A free mouse multi-brain region optical genetic manipulation head-mounted device based on an optical fiber array

Abstract

The application discloses a free mouse multi-brain region optical genetic manipulation head-mounted device based on an optical fiber array, relates to the technical field of optical genetics, and comprises a skull fixing base, the skull fixing base is fixed to the surface of the skull of a mouse through a bone screw, and a glass window is installed in the skull fixing base; the free mouse multi-brain region optical genetic manipulation head-mounted device based on the optical fiber array is characterized in that the signal output end of a light source generator is inserted into a signal input port, different height spacers are selected and cooperated with a limiting ring, the position of a ferrule array is adjusted, the output end of a plurality of ferrules is in contact with the upper surface of the glass window, Z-axis fine adjustment is realized by replacing the different height spacers, the end face of the ferrule is ensured to be closely combined with the surface of the glass window, light loss and scattering are avoided, the spot positioning precision and the spatial consistency of the stimulation depth are improved, the eight-channel ferrule array supports the simultaneous input of optical signals of different wavelengths or modes, and multi-site and multi-parameter parallel optical genetic manipulation is realized.

Description

Technical Field

[0001] This invention relates to the field of optogenetics, specifically to a head-mounted device for optogenetic manipulation of multiple brain regions in free mice based on fiber optic arrays. Background Technology

[0002] Optogenetics, by targeting the expression of light-sensitive protein genes to specific neurons and precisely modulating neural activity using light, has become a core tool in neuroscience research. In behavioral experiments with freely moving mice (especially rats), implanted optical devices are needed to achieve multi-target light stimulation of the deep brain. Currently, the mainstream technology is the traditional fiber optic implantation method.

[0003] The currently widely used fiber optic implantation method involves surgically implanting one or more flexible optical fibers into the skull of a mouse, using ceramic or metal ferrules, and penetrating deep into the target brain tissue. The fiber tail is connected to an external laser source via a standard SMA or FC connector and a rotary joint.

[0004] However, fiber optic implantation methods are limited by the physical size of traditional ferrules and the implantable area in the skull, as well as the complexity of managing multi-channel cables with rotary connectors. Traditional methods struggle to stably and reliably integrate and independently manipulate more than 2-4 deep brain targets on the mouse skull. This significantly restricts the ability to study complex neural circuits involving the synergy or interaction of multiple brain regions (such as reward motivation circuits, fear memory circuits, and multisensory integration circuits). Furthermore, the inherent mechanical friction of the rotary connector and the physical drag of the connecting cables significantly limit the natural range of movement in mice (such as drilling, fighting, and vigorous exploration), distorting their behavioral performance. Fiber optic cables are prone to tangling when mice are active (especially in complex environments or social scenarios), leading to unexpected experimental interruptions. Connectors also frequently loosen due to mouse movement, causing interruptions in light stimulation or unstable power, affecting data reliability. Therefore, current optogenetic experiments are limited by ferrule size and cable management capabilities, resulting in severely insufficient multi-target stimulation capabilities. Simultaneously, the physical constraints of the rotary connector and cable tangling significantly distort the natural behavior of mice. Summary of the Invention

[0005] The purpose of this invention is to provide a head-mounted device for optogenetic manipulation of multiple brain regions in free mice based on fiber optic arrays, in order to solve the problems of insufficient multi-target manipulation capabilities and severely limited animal behavior in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a free mouse multi-brain region optogenetic manipulation headgear based on fiber optic array, comprising a skull fixation base, wherein the skull fixation base is fixed to the surface of the mouse skull by bone screws, and a glass window is installed inside the skull fixation base;

[0007] A limiting ring is provided, with a support cover installed at one end. Several inserts are inserted inside the support cover. The output end of each insert contacts the glass window. A signal input port is provided at the upper end of each insert, and a light source generator is inserted into the signal input port. A gasket is provided at the lower end of the support cover, and the lower end of the gasket contacts the upper end of the skull fixation base.

[0008] Furthermore, a sliding groove is provided at the rear end of the limiting ring, an adjusting plate is slidably installed inside the sliding groove, a limiting plate is installed at the rear end of the adjusting plate, and the limiting plate is fixed to the sliding groove by a pin.

