Jacob Zabara

Inhibition of Experimental Seizures in Canines by Repetitive Vagal Stimulation

Summary: Repetitive electrical stimulation of the canine cervical vagus nerve interrupts or abolishes motor seizures induced by strychnine and tremors induced by pentylenetetrazol (PTZ). Tremors were defined as rhythmic alternating contractions of opposing muscle groups, exerting much less force than seizure contractions. Seizures were induced by injection boluses of strychnine or PTZ at 1‐ to 4‐min intervals until sustained muscle activity was observed electromyographically (EMG). Vagal stimulation terminated seizures in 0.5‐5 s. There were prolonged periods with no spontaneous EMG activity after stimulation. The period of protection was approximately four times the stimulation period. The antiseizure actions of vagal stimulation were not altered by transection of the vagus distal to the stimulating electrode. Optimal stimulus parameters were estimated: strength, ‐20 V (electrode resistance 1‐5 ω); frequency 20–30 Hz; duration, ‐0.2 ms. These data suggest that the antiseizure effects derive from stimulation of small‐diameter afferent unmyelinated fibers in the vagus nerve. These results may form the basis of a new therapeutic approach to epilepsy.

The implantable neurocybernetic prosthesis system.

The neurocybernetic prosthesis system (NCP) is an implantable, multiprogrammable pulse generator that delivers constant current electrical signals to the vagus nerve for the purpose of reducing the frequency and severity of epileptic seizures. The signals are delivered on a predetermined schedule, or may be initiated by the patient with an external magnet. The device is implanted in a subcutaneous pocket in the chest just below the clavicle, similar to pacemaker placement. The stimulation signal is transmitted from the prosthesis to the vagus nerve through a lead connected to an electrode which is a multi‐turn silicone helix, with a platinum band on the inner turn of one helix. The prosthesis can be programmed with any IBM‐ compatible personal computer using NCP software and a programming wand.

An implantable neurocybernetic prosthesis system

Summary: The neurocybernetic prosthesis (Cyberonics, Inc.) is an implantable, multiprogrammable pulse generator that delivers constant current electrical signals to the vagus nerve for the purpose of reducing the frequency and/or severity of epileptic seizures. The device is implanted in a subcutaneous chest pocket just below the clavicle, similar to cardiac pacemaker placement. The stimulation signal is transmitted from the prosthesis to the vagus nerve through a stimulation lead. The prosthesis can be programmed using any IBM‐compatible personal computer with programming software and a programming wand. The electrodes used in the first group of patients were found to break at an unacceptable rate. Design modifications appear to have resolved this problem.

Response reduction in dipteran chemoreceptors after sustained feeding or darkness

Abstract 1. 1. After sustained exposure to darkness, labellar chemoreceptors of flies give brief discharge lasting a few seconds. 2. 2. In normally lighted or fully fasted flies, all sensilla respond and impulse frequencies are higher. 3. 3. For each fast period, impulse frequency distribution is continuous rather than biomodal, indicating a gradual phenomenon. 4. 4. Chemoreceptor modulation could act to safeguard long-term feeding regulation under wide environmental swings.

Suppression of the Gag Reflex by Exaggerated Respiratory Movements

Gagging may be readily induced by touching the back of the throat. The ease with which this can be done varies considerably in different individuals-some have difficulty brushing their posterior teeth without gagging. Although there are some individuals without a gag reflex, the reflex is inherited by most persons. The patient who gags easily during routine dental procedures presents a distressing problem to the dentist. An account of the clinical information related to the possible causes of gagging and methods of treatment has been presented by Faigenblum.1 The following are some experimental precautions to prevent gagging: relax the patient mentally by reassuring him that the procedure will soon be over and he will not choke; relax the patient physically because if he grasps the armrest, tenses the shoulders, or fixes the chest, he will almost certainly gag; and talk to divert the patients attention. Another empirical method suggested to minimize gagging is to have the patient increase the rate of his breathing. The purpose of this study was to investigate the physiologic basis of the latter technic.

Reflex and autorhythmicity: A formal model

Abstract A formal model for the nervous system is indicated by consideration of both the reflex and autorhythmicity. A space R A is presented for the nervous system based upon proposed definitions and axioms of the reflex and autorhythmicity. Experimental observations are described that illustrate and support the definitions and axioms of R A. A theorem suggested for R A is that it has a linear subspace.

Axiomatics for a nervous system

Abstract An axiomatic approach is described for the nervous system as the basis for the construction of a formal model. The model is developed from the primitive undefined term of pulse and the operations of focusing, geometry, and order. The axiom of the model states that a pulsation conducts in a circle unless it is intersected by another pulsation.