Description of a high speed vestibular stimulator for small animals

Physlolog), and Behavior. Vol. 4, pp. 443-444. Pergamon Press, 1969. Printed in Great Britain

BRIEF COMMUNICATION Description of a High Speed Vestibular Stimulator for Small Animals D A V I D L. C L A R K 1

Department of Zoology, Michigan State University, East Lansing, Michigan 48823 (Received 31 January 1969)

CLA~, D. L. Descriptionof a high speed vestibularstimulatorfor small animals. PHYSIOL.BeHAV.4 0) 443--444, 1969.-A rotation device is desert'bed that provides linear angular acceleration for semicircular canal stimulation within a range from 170°/see* to 650*/sect, with a maximum error of 1.2 per cent. Equipment and animal weight on turntable must be limited to under 1000 g. A complete wiring schematic of circuitry controlling turntable performance is included. This device is valuable in studying semicircular canal function in small animals, using maximal and supramaximal stimulation. Angular accelerator

Rotation device

Semicircular canals

THB MAJORITYof studies of semicircular canal function have used threshold to moderately suprathreshold angular acceleration stimulation ranging from 0.1 to 25 degrees per sec squared. Valuable additional information, however, can be ~,ainedfrom studies using maximal and supramaximai stimulation levels. For example, studies involving the age of onset of ocular nystagmus in a developmental series or studies requiring rapid habituation of adult animals could take advantage of these high levels of stimulation. Appropriate vestibular responses, without end organ damage, have been produced with angular acceleration rates up to 1800°/sec * [2]. The rotation device described below is inexpensive to construct and will produce linear angular acceleration within a range of 170°/sect-650 °/sec*. The turntable consists of a 245 g, 16.5 mm dia. steel plate mounted on a tapered bronze bearing. The 500 g animal restraining device is mounted on top of the steel plate. This device is designed for mice, but larger animals, weighing up to about 1000 g including restraining equipment, can be tolerated if the weight is positioned directly over the axis of rotation. The drive system consists of two Globe Industries, Inc., 28 V d.c. electric motors (Part No. C-3A-741). One motor, geared to run at 1540 r.p.m, at 28 V d.c. drives the turntable via rim drive through an idler wheel. The second motor, geared to run at 13.75 r.p.m, at 28 V d.c., drives the rheostat of power supply B (Fig. 1), through a surplus, 90°, 20:1 reduction trnn__smission. Power supply A (Fig. 1) can be set to any value from zero to 28 V d.c. The current from power supply A is fed, via relays, into motor A. Motor A, through the 20:1 reduction transmission, drives the rheostat of power supply B. Motor A runs at a constant speed, and since the

Vestibular stimulation

rheostat of power supply B is linear, the current increase to motor B, the motor driving the turntable, is a linear function. This results in a steady, angular acceleration of the turntable. Setting power supply A at different levels results in different acceleration rates from the turntable. The basic control system is relatively unsophisticated, but, owing to the light weight turntable and the mechanical advantage of rim drive, the resultant acceleration curves are repeatedly accurate (Fig. 2, Table 1). In order to isolate motor and relay noise, the control panel is housed in a room adjacent to that housing the rotation device. Cables lead from this panel to the turntable and a hand held control box in the experimental room. The unit is activated by depressing Push Button Control 2 (PBC2)., This latches Control Relay 2 (CR2) and starts motor A, which is connected to the rheostat of power supply B. When the rheostat on power supply B reaches a pre~set maximum, a cam on the motor control shaft trips Limit Switch 2 (LS2). This enersizes CR8 which, in turn, pulses CR6, interrupting current to motor A. CR6 also latches CR3 which reverses polarity to motor A. By adjusting the cam that trips LS2, the maximum turntable speed and, therefore, the duration of the stimulus can be regulated. If Toggle Switch 1 (Wl) is open, motor A continues to operate but in the opposite direction, turning the rheostat toward minimum current and decelerating the turntable. If Wl is closed, CR1 is unlatched and motor A stops. Motor B, therefore, continues to rotate the turntable indefinitely at the preset maximum velocity. The turntable can be decelerated by depressing PBC1 which latches CRI and starts motor A, which begi'n~ to turn the rheostat of power supply B toward minimum.

IPresent Address: Department of Anatomy, 1645 Neff Avenue, Ohio State Univendty, Columbus, Ohio 43210. ~Symboisadopted from Joint Iadmtry Confefcace (JIC), Knoop, [1]; Benson, A. D. and D. W. Benson, personal commtmication, Control Design & Fabricate, Inc., Novi, Michillan; Peat, Marwick, MiW.heH& Co., Detroit, Michigan. 443

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TABLE 1

minimum, a cam on the rheostat shaft trips limit switch 1 interrupts current to motor A. CR5 also unlatches CR3 which reverses polarity to motor A.

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error cd' 1.2 per c m t within a italic from abottt 1 7 0 ° / ~ s to 650~/seo. A__cc~xation rates above or below these values do not exhibit trial to trial ~ . It should be noted that there is a 0.075 sec delay upon initiation of ~ This is due to the starting ~ of the turntable. This delay is not ptmmt upon ~ of

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~ C I ~ 1. Knoop, A.R. FundamentaisofR¢layCtrcultDesign. NewYork: 2. MeCatbe, B. F. and IL ~ ~ of motion ~ , 1965. sicJm~ in the cat. Ardw Otol~. 1~: 182-187,1~.