Michael F. Dorman

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OBJECTIVE The aim of the present experiment was to assess the consequences of cochlear implantation at different ages on the development of the human central auditory system. DESIGN Our measure of the maturity of central auditory pathways was the latency of the P1 cortical auditory evoked potential. Because P1 latencies vary as a function of chronological(More)
Vowels, consonants, and sentences were processed through software emulations of cochlear-implant signal processors with 2-9 output channels. The signals were then presented, as either the sum of sine waves at the center of the channels or as the sum of noise bands the width of the channels, to normal-hearing listeners for identification. The results(More)
Recent studies have shown that high levels of speech understanding could be achieved when the speech spectrum was divided into four channels and then reconstructed as a sum of four noise bands or sine waves with frequencies equal to the center frequencies of the channels. In these studies speech understanding was assessed using sentences produced by a(More)
We examined the longitudinal development of the cortical auditory evoked potential (CAEP) in 21 children who were fitted with unilateral cochlear implants and in two children who were fitted with bilateral cochlear implants either before age 3.5 years or after age 7 years. The age cut-offs (<3.5 years for early-implanted and >7 years for late-implanted)(More)
OBJECTIVE This study examined morphological changes in the cortical auditory evoked potential (CAEP) waveform as a function of varying stimulation rate. Stimuli were presented in a paradigm which indirectly assesses the refractory properties of the underlying neuronal generators. METHODS CAEPs were recorded in 50 normal-hearing children (3-12 years) and(More)
The goal of this study was to examine the neural encoding of voice-onset time distinctions that indicate the phonetic categories /da/ and /ta/ for human listeners. Cortical Auditory Evoked Potentials (CAEP) were measured in conjunction with behavioral perception of a /da/-/ta/ continuum. Sixteen subjects participated in identification and discrimination(More)
UNLABELLED A basic tenet of developmental neurobiology is that certain areas of the cortex will re-organize, if appropriate stimulation is withheld for long periods. Stimulation must be delivered to a sensory system within a narrow window of time (a sensitive period) if that system is to develop normally. In this article, we will describe age cut-offs for a(More)
OBJECTIVE To compare two methods of minimizing cochlear implant artifact in cortical auditory evoked potential (CAEP) recordings. METHODS Two experiments were conducted. In the first, we assessed the use of independent component analysis (ICA) as a pre-processing filter. In the second, we explored the use of an optimized differential reference (ODR) for(More)
Normally hearing listeners were presented with vowels, consonants, and sentences for identification through an acoustic simulation of a five-channel cochlear implant with electrodes separated by 4 mm (as in the Ineraid implant). The aim of the experiment was to simulate the effect of depth of electrode insertion on identification accuracy. Insertion depth(More)
The aims of this paper are to (i) provide a brief history of cochlear implants; (ii) present a status report on the current state of implant engineering and the levels of speech understanding enabled by that engineering; (iii) describe limitations of current signal processing strategies; and (iv) suggest new directions for research. With current technology(More)