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.
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.
Video shows the view of a subject navigating an on-screen environment including teleportation while their brain waves are recorded from intracranial electrodes. These show that an oscillation that ‘paces’ movement through this maze is internally generated.
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.
About this neuroscience research
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.
Funding: The work was supported by the NIH.
Source: Andy Fell – UC Davis Image Credit: Image is adapted from the UC Davis video. Video Source: The video is credited to Lindsay Vass, UC Davis. Original Research:Abstract for “Oscillations Go the Distance: Low-Frequency Human Hippocampal Oscillations Code Spatial Distance in the Absence of Sensory Cues during Teleportation” by Lindsay K. Vass, Milagros S. Copara, Masud Seyal, Kiarash Shahlaie, Sarah Tomaszewski Farias, Peter Y. Shen, and Arne D. Ekstrom in Neuron. Published online February 25 2016 doi:10.1016/j.neuron.2016.01.045
Oscillations Go the Distance: Low-Frequency Human Hippocampal Oscillations Code Spatial Distance in the Absence of Sensory Cues during Teleportation
Highlights •Novel paradigm that intermittently removes all sensory cues during navigation •Hippocampal low-frequency oscillations persist without sensorimotor processing •Low-frequency oscillations can discriminate short- and long-distance displacement •More spatial updating is associated with more persistent low-frequency oscillations
Summary Low-frequency (delta/theta band) hippocampal neural oscillations play prominent roles in computational models of spatial navigation, but their exact function remains unknown. Some theories propose they are primarily generated in response to sensorimotor processing, while others suggest a role in memory-related processing. We directly recorded hippocampal EEG activity in patients undergoing seizure monitoring while they explored a virtual environment containing teleporters. Critically, this manipulation allowed patients to experience movement through space in the absence of visual and self-motion cues. The prevalence and duration of low-frequency hippocampal oscillations were unchanged by this manipulation, indicating that sensorimotor processing was not required to elicit them during navigation. Furthermore, the frequency-wise pattern of oscillation prevalence during teleportation contained spatial information capable of classifying the distance teleported. These results demonstrate that movement-related sensory information is not required to drive spatially informative low-frequency hippocampal oscillations during navigation and suggest a specific function in memory-related spatial updating.
“Oscillations Go the Distance: Low-Frequency Human Hippocampal Oscillations Code Spatial Distance in the Absence of Sensory Cues during Teleportation” by Lindsay K. Vass, Milagros S. Copara, Masud Seyal, Kiarash Shahlaie, Sarah Tomaszewski Farias, Peter Y. Shen, and Arne D. Ekstrom in Neuron. Published online February 25 2016 doi:10.1016/j.neuron.2016.01.045