Virtual reality simulator and method for small laboratory animals

Abstract

The present invention relates to a virtual reality simulator (10) for small laboratory animals (100), particularly rodents, which includes a head clamping mechanism (20) for securing the laboratory animal (100) and virtual reality glasses (40) with two wings (30), each of which includes a display (34) and a lens system (36) spaced therefrom, connected together by a light barrier cover (32), and the virtual reality glasses (40) are configured so that each of the two wings (30) can be aligned with one of the eyes (101) of the laboratory animal (100). The present invention also relates to a method for applying such a simulator (10).

Description

[Technical field]

[0001] The present invention relates to a virtual reality simulator for small laboratory animals, particularly rodents.

[0002] The present invention also relates to a method for simulating virtual reality for a small laboratory animal. [Background technology]

[0003] Brain electrophysiological (EEG, electrodes) and low-resolution microscopic measurements used in neurobiological research can be easily performed in freely moving laboratory animals (e.g. mice, rats). In contrast, high-resolution in vivo brain imaging, such as two-photon microscopy measurements, is performed in head-fixed conditions through a so-called craniotomy window. However, this condition makes it more difficult to carry out experiments if one wants to study the interaction of the laboratory animal with its environment and the resulting brain activity.

[0004] A solution to the above problems is the creation of a virtual environment (VR). A virtual environment offers the opportunity to carry out controlled animal experiments with a fixed head. There are currently several solutions to implement virtual environments. Their common feature is the display of virtual image content on the walls of the room surrounding the animal, for example by using a projector or a screen. Hoelscher et al. (Rats are able to navigate in virtual reality. J Exp Biol (2005): 208(3): 561-569) The design originally created by remains the basis for most virtual environment systems devised for rodents. Its main components are a properly designed visual stimulus display and a treadmill. In this solution, the animal is surrounded by a torus-shaped dome with a diameter of 140 cm and a height of 80 cm. A projector projects the virtual image content onto the inner surface of this torus. The animal stands on a sphere with a diameter of 50 cm inside the torus, and the movement of the sphere (by sensors that detect the movement of the driving surface) changes the projected virtual environment around the animal. The advantage of this solution is that the projected image almost completely fills the animal's field of view. Further known developments have focused on the main elements of this basic design. For example, a solution called JetBall-Dome by a company called Phenosys uses a spherical dome instead of a torus and "floats" the spherical treadmill without friction by flowing compressed air.

[0005] Although many of the behavioral parameters of animals interacting with the surrounding environment (e.g. running speed, eye movements, feeding, etc.) can be measured during in vivo brain imaging with the virtual environment systems mentioned above, none of the known solutions provide sufficient feedback on the animal's behavior and sensory stimulation. This is because these implementations do not yet fully create an immersive virtual environment (i.e. a level of awareness of the virtual environment as if the animal were truly present in the VR environment), due to lack of depth and filling the binocular field with one continuous surface (only one two-dimensional image is displayed). The inventors have found that for two-dimensional visual content, even if it substantially fills the animal's field of view, the experimental animal still finds sufficient visual reference points from its real environment. Since the animal's head is fixed, its vestibular system does not perceive movement. This is confirmed by these visual "grips" in its field of view. As a result, the animal does not think that it is moving, which can negatively affect the experiment. Another drawback of known solutions is that they are not compatible or ergonomically unusable with multiphoton (e.g. two-photon) microscopes, since a large projection surface is required to cover the field of view, and the dome may impede the free movement of the microscope objective. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Hoelscher et al., J Exp Biol (2005): 208(3): 561-569 Summary of the Invention

[0007] Due to the above mentioned difficulties, existing solutions are only to a limited extent suitable for the creation of virtual experimental environments or for their combination with two-photon microscopy.

[0008] It is an object of the present invention to provide a virtual reality simulator and method for small laboratory animals that does not have the drawbacks of the prior art solutions, i.e. that provides an immersive virtual environment for immobilized laboratory animals and is compatible with two-photon microscopes.

