Whether you’re walking, talking or contemplating the universe, a minimum of tens of billions of synapses are firing at any given second within your brain.
“The weak link in understanding ourselves is really about understanding how our brains generate our minds and how our minds generate our selves,” says MIT neuroscientist Ed Boyden.
One cubic millimeter in the brain contains over 100,000 neurons connected through a billion synapses computing on a millisecond timescale. To understand how information flows within these circuits, we first need a “brain parts” list of neurons and glia. But such a list is not enough. We’ll also need to chart how cells are connected and to monitor their activity over time both electrically and chemically.
Researchers can do this at small scale thanks to a technology developed in the 1970s called patch clamping. Bringing a tiny glass needle very near to a neuron living within a brain allows researchers to perform microsurgery on single neurons, piercing the cell membrane to do things like record the millivolt electrical impulses flowing through it. Patch clamping also facilitates measurement of proteins contained within the cell, revealing characteristic molecules and contributing to our understanding of why one neuron may behave differently than another. Neuroscientists can even inject glowing dyes in order to see the shape of cells. Patch clamping is a technique that has been used in neuroscience for 40 years. Why now does it make an appearance as a novel neuroscience technology?
In a word: robots. Boyden designed a machine to do the tiny job. This is no ordinary robot. It works with neurons, objects so small that hundreds would fit across the tip of a pencil. Currently the robot can “autopatch” an individual cell. Boyden plans to build a massively parallel robot that can do microsurgery on many neurons and reveal their form, shape and function. In the future, we will be able to record dozens, and someday hundreds.
To date, few experiments have recorded two connected cells to decipher how electrical computations in one influence the other, in part because monitoring single cells over time is an ironically monumental task. But that’s changing thanks to autopatching, which also holds promising pharmacological applications. It has already begun to reveal how various drugs influence different cell types in vivo, as opposed to cells in a dish, which behave very differently. Ideally we will eventually be able to examine whole-brain impacts of drugs in an awake and behaving animal.
Thanks to modern synergy between man and machine, the future of neuroscience may become the present sooner than we think.
Editor’s note: This is the third installment in a series about emerging neurotechnologies. Join a pilot class of 12 PhD students at MIT as we explore how neuroscience is revolutionizing our understanding of the brain. Each post coincides with a lecture and lab tour at MIT created by the Center for Neurobiological Engineering. This experiment is supported by MITx and created by EyeWire. Tune in next week as we explore how genetically engineering neurons using a protein found in algae helps researchers match up firing activity with function.