Optogenetic technology combines genetic targeting of specific neurons or proteins with optical technology for imaging or control of the targets within intact, living neural circuits.
As Professor Karl Deisseroth of Stanford University notes, emerging technologies from optics, genetics and bioengineering are currently being combined for studies of intact neural circuits. Indeed, the rapid progression of such interdisciplinary “optogenetic” approaches has expanded capabilities for optical imaging and genetic targeting of specific cell types.
For example, Professor Ada Poon and her Stanford University team recently unveiled a tiny, wireless LED device that can be fully implanted beneath the skin of a mouse.
“The device lets researchers turn on the light and stimulate neurons when the mouse is scampering around, behaving more or less normally,” reports IEEE Spectrum’s Eliza Strickland. “This system, described in the journal Nature Methods, seems a big improvement over previous technology, which used wires or bulky head-mounted devices to activate the light switch.”
As Strickland points out, the first optogenetics systems used fiber optic cables to deliver the light – which meant the mice had wires coming out of their heads and couldn’t move around all that much.
“Over the past five years, researchers have worked on wireless systems, in which a head-mounted device receives the signal to stimulate and triggers an implanted LED,” she continued. “However, some of these receivers are heavier than the mouse’s actual head and they interfere with the animal’s freedom of movement and interactions with other mice.”
In contrast, the new device, which comprises a power-receiving coil, IC and LED, weighs a mere 20-50 milligrams. This enables the device to be implanted in the brain, spine or limbs of a mouse – allowing researchers to more easily experiment with optogenetic stimulation of the spinal cord and peripheral nerves.
“With a radio-frequency (RF) power source and controller, this implant produces sufficient light power for optogenetic stimulation with minimal tissue heating (<1 °C),” researchers stated in the Nature Methods abstract. “This technology opens the door for optogenetic experiments in which animals are able to behave naturally with optogenetic manipulation of both central and peripheral targets.”
Commenting on the above-mentioned report, Rambus Fellow Dr. David G. Stork confirms optogenetic techniques are revolutionizing brain science, as new optical interfaces successfully avoid the longstanding deep challenges of micro-electrode methods that pierce the blood-brain barrier.
“While there have been ‘boutique’ academic demonstrations of optical interfaces to animal brains, we may be on the cusp of the development of implantable brain-machine interfaces, which will help those with degenerative brain diseases such as Alzheimer’s and Parkinson’s and patients with neurological trauma,” he added. “Researchers such as Professor Karl Deisseroth, Professor Ada Poon and Professor Boyden, who leads the MIT Media Lab’s Synthetic Neurobiology research group, stand on the cutting edge of optogenetic developments.”
It should be noted that Boyden’s team is currently developing tools for mapping, controlling, observing and building dynamic circuits of the brain. This research helps scientists better understand how cognition and emotion arise from brain network operation, as well as explore various methods of enabling systematic repair of intractable brain disorders such as epilepsy, Parkinson’s disease and post-traumatic stress disorder. In fact, Boyden’s research group has invented a suite of “optogenetic” tools that are now in use by thousands of research groups around the world for activating and silencing neurons with light.