Electric fish in augmented reality environment using active sensing.

The Electric Sense: How Fish Use Movement to 'See' Their World

Theo Raines in Science & Nature August 2025 • 5 min read.

"Electric fish show us that active sensing, blending movement and perception, is key to understanding how we all interact with our environment"

Our senses constantly feed us information about the world. What’s often overlooked is how much our own movements shape this sensory input. Sometimes, movements stabilize what we perceive, like when our eyes compensate while tracking a moving object. Other times, movements actively enhance the information we gather. Consider when you're searching for keys in your pocket – the complex motions of your hand and fingers help you discern shape, texture, and weight.

This 'active sensing' is widespread across different senses and contexts. However, how we control and adjust these movements based on the situation – say, feeling for a dull versus a sharp object – remains a puzzle. Fortunately, a recent study featured in Current Biology offers fascinating clues. Biswas et al. [3] explored weakly electric fish in an augmented reality setting, revealing how these animals dynamically adjust their movements in response to the sensory feedback they receive.

Gymnotiform weakly electric fish, such as Eigenmannia virescens, use their active electric sense to explore. They generate an electrical field around their body and detect distortions caused by objects in their environment using electroreceptors on their skin. These fish often hide in plant thickets during the day to avoid predators, tracking movements in the thickets to maintain a stable position [4]. The group of Eric Fortune and Noah Cowan has examined how these fish track moving refuges in controlled lab settings [5].

The Active Sensing Dance: Movement and Perception

Electric fish in augmented reality environment using active sensing.

The researchers discovered that these fish perform distinct longitudinal movements, almost like a 'va-et-vient', in addition to tracking the refuge [6]. These movements seem counterintuitive, as they require extra energy and appear to destabilize sensory input. So why do the fish do it? Further investigation showed that these movements, which alter the relative motion between the fish and refuge, are carefully controlled. The amplitude of these movements decreases when visual information is available and increases when water conductivity drops (reducing the effectiveness of electrosensory input). This suggests the movements are part of an active sensing strategy.

Studying active sensing is tricky because the animal's behavior directly influences the sensory input it receives. This calls for clever experimental designs that allow the animal to behave naturally while also enabling precise manipulation of sensory feedback. Biswas et al. [3] tackled this challenge by creating an augmented reality system. This system allowed them to manipulate the sensory feedback the fish received based on its own movements [3]. Specifically, they linked the refuge's motion to the fish's motion and systematically changed the gain of this interaction. For instance, a negative gain made the refuge move in the opposite direction to the fish, while a positive gain caused it to move in the same direction.

Increased Sensing Volume: Movements can expand the area in which fish can detect stimuli.
Counteracting Adaptation: Movements help overcome the sensory system's tendency to filter out constant stimuli.
Information Creation: Active movements may generate new types of information about the surrounding environment.

The most striking finding was that the fish dramatically altered the amplitude of their own movements to keep the variance in sensory input (sensory slip) consistent, regardless of the augmented reality gain (Figure 2B). These results strengthen the idea that sensory slip isn't just an error in tracking but a deliberate outcome of active sensing. More importantly, it suggests that the fish extract information from this self-generated sensory slip to aid in their tracking. One idea is that these movements increase the sensing volume, or the area within which the fish can detect stimuli [7]. Another possibility is that these movements counteract the adaptation properties of the fish's electrosensory neurons [8]. These neurons are more responsive to changing signals but tend to filter out constant signals [9], like the steady movement of a refuge. The active movements might reintroduce these signals at higher frequencies, making them easier to detect. The most intriguing possibility is that these movements create unique information about the environment that wouldn't be available otherwise, which the electrosensory system then decodes [10].

The Future of Active Sensing Research

To understand how active sensing movements enhance sensory input, future research needs to record neural activity in freely swimming fish during refuge tracking. Recent technological advances have made such recordings increasingly feasible in aquatic animals [11]. Sensory input is a mix of external (ex-afferent) and self-generated (re-afferent) signals, and a key question is how the nervous system distinguishes between them during processing. In refuge tracking, the sensory input from the refuge's movement is ex-afferent, while the input from the 'va-et-vient' movements is re-afferent.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1016/j.cub.2018.10.060, Alternate LINK

Title: Active Sensing: Constancy Requires Change

Subject: General Agricultural and Biological Sciences

Journal: Current Biology

Publisher: Elsevier BV

Authors: Volker Hofmann, Maurice J. Chacron

Published: 2018-12-01

Everything You Need To Know

How do electric fish utilize active sensing to explore their environment?

Electric fish like *Eigenmannia virescens* use active sensing by generating an electrical field around their bodies. They possess electroreceptors that detect distortions in this field caused by objects. This active electric sense helps them to navigate, locate objects, and maintain a stable position, particularly when hiding in plant thickets to avoid predators. This combination of generating an electric field and sensing distortions is central to how these fish perceive their surroundings.

What distinct movements do electric fish perform while tracking a refuge, and how are these movements controlled?

Researchers discovered that electric fish perform longitudinal movements, resembling a 'va-et-vient,' while tracking a refuge. These movements, controlled by the fish, alter the relative motion between the fish and the refuge. The amplitude of these movements decreases when visual information is available and increases when water conductivity drops, which reduces the effectiveness of electrosensory input. This indicates that these movements are part of a carefully managed active sensing strategy.

What is 'sensory slip' in the context of electric fish, and why is it considered important for active sensing?

Sensory slip, in the context of electric fish, refers to the variance in sensory input that arises from the fish's own movements. The research indicates that sensory slip isn't just an error in tracking, but is instead a deliberate outcome of active sensing. The fish appear to extract information from this self-generated sensory slip to aid in tracking, which helps them understand changes in their environment and potentially enhances their ability to detect stimuli.

How did the study by Biswas et al. [3] use augmented reality to investigate the active sensing of electric fish?

The study by Biswas et al. [3] used an augmented reality system to investigate the active sensing of electric fish. This system allowed researchers to manipulate the sensory feedback the fish received based on its own movements, specifically by linking the refuge's motion to the fish's motion and systematically changing the gain of this interaction. For example, they could make the refuge move in the opposite direction to the fish (negative gain) or in the same direction (positive gain). This manipulation enabled precise control over the sensory input the fish received during tracking.

What are the key areas of focus for future research on active sensing in electric fish, and what challenges need to be addressed?

Future research should focus on recording neural activity in freely swimming fish during refuge tracking to understand how active sensing movements enhance sensory input. Because sensory input is a mix of external (ex-afferent) and self-generated (re-afferent) signals, it is important to determine how the nervous system distinguishes between these signals during processing. The sensory input from the refuge's movement is ex-afferent, while the input from the 'va-et-vient' movements is re-afferent. Advances in technology are making such recordings increasingly feasible in aquatic animals.