A Rat’s Journey Through Virtual Reality

Virtual EnvironmentFew ideas excite the imagination more than virtual reality. We humans use virtual reality for training, entertaining, and even education, but we can also use it to study human and animal behavior. Adaptive behavior, or the ability to adjust to new situations, is influenced by what we see, hear, and experience in our environment; unfortunately, for this reason, it is difficult to isolate the possible stimuli that affect it. The authors of this recently published PLOS ONE paper developed a virtual reality environment to try to isolate and measure the impact of visual and sound cues on rats navigating through a virtual space.

The virtual reality navigation test is based on an experiment called the Morris Water Maze, a standard lab test where a rat swims through water using visual cues on the walls to Virtual Reality Rat Harnessnavigate. The virtual version uses a 14 square-foot room with visual cues projected on each wall and sounds from 4 sides (pictured above). The rat is at the center of the room, wearing a harness (pictured on the right) on a spherical treadmill placed on a three-foot circular table.

Before beginning the navigation tasks, researchers trained nine male rats to move in virtual reality. The rat started from one of 4 random start locations, facing the wall (see video below). The northeast quadrant of the space was designated as the ‘reward zone,’ indicated by a white dot. Upon entry to this zone, the rat was rewarded with sugar water (if only all video games worked this way).

After training, the researchers tested each rat’s ability to navigate to the reward zone using one of three cues: audiovisual, visual, or auditory. Once the rat found the reward zone, a 2-second blackout period was initiated, and then the rat was ‘moved’ back to one of the 4 random start locations. The video below shows the visual cue test.

Scientists found that rats can learn to navigate to an unmarked location based on visual cues—with a moderate amount of training. However, the rats were unable to use the auditory cues to navigate to the reward zone, and instead moved in circles to try to locate it.

Although the rat’s harness may look a little funny, it is a relatively noninvasive test, and since the animal is not in water, like in the Morris Water Maze test, it is easier to combine this test with tools to measure neural and physical variables in the task. Additionally, the virtual maze may contribute to new methodology evaluating the underlying factors in adaptive behavior, specifically because no other cues besides the audiovisual, visual, and auditory defined the spatial location of reward, something that is difficult to achieve in the real world. Despite humans not yet understanding what virtual reality means to us, we can already use it to better understand animal learning and behavior.

Citation: Cushman JD, Aharoni DB, Willers B, Ravassard P, Kees A, et al. (2013) Multisensory Control of Multimodal Behavior: Do the Legs Know What the Tongue Is Doing? PLoS ONE 8(11): e80465. doi:10.1371/journal.pone.0080465

Image 1: doi:10.1371/journal.pone.0080465

Image 2: doi:10.1371/journal.pone.0080465

Video 1: doi:10.1371/journal.pone.0080465

Video 2: doi:10.1371/journal.pone.0080465

Walk like a Camel (or a Giraffe)

It can be overwhelming to think of  the immense array of special shoes, insoles and orthotics available to relieve any manner of symptoms related to joint impact or stress. We have an entire industry designed to help the human species run and walk without injuries. Then consider the feet and joints of a more massive animal like the elephant or the giraffe, with no such industry to relieve their aches and pains.

A team of researchers studied how the feet and limbs of these animals handle the force of their weight as it hits the ground when they walk or run by analyzing a menagerie of videos.

Their results were published in PLOS ONE last week.

When you watch the plates shudder from the impact of the giraffe walking over the force platforms in the video below,  it seems a wonder that such small hooves manage to support such a massive animal without frequent injury. In view of how important these beasts of burden are for global welfare, understanding the dynamics of their foot design, locomotor behavior and impact forces is critical to ensuring their well-being. The study included elephants, pigs and alpacas as well as several other animals and found that the impact on the animals’ feet was proportional to their body size. But other aspects of the force of impact were distributed differently across their limbs to improve biomechanics and reduce injury. In previous research published in PLOS ONE, Dr. Hutchinson has analyzed locomotion in relation to limb and body dimensions in dinosaurs and cats.

Image Credit: 1 camel, 2 shadows by Sylvain Bourdos on Flickr

Citation: Warner SE, Pickering P, Panagiotopoulou O, Pfau T, Ren L, et al. (2013) Size-Related Changes in Foot Impact Mechanics in Hoofed Mammals. PLoS ONE 8(1): e54784. doi:10.1371/journal.pone.0054784

Citation: Hutchinson JR, Bates KT, Molnar J, Allen V, Makovicky PJ (2011) A Computational Analysis of Limb and Body Dimensions in Tyrannosaurus rex with Implications for Locomotion, Ontogeny, and Growth. PLoS ONE 6(10): e26037. doi:10.1371/journal.pone.0026037

Citation: Zhang KY, Wiktorowicz-Conroy A, Hutchinson JR, Doube M, Klosowski M, et al. (2012) 3D Morphometric and Posture Study of Felid Scapulae Using Statistical Shape Modelling. PLoS ONE 7(4): e34619. doi:10.1371/journal.pone.0034619

Prowling Catfish Catch Pigeons on Land

Cats hunt birds, and sea-birds hunt fish.  And in some odd ecological pockets, catfish hunt pigeons.

In a study published today by researchers at the University of Toulouse, France, scientists have investigated this unusual predator-prey relationship between European catfish and pigeons in the Southwest region of France.

European catfish have been reported to capture the pigeons on land and drag them back into the water.  This surprising behavior has not been known to occur in the native range of the species; however this article discovers that in France, where the fish are an invasive species, they have adapted their natural behavior in order to feed on novel prey in their new environment.

The researchers completed this study along the Tarn River in Southwestern France.  European catfish originate from Europe, east of the Rhine River, but were introduced to the Tarn River in 1983.

From a bridge above a gravel island on the river, the researchers watched the fish from June through October 2011. Over that time they saw 54 pigeon hunting incidents, and in 28% of these cases, the catfish successfully captured their prey on land and dragged them back into the water to eat them. These attacks were nearly always triggered by active pigeons, as catfish never attacked motionless pigeons. This evidence suggests that the catfish used water vibrations to hunt their prey rather than visual cues.

The cause of this unusual predation behavior is still unknown. However, these new findings may bring us closer to understanding the implications of such novel behavior in a new ecosystem.

To view the fascinating catfish behavior described in this article, please see the video below:

Citation: Cucherousset J, Boulêtreau S, Azémar F, Compin A, Guillaume M, et al. (2012) “Freshwater Killer Whales”: Beaching Behavior of an Alien Fish to Hunt Land Birds. PLoS ONE 7(12): e50840. doi:10.1371/journal.pone.0050840