[0009] Furthermore, a connecting belt is installed at the front end of the adjusting plate, and a fixing belt is installed at one end of the limiting ring. The connecting belt and the fixing belt are connected by a connecting component.

[0010] Furthermore, the connecting assembly includes a connecting plate disposed at one end of the fixing belt, and a buckle is installed at one end of the connecting plate, the buckle being configured in a T-shape.

[0011] Furthermore, a limiting box is installed at one end of the connecting belt, and two support shafts are installed opposite each other at the lower end of the limiting box. Hooks are rotatably installed on the outer surface of the two support shafts, and both hooks can engage with the buckle. A spring sheet is installed on one side of each hook.

[0012] Furthermore, a cover plate is installed on the upper end of the limiting box, and two channels are opened opposite each other on the upper end of the cover plate. An elastic element is installed on one side of each of the two channels, and an assisting column is installed on the upper end of each of the two hooks. The assisting column passes through the channel, and one end of the elastic element is connected to one side of the assisting column.

[0013] Furthermore, the buckle has a slot at its front end, and a positioning rod is installed at the lower end of the inner side of the limiting box, and the slot can engage with the positioning rod.

[0014] Furthermore, a connecting plate is provided on the outer surface of the skull fixation base, a connecting box is installed on the upper end of the connecting plate, a connecting cover is installed on the upper end of the connecting box, and a limit groove is formed on the upper end of the connecting cover.

[0015] Furthermore, a support plate is provided on the outer surface of the support cover, and a threaded ring passes through the inside of the support plate. A threaded rod is threadedly connected inside the threaded ring, and a fixing ring is installed at the lower end of the threaded rod. A connecting cylinder is installed at the lower end of the fixing ring, and a sliding rod is movably installed inside the connecting cylinder. A limiting plate is installed at the lower end of the sliding rod. The limiting plate can pass through a limiting groove and enter the interior of the connecting box. A locking post is provided at both ends of the limiting plate, and two locking grooves are opened opposite each other at the lower end of the connecting cover. The locking post engages with the locking groove.

[0016] Furthermore, an elastic element is installed at the lower end of the fixing ring, and a connecting ring is provided on the outer surface of the connecting cylinder, with the lower end of the elastic element connected to the upper end of the connecting ring.

[0017] Compared with the prior art, the optical fiber array-based head-mounted device for optogenetic manipulation of multiple brain regions in free mice provided by the present invention has the following beneficial effects.

[0018] 1. This invention involves inserting the signal output terminal of the light source generator into the signal input port, and then selecting shims of different heights to cooperate with the limiting ring to adjust the position of the ferrule array, so that the output terminals of several ferrules contact the upper surface of the glass window. By changing the shims of different heights, Z-axis fine adjustment is achieved to ensure that the end face of the ferrule is in close contact with the surface of the glass window, avoiding light loss and scattering, improving the spatial consistency of light spot positioning accuracy and stimulation depth. The eight-channel ferrule array supports the simultaneous input of light signals of different wavelengths or modes, realizing multi-site, multi-parameter parallel optogenetic manipulation, and improving experimental throughput and data dimensionality.

[0019] 2. This invention conducts optogenetic experiments on mice by sequentially irradiating light signals through a signal input port, a ferrule, and a glass window to the mouse brain region. The ferrule array directly irradiates the mice, and the head-mounted device fixes the ferrules and light source generator, eliminating the need for optical fibers or external cables. The mice can move freely during the experiment, which is more in line with natural behavior patterns and improves the reliability of experimental data.

[0020] 3. The present invention uses a mechanical snap-fit ​​structure to resist vibrations or micro-displacements caused by mouse head movements after locking. Compared with traditional optical fibers, which are prone to falling off or signal interruption due to mouse movement, this invention can prevent the ferrule from separating from the glass window, ensuring the continuity and stability of optogenetic stimulation. Furthermore, the ferrule and other components can be reused to reduce the cost of optogenetic experiments.

