William J. Mundl

An accelerometer for recording head movement of laboratory animals

Abstract The construction of an inexpensive light-weight accelerometer for use as a head-movement transducer with small animals in brain-recording (or brain-stimulation) experiments is described. The accelerometer can simply be taped to the existing cables, thereby furnishing a sensitive measurement of head movement.

Capacitive sensor for lick-by-lick recording of drinking.

Abstract An electronic device senses the touching of water by the animals tongue; and each lick is recorded distinctly as a deflection on paper by an ascillograph. From these traces lick rate and any variations therein may be determined.

Cardiovascular and respiratory responses to electrical stimulation of the midbrain in the rat

In descending through the midbrains of rats with stimulation electrodes, we have observed some remarkable reversals of pressor and depressor autonomic effects as the electrode was moved from one locus to another. Autonomic effects of stimulating in the midbrain areas that we studied are of special interest because stimulations in some of these midbrain loci have pain-relieving effects (Hosobuchi et al., 1977, 1979; Mayer et al., 1971; Soper, 1976). Our observations of cardiac arrest are of particular concern because of the use that is being made of midbrain electrical stimulation to relieve pain in human patients.

An improved swivel for recording from behaving subjects

Abstract Swivel devices allow free rotation of electric cables which connect a moving test subject to stationary equipment. Advantages and shortcomings of previously described devices are examined. The new design described herein contains two electric circuits and permits artifact-free transmission of microvolt signals. Freely rotating contacts are maintained by platinum wires dipping into concentric pools of mercury.

Restoring rectangular pulses of stimulation current

Abstract The extensively used rectangular pulses for electrical stimulation of laboratory animals are greatly distorted when applied to thin wire electrodes. The large current densities present at the electrode tips cause a capacitive behaviour of the metal-electrolyte interface. Restoring the pulses by simple means to a near-rectangular shape facilitates measuring of the pulse height with an oscilloscope. A satisfactory solution to the problem has been achieved by equalizing the capacitance of the electrode-electrolyte combination with an inductance connected in series into the circuit.

Preamplifier for recording of multiple-unit activity from moving animals

Abstract Recording of multiple-unit activity from moving animals is improved by employing a preamplifier of special design which is insensitive to electrical artifacts generated by the animals movements. The shields of the input cables are driven in synchrony with the input signal in order to reduce shunt-capacitances.

Recording of unit activity on paper charts

Abstract A method is described that makes it possible to record unit pulses on a paper chart recorder. The pulses are widened to allow sufficient time for the oscillograph excursio. The amplitude of each pulse is preserved.

Practical design of low-frequency bandpass filters

THe USEFtJLNESS of bandpass filters for analyzing the EEG frequency spectrum has long been established. The frequency response curves of these filters should have a flat top across the pass band and steep sides to assure maximum attenuation outside the pass band. These requirements can be met by an active filter containhag a number of stagger-tuned, frequency-selective stages, in which each stage consists of a twin-T network connected in the feedback path of an amplifier, qhe twin-T network has been extensively treated in the literature (e.g. HASTINGS, 1946 ; FLEXSHER, 1948 ; COWLES, 1952; BtJCKLrV, 1956, and HYDE, 1957) and fornmlas for stagger-tuning were published by WALLMAN (1948). However, the extent of the calculations, although simple, and the lack of a suitable, easily constructed amplifier circuit have restrained many laboratories from building such filters. This article provides all necessary design data and describes an amplifier circuit developed for purposes of frequency analysis. Bandpass filters with three stagger-tuned stages and five stagger-tuned stages prevail as the most useful in EEG work, where the pass bands of interest are usually of two widths, namely one of approximately 1/4-1/2 octave and one of approximately 3/4-1 octave. Using a stagger-tuned triple for the former and a stagger-tuned quintuple for the latter results in a compromise of adequate rejection outside the pass band and a sufficiently low Q of the individual stages to prevent excessive ringing. In Fig. 1 are shown functional diagrams and typical characteristics of frequency responses. 2. METHOD OF CALCULATION

A locomotion sensor for recording some stereotyped behavior of the rat

Abstract A capacitance sensor can be used for recording an animals position on a test platform. This method of recording was found useful in correlating electrical brain activity with stereotyped behavior.

An ultrasonic auditory stimulator

An auditory stimulator with a frequency range to 40 kHz is described. The onset and cessation of the stimulation tone are carefully shaped in order to eliminate unwanted clicks. Rats have shown marked responses in electrical brain activity to ultrasonic stimulation.