Mouse Head Position and Orientation
University of Wisconsin-Madison Biomedical Engineering Design 200/300 December 10, 2003
Missy Haehn, Yao Lu, Meghan Olson, Ben Sprague, Heather Waldeck, Andrea Zelisko
Client: Matthew I. Banks, Ph.D. Department of Anesthesiology Advisor: Professor John Webster Department of Biomedical Engineering
ABSTRACT
Variations in sounds elicit vibrations in the cochlea which in turn create distinct neural signals. Professor Banks studies the neural pathways of mice in response to audio stimuli and tests their cognition and perception. Since spatial arrangement affects the perception of sound, the location of where the sound is heard relative to where the sound is emitted is vital for research purposes. Monitoring the orientation of the head relative to the speaker box will allow the client to incorporate this data in order to eliminate variation within his results. The final design consisted of LED’s connected to a plastic headpiece, which when lit will allow the client to track movement and orientation with light or without.
INTRODUCTION
Background
People perceive sound by processing information collected by the ear. Sound waves create vibrations in the inner ear, specifically at the cochlea, which are transduced into electrical signals that are sent along different neural pathways in the brain. These action potentials will fire to different parts of the brain depending on how the inner ear vibrates.
2 Figure 1. A sliced diagram of the ear. (Elesea, 1996)
The cochlea is filled with fluid that is divided into two parts by the basilar membrane.
Emitted sound flexes the basilar membrane and produces traveling waves along its length (Elsea,
1996). The shape of the basilar membrane allows the sound wave to increase to a certain amplitude along its length and then quickly die out. The location and amplitude of the sound wave depends upon its frequency.
Figure 2. Diagram shows the middle and inner ear. The oval window is connected the cochlea which stimulates the basilar membrane. Certain hairs on the membrane then stimulate nerve fibers which fire information to different parts of the brain. (Elesea, 1996)
Along the basilar membrane are tiny hairs which are connected to bundles of nerves.
Motion in the basilar membrane bends the hairs which stimulate the associated nerve fibers which carry sound information to the brain. The location of the hair cells which are stimulating the nerve bundles along the basilar membrane depends upon the frequency of the sound.
3 The mechanics of the ear are well know, however the mechanics of interpretation of sounds are currently being studied. We know that a sound of a particular waveform and frequency gives a characteristic pattern of active locations on the basilar membrane (Elsea,
1996). It is speculated that if the pattern repeats enough we learn to recognize that pattern and associate it to a certain sound. We are also able to perceive the direction of the sound source.
Directional perception is done by the brain processing the arrival time of the sound to each ear or perceiving the difference in phase of sounds at each ear. Hence where one’s head is positioned relative to a sound will stimulate different parts of the brain.
Motivation
The client, Prof. Matthew Banks, studies the inhibitory receptor, the GABAA receptor, is related to various cognitive activities in the brain. For his research, he wants to study the auditory system of mice and how GABAA receptors affect the perception and cognition of sound stimuli. The research requires recording of the brain neural activity in response to a specific sound stimulus as well as the position and orientation of the mouse’s head in relation to the location of the sound. This project focuses on developing a device that measures the location as well as orientation of the mouse head.
Current Conditions
Currently, each mouse has an interface board attached to their skull which monitors brain waves when connected and set up with the amplifier. Each mouse is anesthetized and a portion of their head is shaved. Electrodes from an interface board are implanted on the head which detect brain waves. Dental cement is used to secure this interface board to the mouse’s head which is then joined to the amplifier which perceives the brain activity and sends it to the computer through a wire source. The mice are allowed to move freely within an experimental testing cage. In our project we were working with a 10x20cm wire cage that was tested within a
4 dark, sound proof chamber. Lining the inside of the soundproof chamber is foam to ensure that sound is not emitted (see Figure 14).
