Summary: Researchers have identified “nerd cells” that simultaneously encode speed, direction, and position.
Source: University of Oslo
Your brain can do trajectory calculations that rival those used by engineers. New research from the University of Oslo reveals a group of neurons capable of integrating speed, direction and position at the same time.
Think about rushing to catch a bus while holding a hot cup of coffee: your brain estimates the bus’s motion, your own walking or running speed, the direction to take, and how fast you must move to arrive safely. Those real-time calculations are performed by networks of neurons, and until now the precise cellular mechanisms behind them were not fully understood.
After five years investigating the continuous attractor network (CAN) theory, Charlotte Boccara and colleagues at the Institute of Basic Medical Sciences and the Center for Molecular Medicine Norway (NCMM) at the University of Oslo report a major advance.
“We are the first to provide clear evidence that the brain contains the kind of ‘nerd cells’ a CAN model predicts—neurons that jointly encode speed, position and direction,” says Boccara.
Recording 1,400 neurons across multiple brain regions
Boccara and her team analyzed activity from 1,400 neurons recorded in freely moving rats across several parahippocampal regions. In a paper published in Nature Communications titled “Angular and Linear Speed Cells in the Parahippocampal Circuits,” the team describes how they combined high-density electrophysiological recordings with behavioral tracking to link neural firing patterns to motion and orientation.
They implanted small probes with fine electrodes that monitored neuronal activity while rats explored a maze for rewards. Synchronized video tracking allowed the researchers to correlate detailed movement variables—such as linear and angular velocity—with the recorded neuronal signals.
Using advanced data-analysis methods, the group examined activity across cortical layers and brain areas, systematically searching for cells that encode self-motion variables either alone or in combination with position and heading. This comprehensive approach produced robust evidence of neurons tuned to angular and linear speed distributed across the parahippocampal circuit.
Their findings build on earlier work by John O’Keefe and May-Britt and Edvard Moser (Nobel Prize in Medicine, 2014), which established that individual neurons can represent spatial coordinates and contribute to the brain’s internal navigation system.
A missing puzzle piece with implications for Alzheimer’s research
The CAN framework proposes that an internal map of space is continuously updated as an animal moves, relying on neurons that compute derivatives of position and direction—namely speed and angular velocity. Until now, direct evidence for the conjunctive coding of speed with position and direction was limited.
Boccara’s team identified self-motion neurons distributed across the medial entorhinal cortex (MEC), presubiculum, and parasubiculum—except notably in MEC layer II—and found that many of these cells also conjunctively encoded position and/or direction, although these conjunctive responses did not show a clear topographic organization.
Importantly, the regions where these “nerd cells” reside overlap with areas known to be affected early in Alzheimer’s disease. “These neurons tell us where we are and how we are moving. If they fail, navigational deficits and disorientation can result,” Boccara explains. Understanding how these cells encode spatial information could help guide future therapeutic strategies aimed at preserving or restoring spatial memory and orientation.
The study’s results suggest a possible algorithmic principle: linear and angular speed signals—the temporal derivatives of position and direction—might be the computations that allow the brain to update internal representations of space, and potentially other types of cognitive maps.
The parahippocampal region is now recognized as performing multiple roles beyond mapping spatial position: neurons there can also represent sounds, expected rewards, and other contextual information. An open question is whether the speed and direction cells identified by Boccara’s group also participate in these other representations or whether different subpopulations specialize in distinct computations.
“Do some cells act as redundancy or backup, while others perform planning versus reactive functions based on past experience?” Boccara asks. The distribution of these neurons across areas and layers raises hypotheses about parallel and complementary computations within the circuit.
The team also plans to explore how physiological states affect these neurons. Boccara is particularly interested in sleep: if poor sleep slows cognitive processing, altered activity in speed and direction cells could be part of the mechanism. Future experiments will test whether sleep deprivation impairs the precise encoding of self-motion and thereby degrades navigation and decision-making.
About this neuroscience research news
Author: Press Office, University of Oslo
Source: University of Oslo
Contact: Press Office – University of Oslo
Image: The image is in the public domain
Original Research: Open access. “Angular and linear speed cells in the parahippocampal circuits” by Davide Spalla et al., Nature Communications
Abstract
Angular and linear speed cells in the parahippocampal circuits
The hippocampal region plays a central role in integrating information to compute and update internal representations. How integration of self-motion and spatial signals occurs remains debated. Continuous attractor network models posit that neurons encoding navigational correlates—such as position and direction—receive inputs from cells that conjunctively encode position, direction, and self-motion. Empirical evidence for such conjunctive coding in the hippocampal region has been sparse.
This study reports neurons tuned to angular and linear velocity, recorded uniformly across the medial entorhinal cortex, presubiculum and parasubiculum except for MEC layer II. Many self-motion neurons also conjunctively encoded position and/or direction, without a clear spatial organization. These results illuminate how linear and angular speed signals—the temporal derivatives of position and direction—may support continuous updating of spatial representations and suggest a potentially general algorithm for updating internal maps.