A new cuff electrode for reversible conduction blocking.

A cuff electrode of novel design (rigid body and lid) is presented. It contains a closed cavity surrounding the nerve, through which a cooled liquid (Ringer solution) can be circulated. Recording sites at both ends of the cavity permit monitoring of the conduction blocking, which occurs at different temperatures for different units. Reversible blocking with chemical agents is equally possible with this device.

A high speed recoil-free piezo-drive for cell impalement.

A piezoelectric drive system for cell impalement is described. It uses commercially available low voltage piezo elements permitting complete position control by arbitrary voltage signals. Electrode velocities of up to 100 microns/ms are achieved. The recoil momentum to the manipulator is effectively compensated by a second piezo drive oriented in the opposite direction, avoiding for instance a cumbersome lead block or restrictions given by the mounting of the piezo system with respect to the manipulator mass. The actual performance of the system is described and compared to other devices in the literature.

A precision multichannel cuff electrode optimized by simulation and experiment.

The parameters influencing single end and differential en passant extracellular recordings were investigated using two independent simulation methods. The results were compared with measurements from experimental electrodes. The effects of electrode size, electrode distance and leakage can thus be understood and the experiments agree with the simulation results. This led to the optimation of a novel en passant electrode producing very narrow signals with very high reliability. The electrode is used for multichannel recording in a velocity selective recording system.

An improved system for single unit isolation from multiunit nerve recordings by velocity analysis.

A system for recording and decomposition of complex extracellular spike trains by analog computing is presented. Unlike other systems, it is not necessary to establish templates for the analysis. Rather by adjustments of a single knob, the velocity band can be adjusted. The velocity measurement can be made to a precision of better than 1%, where the velocity jitter in individual spikes of a unit becomes apparent. Spike trains on the connective of a stick insect are analyzed which occur during an intersegmental reflex, the CLP reflex.

A modular analog neuron-model for research and teaching.

An analog electronic neuron for modeling neuronal networks and for teaching purposes is presented. The circuitry represents a new approach, since ionic channels are all modeled by fast relay switches in combination with resistors. Thus, the synapse design includes nonlinear PSP superposition and reversal potentials. The spike is modeled with Na+ and K+ currents. Detailed circuit diagrams and examples of performance are given. Besides its use in network research, the model has been successfully used over 3 years of teaching practice.

A radiotelemetry system for analyzing heart rate responses during playback experiments in blackbirds (Turdus merula ).

In acoustical stimulus-response tests on European blackbirds (Turdus merula ) in cages and an outdoor aviary, alteration in heart rate (HR) was used to measure reaction strenght. HR was measured by radiotelemetry. The miniature transmitters newly developed for this task had to fulfill the following requirements: Simultaneous recordings of HR in several interacting animals; uninterrupted transmission of HR signals, sufficient range and battery life combined with low weight and easy handling properties. The miniature transmitters successfully used in this experiment had a quartz-stabilized oscillator. They weighed between 4.1 and 5.2 g and had a range of 3 m and a lifetime of 72 hrs (circuit diagram, Fig.1). The transmitted signal corresponded to a unitary impulse representing the S-wave of the ECG (Fig. 4b). Implanted electrodes were used to record ECG potentials. The transmitter was carried by the birds like a small rucksack tied to their backs. Electrode implantation and transmitter installation are described in detail. HR signals stored on audio tape were later transformed to frequency curves on a chart recorder (Fig. 3, 4a). Typical HR response curves are shown (Fig. 5). Statistical analysis of the data was performed on a DEC-PDP-11 computer using a special set of programs. The system has been successfully used to provide answers to experimental questions not previously obtainable with classical methods.

Neuronal mediation of cardiovascular effects of food arousal in aplysia.

Previous studies have demonstrated that heart rate and blood pressure increase in Aplysia during an arousal state elicited by food stimuli. In addition, during biting, blood flow is routed alternately to the head (during protraction of the buccal mass) and to the digestive system (during retraction). In this study, cutting the pleuroabdominal connectives eliminated 75% of the heart rate response during food arousal, and cutting the pleuroabdominal connectives eliminated 20-50% of the pressor response. Recording in the abdominal ganglion from the RBHE heart excitor and the three LBVC vasoconstrictor motor neurons in a reduced preparation showed that activity in these neurons was increased 50 and 100%, respectively, during food arousal. Activity of the LBVC cells was maximal during the protraction phase of biting. The LBVC vasoconstrictor motor neurons, when fired at the rates recorded during food arousal, can occlude the abdominal aorta completely. We conclude that the RBHE and LBVC neurons mediate, in part, the heart rate and pressor responses recorded during food arousal and that cyclic activity in LBVC contributes significantly to the cyclic alternation of blood flow between the head and the gut during rhythmic biting behavior.