Central Institute for the Deaf

Four chinchillas were trained to respond differently to /t/ and /d/ consonant-vowel syllables produced by four talkers in three vowel contexts. This training generalized to novel instances, including synthetically produced /da/ and /ta/ (voice-on-set times of 0 and +80 milliseconds, respectively). In a second experiment, synthetic stimuli with voice-onset times between 0 and +80 milliseconds were presented for identification. The form of the labeling functions and the "phonetic boundaries" for chinchillas and English-speaking adults were similar.

CERTAIN OF THE CHILDREN who are evaluated and taught at the Central Institute for the Deaf are classified as aphasic because they present a specific deficit in the ability to use speech and 1anguage.l For most of these children the deficit seems to be congenital, since they have failed to acquire the ability to use speech a n d language normally.' Some of them, however, have acquired the ability to use language i n an ap arently normal fashion and have been seen in the last two years. One of the six became aphasic and hemiplegic after a severe head injury; the remaining five developed aphasia in relation to a convulsive disorder. These five cases are reported here.

OBJECTIVE: This study investigated factors contributing to the comprehension and production of English language by children with prelingual deafness after 4 to 7 yr of multichannel cochlear implant use. The analysis controlled for the effects of child and family characteristics so that educational factors most conducive to maximum implant benefit could be identified. DESIGN: A battery of language tests were administered to 181 8- and 9 yr-old children from across the United States and Canada who received a cochlear implant by age 5. Tests of comprehension, verbal reasoning, narrative ability and spontaneous language production were administered either in speech and sign or in the child's preferred communication mode. These constituted the Total Language measures. Spoken Language measures were derived from a speech-only language sample. Type and amount of educational intervention since implantation constituted the independent variables. Characteristics of the child and the family were considered intervening variables. A series of multiple regression analyses determined the amount of variance in Total Language and Spoken Language ability accounted for by the intervening variables and the amount of additional variance attributable to the independent variables. RESULTS: More than half of the children (with performance intelligence quotients in the average range) exhibited language skills that were similar to those of hearing 8 to 9 yr olds on measures of verbal reasoning, narrative ability, utterance length, and lexical diversity. Significant predictors of language ability were similar for Total and for Spoken Language outcomes and included greater nonverbal intelligence, smaller family size, higher socio-economic status and female gender. Age at receiving an implant did not affect language outcome. After the variance due to these variables was controlled, the primary rehabilitative factors associated with linguistic outcome were amount of mainstream class placement and an educational emphasis on speech and auditory skills. CONCLUSIONS: Use of a cochlear implant has had a dramatic impact on the linguistic competence of profoundly hearing-impaired children. More than half of the children in this sample with average learning ability produced and understood English language at a level comparable with that of their hearing age mates. Such mature language outcomes were not typical of children with profound hearing loss who used hearing aids. Use of a visual (i.e., sign) language system did not provide the linguistic advantage that had been anticipated. Children educated without use of sign exhibited a significant advantage in their use of narratives, the breadth of their vocabulary, in their use of bound morphemes, in the length of their utterances and in the complexity of the syntax used in their spontaneous language. An oral educational focus provided a significant advantage for both spoken and total language skills.

Certain of the children who are evaluated and taught at the Central Institute for the Deaf are classified as aphasic because they present a specific deficit in the ability to use speech and language.1 For most of these children the deficit seems to be congenital, since they have failed to acquire the ability to use speech and language normally.2 Some of them, however, have acquired the ability to use language in an apparently normal fashion and have subsequently lost it. Six such children have been seen in the last two years. One of the six became aphasic and hemiplegic after a severe head injury; the remaining five developed aphasia in relation to a convulsive disorder. These five cases are reported here. Case 1 . A white male, third of four children, was born in April 1948. Pregnancy and birth history were unremarkable. He was a healthy infant, sat at about six months, and walked before he was a year old. He learned to talk normally at 15 to 18 months. Further behavioral development was also unremarkable. In 1952 when the boy was four, he had one nocturnal generalized seizure. When he was five (July 1953), he developed several furuncles over his face. A few days later he fell in the yard and was found in a semiconscious condition. He staggered into the house and vomited several times. Following treatment with penicillin, it became apparent to the family that the child was having difficulty understanding what was said to him, a defect interpreted as plain stubbornness. His speech also became garbled. He was hospitalized in August 1953. His electroencephalogram (figure 1A) showed a generalized spike dysrhythmia, most prominent in the temporal leads bilaterally. Neurologic examination was not remarkable except for the deficit in speech. He was considered to have …

