The periodicity and place-pitch modulation data, along with the data on loudness, offers promise of the development of a multielectrode, multichannel cochlear auditory prosthesis. Also, the currents required for cochlear stimulation are of the magnitude which can pass across the electrode-perilymph interface, by double-layer charging, without production of toxic by-products of electrolysis(6), supporting the feasibility of long-term chronic stimulation.

Acoustic Stimulation↗

PubMed1974

Artifical vision for the blind: electrical stimulation of visual cortex offers hope for a functional prosthesis.

Electrical stimulation of the occipital cortex resulted in discrete photic sensations or "phosphenes" in two volunteers who had been totally blind for 7 and 28 years, respectively. Stimulation of multiple electrodes allowed one patient to recognize simple patterns, including letters. Both patients made an uneventful recovery, and the success of these experiments reinforces the hope that a functional visual prosthesis can be developed, although many problems remain to be solved.

Adult↗

PubMed1974

Phosphenes produced by electrical stimulation of human occipital cortex, and their application to the development of a prosthesis for the blind.

1. To explore the feasibility of a visual prosthesis for the blind, human visual cortex has been stimulated during a series of surgical procedures on conscious volunteers undergoing other occipital lobe surgery.2. Area no. 17 seems the most effective locus for such stimulation, at least in sighted or recently hemianopic patients.3. Changes in electrode size and configuration, or in stimulus parameters, have little effect on subjective sensation.4. Thresholds do vary depending on parameters, but not electrode size, and these effects have been studied.5. Painful effects are associated with stimulation of the dura, but not of the calcarine artery and associated vessels.6. Stimulation of a single electrode usually produces one phosphene, whose size ranges from tiny punctate sensations like ;a star in the sky' up to a large coin at arm's length. Very large elongated phosphenes, like those seen by Brindley's second patient, have not been reported despite the number of patients, electrodes, and combinations of stimulus parameters tested. These large phosphenes may be an effect of prolonged blindness.7. Stimulation substantially above threshold may produce a second conjugate phosphene, inverted about the horizontal meridian.8. Stimulation of a single electrode may also produce multiple phosphenes with no differential threshold.9. Chromatic effects and/or phosphene flicker may, or may not occur. This can vary from point to point on the same patient.10. Phosphenes fade after 10-15 sec of continuous stimulation.11. All phosphenes move proportionately with voluntary eye movements, within the accuracy of our mapping techniques.12. Brightness modulation can easily be achieved by changing pulse amplitude.13. The position of phosphenes in the visual field corresponds only roughly with expectations based on classical maps showing the projection of the visual field onto the cortex.14. Patients can usually discriminate phosphenes produced by 1 mm(2) electrodes on 3 mm centres, although this seems to be close to the limit of resolution.15. Patterns of up to four phosphenes produced by four electrodes have been recognized. However, a variety of complex interactions have been reported.16. Multiple phosphenes are co-planar, although patients are unable to estimate their distance.17. Phosphenes appear immediately when stimulation is begun, and disappear immediately upon cessation of stimulation.18. Future work must concentrate on blind volunteers to explore possible differences in subjective sensation produced after prolonged blindness, and to explore more complex pattern presentation which requires substantial periods of time with any given patient.

Adult↗

PubMed1974

The directions for future research on sensory prostheses.

Explore the source record for details and available documents.

Animals↗

PubMedDate not supplied

A prosthesis for the deaf based on cortical stimulation.

Explore the source record for details and available documents.

Anesthesia, General↗

PubMedDate not supplied

Auditory prostheses research with multiple channel intracochlear stimulation in man.

Although single-channel electrode arrays implanted in the scala tympani of deaf patients are useful as an aid to lip reading and for distinguishing some environmental sounds, they do not transmit intelligible speech. However, multichannel electrode arrays, which take advantage of the cochlea's tonotopic organization, may be capable of generating the complex patterns of neural activity necessary for speech discrimination. In this study, multichannel electrodes were implanted in the cochleas of four volunteers, with access to the connecting wires made through the skin via a percutaneous connector. The major portion of the data presented is from two of these subjects: one has been bilaterally deaf since birth and the other has been unilaterally deaf for 15 years. Preliminary results of experiments with two more recently implanted subjects are described as well as experiments with a fifth volunteer who was implanted with five electrodes by House in 1969. Data on pitch and loudness discrimination as well as the effects of stimulation parameters on threshold, impedance, and electrode interaction are presented. Place pitch and periodicity pitch were observed in all five volunteers. The results of pitch-matching experiments with the unilaterally deaf volunteer were consistent with tonotopic maps of the cochlea, and experiments indicated that a pitch continuum may be achieved by combining place and periodicity pitch modulation. Preliminary experiments in tune recognition with one subject demonstrate his ability to recognize simple melodies based on periodicity pitch cues. These results, coupled with the finding that subjective sensations remain stable over the long-term, support the feasibility of providing artificial hearing with a multichannel cochlear stimulation system.

Acoustic Stimulation↗