less than 1s. Large capacity for the senses, and short-term plasticity.
Working memory - seconds to minutes - Holding of experience to achieve behavioural goal (e.g. look for lost item)
Long-term memory - Long term retention via engram (structural network where information is physically laid down). Requires transfer from working memory via consolidation.
Formation of memories depends on motivation and association.
How does attention and motivation affect memories?
The capacity to remember things that interest us is very large. Neuromodulators work to ensure that experiences gained under stress are easily remembered and in great detail.
How does forgetting affect memories?
Items of no importance are forgotten - unused memories deteriorate over time.
Essential mental process to prevent us focusing on ‘trivia’ to the point of preoccupation/incapacitation.
What are the two forms of amnesia?
Anterograde - can’t form new memories.
Retrograde - inability to retrieve already-made memories. Correlated with hippocampus damage.
What systems are involved in declarative memory?
Hippocampus and para-hippocampus involved in short-term and laying down new memories. It encodes and buffers (short term storage), but not storage site. Laid down in association cortices and frontal lobes, but not stored in one place - distributed within networks. However, Wernicke’s area codes for words, and temporal cortex for objects, faces etc.
What systems are involved in non-declarative memory?
More complex and much more integrative than declarative.
Short term storage not known, probably widespread. Longer-term, basal ganglia, premotor cortex, cerebellum, amygdala, and somatosensory cortex. Also requires dopamine as key neuromodulator.
How does memory consolidation occur during sleep?
Sleep improves both non- and declarative learning. Needs NREM deep sleep in the fourth quarter (towards morning) to lay down the memory. Sleep deprivation causes a large drop in performance improvement compared to the same subjects with adequate sleep.
Neuronal connections in hippocampus while sleeping mimic those that were active when completing a task, essentially ‘replaying it’ as it shifts into the entorhinal and neocortex.
Not known how it happens at molecular level.
What are the mechanisms involved in long-term potentiation?
Several different mechanisms. This relates only to Hippocampus CA1.
Induction - immediate via Ca++ in post-synaptic cell via NMDA receptors.
Expression - Within seconds. Ca++ activates kinases (CaMKII, PKC). Phosphorylate AMPA receptors to get them inserted into membrane, increasing current (Na?). NO-synthase also activated, diffiusing back to presynaptic terminal and increasing transmitter release. General excitability increase.
Maintenance - CaMK II can autoactivate. Protein synthesis is activated via PKA and PKC, activating gene cascades to alter gene expression.
What are the molecular mechanisms involved in long-term depression?
Essentially reversal of LTP - uses phosphatases instead of kinases, leading to dephosphorylation and depression.
Induction - Lower concentrations of Ca++ activating Ca-dependent phosphatases.
Expression - Phosphatases reduce expression of AMPA receptors, ultimately reducing synaptic efficacy.
Maintenance - unknown.
What are the key properties of long-term potentiation?
Input specificity - only stimulated synapses potentiate, not all of them.
Associativity - When a weak input is insufficient, a strong stimulation of another input induces LTP at both inputs.
Cooperativity - Several small inputs which are individually insufficient can get it.