[0009] It has been found that a key aspect of behavioral, visual, and learning experiments is immersion, which can be achieved through the perception of depth and complete coverage of the visual field.

[0010] The present invention is based on the finding that a virtual reality simulator with compact virtual reality glasses with a large field of view and binocular depth sensing developed for laboratory animals allows laboratory animals (e.g., mice) to solve realistic behavioral tasks during electrophysiology or brain imaging. According to the present invention, immersion is created virtually immediately, and the laboratory animal can realistically experience the virtual environment in a head-fixed state. This effect was demonstrated in experiments with five animals. During the experiment, the inventors were able to stop the animal at the edge of the virtual abyss with high accuracy without teaching or habituating the system. When the virtual sidewalk was extended, the animal continued to run. This demonstrates that the animal stopped as described above not only for reasons of contrast difference but also for reasons of three-dimensional spatial recognition. The same animal could not be located in the virtual abyss with a conventional monitoring system due to lack of immersion.

[0011] It has also been found that by using the simulator and method of the invention, the time required for learning in visual learning experiments can be unexpectedly shortened by an order of magnitude (from 1-2 weeks to 2-3 days) compared to conventional systems. It is also suitable for examining learning processes, since the inventors have already detected significant learning processes within a time of 40 minutes. The simulator and method of the invention are also suitable for carrying out behavioral experiments described in the literature.

[0012] According to the above findings, the above object of the present invention has been achieved by a simulator according to claim 1 and a method according to claim 14 of the patent claims.

[0013] Preferred embodiments of the invention are set forth in the dependent claims. Further details of the invention will be explained below by way of exemplary embodiments with reference to the drawings. [Brief description of the drawings]

[0014] [Figure 1a] FIG. 1 is a schematic front perspective view of an exemplary embodiment of a simulator according to the present invention in a state where it is attached to a laboratory animal. [Figure 1b] FIG. 1b is a simplified rear perspective view of the main part of the simulator shown in FIG. [Diagram 2] FIG. 1b is a perspective view of the simulator shown in FIG. 1a with the wings removed. [Diagram 3] 1 is a schematic cross-sectional view of an exemplary embodiment of a wing according to the present invention; [Figure 4] FIG. 2 is a schematic diagram illustrating the creation of virtual image content according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] FIG. 1a is a schematic front perspective view of an exemplary embodiment of a simulator 10 according to the present invention, with the simulator 10 attached to a small laboratory animal 100. The simulator 10 is used to create a virtual reality for the small laboratory animal 100. Virtual reality (VR) is a three-dimensional artificial environment generated by a computing device, in which elements of reality are completely excluded. The animal 100 can "tour" the virtual environment and interact with the elements of the environment. Thus, VR is a set of visual (or audio) information generated by a computing device that affects the perception (mainly visual, but also auditory) of the animal 100 as a result of the interaction of the animal 100 with the computing device. In the context of the present invention, the small laboratory animal 100 is primarily a rodent (e.g., mouse, rat, rabbit), but it goes without saying that the animal 100 also includes other small animals (e.g., monkeys, lizards, etc.) commonly used in laboratory experiments, as will be apparent to those skilled in the art.

[0016] The simulator 10 of the present invention comprises a head clamping mechanism 20 for immobilizing the head of the experimental animal 100 and a pair of virtual reality glasses (VR glasses) 40 with two wings 30. The head clamping mechanism 20 may preferably be made of metal or any other material of suitable strength suitable for immobilizing the head of the animal 100 and thereby holding the animal 100 in place. The head clamping mechanism 20 may possibly be made of a single piece or may consist of several parts fastened together by screws, as can be seen for example in Figures 1a and 1b. In a particularly preferred embodiment, the head clamping mechanism 20 comprises an observation hole 22 for a microscope objective 210, through which craniotomy brain imaging can be performed in vivo on the animal 100, as known to those skilled in the art. The head clamping mechanism 20 partially or, if appropriate, completely defines the observation hole 22 (see Figures 1a, 1b and 2).