In Brief Objective This study investigated factors contributing to speech perception outcomes in children with prelingual deafness after 4 to 7 yr of multichannel cochlear implant use. The analysis controlled for the effects of child, family and implant characteristics so that educational factors most conducive to maximum implant benefit could be identified. Design One hundred eighty-one 8- and 9-yr-old children from across the US and Canada who received a cochlear implant by age 5 were administered a battery of speech perception tests. Type and amount of educational intervention since implantation constituted the independent variables. Characteristics of the child, the family, and the implant itself constituted intervening variables. A series of multiple regression analyses determined the amount of variance in speech perception ability accounted for by the intervening variables and the amount of additional variance attributable to independent variables. Results The children achieved an average level of about 50% open-set speech perception through listening alone and almost 80% through lipreading and listening together, but with scores for individual children ranging from 0 to 100% correct. Over half of the variance in speech perception scores was predicted by characteristics of the child, family, implant and educational program. Significant predictors of good speech perception included greater nonverbal intelligence, smaller family size, longer use of the updated SPEAK/CIS processing strategy, a fully active electrode array, greater electrical dynamic range between threshold and maximum comfort level, and greater growth of loudness with increasing stimulus intensity. After the variance due to these variables was controlled, the primary rehabilitative factor associated with good speech perception skill development was educational emphasis on oral-aural communication. Conclusions Children with profound hearing loss achieved unprecedented levels of speech perception skill 4 to 7 yr after cochlear implantation. Use of an updated speech processor, such as SPEAK, contributed significantly to improved speech perception skills, even in children who were initially fitted with an earlier strategy, such as M-PEAK. In addition, the audiologist who programs the cochlear implant makes an important contribution to the child’s successful outcome with the device. A well-fitted map, as evidenced by a wide dynamic range and optimal growth of loudness characteristics, contributed substantially to the child’s ability to hear speech. Finally, the classroom communication mode used in the child’s school affects speech perception outcome. Children whose educational program emphasized dependence on speech and audition for communication were better able to use the information provided by the implant to understand speech. A variety of speech perception skills were assessed in this study of prelingually deaf 8 to 9 year olds after 4 to 7 years of using a cochlear implant: perception of specific features of vowels, consonants and suprasegmentals, perception of words in a closed set of choices, perception of words and sentences in an open set format, and the amount of enhancement provided to lipreading when audition is added. A wide range of speech perception ability was observed, with better skills seen in children with a wellprogrammed, up-to-date speech processor. Children who had used the SPEAK (as opposed to the MSP) processor the longest and had a greater number of active electrodes in their map with a wide dynamic range and those who could reliably order increases in loudness with increased stimulus intensity achieved the highest speech perception scores. After controlling for these implant characteristics, as well as other contributing factors, most of the remaining variance in speech perception outcome was due to oral classroom communication mode, with the best perceivers having received more auditory and speech emphasis in their educational program since receiving a cochlear implant.

PURPOSE: The authors examined the benefits of younger cochlear implantation, longer cochlear implant use, and greater pre-implant aided hearing to spoken language at 3.5 and 4.5 years of age. METHOD: Language samples were obtained at ages 3.5 and 4.5 years from 76 children who received an implant by their 3rd birthday. Hierarchical linear modeling was used to identify characteristics associated with spoken language outcomes at the 2 test ages. The Preschool Language Scale (I. L. Zimmerman, V. G. Steiner, & R. E. Pond, 1992) was used to compare the participants' skills with those of hearing age-mates at age 4.5 years. RESULTS: Expected language scores increased with younger age at implant and lower pre-implant thresholds, even when compared at the same duration of implant use. Expected Preschool Language Scale scores of the children who received the implant at the youngest ages reached those of hearing age-mates by 4.5 years, but those children implanted after 24 months of age did not catch up with hearing peers. CONCLUSION: Children who received a cochlear implant before a substantial delay in spoken language developed (i.e., between 12 and 16 months) were more likely to achieve age-appropriate spoken language. These results favor cochlear implantation before 24 months of age, especially for children with aided pure-tone average thresholds greater than 65 dB prior to surgery.

