Device for controlling the electric charge on stimulating electrodes

Abstract

A device for stimulating living tissue or nerves by individual or repeated stimulating pulses via stimulating electrodes which stimulate living tissue or nerves by stimulating pulses includes an electrical circuit which regulates the electric voltage or charge on the stimulating electrodes as a function of the electric voltage between the stimulating electrodes and reduces or equalises imbalances of electric charges on the stimulating electrodes. This device is capable of equalizing the electric charge on the stimulating electrodes of a stimulation system. The device and the process for using the device have the advantage that imbalances of electric charges on the stimulating electrodes, and the associated disadvantageous effects on the tissue and on the nerves, are avoided or eliminated. Furthermore, the device has a small space requirement.

What is claimed is: 
     
         1 . A device for stimulating living tissue cells or nerves by individual or repeated stimulating pulses via stimulating electrodes, the stimulating electrodes being contacted with living nerve cells or tissue that are/is stimulated by the stimulating pulses of the stimulating electrodes, comprising: an electrical circuit which controls the electric voltage or the electric charge on the stimulating electrodes as a function of the electric voltage between the stimulating electrodes and reduces or equalizes imbalances of electric charges on the stimulating electrodes. 
     
     
         2 . A device according to  claim 1 , wherein the device generates a positive or negative electric current of defined duration and intensity and applies it to at least one stimulating electrode, as a result of which imbalances of electric charges between the stimulating electrodes are reduced or equalizes. 
     
     
         3 . A device according to  claim 1 , wherein the device includes a pulse-generator which generates electrical pulses which are amplified into stimulating pulses by a current/voltage source and passed to at least one first stimulating electrode, to a number of stimulating electrodes. 
     
     
         4 . A device according to  claim 3 , wherein the shape or contour of the electrical stimulating pulses generated by the device or of the current pulses for the charge equalization between the stimulating electrodes is adapted to the type of tissue to be stimulated or to the type of nerve cells to be stimulated. 
     
     
         5 . A device according to  claim 3 , wherein the connection of the electrical circuit to the at least one stimulating electrode can be interrupted or established by a switching contact. 
     
     
         6 . A device according to  claim 1 , wherein the device includes a coulombmeter and/or voltmeter which is connected to the stimulating electrodes and ascertains the electric voltage between the stimulating electrodes or ascertains imbalances at the stimulating electrodes. 
     
     
         7 . A device according to  claim 6 , wherein the coulombmeter and/or voltmeter ascertains the electric voltage between the stimulating electrodes between stimulation cycles, i.e. while the tissue or nerves contacted with the stimulating electrodes is/are not being stimulated by stimulating pulses of the stimulating electrodes, or no load current or stimulating current is being applied to the stimulating electrodes. 
     
     
         8 . A device according to  claim 1 , wherein the device includes a comparator which establishes whether the electric voltage or the differences in charge between the stimulating electrodes lies below, within or above a defined voltage range which is defined by predetermined limiting values. 
     
     
         9 . A device according to  claim 8 , wherein the device includes a charge-injector which generates a positive or negative electric current of defined duration and intensity and applies it to the stimulating electrode, as a result of which imbalances of electric charges on the stimulating electrodes are reduced or equalized. 
     
     
         10 . A device according to  claim 9 , wherein the result ascertained by the coulombmeter and/or voltmeter with respect to the electric voltage between the stimulating electrodes or with respect to the imbalances of electric charges on the stimulating electrodes is passed to the comparator and the result of the comparison carried out by the comparator as to whether the electric voltage or the differences in charge between the stimulating electrodes lies below, within or above a predetermined voltage range is passed to the charge-injector and on the basis of the signals passed by the comparator the charge-injector applies a positive or a negative voltage and with defined current intensity over a defined time-interval to the at least one stimulating electrode, so that the electric voltage between the stimulating electrodes or imbalances of electric charges on the stimulating electrodes are reduced or equalized equalised. 
     
     
         11 . A device according to  claim 1 , wherein the device serves for electrostimulation of a retina of an eye, in particular as a function of incident light, with an electrical circuit in the form of an integrated circuit which is designed to be implanted in the region of the retina, wherein the electrical circuit includes a number of contact-points for contacting retinal cells and a number of light-sensitive elements which drive the contact-points via the electrical circuit as a function of incident light. 
     
     
         12 . A device according to  claim 1 , wherein the electrical circuit comprises electronic components and also metallic conductor tracks for the contacting thereof, which are photolithographically microstructured and accommodated on a chip. 
     
     
         13 . A system for stimulating living tissue or nerves by individual or repeated stimulating pulses via stimulating electrodes, with a device according to  claim 1 , wherein the device is integrated within the stimulation system. 
     
     
         14 . A process for operating a device for stimulating living tissue cells or nerves by individual or repeated stimulating pulses via stimulating electrodes, the stimulating electrodes being contacted with living nerve cells or tissue that are/is stimulated by the stimulating pulses of the stimulating electrodes, comprising the following steps: ascertaining an electric voltage between the stimulating electrodes or ascertaining an imbalance of electric charges between the stimulating electrodes, comparing the ascertained voltage between the stimulating electrodes with a predetermined voltage range, generating and applying a positive or negative electric current of defined duration and intensity to at least one stimulating electrode, as a result of which the electric voltage between the stimulating electrodes or an imbalance of electric charges on the stimulating electrodes is reduced or equalized equalised. 
     
     
         15 . A process according to  claim 14 , wherein the electric voltage between the stimulating electrodes is ascertained also during the equalization of charge on the stimulating electrodes and as soon as the voltage between the stimulating electrodes again lies within the predetermined voltage range or no voltage is present any longer between the stimulating electrodes, the supply of current to the stimulating electrodes for the purpose of charge equalization is interrupted. 
     
     
         16 . A process according to  claim 14 , wherein the ascertainment of an electric voltage between the stimulating electrodes or of an imbalance of electric charges on the stimulating electrodes and/or of the equalisation of charge on the stimulating electrodes is carried out between stimulation cycles, while the tissue or nerves contacted with the stimulating electrodes is/are not being stimulated by stimulating pulses of the stimulating electrodes or no load current or stimulating current is being applied to the stimulating electrodes. 
     
     
         17 . A process according to  claim 14 , wherein the ascertainment of an electric voltage between the stimulating electrodes or of an imbalance of electric charges on the stimulating electrodes is only carried out when no stimulating current is applied to the stimulating electrodes. 
     
     
         18 . A process according to  claim 14 , wherein the ascertainment of an electric voltage between the stimulating electrodes or of an imbalance of electric charges on the stimulating electrodes and/or of the equalization of charge on the stimulating electrodes is only carried out when no stimulating current is applied to the stimulating electrodes and to stimulating electrodes in the vicinity of the stimulating electrodes, wherein neither the stimulating electrodes nor stimulating electrodes in the vicinity of the stimulating electrodes are being stimulated by stimulating pulses. 
     
     
         19 . A process according to  claim 14 , wherein the ascertainment of an electric voltage between the stimulating electrodes or of an imbalance of electric charges on the stimulating electrodes and/or of the equalization of charge on the stimulating electrodes is repeated cyclically. 
     
     
         20 . A process according to  claim 14 , wherein the ascertainment of an electric voltage between the stimulating electrodes or of an imbalance of electric charges on the stimulating electrodes and the supply of an equalizing current with defined duration and amplitude to the stimulating electrodes for the purpose of equalisation equalization of charge on the stimulating electrodes is carried out in alternating manner.