PROBLEM STATEMENT
Our purpose is to develop a system to help study how the auditory system of laboratory mice responds to acoustic stimuli. The system will determine the position and angle of the mouse’s head relative to the speaker emitting the sounds. The system should fit ergonomically with the animal and lab setting, and should not interfere with recording of brain waves.
CLIENT/DESIGN REQUIREMENTS
The client has several requirements for the final system. Any component that fits on the mouse’s head must weigh less than one gram. The device should measure the position and the orientation of the mouse’s head in respect to the sound stimulus location. The system itself and the data must not interfere with the recording of brain waves. The client also prefers the system to be detachable, to require minimal calibration, and easy to operate. The development of the system should cost less than the allotted budge of $5,000. Finally, the device should be user friendly, and not pose any dangers, whether electrical or toxic, on the mice and researchers.
PRELIMINARY SOLUTIONS
Magnetic Sensor
The basic concept of the electromagnetic sensor is that a current will be produced in wires by a magnetic field. These sensors consist of magnetic wire wrapped around a core which
5 produces a capacitance. Depending upon the size, order, and number of turns around the core the capacitance of the sensor will vary. It is also sensitive to the type of material used for a core; iron will produce a greater capacitance than plastic. When exposed to a magnetic field these sensors will produce a voltage which can be measured and the orientation of the field will affect the magnitude of the signal. Although these are simple concepts, various inaccuracies and problems can occur when creating these sensors.
There are commercially available magnetic sensors. The best sensor for this problem we found is made by Honeywell.
Figure 3: Show a Honeywell magnetic sensor (left) and the Wheatstone bridge (right). (Honeywell, 2003)
In this sensor there are four elements in a diamond forming a Wheatstone bridge (Fig. 3). Two ends are connected to a voltage supply while the other two ends are affected by magnetic fields.
The change in voltage between the two ends shows the presence of a magnetic field. The sensors detect the magnetic field at plus and minus 90 or 45 degrees. The angle at which the magnetic field is to the sensor can be computed by looking at the magnitude of the signal (Fig. 4)
Figure 4: Displays the sensor obtaining the angle of the magnetic field. (Honeywell, 2003)
6 An instrumentation amplifier circuit must be designed for this device to derive the difference signal. This circuit will contain an op-amp and a filter to decrease noise.
This design would consist of a sensor grid which will be placed underneath the testing cage. The grid would contain several sensors at equal distance from one another. On the mouse two magnets will be place behind the ears at a known distance. One magnet will be oriented in a way so its magnetic field is positive towards the sensors while the other will be negative. When the mouse travels over certain sensors they will produce a voltage which will indicate the mouse’s location and the direction in which the mouse is looking.
The cost for this device will be minimal. The sensors from Honeywell are approximately
$5 each and we most likely will not need more than 20 sensors. The magnets we will use will most likely be a rare earth magnet called NdFeB which cost $1.25 for 10 1/16” x 1/32” magnets
(Figure 5). The cost for the driving circuits will not be substantial. The most expensive part of this design would be acquiring hardware to display the voltages on a computer.
Figure 5: Show the NdFeB magnets relative to a penny. There are 10 magnets in this picture. (Force field, 2003)
This design has many advantages such as, cost efficient, lightweight, and it is feasible.
Some problems that may arise are complications with interference, drift, and DC offset. This
7 design was not chosen because after careful considerations it was found the sensor was not sensitive enough for our purposes.