Reactive oxygen species (ROS) have been implicated in a growing number of neurological disease states, from acute traumatic injury to neurodegenerative conditions such as Alzheimer's disease. Considerable evidence suggests that ROS also mediate ototoxicant- and noise-induced cochlear injury, although most of this evidence is indirect. To obtain real-time assessment of noise-induced cochlear ROS production in vivo, we adapted a technique which uses the oxidation of salicylate to 2,3-dihydroxybenzoic acid as a probe for the generation of hydroxyl radical. In a companion paper we described the development and characterization of this method in cochlear ischemia-reperfusion. In the present paper we use this method to demonstrate early elevations in ROS production following acute noise exposure. C57BL/6J mice were exposed for 1 h to intense broad-band noise sufficient to cause permanent threshold shift (PTS), as verified by auditory brainstem responses. Comparison of noise-exposed animals with unexposed controls indicated that ROS levels increase nearly 4-fold in the period 1-2 h following exposure and do not decline over that time. Our ROS measures extend previous results indicating that noise-induced PTS is associated with elevated cochlear ROS production and ROS-mediated injury. Persistent cochlear ROS elevation following noise exposure suggests a sustained process of oxidative stress which might be amenable to intervention with chronic antioxidant therapy.

In an attempt to clearly differentiate perceptual effects that are attributable to ’’auditory’’ and ’’phonetic’’ levels of processing in speech perception we have undertaken a series of experiments with animal listeners. Four chinchillas (Chinchilla laniger) were trained to respond differently to the ’’endpoints’’ of a synthetic alveolar speech continuum (0 ms VOT and +80 ms VOT) and were then tested in a generalization paradigm with the VOT stimuli between these endpoints. The resulting identification functions were nearly identical to those obtained with adult English-speaking listeners. To test the generality of this agreement, the animals were then tested with synthetic stimuli that had labial and velar places of articulation. As a whole, the functions produced by the two species were very similar; the same relative locations of the phonetic boundaries, with lowest VOT boundaries for labial stimuli and highest for velar stimuli, were obtained for each animal and human subject. No significant differences between species on the absolute values of the phonetic boundaries were obtained, but chinchillas produced identification functions that were slightly, but significantly, less steep. These results are discussed with regard to theories of speech perception, the evolution of a speech-sound repertoire, and current interpretations of the human infant’s perceptual proclivities with regard to speech-sound perception.

Whereas temporal intervals as short as a few milliseconds are sufficient to separate two brief sounds so that a listener will report that there are two (instead of only one) sounds, a longer separation time of between 15 and 20 msec is required for the listener to report correctly which of the two sounds preceded the other. This minimum temporal interval appears to be independent of the kinds of sounds used: whether short or long, of high or low frequency, of narrow or wide band width. There is some suggestion that rise-time and duration may change this minimum interval, but these somewhat secondary relations are not investigated in detail here. The length of the required temporal interval suggests that the judgment of order requires other mechanisms than those associated with the peripheral auditory system.

This study investigated three questions: Is it realistic to expect age-appropriate spoken language skills in children with cochlear implants (CIs) who received auditory-oral intervention during the preschool years? What characteristics predict successful spoken language development in this population? Are children with CIs more proficient in some areas of language than others? We analyzed language skills of 153 children with CIs as measured by standardized tests. These children (mean age = 5 years and 10 months) attended programs in the United States (N = 39) that used an auditory-oral educational approach. Age-appropriate scores were observed in 50% of the children on measures of receptive vocabulary, 58% on expressive vocabulary, 46% on verbal intelligence, 47% on receptive language, and 39% on expressive language. Regression analysis indicated that, after controlling for the effects of nonverbal intelligence and parent education level, children who received their implants at young ages had higher scores on all language tests than children who were older at implantation. On average, children with CIs performed better on certain language measures than others, indicating that some areas of language may be more difficult for these children to master than others. Implications for educators of deaf children with CIs are discussed.

