METHOD, MULTI-CHANNEL ELECTRODE, MULTI-CHANNEL RECEIVER AND MULTI-FREQUENCY SYSTEM FOR ELECTRICAL STIMULATION

摘要

An audio signal 55 is split into different bands by filter 50 and the different bands processed in respective channels to modulate a transmitter 74, an implanted receiver (Figs. 1, 3,4) having a corresponding number of channels to detect the transmitted signals and thereby apply stimulating signals to electrodes implanted in the cochlea. Each of four channels in the transmitted may comprise a limiter 58, a frequency-to-voltage converter 60 and a voltage-to-frequency converter 62 giving a pulse train 63 having a prf in the range 40 to 400 Hz and related to the band pass filtered audio signal 57 in that channel - the pulse trains 63 of all four channels all being in the same 40 to 400 Hz range. In each channel a monostable 70 gives a pulse train 71 with a prf. determined by the signal 63 and a pulse width determined by the output of a log. amp. 68 which receives the outputs of filter 50 via a rectifier 66. In transmitter 74, the signals 71 from channels 1 and 3 modulate a 12 MHz carrier, and signals 71 from channels 2 and 4 modulate a 31 MHz carrier, the modulated RF signal from channels 1 and 2 being applied to coil 76 and those from channels 3 and 4 to coil 78. Each channel in the receiver has a tuned circuit with a respective pick-up coil (81 to 84, Figs. 3, 4) and passes the detected signal to electrodes located at a position in the cochlea responsive to an audio frequency in that frequency band passed by the filter 50 in the corresponding transmitter channel. The cochleal implant (Fig. 5) may comprise wires in a silicone elastomer body, each wire terminating in a ball acting on an electrode. Reference is also made to apparatus comprising a four channel implanted receiver and a single channel transmitter, and to apparatus comprising a single channel transmitter, a single channel receiver and a single channel electrode fixed at or adjacent to the round window membrane of the ear. IMAGE