Engram Flashcards

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.