In Brief Objective: By age 3, typically developing children have achieved extensive vocabulary and syntax skills that facilitate both cognitive and social development. Substantial delays in spoken language acquisition have been documented for children with severe to profound deafness, even those with auditory oral training and early hearing aid use. This study documents the spoken language skills achieved by orally educated 3-yr-olds whose profound hearing loss was identified and hearing aids fitted between 1 and 30 mo of age and who received a cochlear implant between 12 and 38 mo of age. The purpose of the analysis was to examine the effects of age, duration, and type of early auditory experience on spoken language competence at age 3.5 yr. Design: The spoken language skills of 76 children who had used a cochlear implant for at least 7 mo were evaluated via standardized 30-minute language sample analysis, a parent-completed vocabulary checklist, and a teacher language-rating scale. The children were recruited from and enrolled in oral education programs or therapy practices across the United States. Inclusion criteria included presumed deaf since birth, English the primary language of the home, no other known conditions that interfere with speech/language development, enrolled in programs using oral education methods, and no known problems with the cochlear implant lasting more than 30 days. Results: Strong correlations were obtained among all language measures. Therefore, principal components analysis was used to derive a single Language Factor score for each child. A number of possible predictors of language outcome were examined, including age at identification and intervention with a hearing aid, duration of use of a hearing aid, pre-implant pure-tone average (PTA) threshold with a hearing aid, PTA threshold with a cochlear implant, and duration of use of a cochlear implant/age at implantation (the last two variables were practically identical because all children were tested between 40 and 44 mo of age). Examination of the independent influence of these predictors through multiple regression analysis revealed that pre-implant–aided PTA threshold and duration of cochlear implant use (i.e., age at implant) accounted for 58% of the variance in Language Factor scores. A significant negative coefficient associated with pre-implant–aided threshold indicated that children with poorer hearing before implantation exhibited poorer language skills at age 3.5 yr. Likewise, a strong positive coefficient associated with duration of implant use indicated that children who had used their implant for a longer period of time (i.e., who were implanted at an earlier age) exhibited better language at age 3.5 yr. Age at identification and amplification was unrelated to language outcome, as was aided threshold with the cochlear implant. A significant quadratic trend in the relation between duration of implant use and language score revealed a steady increase in language skill (at age 3.5 yr) for each additional month of use of a cochlear implant after the first 12 mo of implant use. The advantage to language of longer implant use became more pronounced over time. Conclusions: Longer use of a cochlear implant in infancy and very early childhood dramatically affects the amount of spoken language exhibited by 3-yr-old, profoundly deaf children. In this sample, the amount of pre-implant intervention with a hearing aid was not related to language outcome at 3.5 yr of age. Rather, it was cochlear implantation at a younger age that served to promote spoken language competence. The previously identified language-facilitating factors of early identification of hearing impairment and early educational intervention may not be sufficient for optimizing spoken language of profoundly deaf children unless it leads to early cochlear implantation. By age three, typically developing children have achieved extensive vocabulary and syntactic skills that facilitate both cognitive and social development. This study documents the spoken language skills achieved by 76 orally educated three-year-olds who were identified between 1-30 months of age and who received a cochlear implant (CI) between 12-38 months of age. The effects of age, duration and type of early auditory experience on spoken language competence at age 3.5 were examined. Examination of the independent influence of several predictor variables through multiple regression analysis revealed that pre-implant aided PTA threshold and duration of CI use (i.e., age at implant) accounted for 58% of the variance. Age at identification, amplification, and CI aided threshold were unrelated to language outcome. A steady increase in language skill (at age 3.5) was observed for each additional month of use of a cochlear implant after the first 12 months of implant use. The advantage of longer implant use became more pronounced over time. The previously identified language-facilitating factors of early identification of hearing impairment and early educational intervention may not be sufficient for optimizing spoken language of profoundly deaf children unless they lead to early cochlear implantation.

