Nano-MIND Lets Magnetic Fields Control Mouse Brain Circuits

At the simple flick of a magnetic field, mice fitted with nanoparticle-activated 'switches' in their brains were prompted to eat, socialise and behave like attentive new mothers. The experiment was designed to assess an innovative research tool.

Although animal studies involving 'mind control' are nothing new, they have typically depended on unwieldy electrodes linking the animal to an external system. As well as requiring invasive surgery, this arrangement restricts how freely a test subject can move.

Researchers at Korea's Institute for Basic Science (IBS) say they have made a neurological breakthrough by creating a way to target brain pathways through genetics, nanoparticles and magnetic fields.

They have named the technology Nano-MIND, short for Magnetogenetic Interface for NeuroDynamics. While 'mind-control' is a broad yet fairly accurate description, the current system is intended to let researchers remotely trigger neural circuits across a variety of research uses.

"This is the world's first technology to freely control specific brain regions using magnetic fields," says Jinwoo Cheon, senior author and director of the IBS Center for Nanomedicine.

"We expect it to be widely used in research to understand brain functions, sophisticated artificial neural networks, two-way BCI [brain-computer interface] technologies, and new treatments for neurological disorders."

Nano-MIND magnetic stimulation of neural circuits

Magnetic stimulation is an emerging area of neurological research. Pulses of electromagnetism are used to broadly affect entire brain regions, subtly altering their behaviour.

To focus on individual circuits, the team borrowed an approach from optogenetics, a research field in which cells are genetically engineered with mechanisms that can be easily activated by light.

Here, the researchers incorporated ion channels into selected groups of brain cells in mice.

Rather than supplying light through a localised fibre, as optogenetics does, these ion channels could be magnetically turned on by rotating a tiny actuator. It simply needs a surrounding field powerful enough to tug on the nanoparticle.

Feeding and social behaviour in mice

The researchers created three separate tests to evaluate the system. The first focused on receptors involved in complex feeding and reward behaviours in the lateral hypothalamus, a region deep within the brain's central core.

Tracking the animals' movement and food consumption both inside and outside a magnetic field produced marked differences, indicating that a mouse's urge to eat could literally be switched on and off as required.

When exposed to the magnetic field, mice whose excitatory neurones carried the switches consumed only half as much food. During an active magnetic field, a second group with engineered inhibitory neurones ate twice as much.

The lateral hypothalamus also includes pathways linked to sociability. When an appropriately engineered mouse was placed in a chamber with an unfamiliar mouse while magnetic fields were active, the mice could be encouraged to display 'friendly' behaviour.

Parental care and possible applications

A further experiment targeted important receptors in the medial preoptic area, a region associated with parental care.

Female mice with Nano-MIND stimulating the medial preoptic area were put into a chamber containing 'naturalistic' features. While in a magnetic trance, they reacted very differently to baby mice's cries: they approached more quickly and crouched over distressed pups for longer.

Such precise control of particular circuits could benefit researchers attempting to map neurological pathways or assess new treatments.

Eventually, comparable nanotechnology might be used to address poor mental health in humans or become an important part of therapies for disabling neurological conditions, returning full control of a person's mind to the individual.

The research was published in Nature Nanotechnology.