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Neurons that can affect the activity in entire brain regions rather than just a single synapse

--> alter/modulate how neurons transmit + receive signals
--> many diseases that affect learning + memory involve a decline in neuromodulators

ex.: Alzheimers --> reduction in acetylcholine


Synaptic plasticity

The ability of synapses to change as a result of experience

--> learning involves a strengthening/weakening of connections between neurons


Hebbian learning

Two cells that send impulses simultaneously to the same region, will tend to make connections to intermediate cells in common, then no longer act independently

--> the repeated stimulus will thus be more likely to be recognized

"Neurons that fire together, wire together"


How will Hebbian learning help, if one encounters an incomplete version of a familiar stimulus ?

The connections already established through repeated experiences will produce outputs that complete the familiar pattern


Long term potentiation

Refers to the effect when a synaptic transmission becomes MORE effective as a result of recent activity

--> changes can last for hours/days


Long term depression

Occurs when synaptic transmission becomes LESS effective as a result of recent activity

--> connections between neurons that don't fire together weaken
--> opposite to LTP


Cell assemblies

Refer to large groups of cells that tend to be active at the same time because they have been activated simultaneously in the past

--> can encode many different memories with each neuron participating to a greater or lesser extent in a particular memory


Which synaptic changes occur to store memories ?

1. Training results in an increased release of neurotransmitter molecules

2. Increased size of PSP

3. Postsynaptic membrane will have a larger response to same amount of NT release, due to its bigger size

4. Neural circuit increases the number of synaptic contacts

5. More frequently used synapses survive, less used die


Hebbian synapses

Refers to a synapse that uses a time-dependent, highly local, and strongly interactive mechanism to increase synaptic efficacy


Dual trace hypothesis

Formation of a memory involves a brief, transient process:

1. Experience sets up activity that reverberates through the activated neural circuits (STM)
--> held for a short period

2. If sufficient, this activity will lead to stable changes in NS (LTM)


Which were the 3 most common laboratory environments for experiments ?

1. Standard condition (SC)
--> 3 animals kept in stand. laboratory w/ food + water

2. Impoverished/Isolated condition (IC)
--> 1 animal kept in SC-sized cage

3. Enriched condition (EC)
--> 10-12 animals kept in large cage containing a variety of stimulus objects, changed daily


Which cognitive results did the brains of the animals kept in the EC yield ?

1. Greater activity of the enzyme acetylcholine

2. Thicker cerebral cortices

3. Alteration of the expression of a large number of genes
--> may play important roles in learning + memory

4. Increase in synaptic connections + more elaborate information processing circuits


Where is memory stored ?
Where is information processed for memory storage ?

Stored: Cerebral cortex

Processed: Other brain regions (Hippocampus etc)


Process of the induction of LTP

1. Glutamate is released at synapse that has AMPA + NDMA receptors

2. Stimulation will first only activate AMPA receptors
--> NMDA don't respond, due to blockage of Mg ions

3. Sufficient activation of AMPA receptors in same neuron will partially depolarize the membrane, removing Mg+ block

4. NDMA receptors now actively respond to glutamate, thus admit large amounts of Ca+

5. Protein kinases are activated as a result, which change the properties of many proteins

6. CaMs increase the number of AMPA receptors on PS site

--> Membrane will give a larger response to the same weak signal


Portein kinases

Enzymes that catalyze phosphorylation

--> blockage of the kinases can prevent the induction of LTP

(Ca-calmodulin (CaM), Protein kinase a/c)



Adding the element phosphor to an organic molecule

--> changes the properties of the molecule


Calcium-Calmodulin kinase

Remains active once it is put into that state by Ca2+, even if the level of Ca2+ falls

--> plays a main role in maintaining LTP


In which ways does CaM affect AMPA receptors ?

1. Increases the conductance of AMPA receptors already present in the membrane

2. Promotes the movement of the AMPA receptors from the interior of the spine into the membrane

--> more receptors are available to stimulate the spine


Immediate early genes

Refer to a class of genes that are rapidly but transiently expressed in response to extracellular signals

--> are expressed within min

ex.: neurotransmitters, NGFs



Its activation leads to an increase in the expression of IEGs, due to transcription

--> Transcription factor


Steps in the neurochemical cascade during the induction of LTP

1. Increase in intracellular Ca2+

2. Activation of protein kinases, which phosphorylate proteins

3. Activated kinases bind to CREB

4. IEGs enter nucleus, + regulate the expression of LEGs

5. Transcription of LEGs leads to synthesis of proteins
--> necessary to induce LTP

6. Proteins are then transported down the axon to alter the response of the neuron to further stimuli


Late effector genes

Genes that are transcribed to produce proteins necessary for the induction of LTP

--> are expressed within hours


Why is Calcium so important in cellular consolidation ?

1. Facilitates processes that can help with the insertion of additional AMPA receptors (Postsyn. membrane)

2. Changes the efficiency of exocytosis of glutamate vesicles (Presyn. membrane)


What needs to happen for a memory trace to be long lasting + stable ?

A condition in which 2 cells are coactivated multiple times needs to be created

--> increase in synaptic strength, which will be permanent


Early LTP/
Synaptic consolidation

Refers to a single burst that will lead to a temporary increase in synaptic efficiency

--> doesn't need gene expression + protein synthesis


Late LTP/
Synaptic consolidation

Refers to a repetition of bursts of electrical activity, leading to a permanent change in synaptic efficiency

--> lasts for days, faster than systems consolidation (min)
--> requires gene expression + protein synthesis


Spacing effect

Distributed learning enhances consolidation

--> learning over the course of 24h will decrease the rate of forgetting


Which are the most important factors in the formation of memories ?

1. Protein synthesis

2. Plasticity

3. Co-activation


What are the preconditions of the hippocampus to be able to play its coordinating role in memory formation ?

1. Hippocampus connects to pretty much everywhere in the brain

2. Initial plasticity between cortical neurons + hippocampal neurons must happen very quickly after the experience


In which way does the role of the hippocampus relate to the one of a tutor ?

By reactivating itself + all neurons connected to it, it co-activates neuron that encode an experience

--> turns them into a memory trace
--> happens during day, especially sleep