Field focusing and mapping in an electrode array

Abstract

The present invention is a system for mapping a high resolution image to a lower resolution electrode array and, by applying varying stimulus to neighboring electrodes, creating a perceived image greater in resolution than the electrode array. The invention is applicable to a wide range of neural stimulation devices including artificial vision and artificial hearing. By applying a sub-threshold stimulus to two neighboring electrodes where the sum of the stimuli is above the threshold of perception, a perception is created in neural tissue between the two electrodes. By adjusting the stimulus on neighboring electrodes, the location of stimulation can be altered. Further, noise can be applied to the stimulating electrode or its neighboring electrodes to reduce the threshold of stimulation.

1 . A method of stimulating neural tissue comprising: 
 providing an electrode suitable for contact with the neural tissue, said electrode having a predetermined threshold of stimulation;    energizing said electrode with a noise signal at a level less than said threshold of stimulation; and    energizing said electrode with a signal at a level more than said threshold of stimulation immediately after energizing said electrode with said noise signal.    
     
     
         2 . The method according to  claim 1 , wherein said noise signal is white noise.  
     
     
         3 . The method according to  claim 1 , wherein said noise signal is pink noise.  
     
     
         4 . The method according to  claim 1 , wherein said noise signal is Gaussian noise.  
     
     
         5 . A visual prosthesis comprising: 
 a camera for receiving a pixilated image;    a plurality of electrodes suitable for contact with neural tissue; and    an image possessing circuit receiving said pixilated image from said camera and    mapping said image to said plurality of electrodes, wherein some pixels are mapped to neural tissue between said electrodes.    
     
     
         6 . The visual prosthesis according to  claim 5 , wherein said plurality of electrodes are suitable for contact with a retina.  
     
     
         7 . The visual prosthesis according to  claim 5 , wherein pixels from said pixilated image are mapped to said electrodes in rapid succession such that they form the perception of a single image.  
     
     
         8 . The visual prosthesis according to  claim 5 , wherein said some pixels are mapped to said plurality of electrodes wherein a signal from an individual of said plurality of electrodes is insufficient to create the perception of light, but the sum of signals from said plurality of electrodes is sufficient to create the perception of light.  
     
     
         9 . The visual prosthesis according to  claim 8 , wherein said signals from said plurality of electrodes are of opposite polarity.  
     
     
         10 . The visual prosthesis according to  claim 9 , wherein said signals from said plurality of electrodes have a net charge of zero.  
     
     
         11 . The visual prosthesis according  claim 9  wherein a series of said signals from said plurality of electrodes have a net charge of zero.  
     
     
         12 . The visual prosthesis according to  claim 5 , wherein varying signals from said plurality of electrodes create the perception of light at varying locations between said plurality of electrodes.  
     
     
         13 . The visual prosthesis according to  claim 8 , wherein said signals are repeated in rapid succession such that multiple signals are perceived as a single image.  
     
     
         14 . The visual prosthesis according to  claim 13 , wherein said multiple signals are repeated within 1/50 second.