Lecture 26 - Engrams Flashcards
Module 4 (21 cards)
____ is the enduring offline physical and/or chemical changes that were elicited by learning and underlie the newly formed memory associations.
Engrams
____ ____ are cells that constitute critical cellular components of a given engram (which may or may not also be critical components of engrams for other memories)
engram cells
3 characteristics of engram cells:
1. Activated by a ____ experience
2. physically or chemically modiefied by it (have ____)
3. reactivated by subsequent presentation of the ____ present at the learning experience, resulting in memory ____
- learning
- plasticity
- stimuli; retrieval
____ ____ ____ is the collection of engram cells localized within a brain region
engram cell ensemble
____ ____ is the entire brain-wide engram supporting a memory that is stored in sets of engram cell ensembles in different brain regions connected via an engram cell pathway
engram complex
What was one of the reasons why Karl Lashley didn’t find the engram?
He didn’t lesion the hippocampus, where distributed suset of neurons represent a given environment or experience (distributed representation)
What did researchers find when they ablate random neurons vs. engram neurons after fear conditioning?
There was no difference between memory of the fear conditioning when random neurons were ablated, but memory became poorer when engram cells that coded for the memory were lesioned
____ ____ ____ (IEGs) are genes that are rapidly (~5-30min) and transiently expressed in response to neural activation - often associated with neural ____
Immediate early genes; plasticity
What are two examples of IEGs?
c-Fos and Arc
When a rat runs in a novel open field, the set of ____ cells that represent that environment will express high levels of ____ (IEG), which can be used to identify ____ cells.
place; c-Fos; engram
In ____, light sensitive proteins (opsins) are engineered to be expressed in specific populations of neurons to respond to wavelengths of light. Some opsins inhibit neurons (____), while others excite neurons (____). This is considered to be a ____ lesion.
optogenetics; halorhodopsin; channelrhodopsin; reversible
Steps of “tagging” an engram
1. A virus injected into the ____ ____ of the hippocampus
2. The virus invade neurons there and generate optogenetic protein ____ (ChR2) when 2 conditions are met:
2.1. neurons must express ____ (=those that still have plasticity)
2.2. “off” ____ (a drug provided in the animal’s food that stops optogenetic protein from being made)
- dentate gyrus
- channelrhodopsin
2.1. c-Fos
2.2. doxycycline
What happens when a mouse has its engrams tagged in context A (off Dox), then exposed to fear conditioning on Dox, and then exposed to context A again?
The mouse will freeze in response to the “conditioned” context (->”tagged” engram cells were conditionally paired with shock)
What happens when a mouse has its engrams tagged in context A (off Dox), then exposed to fear conditioning on Dox, and then exposed to a novel context?
The mouse will not freeze (->”tagged” engram cells doesn’t recognize this environment and thus doesn’t retrieve info about shock)
While research has shown that ____ ____ is responsible for engram availability (tagging engrams there creates stronger “false memory” than using cells in the CA1), the ____ can be activated by both real and false fear memory recall.
dentate gyrus; amygdala
In a 3 box test, the rat would avoid the side where they had ____ tagged and ____ conditioned in, suggesting an artificial association between them.
engrams; fear
In an experiment where mice were tagged wth positive/neutral/negative memory, researchers found that mice with ____ memory tagged&activated showed more time struggling in the ____ ____ ____ (TST) and more preference for sucrose in ____ ____ ____ (SPT), suggesting positive memory can leviate ____-like behavior.
positive; tail suspension test; sucrose preference test; depression
In an experiment where mice were tagged wth positive/neutral/negative memory, researchers found that mice with ____ memory tagged&activated showed no change in average time in centre and duration in open arms, suggesting positive memory had no impact for ____-like behavior.
positive; anxiety
Aside from tagging positive memories and activating them later, ____-like behavior could also be ameliorated by ____ stimulation of the positive memory ____ outside of the performance of the tasks
depression; chronic; engrams
In a study called “Brain-wide mapping reveals that engrams for a single memory are distributed across multiple brian regions”, they found that ____ and ____ ____ are part of the engram, while primary ____ cortex and ____ ____ are not.
hippocampus; basolateral amygdala; visual; mediodorsal thalamus
In a study called “Cold memories control whole-body thermoregulatory responses”, experimenters tagged neurons activated during exposure to ____ temperature, and activated then when the mouse is in ____ temperature. They found that the activation results in ____ compensatory bodily responses.
cold; warm; thermoregulatory
