Engram Flashcards

Questions and Answers

What is an engram?

Memories defined by a constant set of neurons.

When are engrams active?

During encoding and retrieval.

What is CREB?

CyclicAMP Response Element Binding Protein.

What is the effect of CREB on engram formation?

It increases a neuron's likelihood of being incorporated in an engram. Signup and view all the answers

How did Sheena Jocelyn selectively ablate CREB cells of the engram?

Using Cre-dependent DTR toxicity mice injected with CREB/Cre in certain cells. Signup and view all the answers

What was the effect of selectively killing CREB producing neurons?

Memory loss occurred only when those neurons were selectively killed. Signup and view all the answers

What is used as a promoter in the Ramirez Tet-tag system?

c-fos. Signup and view all the answers

When is viral tagging possible in the Ramirez Tet-tag system?

When the window is open (no antibiotics / no food). Signup and view all the answers

What is the effect of stimulating the context A engram while fear-conditioning in context B?

Fear during context A, even though nothing bad happened there. Signup and view all the answers

How does context B retrieval compare in mice fear conditioned in context B with and without context A activation?

Without A activation: high freezing with A light off; lower freezing with A light on. With A activation: low freezing with A light off; higher freezing with A light on. Signup and view all the answers

Study Notes

Engram Overview

Engrams are defined as a specific set of neurons that represent memories.
Engrams are active during the processes of encoding and retrieval, but not during the storage phase.

CREB and Memory Formation

CREB stands for Cyclic AMP Response Element Binding Protein; it functions as a transcription factor.
CREB enhances the probability of neurons becoming part of an engram, promoting memory formation.

Selective Ablation of CREB Cells

Sheena Jocelyn utilized Cre-dependent diphtheria toxin receptor (dtr) mice to selectively ablate CREB-expressing cells.
Mice underwent training and testing phases, followed by targeted cell poisoning, leading to memory loss only when specific CREB-producing neurons were destroyed.

Ramirez Tet-tag System

The c-fos gene is employed as a promoter in the Ramirez Tet-tag system.
Viral tagging occurs only when specific conditions are met, such as the absence of antibiotics and food, creating an open window for manipulation.

Conditioning and Contextual Fear

In the Ramirez Tet-tag study, activating the context A engram during fear conditioning in context B led to a fear response in context A, despite there being no aversive events in that context.

Context Retrieval and Freezing Behavior

Mice fear-conditioned in context B showed distinct freezing behaviors when tested:
- In the absence of context A activation during fear, mice exhibited high freezing with A light off, but lower freezing when A light was on due to the activation of a positive memory of context A.
- When context A was activated during fear conditioning, mice displayed lower freezing with A light off (reflecting incomplete activation of the positive context) and increased freezing with light on, aligning with the original conditioning context.

Description

Test your knowledge on engrams and their role in memory formation with this flashcard quiz. Topics include the definition of engrams, the function of CREB, and its impact on memory encoding and retrieval.