virtual reality

Ever wonder how flies navigate?

dr. dolittle — Thu, 21 May 2015 00:20:48 +0000

Ever wonder how flies navigate?

Dr. Vivek Jayaraman and colleagues at the Howard Hughes Medical Institute Janelia Research Campus discovered that the ellipsoid body located in the middle of a fly's brain acts like a compass to help navigate flight even in darkness. By placing the flies into a small virtual reality arena and having the flies walk on a rotating ball, they could study the activity of neurons within the ellipsoid body while the animal was moving.

These videos show how the fly experiment was done:

Check out the news release for more information about this neat study.

dr. dolittle Wed, 05/20/2015 - 20:20

Tags

Life Science

ellipsoid

flight

fly

navigation

virtual reality

And how did the flies get their navigation system?
The same way the "birds got their beaks".
See article nearby.

Mice navigate a virtual reality environment

neurophilosophy — Sun, 18 Oct 2009 17:30:38 +0000

Mice navigate a virtual reality environment

USING an inventive new method in which mice run through a virtual reality environment based on the video game Quake, researchers from Princeton University have made the first direct measurements of the cellular activity associated with spatial navigation. The method will allow for investigations of the neural circuitry underlying navigation, and should lead to a better understanding of how spatial information is encoded at the cellular level.

In mice, spatial navigation involves at least four different cell types located in the hippocampus and surrounding regions. Place cells increase their activity when the animal is in a specific location within its environment, called the place field. Grid cells, by contrast, fire periodically as the animal traverses a space; each has a unique periodicity, and apparently measures out the space using its own scale. Head direction cells, as their name implies, fire when the animal is facing a particular direction and border cells, which were identified only last year, encode the animal's distance from the borders within its environment.

Place cells were discovered almost 40 years ago and are the most extensively studied of these cell types. Their activity is typically recorded using small arrays of microelectrodes implanted within the hippocampus of a freely moving rodent. The arrays can remain in place for days or weeks, during which time they can be used to monitor changes in place cell firing rates, and how the acitivty of cells is related to the animal's movements within its environment. They record from afar, because the animal's movements prevent them from coming into, and maintaining, close contact with the cells.

In the ingenious set-up devised by members of David Tank's laboratory, the mice were restrained, and ran on a spherical treadmill supported by a jet of air. Information about the rotation of the treadmill was used to control the animals' movements along a computer-generated track which was projected onto a surrounding screen.

In this virtual environment, the place cells behaved as expected. All the cells from which recordings were made generated short, regular bursts of nervous impulses, separated by intervals of about one tenth of a second,. This produced a low level of background activity called the theta oscillation, which has a frequency of 6-10 cycles per second, and which is characteristic of the hippocampus. The actvity of individual place cells was modulated by location. As the animal entered a given place field, the corresponding place cell increased its firing rate almost five-fold, to generate a rhythmic discharge with a higher frequency than the background.

Because the animals were stationary, the electrodes could be used to record directly from the place cells, enabling the researchers to measure their dynamical electrical properties. This revealed how their firing rate increases: as the mouse approached a place field, the corresponding cell would ramp up its resting membrane voltage. This would cause the cell to increase the frequency of its impulses while the mouse ran through the field. When the animal emerged from the other side of the field, the membrane voltage would go back down to its normal level, and the frequency of impulses would decrease again. The background activity of single cells was also found to increase while the animal was in the appropriate location.

These findings are consistent with the predictions of a model which states that place cell activity is modulated by interactions between two separate oscillating inputs. The data do not exclude other possibilities, however, and the availablity of this virtual reality system will enable researchers to study the activity of place cells in greater detail, because it offers researchers the ability to design highly customized environments, and can be used in combination with other techniques such as two-photon laser scanning microscopy.