[0021] 4. This invention achieves rigid locking between the support cover and the skull fixation base by automatically engaging the corresponding slot with the locking pin. The elastic component maintains a constant pull force after locking, ensuring the limiting plate always presses against the lower surface of the connecting cover, eliminating gaps between parts. The insert array and the glass window achieve displacement-free floating. After rotating within the connecting box, the limiting plate is bidirectionally tightened by the elastic component, forming a "self-locking wedge" structure. This resists mouse movement or violent head swinging, preventing displacement of the insert irradiation position. Furthermore, the coordinated adjustment of the threaded rod and elastic component allows for compatibility with gaskets of varying thicknesses, ensuring constant locking force. Finally, the modular snap-fit-elastic self-locking structure avoids repeated screw tightening and loosening, preventing repeated stress on the skull fixation base, reducing the risk of implant loosening. Installation is simple, convenient, and quick, and rapid disassembly reduces mouse restraint and stress time. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0023] Figure 1 This is a schematic diagram of the first-view structure provided in an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the skull fixation base structure provided in an embodiment of the present invention;

[0025] Figure 3 Provided for embodiments of the present invention Figure 1 Enlarged view of a portion of point A in the middle;

[0026] Figure 4 This is a schematic diagram of the internal structure of the limiting box provided in an embodiment of the present invention;

[0027] Figure 5 This is a schematic diagram of the engagement structure of the connecting component provided in an embodiment of the present invention;

[0028] Figure 6 This is a schematic diagram of a second-view structure provided in an embodiment of the present invention;

[0029] Figure 7 This is a partial exploded view of the structure provided in an embodiment of the present invention;

[0030] Figure 8 Provided for embodiments of the present invention Figure 6 Enlarged view of section B;

[0031] Figure 9 A partial structural schematic diagram provided in the embodiments of the present invention.

[0032] Explanation of reference numerals in the attached figures:

[0033] 1. Skull fixation base; 2. Glass window; 3. Limiting ring; 4. Slide groove; 5. Adjusting plate; 6. Limiting plate; 7. Pin; 8. Connecting strap; 9. Fixing strap; 10. Connecting assembly; 101. Connecting plate; 102. Buckle; 103. Groove; 104. Limiting box; 105. Support shaft; 106. Hook; 107. Spring plate; 108. Cover plate; 109. Channel; 110. Elastic element; 111. Assist column; 112. Positioning rod; 11. Support cover; 12. Insert; 13. Signal input port; 14. Light source generator; 15. Gasket; 16. Connecting plate; 17. Support plate; 18. Connecting box; 19. Connecting cover; 20. Limiting groove; 21. Threaded ring; 22. Threaded rod; 23. Fixing ring; 24. Connecting cylinder; 25. Sliding rod; 26. Elastic component; 27. Connecting ring; 28. Limiting plate; 29. ​​Slot; 30. Locking post. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0035] Example 1:

[0036] refer to Figures 1 to 7 The present invention provides a head-mounted device for optogenetic manipulation of multiple brain regions of free mice based on fiber optic array, comprising a skull fixation base 1, wherein the skull fixation base 1 is fixed to the surface of the mouse skull by bone screws, and a glass window 2 is installed inside the skull fixation base 1.

[0037] A limiting ring 3 is provided, with a support cover 11 installed at one end. Several inserts 12 are inserted inside the support cover 11. The output end of the inserts 12 contacts the glass window 2. A signal input port 13 is provided at the upper end of the inserts 12. A light source generator 14 is inserted into the signal input port 13. A gasket 15 is provided at the lower end of the support cover 11. The lower end of the gasket 15 contacts the upper end of the skull fixation base 1.

[0038] The rear end of the limiting ring 3 is provided with a sliding groove 4, and an adjusting plate 5 is slidably installed inside the sliding groove 4. A limiting plate 6 is installed at the rear end of the adjusting plate 5, and the limiting plate 6 and the sliding groove 4 are fixed by a pin 7.

[0039] The front end of the adjusting plate 5 is equipped with a connecting belt 8, and one end of the limiting ring 3 is equipped with a fixing belt 9. The connecting belt 8 and the fixing belt 9 are connected by a connecting component 10.

