Optogenetics, Engrams, and Total Recall

clips/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 (Gelbard-Sagiv et al., Science, 2008) A specific memory of object, person, or event can be stored in a specific set of neurons. (Quiroga et al., Nature, 2005) Halle Berry or

The Neural Cartographer ~5% of patients reported vivid recall of memories, recent and distant, and sometimes even hallucinations after temporal lobe stimulation present

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 1.Find and label a memory engram. 2.Turn it on and off by a switch. Two easy steps of memory control:

What kind of memories Would you want? fml

How algae changed neuroscience

Channelrhodopsin can activate neurons with millisecond resolution Halorhodopsin can inactivate neurons at the same timescale

In Vivo applications

Activity-dependent and inducible optogenetics c-fos ChR2 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 TRE Gene Of Interest tTA c-fos promoter tTA Protein DOX

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? In Search of the Engram 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… (Martin and Morris, 2002) …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.”

Labeling Engram-bearing Cells Used to induce activity- dependent labeling in the hippocampus. Behavior eYFP TRE ChR2 tTA Fos-prom tTA DOX ChR2

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 A Technique for Activity-dependent Labeling and Rapid Manipulation BOO

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 8fAuI Try it yourself!

Behavioral Test: Contextual Fear Conditioning Context A TrainingTesting Context A Context B Day 1 Day 2 Context A Context B Freezing No Freezing Context B Freezing?

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 + Experimental N = 12: Label cells with fear conditioning + Control 2 N = 12: No Shock (NS) Label a similar proportion of cells but these animals do not receive a shock +

=3YG4h5GbTqU The world that a tiny cue Can bring back to life

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)

=O0mApp-2Plo Total Blah ending Can we activate more complicated memories?

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?