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Talking Back to the Brain: How neuroscientists
use light to uncover the language of neurons
October 23, 2013
Introduction
Studying the brain is like learning a foreign language – the language by which neurons communicate.
Neuroscientists have made great progress by listening in on the neurons’ conversations. But, to be sure that
we understand their language correctly, we have to be able to talk back to the neurons and then study their
reaction. Optogenetics is a revolutionary new research technique that allows us to do exactly that. This
technique equips neurons with the ability to sense light and convert it into the neuronal language of
electrical impulses. Tonight, we start out with some background on the way neurons communicate with each
other in the brain. We will then introduce optogenetics and how we can use it to manipulate the activity of
specific neurons with flashes of light. Finally, we will dive into a few ingenious studies that used
optogenetics to understand how neurons work together to give us the ability to think and act.
Speakers
Andrea Yung grew up in the Bay Area and received her B.S. in Biology from
Stanford University. She is a second year graduate student in the Program in
Neuroscience and recently joined the lab of Lisa Goodrich, where she will study
how neural circuits are assembled in the inner ear to form the basis of how we
hear. In her free time, Andrea enjoys cooking and exploring bookstores and
restaurants in Boston. Christina Welsh is a second year graduate student in the Harvard Program in
Neuroscience. She is a member of the Stevens lab, where she studies the
interactions between synapses and immune cells in the healthy brain. Specifically,
she is interested in how neuronal activity affects immune cell function, and she
pursues this question using both in vitro models and live imaging in mice. When not
in lab, Christina enjoys reading about history, going to concerts, and practicing far
too little piano.
Matthias Minderer is a graduate student in Dr. Christopher Harvey’s lab at Harvard
Medical School. He studies how individual neurons cooperate to store short-term
memories and make decisions. Working with animals trained to solve memory tasks,
optogenetics allows him to change the activity of a few neurons during the
formation of a memory, with the goal to understand how each neuron contributes
to the overall result. Matthias is from Munich, Bavaria, and studied in England and
Switzerland before coming to Boston. In his free time, he likes to conduct research
in comparative beer culture.
Glossary of Important Terms
Action potential: A stereotyped electrical impulse generated by the movement of positive ions into, then out of, a
neuron. Such impulses are the words in the language of neurons.
Amygdala: Brain structure of higher vertebrates (including humans) that has a primary role in the control of emotions.
Axon: Wire-like appendages that neurons use to send out impulses (axons make synapses onto dendrites).
Channelrhodopsin: A protein that can be artificially introduced into neurons to give them the ability to convert light
into electrical impulses.
Dendrite: Wire-like appendages that neurons use to receive impulses from other neurons (axons make synapses onto
dendrites).
DNA: Genetic material of cells. Contains instructions for cells to make almost everything they need to function.
Electrode: Metal needle that neuroscientists use to measure the membrane voltage and action potentials of neurons.
Can also be used in reverse to lead electric current into the neuron and thereby stimulate it to fire action potentials.
Excitatory: Describes a neuron or neurotransmitter that makes other neurons more likely to send an impulse.
Inhibitory: Describes a neuron or neurotransmitter that makes other neurons less likely to send an impulse.
Ion: Electrically charged molecule.
Ion channel: Openings in the membrane that surround all cells to allow and control the flow of ions. The membrane is
otherwise impermeable to ions.
Membrane voltage: Electrical force due to the imbalance of ions inside and outside of a neuron. This voltage is
affected by neurotransmitters and changes rapidly when the neuron “fires” an action potential.
Neuron: Nerve cell.
Neurotransmitter: Chemicals that neurons use to send signals from one neuron to another across synapses. E.g.
serotonin, dopamine, acetylcholine.
Optogenetics: Technique that give neurons the ability to convert light into electrical signals.
Synapse: A connection between the axon of one neuron and the dendrite of another neuron. Signals are sent from one
neuron to another through this connection.
Resources to learn more
1. The Optogenetics Wiki, a collection of articles about how optogenetics works and was developed
http://www.openoptogenetics.org/index.php?title=Press,
2. Carl E. Schoonover and Abby Rabinowitz, “Control Desk for the Neural Switchboard,” an article about the research
Matthias discusses www.nytimes.com/2011/05/17/science/17optics.html?pagewanted=all&_r=0,
3. Eric R. Kandel, “The New Science of Mind,” An op-ed by Nobel Prize winning neuroscientist Eric Kandel about our
growing understanding of neuropsychiatric diseases
http://www.nytimes.com/2013/09/08/opinion/sunday/the-new-science-of-mind.html?pagewanted=2,
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