[0040] The connecting assembly 10 includes a connecting plate 101 disposed at one end of the fixing strap 9, and a buckle 102 is installed at one end of the connecting plate 101. The buckle 102 is configured in a T-shape.

[0041] One end of the connecting belt 8 is equipped with a limiting box 104. Inside the limiting box 104, two support shafts 105 are installed opposite each other at the lower end. The outer surfaces of the two support shafts 105 are rotatably equipped with hooks 106. Both hooks 106 can engage with buckles 102. A spring sheet 107 is installed on one side of each hook 106.

[0042] The upper end of the limiting box 104 is equipped with a cover plate 108. Two channels 109 are opened opposite each other on the upper end of the cover plate 108. An elastic element 110 is installed on one side of each of the two channels 109. An assisting column 111 is installed on the upper end of each of the two hooks 106. The assisting column 111 passes through the channel 109. One end of the elastic element 110 is connected to one side of the assisting column 111.

[0043] The buckle 102 has a slot 103 at its front end, and the lower end of the limiting box 104 is equipped with a positioning rod 112. The slot 103 can engage with the positioning rod 112.

[0044] Working principle: The skull fixation base 1 is fixed to the surface of the mouse skull by bone screws, providing a stable support base.

[0045] The limiting ring 3 is placed around the neck of the mouse, and the optogenetic irradiation point is calibrated intraoperatively using a calibration plate to determine the position of the support cover 11 and the inserts 12. The inserts 12 consist of eight parts, forming an array of inserts 12. The signal output end of the light source generator 14 is inserted into the signal input port 13. Then, shims 15 of different heights are selected to cooperate with the limiting ring 3 to adjust the position of the insert 12 array so that the output ends of several inserts 12 are in contact with the upper surface of the glass window 2. By changing the shims 15 of different heights, Z-axis fine adjustment is achieved to ensure that the end face of the insert 12 is in close contact with the surface of the glass window 2, avoiding light loss and scattering, improving the spatial consistency of light spot positioning accuracy and stimulation depth. The eight-channel insert 12 array supports the simultaneous input of light signals of different wavelengths or modes, realizing multi-site, multi-parameter parallel optogenetic manipulation, improving experimental throughput and data dimensionality.

[0046] Slide the adjusting plate 5 back and forth along the slide groove 4 until the connecting component 10 can be inserted. Insert the pin 7 to lock the limiting plate 6 in the slide groove 4, completing the size fixation. Simultaneously push the assist column 111 outward with both hands, and the elastic element 110 is compressed. At this time, the hook 106 opens around the support shaft 105 and compresses the spring sheet 107. The two hooks 106 tilt and open towards the inside sides of the limiting box 104. Insert the T-shaped buckle 102 into the limiting box 104 until the slot 103 automatically engages with the positioning rod 112. Release the assist column 111, and the elastic element 110... Release pushes the auxiliary column 111 to release, the spring plate 107 releases and drives the hook 106 to rebound, forming a reliable lock with the buckle 102, completing the connection between the fixing strap 9 and the connecting strap 8. The mechanical locking structure can resist the vibration or micro-displacement caused by the mouse's head movement after locking. Compared with traditional optical fibers, which are prone to falling off or signal interruption due to the pulling of the mouse, it can prevent the ferrule 12 from separating from the glass window 2, ensuring the continuity and stability of optogenetic stimulation. Moreover, the ferrule 12 and other components can be reused to reduce the cost of optogenetic experiments.

[0047] When the light source generator 14 is activated, the light signal is sequentially irradiated into the mouse brain region through the signal input port 13, the insert 12, and the glass window 2. Optogenetics experiments are performed on the mice. The components such as the insert 12 and the light source generator 14 are fixed by direct irradiation through the insert 12 array and the head-mounted device. No optical fiber or external cable is required. The mice can move freely during the experiment, which is more in line with the natural behavior pattern and improves the reliability of the experimental data.

[0048] Example 2:

[0049] refer to Figures 1 to 2 as well as Figures 6 to 9 This embodiment is basically the same as the previous embodiment, except that it includes a skull fixation base 1, which is fixed to the surface of the mouse skull by bone screws, and a glass window 2 is installed inside the skull fixation base 1.