Electrical Potential Design Option
The second design option involves creating an electrical field from which the position of the mouse’s head can be determined by measuring the electrical potential at a certain point. To do this, three different spherical charges will be created at known positions above the mouse’s head by applying charge to conducting spheres (Figure 6). A voltmeter will be used to determine the voltage at a set position which indicates the electrical potential at that point. By using the equation:
V = ke( q1/r1 + q2/r2 + q3/r3 ) the distance to each ball can be determined and therefore the position of the mouse’s head can be determined including the angle of the head in comparison to the
Figure 6: Sketch of the relative position of the charged spheres to the position of measurement.
speaker. As the mouse shifts its head around and up and down, the electrical potential will change. However, in order to use this method, another variable must be known such as the depth of the mouse, so that r1, r2, and r3 can be related to one another. In other words, there must be only one unknown variable in the equation. To determine the depth of the head, an LED would
8 be attached to its head and a light sensor will detect its position by measuring the time the light takes to reach the sensor. After the depth in the cage of the center of the head is determined by the light sensor near the voltmeter, the orientation of the head can be determined by its relation to the electrical potential. The light sensors and voltmeter will detect record simultaneously and the analog voltages which are produced will need to be analyzed later by a software program. This design allows the determination of the three dimensional position of the mouse’s head.
The major reason that this design was not chosen is the fact that the electrical field produced may cause interference with the experimental data. In order to prevent this interference, the mouse head and the wiring from the electrodes must be very well insulated from outside noise which would be difficult to achieve. Also, this method has the potential to become quite heavy and could be unsafe for the mouse if not properly constructed. Finally, the overall complexity of the design made it an unfavorable option for the time constraints placed on the completion of the project.
Optical Design
The last design alternative is to use optical tracking devices such as cameras and infrared
LED’s (Light Emitting Diodes) to measure head location and orientation. There are two basic set ups that can be constructed. In one setup, one or more cameras are mounted on the object to be tracked and a set of LED’s are situated above the head in known locations. A camera located on the head of a mouse would not be feasible due to the size constraints. Instead, the other setup, with a few LED’s placed in fixed and known positions on the head and a camera mounted on the frame, would be more reasonable due to the small size of a mouse’s head. In this specific design, four LED’s can be arranged in a pattern on the mouse’s head and would be monitored by a camera that is located in concrete position. As the LED’s move with the mouse’s movements, the camera records the positions of the LED’s. The video footage can be fed into a computer and
9 a special software can be used to determine the position of the LED’s at any given time (Baratoff and Blanksteen). This system will be used to continuously monitor the mouse head (Figure 7).
Mouse’s Head Emit light Camera ComputerComputer with four LED’s
Figure 7: The block diagram of the optical tracking system. The LED’s on mouse head emit light which is captured by a camera and then processed by a computer.
A positive aspect of this design is that optical tracking has a high update rate and significantly short lags. Ambient light can negatively affect the optical tracking, however in the closed set up of the experiment, this will not be a concern. Other advantages are that the LED's are lightweight and very inexpensive to purchase (Simon). This system is also relatively easy to use since a software can handle the complex calculations and calibrations. A disadvantage to this design is that there always needs to be a clear line of sight to the object being tracked and if this line is blocked or disrupted the performance of the tracking is degraded. A concern with this system is finding the appropriate camera that fits within the monetary budget.
10 EVALUATION MATRIX
The design options were evaluated using five different categories, which were derived from our design specifications: cost, interference with current equipment used in the experiment, ease of use, feasibility, and weight (Table 1). Each design was given a rating of 1 to 3, with 3 being the most desirable and 1 being least desirable in each of the categories; details on the rating system are described in the table.
Interferenc
e with
current Feasibilit
Designs Cost equipment Ease of use y Weight Total Magnetic Sensors 3 3 2 1 1 10 Electronic
Potential & LED 2 1 1 2 3 9 Optical Tracking 3 3 2 3 3 14
Table 1: Each design was evaluate using criteria as stated in the matrix. These criteria were cost
(0-$200 = 3, $201-$3,000 = 2, >$3000 = 1), interference with current equipment (causes interference =
1, no interference = 3), ease of use (needs almost no calibration = 3, may have to calibrate every so often = 2, must calibrate with every use = 1), feasibility (can be constructed in semester = 3, most will be able to be constructed in semester = 2, can not be made = 1), and weight (W<1 gram = 3, W>1 gram = 1). Values were given to each design based on the points stated above.