Related:

Harvey, C., et al. (2009). Intracellular dynamics of hippocampal place cells during virtual navigation. Nature 461: 941-946. DOI: 10.1038/nature08499.

neurophilosophy Sun, 10/18/2009 - 13:30

Tags

this is a good experiment for virtual reality good progress
for future

ahaha :)

so informative, thanks to tell us.

Did they get virtual cheese?

Haha - nice one Capitano! No, they were given real water.

In the figure, I see the optical mouse; the biological mouse should rightfully be labeled as well. Or is the biological mouse 'virtual'? Very clever experimental design!

Next step: teach the mice to play Halo and send them off to Afghanistan. Hmmm.... The Mouse that Fragged?

Was the mouse using a mouse?

The virtual body illusion and immersive Second Life avatars

neurophilosophy — Thu, 08 Oct 2009 14:00:32 +0000

The virtual body illusion and immersive Second Life avatars

SECOND LIFE is an online "virtual world" which enables users to create a customised avatar, or digital persona, with which they can interact with each other. It has become incredibly popular since its launch just over 6 years ago, with millions of "residents" now using it regularly to meet others, socialize and even to have virtual sex. Second Life is now filled with virtual communities and institutions - it has businesses and universities, and its own virtual economy.

Now, imagine a futuristic version of Second Life, in which avatars can transfer sensations to the bodies of their users. Such a scenario may seem far-fetched, but a team of European researchers has just taken us one step closer it. They demonstrate a perceptual illusion in which a computer-generated virtual body can be made to feel like one's real body, so that one can feel sensations from it and respond to it as if it were real.

The new work, led by Mel Slater of the Experimental Virtual Environments for Neuroscience and Technology (EVENT) lab at the Universitat de Barcelona in Spain, builds on earlier studies which demonstrate that the brain's representation of the body can be manipulated very easily. The first of these, published in 1998, described the rubber hand illusion, whereby the brain incorporates a prosthetic limb into the body (or takes "ownership" of it), so that stimuli applied to the prosthesis are perceived to originate from one's real hand. More recently, it has been found that this effect can be induced for the whole body, resulting in the body swap illusion, in which subjects perceive the body of another person to belong to themselves, so that tactile sensations appeared to arise from the other person's body and not their own.

Following on from this earlier work, Slater and his colleagues now show that these illusions can be easily reproduced in virtual reality. The virtual hand illusion was induced in almost exactly the same way as the rubber hand illusion. Participants placed an arm out of sight behind a screen, and looked at a three dimensional computer-generated image of an arm, which was projected onto a large screen directly in front of them (below). An electronic wand was then used to stroke the participants' arms. In some cases, the movements of the wand were synchronized with those of a small yellow ball on the screen, so that the participants saw the ball touching the virtual arm as they felt their real arm being touched in the same way. In others, the movements of ball on the screen were pre-recorded, and did not correspond to the touches applied to their real arm.

During the condition in which the movements of the wand and the ball were synchronized, but not in the asynchronous condition, the participants reported that the virtual arm felt like their own, and that the sensations they experienced were caused by the ball on the screen rather than by the wand. Five minutes into each trial, the virtual arm was rotated back and forth; at the same time, electrodes placed on the participants' real arms recorded electrical activity from the muscles, as if they were also moving. The brain had incorporated the virtual arm into its representation of the body, treating it as if it were part of the body. In other words, the participants had taken full ownership of the virtual arm.

In a second set of experiments, the participants wore a data glove which detects finger movements and transfers them to a computer in real time. In one condition, the data were used to control the movements of the virtual arm, while in another, the virtual arm performed a series of pre-recorded movements which did not correspond to those of the participants' hands. Only when the movements of the real and virtual arms were the same did the participants report feeling that their arm weas located where the virtual arm was, or that the virtual arm felt like their own.

