Chapter 7 Flashcards
(29 cards)
What comprises the neurobiology of memory?
Identifying where and how different types of information are stores
What is Hebbian Plasticity (Hebb)
The concept that memory results from synaptic modifications
How do we acquire a short term memory?
- Physical modification of brain caused by incoming sensory information
- Modifying synaptic transmission between neurons
How do we consolidate a long-term memory?
- Requires new gene expression and protein synthesis
- Protein synthesis inhibitors: deficits in learning and memory
What does the neural network model show us?
Unique pattern or ratio of activity of neuronal activity
- Distributed memory
- No single neuron represents specific memory
*Advantage: Memories survive damage to individual neurons
Physical change of memory leads to….
Modification of synaptic weight
Gradual neuron loss leads to…
Graceful degradation of memories
Patient Henry Molaison (H.M)
- 1926-2008
- Start developing seizures at the age of 10, becoming progressively more frequent and severe with age including convulsions, tongue biting, and loss of consciousness
- In 1953 at age 27, surgical procedure was performed, removing 8 cm length of the medial temporal lobe including the cortex, underlying amygdala, and 2/3s of the hippocampus
- Surgery was successful in alleviating seizures, but left him with severe anterograde amnesia and inability to form new memories
What 2 components does synaptic plasticity consist of?
- Long-term potentiation (LTP)
- Long-term depression (LTD)
What is the trisynaptic circuit of the hippocampus?
- Entorhinal cortex-> dentate gyrus (perforant path) synapses
- Dentate gyrus->CA3 (mossy fiber) synapses
- CA3-> CA1 (Schaffer collateral) synapses
What do glutamate receptors mediate?
Excitatory synaptic transmission
- NMDA receptors and AMPA receptors
Calcium influx through NMDA receptors triggers alteration in AMPA receptors. What is the sequence of events of this?
- Activation of kinases that phosphorylate AMPA receptors already at the synapse (this increases permeability)
- Calcium mediated insertion of additional AMPA receptors at the synapse
What produces homosynaptic long term depression (LTD)?
Low frequency electrical stimulation (tetanus - 1 Hz) of excitatory pathway
There are two forms of homosynaptic LTD receptors at Schaffer collateral-CA1 synapse. What are they?
- G-protein coupled with metabotropic glutamate receptors (mGluRs)
- NMDA receptors
***Rise in postsynaptic [Ca2+] is necessary to trigger LTD
What 2 rules govern the bidirectional plasticity of LTP vs. LTD?
- Synapses during strong depolarization of postsynaptic neuron causes LTP
- Synapses during weak depolarization of postsynaptic neuron causes LTD
Postsynaptic membrane at resting potential
Postsynaptic membrane at depolarized potential
What protein can trigger both LTP and LTD in the hippocampus?
Ca2+
How does phosphorylation serve asa long-term memory consolidation mechanism?
Phosphorylation is insufficient as long term memory consolidation mechanism
- Phosphorylation of a protein is not permanent, so memories would be erased
There are other mechanisms needed for long-term consolidation
Ex: protein synthesis, structural changes
What is long term memory associated with?
The formation of new synapses
Altering visual or tactile environment stimulates formation of new dendritic spines
Ex: rat in a complex environment shows increase in number of neuron synapses by about 25%
Dynamic structural plasticity is evident in the developing brain, influenced by stimuli
There are limits to structural plasticity in the adult brain, but the end f a critical period does not necessarily signify an end to structural changes