[0017] Each of the two wings 30 has a display 34 and a lens system 36 spaced therefrom, which are connected together by a light barrier cover 32. The display 34 can be any type of display using known technologies such as LCD, OLED, etc., with a resolution suitable for creating a virtual reality experience. The resolution of the display 34 is preferably at least full HD, and more preferably at least 2K, as known to those skilled in the art. In one exemplary embodiment, the display 34 is a commercially available 2.9-inch diameter IPS LCD display with a resolution of 1440 x 1440 pixels. In a particularly preferred embodiment, the display 34 is designed as a bidirectional display 34 to monitor the pupil and eye movements of the experimental animal 100. In this case, the display 34 also functions as a CMOS camera sensor, so that in addition to displaying images, digital images can also be captured by the display 34. Such a display 34 can be, for example, a 0.6-inch diameter 2K resolution OLED display manufactured by Fraunhofer FEP.

[0018] In the context of the present invention, lens system 36 should be broadly understood to include an optical element consisting of one or, where appropriate, multiple lens elements. The lens system 36 is sized to image (project) the associated display 34 onto the retina of the experimental animal 100. Preferably, lens system 36 is corrected for optical aberrations (e.g., spherical aberration, chromatic aberration), as will be apparent to those skilled in the art. It should be noted that lens system 36 may optionally be a single aspheric lens, or a Fresnel lens for size reduction.

[0019] 3 is a schematic cross-sectional view of an exemplary embodiment of the wing 30, showing a possible configuration of the display 34 and the lens system 36 connected by the light barrier cover 32, as well as the positioning of the wing 30 relative to the eye 101 of the animal 100. The cover 32 serves to firmly connect the display 34 and the lens system 36 to each other, and defines an interior space between the display 34 and the lens system 36 that is isolated from the outside world. The cover 32 is at least partially a solid wall. In terms of material, the cover 32 may be made of a material that provides sufficient structural strength and light barrier, i.e., a material that firmly fixes the display 34 and the lens system 36 to each other and does not allow outside light to enter the interior defined by the cover 32, such as metal, plastic, etc. In a preferred embodiment, at least a part of the light barrier cover 32 is made of an elastic material, preferably a light-shielding fabric. The function of this will be described in detail later. The design of the wings 30 is such that the optical axis of the lens system 36 is preferably perpendicular to the plane of the display 34 .

[0020] The virtual reality glasses 40 of the present invention are shaped so that the two wings 30 can be aligned with one or the opposite eye 101 of the experimental animal 100, respectively, and are preferably fixed to the head clamping mechanism 20 by fasteners 50. When wearing the simulator 10, one eye 101 of the animal 100 can only see the image on one display 34, and the opposite eye 101 of the animal 100 can only see the image on the other display 34. In a particularly preferred embodiment, the fastening element 50 is designed as a mechanism, such as a ball-and-socket mechanism, to allow the individual wings 30 to rotate about any axis and to move along at least one axis, preferably a vertical axis. In this embodiment, the cover 32 of each wing 30 is provided with a hole 38 into which the socket 52 of the ball-and-socket joint of the fastening element 50 can be tightened and fixed. The ball joint socket 52 is fitted with a ball head 54 having a shaft 56, and the ball head 54 is freely rotatable within the ball joint socket 52. The end of the shaft 56 opposite the ball head 54 is removably fixed (e.g., by a screw) within a substantially elongated bore 24 formed in the head clamping mechanism 20, as shown in Figs. 1b and 2. In this way, the end of the shaft 56 can be fixed at a desired position along the elongated bore 24, so that the height of the wings 30 relative to the head clamping mechanism 20 can be adjusted. The advantage of the ball-and-socket type mechanism is that each wing 30 can be independently aligned with the eye 101 of the animal 100, i.e., the optical axis of the lens system 36 can be accurately aligned parallel to the ocular axis of the eye 101, separately for each eye. It should be noted that other fixing methods than those mentioned above may also be considered.