The design values were totaled and the design with the most points was chosen.
11 Through this evaluation process, the optical tracking system was found to be the best option. It would not cause any interference with the current data collection system used in the experiment, depending on the camera used it can be inexpensive, it would be very easy to set up, and it can be very light weight. However, the main problem with this design is that it would not be able to track the angle of the head in comparison with the speaker. The client specified, however, that the most important data which needs to be collected is the position and orientation of the mouse’s head. Therefore, the optical tracking system was chosen as the final design with the intent that future improvements on the design would allow the angle of the head to also be determined. Initially, the main issues that were of concern in the final construction of the tracking system were making the device weigh less than one gram, compensating for the possibility that one of the LED’s may be obstructed from the camera view by the wires or top of the cage, and finding a camera which fits inside the experimental area and has the correct frequency and resolution.
FINAL DESIGN
The final design of the optical tracking system consists of three separate components: the headpiece along with its circuitry, the camera, and a camera stand to position the camera correctly in the experimental area (Figure 8). The camera should be positioned above the cage to provide a viewing angle of as close to 90 degrees as possible to allow the best view of the LED’s on the mouse head. A direct connection will be present between the camera and computer to allow the images to be received and interpreted by a software program during the experiment.
All LED’s will be powered by a DC power source.
12 Came ra Speaker
Figure 8: An overview of the final design of the optical tracking system. DC Power DC Power
Headpiece design
The initial headpiece design was in the shape of an isosceles triangle and an LED at each point with the point formed by the two equal sides facing the nose to indicate the front of the mouse. However the wires that are attached to the preamplifier may block the line of sight between the LED’s and the camera. In order to compensate for the possibility that an LED is
Figure 9: Diagram of the relative position of the LED’s on the mouse head and around the cage.
13 obstructed from the view of the camera, four LED’s are present on the headpiece in a diamond shape which is symmetrical along one axis (Figure 9).
The top portion of the diamond will face the mouse’s nose in order to indicate which direction the mouse is facing. If one LED is obstructed, the differences in distance between each
LED will allow for a determination to be made about the direction of the mouse. One issue that may need to be resolved is the possibility that the mouse tips it head completely to the side or completely forward which causes the LED’s to be linearly aligned. This occurrence is highly unlikely due to the lower activity of the mice used in these experiments. In addition, it would be extremely difficult for the mice to move their head in such a way when a relatively thick wire is attached to their head. However, if a mouse does turn its head all the way to the side, the positioning of the LED’s would cause a greater intensity of light to be seen near the back of the head and thus the orientation of the head can still be determined. Four other LED’s will be positioned around the edge of the cage to serve as reference points of distance when the data is interpreted. One additional LED will be directly linked to the speaker and will only turn on when the speaker is emitting sound. This will allow the experimental data to be isolated for analysis.
When fabricating the headpiece, the size and weight of the material and LED’s were carefully considered to ensure that the prototype weight falls under 1 gram. The headpiece in constructed from a thin Plexiglas which measured about 3 cm2 across the entire area. The sharp edges of the Plexiglas were filed down in order to prevent injury to the mouse in case it raised its paws to its head. All wires were also secured on the top side of the Plexiglas in order to prevent injury to the mouse and also to prevent damage to the headpiece by the mouse or by the research staff when handling it to attach it to the mouse. The weight of the entire headpiece including the
LED’s, Plexiglas, and wires is about 0.7 grams. The headpiece is attached to the head of the
14 mouse by fitting the headpiece onto an amplifier already attached to the head (Figure 10). In this way, the headpiece sits directly on the dental cement cap and does not directly touch the mouse.
