MIT imaging technique sheds light on the brain's electrical activity
Researchers at MIT havedeveloped an imaging technique that will help study exactly howelectrical signals propagate through the brain, in an advance thatcould help us better understand Alzheimer's, epilepsy, and otherbrain disorders, as well as how thoughts and feelings are formed.
BrainMRIs offer important insight into how our brains work, but they canonly produce crude approximations of the areas that are activated bya given stimulus. In order to unravel the minutiae of how neuronscommunicate and collaborate to form thoughts and feelings, we wouldneed imaging tools with vastly improved resolutions.
Today,far from being able to tackle the 86 billion neurons in the human brain, neuroscientists must settlefor studying simple organisms like worms and fish larvae (with neuroncounts in the hundreds), relying on slow and cumbersome methods likeimplanting electrodes into brain tissue to detect electrical signals.
This,however, could soon change. The group of researchers led by Prof. EdBoyden at MIT has built on previous work to perfect an imaging technique that provides a much fullerpicture of the brain's activity. When exposed to red light, acarefully selected fluorescent protein bound to the cellular membraneof neurons reacts to electrical signals by lighting up, to reveal theexact neural path of a thought.
Boydenand team developed a sophisticated robot to select the protein amongnearly 10 million candidates and 13point mutations. Therobot injected each protein candidate into a mammalian cell, grew thecells in lab dishes, and took a picture of the results, while asoftware component selected the compound with the best-suitedcharacteristics, including brightness, the protein's location withinthe cell, and its resistance to photobleaching.
Applyingthe protein to zebrafish larvae, the worm Caenorhabditiselegans,as well as mouse brain tissue allowed theresearchers to visualize and measure electrical activity in theseorganisms as it propagated through the brain.What's more, this technique can be used in tandem with so-called"optogenetic proteins" that can silence or stimulate singleneurons at will. The researchers showed they could stimulate anisolated neuron in this way, and then use the fluorescent protein tofollow along the path of neurons that fired in response to thatsingle input.
Next, the researchers will be attempting to comprehensively map thebrain activity of mice as they perform various tasks, with the goalto discover exactly how some neural circuits produce specificbehaviors.
"Wewill be able to watch a neural computation happen," says Boyden."Over the next five years or so we're going to try to solve somesmall brain circuits completely. Such results might take a steptoward understanding what a thought or a feeling actually is."
Theopen-access study appears in the Feb. 26 issue of NatureChemical Biology.