[0021] In embodiments in which the head clamping mechanism 20 comprises a hole 22, the wings 30 are attached to the head clamping mechanism 20 in such a way that the viewing hole 22 is not obstructed, as shown for example in Fig. 1a. In a particularly preferred embodiment, the shape of the wings 30 is such that the objective lens 210 of the microscope can be fitted into the viewing hole 22 when the wings 30 are attached to the head clamping mechanism 20. This can be ensured on the one hand by an appropriate size of the wings 30 and on the other hand by an appropriate selection of the material of the cover 32. For example, an embodiment is possible in which the part of the cover 32 close to the lens is made from a flexible light-tight fabric or other flexible light-tight material, such that deformation of the fabric of the cover 32 allows the lens 210 to be brought closer to the opening 22.

[0022] In one particularly preferred embodiment shown in Fig. 1a, the size of the wings 30 is such that the whiskers of the experimental animal 100 remain free when applied, i.e. the wings 30 do not touch the whiskers of the animal 100. This can be achieved by choosing an appropriate size of the display 34 depending on the species of the animal 100. The advantage of this embodiment is that the simulator 10 does not interfere with the tactile sense of the animal 100, thereby improving immersion and the effectiveness of the simulation.

[0023] In a particularly preferred embodiment, the simulator 10 includes a tread 60, preferably in the form of a treadmill, rotating disk, or spherical treadmill, underneath the head clamping mechanism 20. The tread 60 may be adapted for movement by the experimental animal 100, as known to those skilled in the art. The tread 60 is positioned underneath the head clamping mechanism 20 such that the experimental animal 100, whose head is secured by the head clamping mechanism 20, stands on the tread 60. The animal 100 secured by the head clamping mechanism 20 may simulate forward motion by moving the tread 60, similar to a human running on a treadmill. In a preferred embodiment, the tread 60 includes one or more displacement sensors 62 for measuring the speed or direction of the simulated running of the animal 100.

[0024] The simulator 10 according to the present invention preferably further comprises a controller 70 having at least one processor and a storage device in data communication with the display 34 and the sensor 62. The term controller 70 should be understood broadly as used herein to include any hardware device capable of receiving, processing, storing and electronically transmitting processed digital data. In a particularly preferred embodiment, the controller 70 is in the form of a personal computer (e.g., a desktop or laptop computer) having a storage device for storing data received from the sensor 62 as well as computer programs, and a processor for processing the received data and running the computer programs. The controller 70 may optionally comprise one or more input devices (e.g., keyboard, mouse, etc.) in addition to the usual elements (e.g., direct access memory, network cards, etc.), or may comprise an interface that functions as both an output and input device (e.g., CD / DVD burner / reader, etc.), as will be appreciated by those skilled in the art. The data processed by the controller 70 can be transmitted to the display 34 by a data communication connection between the controller 70 and the display 34, which can be made, for example, via a MIPI interface or HDMI®. This data connection may be wired, or possibly wireless (eg, WiFi, Bluetooth, etc.), as known to those skilled in the art.

[0025] The control device 70 is configured to display virtual image contents on the displays 34 corresponding to each of the two visual fields detected by the eyes 101 of the experimental animal 100 by executing at least one computer program. In other words, the control device 70 sends different virtual image contents to each display 34 so that the right eye 101 and the left eye 101 of the animal 100 see different right and left images, respectively, according to the rules of stereoscopic displays that the brain of the animal 100 perceives as a single three-dimensional image. For example, in the embodiment shown in FIG. 4, the virtual object is a slice of cheese, the two images of which are displayed on each display 34 with different sizes, angles, etc., as known to those skilled in the art. The overlap of the visual fields perceived by the eyes 101 of the animal 100 results in binocular vision (spatial perception) on the one hand and monocular vision on the other. This means a binocular visual field of approximately 40 degrees (for example, for a mouse) and a peripheral visual field of 270 degrees. As already mentioned, when the simulator 10 is worn, the optical axis of the lens system 36 is preferably parallel to the ocular axis of each eye 101. If this is not possible (e.g. because the wings 30 need to be better tilted relative to the eye axis to allow space for the objective lens 210 used to examine the experimental animal 100, or because the wings 30 cannot be tilted / rotated in the desired direction), in a preferred embodiment, the virtual image content is displayed on the display 34 with a three-dimensional perspective correction for the experimental animal 100, as known per se. The virtual image content generated by the control device 70 during the execution of the computer program may contain not only visual data, but also auditory data (audio track), if appropriate, since image data and content also means video data containing both visual and auditory elements. In an exemplary embodiment, the simulator 10 is equipped with a sound generating device (not shown) controlled by the control device 70 for generating sound, preferably a speaker for emitting the sound of the audio track of the virtual image content generated by the control device 70.In another possible embodiment, the virtual image content also includes tactile data that is just transmitted to the animal 100 using devices designed for this purpose (e.g., vibration motors), as known to those skilled in the art.