Figure 10: The headpiece fits directly onto the amplifier which is attached to the dental cement cap on the mouse’s head
Several different headpieces were made which contained different types of LED’s that were all connected in series. Ideally, infrared LED’s would be used in the dark conditions of the experiment in order to prevent distraction to the mouse since the mouse cannot see infrared wavelengths. However, several other headpieces were made in order to give the client options if he encountered different situations throughout the experimental process. First, a headpiece of all red LED’s was made to provide the brightest intensity of light possible and also allow the client to view the position of the mouse without the assistance of a camera. Other headpieces used
LED’s of varying colors which allow the position to be determined, not just by the varying distances between LED’s, but also by the position of each color. The use of varying colors of
LED’s would also allow orientation to be determined easily if the LED’s became aligned linearly. However, the LED which will be connected to the speaker must be infrared since a flashing light will definitely distract the mouse and cause erroneous brain waves.
15 In order to allow the different headpieces to be interchangeable, a switch box was constructed which is attached to the headpiece using plugs. Thin wires were soldered and secured with heat shrink tubing to each head piece. These wires were then connected to the sprocket part of a plug, while the other part of the plug was wired to the switch box (Figure 11).
This design not only allows the different types of headpieces to be used, but also allows a headpiece to be easily replaced if it becomes damaged and lowers cost since the switch box only needs to be constructed once.
Figure 11: Shows a diagram of the head piece plug ins for ease of use.
Figure 12: Components of circuitry contained within the switch box include the switch, resistors, and the LED power indicator.
16 An AC to DC power converter was used so that the client would have easy access to a power source. The converter changes the 120 AC voltage from a wall plug-in to a 17.5 DC voltage.
This power source was then incorporated with the switch box so that it can be turned on and off with out difficulty. However, the power supply produced too much current to the LEDS on the head piece, approximately 2 amps. The ideal amperage to an LED is 20 mA. Because of this, three resistors in series where chosen based on ohms Law to account for the excess amperage.
The components inside the switch box provide 18 mA of current (optimal current as set by the manufacturer) to each LED. It also includes a LED power indicator which is especially useful when using the infrared LED headpiece. The switch box provides easy access to a power source and the interchangeability of the headpieces means the switch box must only be constructed once which is convenient due to the higher possibility of damage or burn-out with the headpieces.
Camera and Camera Stand
Currently, the client owns a digital camcorder, model Sony DCR-TRV340, which is acceptable for use in the design (Figure 13).
Figure 13: Sony DCR-TRV340
17 The camera is able to connect directly to the computer through a Firewire connection and can record infrared light. It has a shutter speed of ¼ - 1/4000 which means that the shutter may open and close in as little as 1/4000 seconds; this speed is more than adequate to record the reaction of the mouse to sound stimuli. It operates using a single 1/6 inch CCD which translates into
460,000 pixels of resolution. The camera is 85 x 101 x 206mm in size and weighs 985 grams which is relatively large compared to the size of the experimental chamber.
In order to compensate for the large size of the camera, a camera stand was built to position the camera at the best angle possible in the experimental chamber (Figure14).
Figure 14: Area in which the camera and the camera stand must fit.
The camera stand must be sturdy and heavy enough to remain in place without tilting; it must also safely support the camera without allowing the camera to fall off. A ring stand fitted with two iron rings will be placed in the cage with the base placed under the foam. The bottom ring has a diameter of 13.5cm and is 32 cm above the bottom of the chamber; the top ring has a diameter of 12 cm and is at a height of 40 cm. The rings were then wrapped in foam to protect
18 the camera and to prevent it from slipping from a constant position. The camera sits between the two rings and is affixed with a strap to provide extra stabilization. Even though the stand stretches the entire height of the experimental area, in order for the entire cage to be in the camera’s view, the camera is angled at approximately 15 degrees from vertical with its highest point touching the top of the chamber
The resulting cost of the final design was less than $40 (Table 2). Since the design is so inexpensive, this will allow for more improvements to be made in the future if the client so desires.
