Brain hack: Cockroach neurons hijacked to control movement
According to the team at Case Western Reserve University, Ohio, this provides insights not only into cockroach motor systems, but those of animals in general, including humans. The findings could well lead to improvements in the development of drones, robots and self-driving cars.
Scientists already knew that brain reflexes change when the animal decides to turn or speed up. But the new study sheds light on how exactly brain activity influences motion, and what buttons to press to control it precisely.
"The central complex appears to be an area of the insect brain that monitors many forms of sensory information as well as the insect's internal state, and then influences various forms of movement," biology professor at Case Western Reserve, Roy Fitzmann, said.
"It's like a joystick on the animal,” postdoctoral researcher and study partner Joshua Martin added. "We can control its direction and alter its speed."
To probe around in the roaches’ brains, researchers inserted tiny wires into 27 of them, recording the neural activity when movements were made. The electrodes were attached to the area that processes visual and antennae information, which gets processed to decide on movement.
According to Martin, neural activity starts in the center of the brain, before “the outputs from the central complex are sent to the motor center in the thoracic ganglia – its version of the spinal cord – and on to the limbs.”
The team hit jackpot when they saw specific centers light up and overexert themselves at the precise moments the roaches were turning, increasing speed or slowing down. These spikes were then converted into a probability map, before the researchers watched a repeat of the roaches moving about in slow motion. When compared, the neural readings and video recording showed movement at the precise moment of each neural spike.
The researchers were able to zero in on the precise buttons for left-right/slow-fast commands.
"For the vast majority of cockroaches we tested, if you stimulate the cells you saw were active before the turn or slow or fast walk, you get the same movement every time you stimulate them," Martin said.
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The researchers pinpointed the precise areas for stimulation to achieve certain movements, like a knee-jerk reaction tested at the doctor’s office. They were consequently able to change reflexes from one leg motion to another. There were also changes in the neural coding system, depending on the task. For example, the same set of nerve cells responsible for one motion changed their role when a new type of obstacle presented itself.
"So it appears that the motor maps that we identified act on the motor system by altering the sign of these reflexes," according to Ritzmann.
And it is highly likely, researchers say, that the system applies to more animals than just cockroaches.
Armed with this knowledge, the researchers say they can now apply it to designing robots and machines that mimic these sensorimotor relationships. Ritzmann is one of the scientists at Case Western Reserve who is a proponent of this approach, but believes “we have to better understand how animals solve these issues first.”
The study was published in the current issue of the journal Current Biology.