[0026] In the embodiment with the tread 60, the control device 70 is preferably designed to take into account the displacements measured by the one or more sensors 62 when generating and sending the virtual image content to the display 34. That is, for example, if the animal 100 is imitating running straight on the tread 60, the virtual image content will change accordingly as if the animal 100 was running straight in the virtual space. For example, if the animal 100 moves the tread 60 in such a way that it tries to turn left, the generated virtual image content will also change as if the animal 100 turned left in the virtual space. In one possible embodiment, the simulator 10 is provided with a locking means (e.g. a brake) for preventing the movement of the tread 60. By this means, the tread 60, which is being moved by the animal 100, can be stopped at a desired time so that the animal 100 cannot move the tread any further. This locking means is preferably designed to be operated by the control device 70. In this way, when the animal 100 reaches a virtual object (e.g., a wall) in the virtual environment during the simulation and attempts to move further forward, the tread 60 can be immediately stopped by the locking means so that the animal 100 perceives that it cannot move through the virtual object as if it were real. If the animal 100 moves in a direction that would cause it to move around the virtual object, the locking means can be released to unblock the tread 60 so that the animal 100 can continue to move through the virtual environment. The locking of the tread 60 may be supplemented with other effects (e.g., sound or haptics) to make the simulation of the virtual environment even more realistic.

[0027] The invention further relates to a method for simulating virtual reality for small laboratory animals.In the following, the operation of the simulator 10 according to the invention will be described together with a method according to the invention.

[0028] In a particularly preferred embodiment, the method according to the invention is carried out by the simulator 10 according to the invention described above. During the method, the head of the experimental animal 100 is fixed by a head clamping mechanism 20. The animal 100 may be secured by any known method, such as gluing. The head clamping mechanism 20 carries two virtual reality glasses 40, each with a wing 30, each of which includes a display 34 and a lens system 36 spaced apart therefrom, which are connected together by a light barrier cover 32. In a preferred embodiment, the glasses 40 are attached to the head clamping mechanism 20 by a ball and socket type mechanism as shown above, whereby the two wings 30 are adjusted to fit the eye 101 on one side or the other side of the experimental animal 100, respectively. When adjusting the wings 30, care must be taken to ensure that the optical axis of the lens system 36 is as close as possible to the ocular axis of the eye 101 of the animal 100, and that the lens system 36 is spaced away from the eyes of the animal 100 to project the image of the display 34 onto the retina of the animal 100. In order to create the best possible virtual experience, it is also preferable to design the wings 30 to cover the space between each eye 101 and the lens system 36. In this way, the animal 100 does not visually perceive anything from the outside world. After adjusting the wings 30, the display 34 displays virtual image contents on the display 34 corresponding to each field of view of the two eyes of the experimental animal 100, i.e., virtual image contents that look slightly different from each other in the two eyes 101, so that the brain of the animal 100 perceives them as a single three-dimensional image. The virtual image contents displayed on the display 34, i.e., the computer program operated by the control device 70, are selected according to the type of experiment to be performed. For example, if one wants to carry out a learning experiment with 100 animals, the virtual reality created by the virtual visual content can be, for example, a virtual maze, and so on.In one particularly preferred embodiment, a tread 60, preferably a treadmill, rotating disk or spherical treadmill, is mounted beneath the head clamping mechanism 20 in a position where the experimental animal 100 can be moved to run on it. The displacement of the tread 60 is detected by one or more sensors 62, and the display 34 displays virtual image content corresponding to the detected displacement. In other words, a virtual environment is generated according to the signals of the sensors 62, so that the animal 100 feels like it is inside the virtual environment and can move through it.

