Biomedical subjects
Publications and source records attributed to U T Koch.
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 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.
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.
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.
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.
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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.