A Harvard Medical School team has developed a non-invasive brain-to-brain interface that allows a human to control a rat’s tail.
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Radiologist Seung-Schik Yoo and colleagues have developed a technique that allows for brain-to-brain communications without the implantation of any electrodes via surgical means.

Brain-to-computer interfaces are more often than not one directional. That is to say that commands originating in the brain are directed to operate a computer. There are many non-invasive devices that can be used to do this, using electroencephalogram (EEG) imaging (such as Evotiv’s headsets). Meanwhile Yoo and colleagues have already shown the functional magnetic resonance imaging (fMRI) can also be combined with real-time processing to provide computer cursor directional commands based on brain activity.

In order to establish a bidirectional interface between the brain and computer, a computer-to-brain interface is necessary. This would have to take computer-generated commands and use them to modulate the function of a specific brain area without engaging the peripheral nervous system and sensory pathways. This, in turn, could lead to a brain-to-brain interface, where neural activities from different brains could be linked by computers.

Most computer-to-brain interfaces require direct electrical stimulation of, for example, the motor cortex through surgically implanted electrodes. These can be used to cause limb motion, for example.

Yoo’s team has been trialling the non-invasive transcranial sonication of focused ultrasound (FUS) to stimulate the brain. This delivers highly focused acoustic energy to the specific, deep regions of the brain. It has been used as a way of blasting brain tumours, but when used in a pulsed mode at a lower energy it can also be used to stimulate certain brain tissues without damaging them.

The team decided to try building a brain-to-brain interface that combined an EEG-based brain-computer-interface and a FUS-based computer-to-brain interface. This means that a human thought process (the intention to stimulate a rat brain) could be detected by an EEG and fed to a computer which triggers the operation of the FUS that stimulates the motor cortex of the rat. This, in turn, causes the rat’s tail to move.

In this experiment, the team harnessed Steady State Visually Evoked Potentials (SSVEP). These are natural responses to visual stimulation at specific frequencies. A human subject was placed in front of a computer showing an image of a circle that was flashing on and off at a particular frequencies. This, in turn, generates electrical activity in the brain at the same frequency of the visual stimulus. It is a technique often used in research because it has an excellent signal-to-noise ratio and can be used in subjects without training. So in this experiment, humans could express that they wanted to move the rat’s tail by intentionally looking at the strobing circle.

Six individuals were connected up to six different rats. The participants were instructed to gaze at the computer monitor for between four and five seconds in order to express their intention to stimulate the rat’s motor cortex. They had to also do a thumbs-up gesture to show that this is what they were doing. They could then take a break of at least 25 seconds before trying again. Each time they focused on the monitor, this triggered the focused ultrasound to stimulate the motor area of the rat’s brain and cause it to wag its tail.

The team found that the brain-computer-interface was on average 95 percent accurate in detecting the intention of the human participants. The focused ultrasound-mediated computer brain interface was also very accurate at stimulating the rat motor cortex without causing any long-term biological damage. There was a time delay between the user-intention and the triggering of the ultrasound apparatus of an average of 1.59 seconds, and it was a further quarter second before the rat’s tail moved.

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Mind Control Machine: Human wags rat’s tail using mind control interface | WIRED
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