[0029] In a particularly preferred embodiment, the head clamping mechanism 20 is provided with an observation hole 22 for a microscope objective 210 through which brain activity of the experimental animal 100 is measured using a microscope (e.g., a two-photon microscope) during the simulation of the virtual reality. In this embodiment, as will be apparent to those skilled in the art, a craniotomy window is made in the skull of the animal 100 before the animal 100 is fixed in the apparatus. With the aid of the microscope, brain processes can be examined through the observation hole 22, so that several behavioral parameters of the animal 100 interacting with the virtual environment can be measured. The type of experiment can be changed by changing the virtual environment.

[0030] Since the virtual image content displayed on the displays 34 covers substantially the entire visual field of the animal 100, it is desirable to determine which part of the virtual environment the animal 100 is looking at in order to determine more accurately the interaction of the animal 100 with the virtual environment. To this end, in a preferred embodiment, an interactive display 34 is provided adapted to monitor the eye movements, preferably pupil movements, of the experimental animal 100. From the measured eye movements, preferably pupil movements, data, the direction of gaze is determined, which allows identifying the currently displayed image portion or virtual object on each display 34 that belongs to the image portion on which the animal 100 is focused at a given moment. For example, in an experiment, it can be determined whether the animal 100 notices a virtual object (e.g. food, predator, etc.) in the virtual environment that is important for the experiment. In this way, the interaction of the animal 100 with the virtual environment can be studied more effectively.

[0031] The simulator 10 and method according to the present invention allow immediate effect experiments to be performed, and learning can be achieved significantly faster than with conventional methods. Whereas the visual learning process typically requires 1-2 weeks with the prior art solutions, the simulator 10 and method according to the present invention can reduce the required time to a scaled-up time of a few days (e.g., 3-4 days). In the context of the present invention, learning a task means that the animal 100 is able to solve the task with a certain success rate, for example, to stably distinguish between two samples with at least an 80% success rate. In our experiments, we have found that with the simulator 10 and method according to the present invention, a significant success rate of 10-20% can be achieved even after a short period of use of 20-40 minutes. That is, with the simulator 10 and method according to the present invention, at least a superficial understanding of the task can be ensured very quickly. A further advantage is that, compared to other VR solutions, there are no distracting visual reference points outside the virtual environment in the animal's field of view that can devastate the virtual reality experience. Thus, immersion occurs for the animal 100 virtually immediately upon placement of the glasses 40, unlike prior art techniques that either do not produce a virtual reality experience at all or require weeks of habituation of the animal 100 for immersion. The glasses 40 of the present invention provide the animal 100 with binocular vision, thereby providing perspective and depth that are not suitable in prior art systems. Another advantage of the present simulator 10 is that it can be easily and flexibly adapted to the desired position of the animal 100 under the microscope and to the current position of manipulation in the skull and size of the animal 100. The present simulator 10 is applicable to small laboratory animals 100 (e.g. mice, rats, marmosets) and is designed to be compatible with multiphoton microscopy techniques and electrophysiological measurement procedures. [Explanation of symbols]

[0032] 10: Virtual reality simulator 20: Head clamping mechanism 22: Observation hole 30: Wing 32: Light barrier cover 34: Display 36: Lens system 40: Virtual reality glasses 50: Fastening elements 52: Socket 54: Ball head 60: Tread 62: Displacement sensor 70: Control device 100: Laboratory animals 101:Eye 210: Objective lens

Claims

1. A virtual reality simulator (10) for a small laboratory animal (100), comprising: a head clamping mechanism (20) for restraining the laboratory animal (100); and virtual reality glasses (40) having two wings (30), each of which has a display (34) and a lens system (36) spaced therefrom, the display (34) and the lens system (36) being connected together by a light barrier cover (32), the virtual reality glasses (40) being configured such that each of the two wings (30) can be aligned with one of the eyes (101) of the laboratory animal (100).