[0050] A limiting ring 3 is provided, with a support cover 11 installed at one end. Several inserts 12 are inserted inside the support cover 11. The output end of the inserts 12 contacts the glass window 2. A signal input port 13 is provided at the upper end of the inserts 12. A light source generator 14 is inserted into the signal input port 13. A gasket 15 is provided at the lower end of the support cover 11. The lower end of the gasket 15 contacts the upper end of the skull fixation base 1.

[0051] The outer surface of the skull fixation base 1 is provided with a connecting plate 16, a connecting box 18 is installed on the upper end of the connecting plate 16, a connecting cover 19 is installed on the upper end of the connecting box 18, and a limiting groove 20 is formed on the upper end of the connecting cover 19.

[0052] The outer surface of the support cover 11 is provided with a support plate 17, and a threaded ring 21 passes through the inside of the support plate 17. A threaded rod 22 is threadedly connected inside the threaded ring 21. A fixing ring 23 is installed at the lower end of the threaded rod 22. A connecting cylinder 24 is installed at the lower end of the fixing ring 23. A sliding rod 25 is movably installed inside the connecting cylinder 24. A limiting plate 28 is installed at the lower end of the sliding rod 25. The limiting plate 28 can pass through the limiting groove 20 and enter the interior of the connecting box 18. The limiting plate 28 is provided with locking posts 30 at both ends. The lower end of the connecting cover 19 has two opposite locking grooves 29, and the locking posts 30 engage with the locking grooves 29.

[0053] The lower end of the fixing ring 23 is equipped with an elastic element 26, and the outer surface of the connecting cylinder 24 is provided with a connecting ring 27. The lower end of the elastic element 26 is connected to the upper end of the connecting ring 27.

[0054] Working principle: After the support cover 11 and the insert 12 are positioned, to further increase the stability of the insert 12, the threaded rod 22 is rotated according to the height of the gasket 15, causing it to screw downwards within the threaded ring 21. This drives the fixing ring 23, connecting cylinder 24, sliding rod 25, and limiting plate 28 to move downwards as a whole. The distance between the limiting plate 28 and the connecting box 18 is adjusted, and the connecting ring 27 is pulled downwards. The elastic element 26 is stretched, and the sliding rod 25 slides downwards inside the connecting cylinder 24, causing the limiting plate 28 to enter the connecting box 18 through the limiting groove 20. Then, the connecting ring 27 is rotated 90°, and the sliding rod 25 rotates 90° inside the connecting cylinder 24, thereby causing the limiting plate 28 to rotate 90° inside the connecting box 18. When the downward pressure on the connecting ring 27 is released, the elastic element 26 is released, and the connecting ring 27 is pulled back, causing the locking pin 30 to automatically engage with the corresponding locking groove 2. 9. The rigid locking of the support cover 11 and the skull fixation base 1 is completed. The elastic element 26 maintains a constant pull force after locking, so that the limiting plate 28 always presses against the lower surface of the connecting cover 19, eliminating gaps between parts. The array of inserts 12 and the glass window 2 achieve displacement-free floating. After the limiting plate 28 rotates 90° inside the connecting box 18, it is tightened in both directions by the elastic element 26 to form a "self-locking wedge" structure, which can resist the movement of the mouse or violent head swing, and prevent the irradiation position of the insert 12 from moving. Secondly, through the coordinated adjustment of the threaded rod 22 and the elastic element 26, it can be compatible with the gaskets 15 of different thicknesses to ensure constant locking force. Finally, the modular buckle-elastic self-locking structure can avoid repeated tightening and loosening of screws, avoid repeated stress on the skull fixation base 1, reduce the risk of implantation loosening, and make installation simple, convenient and quick. Quick assembly and disassembly reduce mouse restraint and stress time.

