NRSC4032 - Chapter 14: Hunting for Engrams

____ is used to temporally control when a neuron can be tagged

DOX

The study of neural dynamics by Inokuci's group (Gandour et al.) revealed several important discoveries. Describe two.

Not all ensembles activate by the learning experience were activated by the retrieval test. Only ensembles active during sleep became were activated by retrieval.

How did Josselyn demonstrated that neurons that overexpress CREB became engram cells?

She coinfected these cells with an inducible diphtheria toxic receptor and after the fear memory was established she administered the diphtheria toxin that selective killed only those cells with the receptor. This treatment eliminated the memory.

Why does the optogenetics method require the use of a viral vector system.

The viral vector system delivers the ChR2 gene.

What is the role of CREB in determining what neurons are selected to become engram cells.

Then intrinsic excitability of neurons expressing CREB is higher than other neurons. This property enables CREB-expressing neurons to out compete the other neurons in the competition for participating in the engram.

How was Mayford able to temporally control when neurons in TetTag mouse could be labeled with the fluorescent tag?

This was possible because when Dox was in the drinking water the processes needed to activate the tag were not available. So, the cells could only be labeled with Dox was removed.

In the optogenetics experiment what was the role of the blue light?

To activate neurons expressing ChR2 and theoretically to activate the engram.

In the optogenetics experiment what was the role of DOX?

To temporally control when the ChR2 gene could be expressed.

(T/F) All neurons activated by the learning experience will become engram cells that support the memory.

false

(T/F) If a brain lesion of a particular regions disrupts memory storage or retrieval it can be concluded that this region contains engram cells.

false

(T/F) If engram cells is deleted this should have no effect on retrieval.

false

(T/F) If following a retrieval test a neuron expresses a marker for an immediate early gene, it can be concluded that this neuron is an engram cell.

false

(T/F) Immediate early genes can serve as markers or tags for neuron activated by a behavioral experience.

false

(T/F) Karl Lashley invented the term engram?

false

(T/F) Regarding the TetTag mouse, if a neuron expresses the marker a time of the behavioral retrieval test then it can be concluded that it is an engram cell.

false

The TetTag mouse was an improvement over the sole use of the immediate early gene Arc to tag cells because

immediate early gene markers do not persist, the tag established during learning can persist for many days in the TetTag mouse, and the TetTag mouse permits temporal control over when the tag can occur.

The increased excitability of CREB expressing neurons enables them to _______other neurons and prevent them from becoming engram cells.

inhibit

Optogenetic stimulation is critical in the search for engrams because

it is critical to tagging neurons. This method also allows for the activation of tagged engram neurons that responded to behavioral training

What would be your conclusion if there was no overlap in the cells tagged by the training experience and those labeled by the retrieval test.

no engram cells were identified

Neurons that ________ CREB win in the competition for becoming engram cells

overexpress

What should happen during the retrieval test if engram cells are inhibited.

performance of the test will be impaired

In order to conclude that a neuron is an engram cell it must be activated by the learning experience and by ________.

retrieval

(T/F) An engram is the physical basis of a memory.

true

(T/F) Brain lesions can be considered as a starting point for locating engrams.

true

(T/F) Hebb's concept of a cell assembly is still generally accepted as correct

true

(T/F) If following a retrieval test a neuron expresses a marker for an immediate early gene and the fluorescent marker, it can be concluded that this neuron is an engram cell.

true

(T/F) In order to conclude that a set of neurons are engrams, these neurons must be active both by the learning event and by the retrieval test.

true

(T/F) Neurons that overexpress CREB win in the competition for becoming engram cells because their intrinsic excitability is increased.

true

(T/F) Richard Simon invented the term engram

true

(T/F) The term ecphory is roughly equivalent to the term retrieval.

true

(T/F) cells expressing CREB inhibit those cells not expressing CREB.

true

Neuronal sub-ensembles activated by the learning experience but not replayed during sleep ________ become engram assembles.

will not