2. 2. The simulator (10) according to claim 1, characterized in that the virtual reality glasses (40) are fixed to the head clamping mechanism (20) by means of fastening elements (50).

3. 3. The simulator (10) according to claim 1 or 2, further comprising a control device (70) having at least one processor and a memory device and associated with a display (34), wherein the memory device stores one or more computer programs, and the control device (70) is configured to execute the at least one computer program to display virtual image content on the display (34) corresponding to a field of view detected by an eye (101) of an experimental animal (100).

4. Simulator (10) according to any one of claims 1 to 3, characterized in that the fastening elements (50) are provided as mechanisms allowing the rotation of the individual wings (30) about any axis of rotation and their displacement in at least one axis, preferably vertical.

5. 5. The simulator (10) of claim 1, wherein the lens system (36) includes one or more lens elements and is sized to image the displayed image of the associated display (34) onto the retina of the experimental animal (100).

6. The simulator (10) according to any one of the preceding claims, characterized in that the display (34) is an interactive display (34) for monitoring pupil and eye movements of a laboratory animal (100).

7. 7. The simulator (10) according to claim 1, wherein the head clamping mechanism (20) includes an observation hole (22) for a microscope objective lens (210), and the wings (30) are fixed to the head clamping mechanism (20) so as not to block the observation hole (22).

8. 8. The simulator (10) of claim 7, wherein the wings (30) are designed to allow a microscope objective lens (210) to fit into the observation hole (22) when the wings (30) are attached to the head clamping mechanism (20).

9. Simulator (10) according to any one of the preceding claims, characterized in that a part of the light barrier cover (32) is made from a flexible material, preferably a light-blocking fabric.

10. The simulator (10) according to any one of claims 7 to 9, characterized in that the head clamping mechanism (20) partially or completely defines a viewing hole (22).

11. The simulator (10) according to any one of claims 1 to 10, characterized in that the wings (30) are dimensioned such that when applied to the experimental animal (100), the wings (30) do not touch its whiskers.

12. The simulator (10) according to any one of the preceding claims, characterized in that under the head clamping mechanism (20) there is provided a tread (60) preferably in the form of a treadmill, a rotating disk or a spherical treadmill, on which the experimental animal (100) can move.

13. 13. The simulator (10) according to claim 12, characterized in that the tread (60) comprises a displacement sensor (62).

14. A method for simulating virtual reality for a small experimental animal (100), comprising: holding the head of the experimental animal (100) immobile with a head clamping mechanism (20); mounting virtual reality glasses (40) having two wings (30) on the head clamping mechanism (20); each wing (30) having a display (34) and a lens system (36) spaced therefrom, the display (34) and the lens system (36) being connected together with a light barrier cover (32); adjusting the two wings (30) so that they are aligned with one eye of the experimental animal (100), respectively; and displaying virtual image content corresponding to each visual field of the experimental animal (100) on each display (34).

15. 15. The method according to claim 14, characterized in that the head clamping mechanism (20) is provided with an observation hole (22) for a microscope objective lens (210) and the brain activity of the experimental animal (100) is measured by a microscope through the observation hole (22) during a virtual reality simulation.

16. 16. The method according to claim 14 or 15, further comprising providing a tread (60), preferably in the form of a treadmill, rotating disk or spherical treadmill, on the underside of the head clamping mechanism (20), on which the experimental animal (100) can perform a running movement, the movement of the tread (60) being detected by a sensor (62), and displaying on the display (34) a virtual image content corresponding to the detected movement.

17. providing an interactive display (34) adapted to monitor eye movements, preferably pupil movements, of the experimental animal (100), determining gaze direction from the measured eye movement, preferably pupil movement data, during a virtual reality simulation; A method according to any one of claims 14 to 16, characterized in that the image portion on the virtual image content displayed on the display (34) is identified based on the gaze direction.

Images