Using two cutting-edge technologies, researchers have found a new way to understand how the brain works. In the Nature Methods journal, they report how they used flashes of light, to both “read” and “write” electrical signals sent by individual neurons.

neurons lit up as smileyShare on Pinterest
The team activated six neurons in the shape of a smiling face. The color-coded response – in green – proves the method used to activate the pattern of neurons works.
Image credit: Lloyd Russell, Hausser lab, UCL.

The team from University College London (UCL) says the approach they have developed “extends the optogenetic toolkit.”

The read and write techniques allow them to activate selected brain cells in different patterns and measure how the circuit responds – essentially enabling them to “interrogate” a brain circuit in a particular way.

Senior author Michael Hausser, Professor of Neuroscience in UCL’s Wolfson Institute for Biomedical Research, says they hope to use the technique to ask the brain questions, and, from the answers it gives, better understand how it works:

“Combining reading and writing of activity in the same neurons in the intact brain could revolutionize how neuroscientists can interact with and understand brain activity.”

It is like having a conversation with the brain. Prof. Hausser explains that with time, the responses you get give you a feel for the key questions to ask:

“Just as we combine specific words into sentences that elicit a reply from someone we talk to, we used light to activate specific combinations of nerve cells in the intact brain and record how the other cells respond.”

In their paper, Prof. Hausser and colleagues describe how they engineered nerve cells in the brains of mice so they could read and write brain signals.

To read brain signals they genetically encoded activity sensors in the nerve cells to light up when the cells are active. And to write brain signals, they engineered the same nerve cells to express light-sensitive proteins that can be activated with flashes of light.

Combining the techniques allowed the team to observe and control brain activity in the mice.

The paper also describes how the team found a way to activate several brain cells at the same time. Using a holographic technique, they split a beam of light into smaller beamlets that they directed to individually selected brain cells.

They tested the approach on a group of cortex brain cells that respond to touch. When they activated the chosen neurons with the beamlets, they saw flashes of activity not only in the activated neurons but also in hundreds of their neighbors.

They activated selected brain cells in different patterns and measured how the circuit responded – demonstrating how the technique offered a way to “interrogate” the chosen brain circuit.

They repeated the experiments in the same group of neurons in the same mice over days and weeks, allowing them to have an extended “conversation” with the brain circuit.

First author Dr. Adam Packer, also of UCL’s Wolfson Institute for Biomedical Research, says their work provides neuroscientists with the means to have “a long-term and engaging conversation with the cerebral cortex in the brain of a mouse.”

“Crucially,” he adds, “since the methods of both recording and activation rely on light, this technique is flexible and non-invasive.”

The team hopes eventually to crack the “neural code” of sensory perception – the language our brain cells use to tell each other about the information our senses gather from our environment. This would be a game-changer for neuroscience.

The insights gained could also extend beyond understanding neural code – they could reveal how brain activity goes haywire in disorders like autism and dementia.

Dr. John Isaac, Head of Neuroscience and Mental Health at the Wellcome Trust – a sponsor of the study – says:

This new approach helps us understand how complex behavior is produced by the nervous system. The work is a step towards realizing one of the ultimate challenges of modern science: understanding how the brain processes information to produce appropriate actions.”

Funds for the study came from the European Commission, the European Molecular Biology Organization, the European Research Council, the Medical Research Council, the Gatsby Charitable Foundation, and the Wellcome Trust.

In July 2014, Medical News Today reported a study where neuroscientists inhibited muscle contractions with optogenetics. A team from MIT showed for the first time how they could control muscle movement by shining light on the spinal cords of animals while they were awake and alert.