Finally, the researchers found that the illusion could also be induced when the virtual arm was controlled by a non-invasive brain-computer interface (BCI, bottom right panel in the figure above). Participants were first trained to use the BCI to open and close the virtual hand, by imagining that they were performing the movements. The BCI records the electrical activity associated with this motor imagery, and translates it into computer commands which can be used to control the movements of the virtual hand. In one condition, the movements of the virtual arm were synchronous with the participants' motor imagery; in the other, they were not. Again, only in the synchronous condition did the participants report a sense of ownership over the virtual limb, and only in that condition was electrical activity from the arm muscles recorded. The illusion was somewhat weaker, but nevertheless still robust.

The illusion has not yet been extended to a full virtual body, but there is good reason to believe that this is possible. In the body swap illusion, ownership of the participants' entire body was transferred to that of another person, and out-of-body experiences have been induced using a similar method (both involve viewing one's own body from a third-person perspective). This strongly suggests that the illusion of ownership over an entire virtual body could easily be induced, and Slater and his colleagues are already working towards this, using head-mounted, movement tracking displays to project virtual bodies into the spaces normally occupied by real ones.

And what of Second Life avatars which can be perceived as being real? These findings show that this is possible, at least in theory. Some of the necessary technologies are already available, but in practice, it cannot currently be achieved. Sensations could be transferred from the avatar to the user by a full-body haptic suit, but the experience would only feel "real" if the suit could also transmit the movements of the user to the avatar, precisely and in real time. Immersive avatars are, therefore still a long way off. Meanwhile, control of virtual bodies with BCIs could prove to be very useful in enabling fully paralyzed patients to communicate with others in virtual environments.

Related:

Subscribe to my RSS feed and follow me on Twitter.

Slater, M. et al (2009). Inducing illusory ownership of a virtual body. Front. Neurosci. [Full text]

Petkova, V.I. & Ehrsson, H. H. (2008). If I Were You: Perceptual Illusion of Body Swapping. PLoS One 3 (12): e3832. [Full text]

The experimental induction of out-of-body experiences. Ehrsson, H. H. (2007). Science 317: 1048. [PDF]

Botvinick, M., & Cohen, J. (1998). Rubber hands 'feel' touch that eyes see. Nature 391: 756-756. [PDF]

neurophilosophy Thu, 10/08/2009 - 10:00

Tags

Damn you, now I'm dying to try it.

This is old stuff! Didn't you see "Surrogates", Mo?!

You mean the recent science fiction film? No, I'll have to check it out

Ahh - Issac Asimov, you left us too soon - you'd love this...

Even to have sex? You mean, primarily to have sex.

anyone ever read Snowcrash?

This seems to tie directly into the work Ramachandran has done in "body extension" illusion and the neural capacity to map exogenous items onto the endogenous body-map representation. I can dig up the citations if they aren't already familiar for you.

Fausty | www.cultureghost.org

Morning dip - Finding Waldo, not finding serotonin, and Varmus goes Daily Show

ddobbs — Thu, 05 Mar 2009 08:40:00 +0000

Morning dip - Finding Waldo, not finding serotonin, and Varmus goes Daily Show

Notables from my morning feedscan:

The vision folks at Barrow study "Where's Waldo?" to figure out search strategies.

A virtual-reality helmet claims to to feed all five senses. Interesting if true.

Winner best-and-worsrt headline writing in a press release: Prawnography shows captive bred prawns lack lust And in second place, running, um, close behind: Scatological clues lead to an intimate view, which actually looks at some pretty interesting group dynamics in lemurs during their annual birthing time, when babies are at risk of being murdered.

Neurotopia continues a good series on the problems with the serotonin theory of depression.

Science goes cool: Harold Varmus, head of Sloan-Kettering, of Obama's science advisory council, Nobelist, former NIH director, and author of "The Art and Politics of Science," goes on Jon Stewart's Daily Show. In which we learn -- hurray! -- Varmus was once an English Ph.D. student. Man is also funny. "As you know from ... having a few moments with my book ..."

ddobbs Thu, 03/05/2009 - 03:40

Tags