Summary: Researchers have discovered that the common marmoset, a diurnal primate, navigates its surroundings differently from previously studied rats, reflecting its unique ecological adaptations.
Marmosets use visual cues, relying on rapid head-gaze shifts while stationary, and minimize head movements while navigating. In contrast, rats use low-velocity head movements and tactile whisker explorations.
On a cellular level, the marmoset’s hippocampal regions show selectivity for 3D view and head direction, suggesting that gaze, not place, is key to their spatial navigation.
- Marmosets and rats use different strategies for exploring their environment, reflective of their distinct ecological niches. Marmosets rely heavily on visual cues and minimize head movements while navigating.
- In the hippocampal regions of marmosets, researchers observed selectivity for 3D view and head direction, suggesting a “gaze-based” spatial navigation, contrary to the “place-based” navigation observed in rats.
- Unlike rats, marmosets lack rhythmic theta oscillations during locomotion. Instead, they show a resetting of theta oscillations triggered by head-gaze shifts, which coincides with the activation of interneurons.
Source: Neuroscience News
In a new study, scientists discovered that the common marmoset, a primate known for its unique diurnal vision, navigates its world in a way starkly different from the previously studied rats.
The research sheds light on the role of the hippocampus – often likened to a Global Positioning System (GPS) of the brain – in spatial navigation.
Marmosets, unlike rats, use a strategy of visual exploration while stationary and navigate towards goals by minimizing head movements. They rely on rapid head-gaze shifts to explore their environment, an interesting contrast to rats’ low-velocity head movements and tactile whisker explorations.
“We’re seeing that the strategies of exploration and navigation are reflective of each species’ adaptation to its ecological niche,” explained the researchers. “For marmosets, the reliance on visual cues aligns with their natural behavior during the day.”
On the cellular level, the distinctions become more pronounced. Marmosets’ hippocampal CA3/CA1 regions show selectivity for 3D view, head direction, and, to a lesser extent, place.
This appears to be for combinations of these variables, suggesting that marmosets primarily use gaze for spatial navigation.
Contrary to rats, marmosets lack rhythmic theta oscillations of local field potentials during locomotion. Instead, they display a resetting of theta oscillations triggered by head-gaze shifts.
This resetting coincides with the activation of interneurons, followed by various modulations in the activity of pyramidal cells.
This divergence in marmoset navigation from the rat model reflects the far-sensing capabilities of marmoset adaptations to diurnal vision. The findings led the researchers to think about the marmoset hippocampus as a GPS system where the ‘G’ stands for gaze.
This fascinating study not only opens the door to a deeper understanding of spatial navigation across species but also could potentially lead to advancements in the study of human brain function and navigation.
About this neuroscience research news
Original Research: Closed access.
“The hippocampus of the common marmoset is a GPS, but G is for gaze” by Diego B. Piza et al. BioRxiv
The hippocampus of the common marmoset is a GPS, but G is for gaze
The mammalian hippocampus has been compared to a Global Positioning System (GPS) that enables spatial navigation. This notion has been primarily drawn from studies conducted in nocturnal mammals, such as rats; that lack many adaptations to daylight vision compared to diurnal primates.
Here we demonstrate that during foraging in a 3D maze, the common marmoset, a new world diurnal primate with foveal, stereo-color vision, predominantly uses rapid head-gaze shifts while stationary to visually explore their surroundings and then navigates towards goals minimizing head movements. On the other hand, rats, move their head at low velocities while locomoting to explore the environment using their whiskers.
These differences in exploration-navigation strategies reflect the two species’ sensory adaptations to their ecological niches. In the marmoset hippocampus CA3/CA1 regions putative pyramidal neurons show selectivity for 3D view, head direction, and less for place, but mainly for combinations of these variables.
Inhibitory interneurons are tuned to 3D angular head velocity and translation speed, with most cells showing mixed selectivity for both variables.
Marmosets lack the rhythmic theta oscillations of local field potentials seen during locomotion in rats. Instead, they show resetting of theta oscillations triggered by head-gaze shifts that co-occurred with the activation of interneurons, followed by various modulations in the activity of pyramidal cells.
Our results show that the marmoset visual exploration/navigation strategies and the hippocampal specializations supporting them diverge from those observed in rats, reflecting the far-sensing capabilities of the marmoset adaptations to diurnal vision. Thus, the marmoset hippocampus may be considered a GPS, but G is for gaze.