How the brain handles teleportation

(SACRAMENTO, Calif.) —

Technology may not have caught up to the teleportation devices of science fiction, but now we have some idea of how the brain handles “beaming up” from one location to another, thanks to research by neuroscientists at the University of California, Davis, involving some specially wired volunteers.

Arne Ekstrom

The work is published online Feb. 25 in the journal Neuron.

Arne Ekstrom, associate professor at the UC Davis Center for Neuroscience, wants to know how we memorize places and routes, and learn to find our way around. It’s long been known that as a rat navigates a maze, its brain gives off a rhythmic oscillation, Ekstrom said. This also happens when humans travel around a virtual landscape on a computer screen. Most models of brain function assume that the oscillations, emanating from the hippocampus deep inside the brain, are at least partly driven by external inputs.

“There is this rhythmic firing in the brain during navigation and while remembering things, but we don’t know if it is triggered by sensory input or by the learning process,” Ekstrom said.

Ekstrom, postdoc Lindsay Vass and graduate student Milagros Copara were able to solve this problem by working with a group of patients being treated at UC Davis’ Department of Neurological Surgery. These patients have a severe form of epilepsy, and surgeon and study coauthor Kia Shahlaie implanted electrodes on their brains, inside the skull, to find out where seizure activity begins and identify treatment options.

In between seizures, the electrodes recorded normal brain activity, and three patients volunteered to take part in the experiment. They were asked to navigate through a streetscape on a computer screen. At some points, they entered a teleporter and jumped to a different, known location in the map. During teleportation, the screen went black for a random period of time.

Teleportation did not interrupt the oscillations at all, but the rhythm did change with the distance travelled during teleportation, Ekstrom said.

The results show that these oscillations are driven entirely by memory and learning processes in the brain, and do not depend on external senses. They also show that the oscillation carries information about speed and distance travelled, even when that travel is virtual teleportation.

Additional coauthors on the study are Masud Seyal, Sarah Tomaszewski Farias and Peter Shen at the departments of neurology, neurological surgery and radiology, UC Davis Health System. The work was supported by the NIH.

SOURCE: https://www.ucdmc.ucdavis.edu/publish/news/neurology/10812

This is your brain on exercise

(SACRAMENTO, Calif.) —

People who exercise have better mental fitness, and a new imaging study from UC Davis Health System shows why. Intense exercise increases levels of two common neurotransmitters — glutamate and gamma-aminobutyric acid, or GABA — that are responsible for chemical messaging within the brain.

Richard Maddock

Published in this week’s issue of The Journal of Neuroscience, the finding offers new insights into brain metabolism and why exercise could become an important part of treating depression and other neuropsychiatric disorders linked with deficiencies in neurotransmitters, which drive communications between the brain cells that regulate physical and emotional health.

“Major depressive disorder is often characterized by depleted glutamate and GABA, which return to normal when mental health is restored,” said study lead author Richard Maddock, professor in the Department of Psychiatry and Behavioral Sciences. “Our study shows that exercise activates the metabolic pathway that replenishes these neurotransmitters.”

The research also helps solve a persistent question about the brain, an energy-intensive organ that consumes a lot of fuel in the form of glucose and other carbohydrates during exercise. What does it do with that extra fuel?

“From a metabolic standpoint, vigorous exercise is the most demanding activity the brain encounters, much more intense than calculus or chess, but nobody knows what happens with all that energy,” Maddock said. “Apparently, one of the things it’s doing is making more neurotransmitters.”

The striking change in how the brain uses fuel during exercise has largely been overlooked in brain health research. While the new findings account for a small part of the brain’s energy consumption during exercise, they are an important step toward understanding the complexity of brain metabolism. The research also hints at the negative impact sedentary lifestyles might have on brain function, along with the role the brain might play in athletic endurance.

“It is not clear what causes people to ‘hit the wall’ or get suddenly fatigued when exercising,” Maddock said. “We often think of this point in terms of muscles being depleted of oxygen and energy molecules. But part of it may be that the brain has reached its limit.”

To understand how exercise affects the brain, the team studied 38 healthy volunteers. Participants exercised on a stationary bicycle, reaching around 85 percent of their predicted maximum heart rate. To measure glutamate and GABA, the researchers conducted a series of imaging studies using a powerful 3-tesla MRI to detect nuclear magnetic resonance spectra, which can identify several compounds based on the magnetic behavior of hydrogen atoms in molecules.

Brain on exercise © UC Regents
Richard Maddock and his team conducted MRI exams of people before and after cycling on a stationary bicycle to determine the effect of exercise on neurotransmitters.

The researchers measured GABA and glutamate levels in two different parts of the brain immediately before and after three vigorous exercise sessions lasting between eight and 20 minutes, and made similar measurements for a control group that did not exercise. Glutamate or GABA levels increased in the participants who exercised, but not among the non-exercisers. Significant increases were found in the visual cortex, which processes visual information, and the anterior cingulate cortex, which helps regulate heart rate, some cognitive functions and emotion. While these gains trailed off over time, there was some evidence of longer-lasting effects.

“There was a correlation between the resting levels of glutamate in the brain and how much people exercised during the preceding week,” Maddock said. “It’s preliminary information, but it’s very encouraging.”

These findings point to the possibility that exercise could be used as an alternative therapy for depression. This could be especially important for patients under age 25, who sometimes have more side effects from selective serotonin reuptake inhibitors (SSRIs), anti-depressant medications that adjust neurotransmitter levels.

For follow-up studies, Maddock and the team hope to test whether a less-intense activity, such as walking, offers similar brain benefits. They would also like to use their exercise-plus-imaging method on a study of patients with depression to determine the types of exercise that offer the greatest benefit.

“We are offering another view on why regular physical activity may be important to prevent or treat depression,” Maddock said. “Not every depressed person who exercises will improve, but many will. It’s possible that we can help identify the patients who would most benefit from an exercise prescription.”

Additional authors were Gretchen Casazza, Dione Fernandez and Michael Maddock of UC Davis. The research was funded in part by the UC Davis Department of Psychiatry and Behavioral Sciences.

A copy of the study, titled “Acute Modulation of Cortical Glutamate and GABA Content by Physical Activity,” is available through Coleen Herbert of the Society for Neuroscience, 202-962-4000, cherbert@sfn.org

More information about UC Davis Health System and its Department of Psychiatry and Behavioral Sciences is at www.ucdmc.ucdavis.edu.

SOURCE: https://www.ucdmc.ucdavis.edu/publish/news/neurology/10798

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