Transcript Total Recall - The Ramirez Group

Optogenetics, Engrams, and Total Recall
http://www.wingclips.com/movieclips/total-recall/something-more
Objective vs subjective reality
In 3 minutes come up with a story
of memories you’d implant in a group
member
Today’s Forecast
1) Beginning
a: Engrams in the brain
b: Combining optogenetics and transgenics
2) Middle
a: Optically activating a hippocampal engram
3) End
a: Quiz
The kinds of memories worth having
Memory Engrams in the Brain
•We all have a brain.
•We all have memories.
•How are memories stored in the brain?
Engrams are a hypothetical means
by which memory traces are stored
as biophysical or biochemical
change in the brain (and other
neural tissue) in response to
external stimuli.
Wikipedia
The Halle Berry Cell and the Homer Simpson Cell
or
(Quiroga et al., Nature, 2005)
or Halle
Berry
(Gelbard-Sagiv et al., Science, 2008)
A specific memory of object, person, or event can be stored in a specific set of neurons.
The Neural Cartographer
~5% of patients reported vivid recall of memories, recent and distant,
and sometimes even hallucinations after temporal lobe stimulation
http://www.wingclips.com/movie-clips/total-recall/heart-is-in-thepresent
http://www.youtube.com/watch?v=zj8oa
5lj2Ik
Waking up in a “memory”
Group Exercise
Let’s say someone you know just wants to live in these artificial
memories because they’re much more exciting than average
life.
Moreover, this person argues that since you’re just your
brain’s chemistry, it’s just as real to to him/her and it’s the
reality they choose to live in. What is your response?
How to Activate a Memory Engram
Two easy steps of memory control:
1. Find and label a memory engram.
2. Turn it on and off by a switch.
fml
http://www.youtube.com/watch?v=CqDkDyA7QHE
What kind of memories
Would you want?
How algae changed neuroscience
PRO GRESS
PRO GRESS
Protein expression in neuron subtypes
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Activation
Activation
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Channelrhodopsin can activate neurons with millisecond resolution
Halorhodopsin can inactivate neurons at the same timescale
In Vivo applications
Activity-dependent and inducible optogenetics
ChR2
tTA
c-fos promoter
c-fos
tTA
DOX
tTA
TRE
Gene Of Interest
Protein
ChR2 makes cells
responsive to light
c-Fos is only expressed in active neurons
Dox can open and close windows
for expressing a given gene
In Search of the Engram
• A question of sufficiency:
• Is it possible to tag a specific neural network that was naturally involved in
learning an event , and to then to repeatedly reactivate and reproduce
(mimic) the associated behavior?
• How to label cells active during 1 memory
• Activity-dependent gene promoters (c-fos)
• How to activate these cells rapidly
• Channelrhodopsin-2 (ChR2) coupled with (c-fos promoter)
• How to make sure only 1 memory is labeled
• Dox system to regulate the expression of c-fos-driven ChR2
“The final test of any hypothesis concerning memory
encoding and storage must be a mimicry experiment, in
which apparent memory is generated artificially without
the usual requirement for sensory experience…
…In one sense, such an experiment would constitute
a practical demonstration of the fact that we really do
understand how memory works, in the same way that
successful engineering feats validate our hypotheses
about the nature of the physical world.”
(Martin and Morris, 2002)
Labeling Engram-bearing Cells
tTA
Fos-prom
DOX
tTA
tTA
TRE
eYFP
ChR2
ChR2
Used to induce activitydependent labeling in the
hippocampus.
Behavior
A Technique for Activity-dependent
Labeling and Rapid Manipulation
•
•
•
•
•
•
•
•
Rapid
Engram labeling using a
Doxycycline
Suppressible and
Optogeneticically-modulated
C-fos driven
Knock-in
System
A Technique for Activity-dependent
Labeling and Rapid Manipulation
•
•
•
•
•
•
•
•
Rapid
Engram labeling using a
Doxycycline
Suppressible and
Optogeneticically-modulated
C-fos driven
Knock-in
System
Today’s Forecast
1) Beginning
a: Studying memory in animals
b: Combining optogenetics and transgenics
2) Middle
a: Optically activating a hippocampal engram
3) End
a: A proposed model and future plans
Dwight is like a mouse
http://www.youtube.com/watch?v=nE8pFWP5QDM
http://www.youtube.com/watch?v=Eo7jcI
8fAuI
Try it yourself!
Behavioral Test: Contextual Fear Conditioning
Training
Day 1
Testing
Day 2
Freezing
Context A
Context A
Context A
No
Freezing
Context B
Freezing?
Context B
Context B
Group Exercise
What is a good control for this experiment?
In other words, what experiment (or variation of this
experiment) could we do that would truly let us know light is
reactivating a fear memory and not doing something else?
Experimental and Control Subjects
Control 2
N = 12: No Shock (NS)
Label a similar
proportion of cells but
these animals do not
receive a shock
Experimental
N = 12:
Label cells
with fear
conditioning
+
+
+
The world that a tiny cue
Can bring back to life
http://www.youtube.com/watch?v
=3YG4h5GbTqU
Total Recall for Mice?
Fear memory

ChR2 label

Light-induced freezing ✔

Fear memory

ChR2 label
Light-induced freezing ✖
Conclusion: Reactivating hippocampus cells that were active during the
formation of a fear memory caused the recall of the fear memory.
Significance: This is the direct proof that memory engram-bearing cells
are sufficient for memory recall.
(Liu & Ramirez et al., Nature, 2012)
Can we activate more complicated memories?
Total Blah ending
http://www.youtube.com/watch?v
=O0mApp-2Plo
OMG QUIZ
____________ is a protein activated by blue light
____________ is a protein activated by yellow light
Which one turns brain cells on? Which one off?