Item Cost
Heat shrink tubing $0.13/inch
Plugs $0.99
Wire, switch, resistors, plastic box Provided
AC/DC converter $10.00
LED’s $0.10/LED
Plexiglas Provided
Camera stand $16
Table 2: Breakdown of costs for the final design.
ETHICS
19 The system is designed and constructed in full consideration of the comfort and well- being of the mice. The client required that the headpiece which will fit on the mouse head to weigh less than one gram. The weight requirement is set so that the mice will not be burdened down with excessive weight. Extra weight can be a discomfort for the mice, especially in light of their own small bodies. The headpiece prototype weighs approximately 0.6 grams.
Another consideration is that the headpiece does not actually physically contact the mouse, thus eliminating the possibility of any danger or distress that may occur as a result of directly placing something onto the mouse head.
FUTURE WORK
In order to make this design system complete and functional, there are some continued work and projects that must be completed. First, the digital connection from the camera to a computer via Firewire must be fixed. The streaming video of the mouse’s movement within the cage should be able to be shown directly on the computer monitor and recorded within the computer.
Once this is set up, a computer program could be designed so as to interpret direction and location of the pattern of LED’s of the head piece. The most ideal output of this program would be location and orientation coordinates of the mouse’s head in numerical fashion at all times.
The stationary LED’s placed on the corners of the testing cage can serve as reference points for the computer program to produce this data.
If this is too difficult, numerical coordinates of the mouse head just before, during and after a sound is emitted by the speaker. Currently a student in Dr. Banks’ lab is working on
20 attaching a LED to the top of the speaker, wired to the speaker input, to create a visual indication on the streaming video, of when the sound is emitted by the speaker.
21 REFERENCES
Alusi, G., Hadjiprocopis A., Linney, A., Wright, A. “Three Dimensional Tracking with Ultrasound for Virtual Reality Applications in Surgery.” Accessed: September 25, 2003. URL: http://www.soi.city.ac.uk/~livantes/DOCUMENTS/Tracking.doc
Auer, V., Bonfim, M.J.C., Lamar M.V., Maes M.M., Wanderley M.M. “3D Positioning Acquisition System with Application in Real-Time Processing.” Accessed: October 1, 2003. URL: http://www.ircam.fr/equipes/analyse- synthese/wanderle/gestes/externe/ICSPAT96.pdf
Barafoff, G., Blanksteen, S. “Tracking Devices.” Accessed: September 29, 2003. URL: http://www.hitl.washington.edu/scivw/EVE/I.D.1.b.TrackingDevices.html
Birnir, B. ”GABAA Receptors: Structure, Function and Pharmacology”. Accessed September 17th, 2003. URL: http://www.medfak.lu.se/forskning/medfak/projects_details.php?Proj=51.
Griffths, D.T., et al. “Right Parietal Lobe is Involved in the Perception of Sound Movement in Humans”. Nature Neuroscience 1, pp74-79. May 1998.
“Honeywell Magnetic Position Sensors”. Accessed September 25th, 2003. URL: http://content.honeywell.com/sensing/prodinfo/solidstate/#technical.
Poldrack, Russell A. and Gabrieli, John D. E. Characterizing the neural mechanisms of skill learning and repetition priming. Brain. 124: 67-82. 2001.
Reyes, S. “The Auditory Central System”. Accessed September 19th, 2003. URL: http://serous.med.buffalo.edu/hearing/.
“Sensing in VR”. Accessed September 21th, 2003. URL http://www.cybertherapy.info/pages/sensing.htm.
Simon, D.A. “Intra-Operative Position Sensing and Tracking Devices”. Accessed: September 20th, 2003. URL: www.mrcas.ri.cmu.edu/papers/caos97_sense.pdf.
Troost, B.T, Waller, M.A. Diagnostic Principals in Neuro-Otology: The Auditory System. In: Rosenberg RN, Pleasure DE, eds. Comprehensive Neurology (2nd Ed), Wiley and Sons, Inc., New York, New York. 1998:611-623.