In Brief Objective The present study sought to document the word reading and comprehension levels attained by children who were implanted by 5 yr of age. It was hypothesized that the improved speech perception abilities acquired with cochlear implantation would promote phonological coding skills and facilitate the acquisition of beginning reading skills. Design Three subtests from diagnostic reading assessment batteries standardized on hearing children were administered to 181 children between 8 yr 0 mo and 9 yr 11 mo of age who had 4 to 6 yr of implant experience. In addition, a battery of processing measures was administered including a lexical decision task, a rhyme task and the digit span subtest of the Wechsler Intelligence Scale for Children. Results Over half of the children scored within the average range for their age compared with the normative data for hearing children. Reading competence was associated with higher nonverbal intelligence, higher family socio-economic status, female gender and later onset of deafness (between birth and 36 mo). After variance due to these child and family characteristics was removed, reading competence was associated with mainstream educational placement, use of an updated implant speech processor with a wide dynamic range, and speech processing characteristics that included longer memory span and use of phonological coding strategies. Reading outcome was most highly predicted by linguistic competence and, secondarily, by speech production skill. Conclusion Children who experience severe to profound deafness early in their development have a better prognosis for normal literacy development than ever before. To the extent that use of a cochlear implant is associated with greater use of phonological coding strategies for decoding print, longer working memory spans for short-term storage of phonemes, words and sentences and accelerated language development for reading comprehension, it should have a facilitative effect on the acquisition of literacy. Delayed reading development has been reported in most studies of academic achievement in the prelingually deaf population. In this study, reading scores averaged mid-2nd grade, which is close to an age-appropriate level compared with hearing children. There was, however, a wide range of individual performance, from 1st to 10th grade level. Characteristics of the children and their families accounted for 25% of this variance. There was a significant advantage for 9 year olds over 8 year olds, for girls over boys, for children with acquired over congenital hearing loss, for children with greater intelligence and from families with higher incomes/education. This study highlighted the importance of controlling for these characteristics before analyzing any other sources of variance in reading outcome. The use of phonological coding strategies and longer memory spans also was conducive to early reading acquisition. However, the largest amount of added variance in reading scores was accounted for by the children's speech and language skills. Children with the most intelligible speech and highest level of syntactic complexity and lexical diversity in their language were the best readers.

The objective of this study was to document the development of speech, language, and reading skills between primary and secondary school ages in children who received cochlear implants during preschool years. Subjects were a sample of 85 North American adolescents recruited from a larger sample of 181 participants from a previous investigation. Students were first tested in early elementary school (ages eight to nine years) and were re-evaluated in high school (ages 15-18 years) for this study. The methods used were: performance on a battery of speech perception, language, and reading tests. These were compared at both test ages and significant predictors of outcome level identified through multiple regression analysis. Speech perception scores improved significantly with long-term cochlear implant use. Average language scores improved at a faster than normal rate, but reading scores did not quite keep pace with normal development. Performance in high school was most highly correlated with scores obtained in elementary grades. In addition, better outcomes were associated with lower PTA cochlear implant threshold, younger age at implantation and higher nonverbal IQ. In conclusion, early cochlear implantation had a long-term positive impact on auditory and verbal development, but did not result in age-appropriate reading levels in high school for the majority of students.

My theory for the excitation of nerve impulses in the cochlea is both old and obvious. I t differs only in detail from my original presentations of 1953 and 1956 and hardly at all from my restatements of it in 1958 and 1961. In broad principle it is merely an application of the general theory of sensory ac-tion to the particular anatomical structure and electrical polarization of the cochlea. Dr. Wersall has given us a beautiful account of the fine structure of the sensory cells of the cochlea and their nerve endings as seen under the electron microscope. The detailed knowledge of the inner-vation of the cochlea, with its efferent supply in addition to the afferent fibers, and also the cilia, both their structure and their arrangement, repre-

Audio-visual observation of spoken spondaic words was found to be superior to recognition via audition-only under a wide range of S/N conditions. Data from five subjects supported the notion that observers rely increasingly more on visual cues for speech information as S/N ratio is degraded. Audition-only performance was found to be less variable among subjects than was audio-visual recognition. Increased variability in audio-visual scores at poorer S/N ratios was attributed to differences in lip-reading skill among untrained subjects. Speech levels so low that recognition by audition-only approximated chance behavior were found, nevertheless, to systematically improve observers' audio-visual scores as a function of increasing S/N ratio.