[0055] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention. In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

Claims

1. A head-mounted device for optogenetic manipulation of multiple brain regions in free mice based on fiber optic arrays, characterized in that, Includes a skull fixation base (1), which is fixed to the surface of the mouse skull by bone screws, and a glass window (2) is installed inside the skull fixation base (1). A limiting ring (3) is provided with a support cover (11) at one end. Several inserts (12) are inserted inside the support cover (11). The output end of the inserts (12) is in contact with the glass window (2). A signal input port (13) is provided at the upper end of the inserts (12). A light source generator (14) is plugged into the signal input port (13). A gasket (15) is provided at the lower end of the support cover (11). The lower end of the gasket (15) is in contact with the upper end of the skull fixation base (1). A connecting plate (16) is provided on the outer surface of the skull fixation base (1). A connecting box (18) is installed at the upper end of the connecting plate (16). A connecting cover (19) is installed at the upper end of the connecting box (18). A limiting groove (20) is opened at the upper end of the connecting cover (19). The outer surface of the support cover (11) is provided with a support plate (17), and a threaded ring (21) runs through the inside of the support plate (17). A threaded rod (22) is threadedly connected inside the threaded ring (21). A fixing ring (23) is installed at the lower end of the threaded rod (22). A connecting cylinder (24) is installed at the lower end of the fixing ring (23). A sliding rod (25) is movably installed inside the connecting cylinder (24). A limiting plate (28) is installed at the lower end of the sliding rod (25). The limiting plate (28) can pass through the limiting groove (20) and enter the connecting box (18). A locking post (30) is provided at both ends of the limiting plate (28). Two locking grooves (29) are opened opposite each other at the lower end of the connecting cover (19). The locking post (30) engages with the locking groove (29). The lower end of the fixed ring (23) is equipped with an elastic element (26), and the outer surface of the connecting cylinder (24) is provided with a connecting ring (27). The lower end of the elastic element (26) is connected to the upper end of the connecting ring (27).

2. The optical fiber array-based optogenetic manipulation headset for multiple brain regions of free mice, as described in claim 1, is characterized in that... The limiting ring (3) has a sliding groove (4) at its rear end. An adjusting plate (5) is slidably installed inside the sliding groove (4). A limiting plate (6) is installed at the rear end of the adjusting plate (5). The limiting plate (6) and the sliding groove (4) are fixed by a pin (7).

3. The optical fiber array-based optogenetic manipulation headset for multiple brain regions of free mice, as described in claim 2, is characterized in that... The front end of the adjusting plate (5) is equipped with a connecting belt (8), and one end of the limiting ring (3) is equipped with a fixing belt (9). The connecting belt (8) and the fixing belt (9) are connected by a connecting component (10).

4. The optical fiber array-based optogenetic manipulation headset for multiple brain regions of free mice according to claim 3, characterized in that, The connecting assembly (10) includes a connecting plate (101) disposed at one end of the fixing strap (9), and a buckle (102) is installed at one end of the connecting plate (101), the buckle (102) being configured in a T-shape.

5. A fiber optic array-based optogenetic manipulation headset for multiple brain regions of free mice, as described in claim 4, is characterized in that... One end of the connecting belt (8) is fitted with a limiting box (104). The lower end of the limiting box (104) is fitted with two support shafts (105) facing each other. The outer surfaces of the two support shafts (105) are rotatably fitted with hooks (106). The two hooks (106) can engage with the buckle (102). A spring sheet (107) is installed on one side of each of the two hooks (106).

6. The optical fiber array-based optogenetic manipulation headset for multiple brain regions of free mice according to claim 5, characterized in that, The upper end of the limiting box (104) is equipped with a cover plate (108). The upper end of the cover plate (108) has two channels (109) opposite each other. An elastic element (110) is installed on one side of each of the two channels (109). An assisting column (111) is installed on the upper end of each of the two hooks (106). The assisting column (111) passes through the channel (109). One end of the elastic element (110) is connected to one side of the assisting column (111).

7. A fiber optic array-based optogenetic manipulation headset for multiple brain regions of free mice, as described in claim 6, is characterized in that... The buckle (102) has a slot (103) at its front end, and a positioning rod (112) is installed at the lower end of the inner side of the limiting box (104). The slot (103) can engage with the positioning rod (112).

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