Winmaier, Eric P., Raft, Hershel, Strang, Kevin T. 2004. Human Physiology: The Mechanisms of Body Functions, 9th ed. McGraw-Hill, NY.
22 Appendix
Product Design Specifications
Date: December 9, 2003
Title: Mouse Head Positioning System
Group members: Melissa Haehn, Yao Lu, Meghan Olson, Ben Sprague, Heather Waldeck, and
Andrea Zelisko.
Problem Statement: Our purpose is to develop a system to help study how the auditory system of laboratory mice responds to acoustic stimuli. The system will determine the position and angle of the mouse’s head relative to the speaker emitting the sounds. The system should fit ergonomically with the animal and lab setting, and should not interfere with recording of brain waves.
Client Requirements:
Head piece less than 1g and fits on mouse head
Detachable
Data on position and angle of mouse head relative to sound
No interference with experimental data
Data preferred in analog voltage format
Design requirements:
1. Physical and Operational Characteristics
a. Performance requirements:
23 Signal emitting system must either be positioned on mouse head or
on preamplifier.
Batteries or electrical power source
Minimal calibration for each trial
Data output is analog voltage signal
Voltage signals should either be less than 1µV or greater than
20KHz
Must not interfere with the sound stimuli presented to the mice
Camera stand must hold the camera at the required height and 75
from the vertical
Must provide LED’s with the optimal current b. Safety:
System should be made from non-toxic and non-corrosive
materials
should not pose any electrical dangers
Stand should minimize dangers to the camera
Electrical components should be enclosed safely
There should not be any exposed wires or electrical parts c. Accuracy and Reliability:
data provides orientation of head within quadrants (at a minimal)
24 Camera stand must be sturdy enough to hold camera until at least
end of experiment d. Life in Service:
Each trial lasts 2 hours
Mouse tested 5 days per week e. Shelf Life:
Sterile environment
Room temperature
Standard lab condition
Camera stand must last for minimal of 5 years with normal
experimental use
LED’s must last until its mechanical failure f. Operating Environment:
Sound proof chamber (50 x 54.5 x 75 cm)
Standard lab environment
Close proximity to mice
Room temperature
Professor and associates will handle system g. Ergonomics:
25 System easy to attach and detach
different frequencies than what is tested at
able to withstand handling by researchers
Requires an easy set up (flip of a switch)
Camera easily placed on and removed from camera stand h. Size:
small enough to fit on pre-amplifier (3 x 2 x 1mm) or on the
mouse’s head.
Camera stand must fit within chamber i. Weight:
Head piece less than 1g
Camera stand heavy enough to remain stable j. Materials:
Non-corrosive and non-toxic materials that is not harmful to the
researchers and mice.
Material should not deteriorate under normal usage circumstances. k. Aesthetics, Appearance, and Finish:
Professional appearance
non-hazardous edges or wires
26 Camera stand soft to prevent damage to camera
LED’s are constantly on during experiment to minimize unwanted
stimuli
Any wires or cords should be neatly organized
A method of knowing when system is malfunctioning
2. Production Characteristics
a. Quantity:
At two one head pieces to fit on the preamplifier, preferably
several different prototypes (infrared and visible to increase
options for client)
Camera stand
b. Target Product Cost:
Less than $5,000
Preferably less than $200
3. Miscellaneous
a. Standards and Specifications:
System must meet RARC guidelines for contact with research
animals.
Minimize discomfort of mice
27 b. Customer: specific information on customer likes, dislikes, preferences, and prejudices should be understood and written down.
System should be reusable
Small and lightweight enough to fit on mouse head
System does not distract mice or if provides stimulus, must be a
constant stimulus
Output signal does not interfere with experimental signal c. Patient-related concerns:
The project does not deal with human patients. d. Competition:
Current tracking systems available at much larger scale such as
tracking of a human limb.
No systems marketed for tracking of small animals such as mice.
28