Moths and perhaps other animals rely on precise timing of neural spikes

December 17, 2019

Extracting nectar from flowers that may be dancing in the wind requires precise, millisecond timing between the brain and muscles.

By capturing and analyzing nearly all of the brain signals sent to the wing muscles of hawk moths (Manduca sexta), which feed on such nectar, researchers have shown that precise timing within rapid sequences of neural signal spikes is essential to controlling the flight muscles necessary for the moths to eat.

The research shows that millisecond changes in timing of the action potential spikes, rather than the number or amplitude of the spikes, conveys the majority of information the moths use to coordinate the five muscles in each of their wings. The importance of precise spike timing had been known for certain specific muscles in vertebrates, but the new work shows the general nature of the connection.

"We were able to record simultaneously nearly every signal the moth's brain uses to control its wings, which gives us an unprecedented and complete window into how the brain is conducting these agile and graceful maneuvers," said Simon Sponberg, Dunn Family Professor in the School of Physics at the Georgia Institute of Technology. "These muscles are coordinated by subtle shifts in the timing at the millisecond scale rather than by just turning a knob to create more activity. It's a more subtle story than we might have expected, and there are hints that this may apply more generally."

The research was reported December 16 in the journal Proceedings of the National Academy of Sciences. The work was supported by the National Science Foundation, the Esther A. & Joseph Klingenstein Fund, and the Simons Foundation.

Researchers Joy Putney, Rachel Conn and Sponberg set out to study how the brain coordinates agile activities such as running or flying that require compensating for perturbations in the air or variations on the ground. While the size of the signals could account for gross control of the behavior, the fine points of choreographing the tasks had to come from elsewhere, they reasoned.

Recording motor control signals in humans and other vertebrates would be a daunting task because so many neurons are used to control so many muscles in even simple behaviors. Fortunately, the researchers knew about the hawk moth, whose flight muscles are each controlled by a single or very few motor neurons. That allowed the researchers to study neural signals by measuring the activity of the corresponding muscles, using tiny wires inserted through the insect's exoskeleton.

Putney and Conn determined the location of each wing muscle inside the moth exoskeleton, and learned where to create tiny holes for the wires - two for each muscle - that capture the signals. After inserting the wires in the anesthetized moths, the graduate students closed the holes with superglue to hold the wires in place. Connections to a computer system allowed recording and analysis.

"The first time I did the surgery by myself, it took six hours," said Putney. "Now I can do it in under an hour."

While connected to the computer, the moths were able to fly on a tether as they viewed a moving 3D-printed plastic flower. To measure the torque forces the moths created as they attempted to track the flower, the wired-up moths were suspended from an accelerometer. The torque information was then correlated with the spiking signals recorded from each wing muscle.

The importance of the work relates to the completeness of the signal measurement, which brought out the importance of the timing codes to what the moth was doing, Putney said.

"People have recorded lots of muscles together before, but what we have shown is that all of these muscles are using timing codes," she said. "The way they are using these codes is consistent, regardless of the size of the muscle and how it is attached to the body."

Indeed, researchers have seen hints about the importance of precision timing in higher animals, and Sponberg believes the hawk moth research should encourage more study into the role of timing. The importance and prevalence of timing across the moth's motor program also raises questions about how nervous systems in general create precise and coordinated motor commands.

"We think this raises a question that can't be ignored any longer - whether or not this timing could be the real way that the brain is orchestrating movement," Sponberg said. "When we look at specific signals in vertebrates, even up to humans, there are hints that this timing could be there."

The study could also lead to new research on how the brain produces the agile motor control needed for agile movement.

"Now that we know that the motor control is really precise, we can start trying to understand how the brain integrates precise sensory information to do motor control," Sponberg said. "We want to really understand not only how the brain sets up signals, but also how the biophysics of muscles enables the precise timing that the brain uses."
This material is based upon work supported by National Science Foundation Graduate Research Fellowships DGE-1650044 and DGE-1444932, by an NSF CAREER award (1554790) and a Klingenstein-Simons Fellowship Award in the Neurosciences. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the sponsoring organization.

Georgia Institute of Technology

Related Brain Articles from Brightsurf:

Glioblastoma nanomedicine crosses into brain in mice, eradicates recurring brain cancer
A new synthetic protein nanoparticle capable of slipping past the nearly impermeable blood-brain barrier in mice could deliver cancer-killing drugs directly to malignant brain tumors, new research from the University of Michigan shows.

Children with asymptomatic brain bleeds as newborns show normal brain development at age 2
A study by UNC researchers finds that neurodevelopmental scores and gray matter volumes at age two years did not differ between children who had MRI-confirmed asymptomatic subdural hemorrhages when they were neonates, compared to children with no history of subdural hemorrhage.

New model of human brain 'conversations' could inform research on brain disease, cognition
A team of Indiana University neuroscientists has built a new model of human brain networks that sheds light on how the brain functions.

Human brain size gene triggers bigger brain in monkeys
Dresden and Japanese researchers show that a human-specific gene causes a larger neocortex in the common marmoset, a non-human primate.

Unique insight into development of the human brain: Model of the early embryonic brain
Stem cell researchers from the University of Copenhagen have designed a model of an early embryonic brain.

An optical brain-to-brain interface supports information exchange for locomotion control
Chinese researchers established an optical BtBI that supports rapid information transmission for precise locomotion control, thus providing a proof-of-principle demonstration of fast BtBI for real-time behavioral control.

Transplanting human nerve cells into a mouse brain reveals how they wire into brain circuits
A team of researchers led by Pierre Vanderhaeghen and Vincent Bonin (VIB-KU Leuven, Université libre de Bruxelles and NERF) showed how human nerve cells can develop at their own pace, and form highly precise connections with the surrounding mouse brain cells.

Brain scans reveal how the human brain compensates when one hemisphere is removed
Researchers studying six adults who had one of their brain hemispheres removed during childhood to reduce epileptic seizures found that the remaining half of the brain formed unusually strong connections between different functional brain networks, which potentially help the body to function as if the brain were intact.

Alcohol byproduct contributes to brain chemistry changes in specific brain regions
Study of mouse models provides clear implications for new targets to treat alcohol use disorder and fetal alcohol syndrome.

Scientists predict the areas of the brain to stimulate transitions between different brain states
Using a computer model of the brain, Gustavo Deco, director of the Center for Brain and Cognition, and Josephine Cruzat, a member of his team, together with a group of international collaborators, have developed an innovative method published in Proceedings of the National Academy of Sciences on Sept.

Read More: Brain News and Brain Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to