Search PubMed⌕ Search

PubMed · 442995

Neurophysiological requirements for implanted cochlear prostheses.

Abstract

Regarding the neurophysiological requirements for implanted cochlear prostheses, we have discussed (i) the complexity of speech sounds, (ii) problems of intensity, then (iii) the frequency problem, and (iv) finally the possibility of a frequency transposition to the genuine frequency range of a single fibre of any mechanoreceptor and its connecting nerve fibre (less than 1 kHz) for the construction of an intracochlear prosthesis. In general it would seem necessary to seek compromises based on the fact that speech, at least the vowels, contains redundancy and that the use of additional sensory channels might be helpful for cochlear implants. Certainly besides other preprocessing techniques for speech information, the multichannel stimulation set-up of special electrodes has to be used to convey a sufficient amount of speech information to restore the faculty of speech perception in completely deaf patients. Decompression of intensity range and compression of frequency range might be especially useful.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

W D Keidel. Neurophysiological requirements for implanted cochlear prostheses.. https://doi.org/10.3109/00016487909126402

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

Acoustic startle, prepulse inhibition, and fear-potentiated startle measured in rhesus monkeys.

BACKGROUND: Modulation of the acoustic startle response is a simple and objective indicator of emotionality and attention in rodents and humans. This finding has proven extremely valuable for analysis of neural systems associated with fear and anxiety. Until recently, there have been few efforts to develop acoustic startle measurement in nonhuman primates. We report here development of a whole-body acoustic startle protocol in rhesus monkeys. METHODS: Eight juvenile rhesus monkeys were tested in a new whole-body (somatic) acoustic startle protocol. Startle responses were assessed in three paradigms: 1) stimulus intensity-response amplitude, 2) prepulse inhibition (PPI), and 3) fear-potentiated startle. RESULTS: Initial studies revealed that the amplitude of whole-body startle in monkeys, as in rodents and humans, is directly proportional to acoustic stimulus intensity and gradually habituates with repeated exposures. Presentation of a weak acoustic stimulus 45-2020 msec before a startle stimulus reduces startle amplitude by 40%-50%, depending on interstimulus interval length (PPI). We have also measured significant potentiated startle amplitude in the presence of a visual stimulus after pairing it with an inescapable pulse of pressurized air (fear-potentiated startle). CONCLUSIONS: Our data demonstrate that acoustic startle in nonhuman primates successfully bridges rodent and human research in two broad areas: stimulus-response relationships and behavioral plasticity represented by habituation, PPI, and fear potentiation. The opportunity now emerges to link concepts developed in rodents to the more complex neuroanatomical and cognitive processes common to monkeys and humans.

Acoustic Stimulation↗

Vascular defects and sensorineural deafness in a mouse model of Norrie disease.

Norrie disease is an X-linked recessive syndrome of blindness, deafness, and mental retardation. A knock-out mouse model with an Ndp gene disruption was studied. We examined the hearing phenotype, including audiological, histological, and vascular evaluations. As is seen in humans, the mice had progressive hearing loss leading to profound deafness. The primary lesion was localized to the stria vascularis, which houses the main vasculature of the cochlea. Fluorescent dyes showed an abnormal vasculature in this region and eventual loss of two-thirds of the vessels. We propose that one of the principal functions of norrin in the ear is to regulate the interaction of the cochlea with its vasculature.

Acoustic Stimulation↗

Context-dependent adaptive coding of interaural phase disparity in the auditory cortex of awake macaques.

In the ascending auditory pathway, the context in which a particular stimulus occurs can influence the character of the responses that encode it. Here we demonstrate that the cortical representation of a binaural cue to sound source location is profoundly context-dependent: spike rates elicited by a 0 degrees interaural phase disparity (IPD) were very different when preceded by 90 degrees versus -90 degrees IPD. The changes in firing rate associated with equivalent stimuli occurring in different contexts are comparable to changes in discharge rate that establish cortical tuning to the cue itself. Single-unit responses to trapezoidally modulated IPD stimuli were recorded in the auditory cortices of awake rhesus monkeys. Each trapezoidal stimulus consisted of linear modulations of IPD between two steady-state IPDs differing by 90 degrees. The stimulus set was constructed so that identical IPDs and sweeps through identical IPD ranges recurred as elements of disparate sequences. We routinely observed orderly context-induced shifts in IPD tuning. These shifts reflected an underlying enhancement of the contrast in the discharge rate representation of different IPDs. This process is subserved by sensitivity to stimulus events in the recent past, involving multiple adaptive mechanisms operating on timescales ranging from tens of milliseconds to seconds. These findings suggest that the cortical processing of dynamic acoustic signals is dominated by an adaptive coding strategy that prioritizes the representation of stimulus changes over actual stimulus values. We show how cortical selectivity for motion direction in real space could emerge as a consequence of this general coding principle.

Acoustic Stimulation↗