Memory Flashcards
What is Santiago Ramon y Cajal’s theory of memory storage?
That memories are stored via physical changes to neurons.
What is Holger Hyden’s RNA theory of memory?
That in order for there to be physical change to neurons, there must be gene transcription, RNA and protein production.
What 3 conditions must be met according to Hebbian theory in learning?
- Homosynaptic plasticity: the strengthening event and synaptic strengthening must occur at the same time
- Association: the firing of the pre and post-synaptic neurons must be closely correlated in time
- Input specificity: the connection must be distinct from the other 50,000 connections each neuron has
What did work by a) Seymour Benzer and b) Eric Kandel demonstrate about short-term memory?
a) That it involves signal transduction cascades (created drosophila mutants)
b) That it involves existing enzymes to increase NT release (worked on sea snails)
What is the signalling cascade in short-term memory? Use 5HT transmission as an example.
5HT binds its GPCR. The GPCR activates adenylate cyclase. Adenylate cyclase causes the formation of cAMP. cAMP activates PKA. PKA increases NT release.
Long term memory requires RNA synthesis. This was demonstrated in work by Seymour Benzer on drosophila. What difference is there in the signalling cascade in short and long-term memory?
In LTM the cascade is the same, with the addition that PKA’s catalytic subunit 5L translocates to the nucleus and phosphorylates genes, causing transcription. This causes lasting effects by permanently increasing NT release.
There are 2 types of memory. What are they?
- Declarative: memories can be expressed, e.g. episodic or semantic.
- Non-declarative: memories are procedural (non-verbal)
What are the 4 stages in memory?
- Acquisition
- Consolidation
- Retrieval
- Extension
Describe memory acquisition.
STM is encoded by the hippocampus.
Describe memory consolidation.
There are 2 stages: first there is synaptic consolidation, or strengthening, in the hippocampus. Secondly there is systems consolidation whereby the memory trace is transferred to the neocortex for storage. In consolidation, STM becomes LTM.
When can the process of consolidation be observed?
During sleep in the phenomenon of replay, e.g. place cell activity.
What is the basis of memory extension?
Multiple trace theory: each time you are presented with information, the memory is neutrally encoded in a unique memory trace which is a combination of its attributes.
Basically each time you encounter something, the memories of that encounter are added to the catalogue of memories you already have of that thing.
How is memory organised in the brain?
Synapses are the outputs of memory, thus memory circuits are distributed around the brain.
A memory involves only a single synapse. True or false?
False: a single memory involves multiple synapses.
What evidence is there for numerous mechanisms acting in memory formation?
New memories can be made in under a second, and some memories last for years.
STM involves existing enzymes to modulate NT release, showing that in STM existing synapses are modified. How do we know new synapses are not created in STM?
A new synapse cannot form in under a second, as new memories can.
If synapses are the outputs of memory, strengthening a synapse will increase its output and thus the strength of the memory trace. List 3 ways in which this can be achieved.
- Increasing the no. of post-synaptic receptors
- Changing the properties of the receptors
- Increasing neurotransmission