The average amplitude of the slow, diffuse, nonspecific electrical response of the human cortex, called the V potential, evoked by tone pips or by tactile stimuli to thumb and forefinger, follows a power law with exponent about 0.24 (re sound pressure). The variability of the responses is great, across both trials and subjects. If auditory or tactile stimuli are judged equally strong, across frequency or modality, the V potentials tend to be equal. Both the latency and the amplitude of the V potential are independent of the rise time of a tone burst, at least up to 100 msec. The amplitude also remains nearly constant as the duration of the plateau of a burst, with rise and fall times of 5 msec, is varied from 2 to 320 msec. An off response that closely resembles the on response in waveform, latency, and amplitude appears at the end of any burst that is long enough, but an off response that follows an on response by 1 sec or less is much reduced in amplitude, and so is an on response that too closely follows an off response. The V potential is a response to change in stimulation either on or off.

Intracochlear electrodes in the guinea pig are used to measure the relations among cochlear potentials in response to slow acoustic transients. The traveling wave of Békésy is described in terms of cochlear-microphonic (CM) voltage as functions of time and place along the cochlear partition. The results are consistent with previous observations in the ear and on models of the basilar membrane. Interpolations of wave velocity and wave amplitudes between places used for the measurements allow continuous representations of the traveling-wave pattern of CM in either space or time. From these representations, it is clear that the duration of the stimulating phase of CM along the cochlear partition significantly exceeds the apparent duration of the whole-nerve action-potential (AP) response to these transients. Selective changes in the waveforms of the AP responses, as opposed to simple reductions in amplitude, are observed when the transients are accompanied by bands of noise and after local chemical or mechanical injury to the organ of Corti. The selective changes in waveform allow consideration of the waveform removed from the normal AP response by the noise as well as the response remaining during noise. The responses removed by each of successive increases the bandwidth of the noise reveal the presence of AP responses at times not apparent in the normal whole-nerve AP waveform. These observations are most easily explained by assuming that the basic neural response is diphasic as conventionally recorded. When neurons become active in an orderly sequence, the positive phases of the earlier individual responses coincide with and may conceal the negative phases of later responses. The whole-nerve AP waveform is thus considered as the convolution (complex product) of two functions in time, the diphasic unit of response and the numerical sequence of newly active neurons. An empirical model for the diphasic unit of response “divided” into the AP waveform reveals patterns of neural activity that are compatible with the traveling wave of CM. The same model satisfactorily explains several details of the whole-nerve AP waveform recorded during stimulation with a burst of high-frequency tone.

Hearing-impaired persons usually perceive speech by watching the face of the talker while listening through a hearing aid. Normal-hearing persons also tend to rely on visual cues, especially when they communicate in noisy or reverberant environments. Numerous clinical and laboratory studies on the auditory-visual performance of normal-hearing and hearing-impaired children and adults demonstrate that combined auditory-visual perception is superior to perception through either audition or vision alone. This paper reviews these studies and provides a rationale for routine evaluation of auditory-visual speech perception in audiology clinics.

The major issues in relating acoustic waveforms of spoken vowels to perceived vowel categories are presented and discussed in terms of the author's auditory-perceptual theory of phonetic recognition. A brief historical review of formant-ratio theory is presented, as well as an analysis of frequency scales that have been proposed for description of the vowel. It is illustrated that the monophthongal vowel sounds of American English can be represented as clustered in perceptual target zones within a three-dimensional auditory-perceptual space (APS), and it is shown that preliminary versions of these target zones segregate a corpus of vowels of American English with 93% accuracy. Furthermore, it is shown that the nonretroflex vowels of American English fall within a narrow slab within the APS, with spread vowels near the front of this slab and rounded vowels near the back. Retroflex vowels fall in a distinct region behind the vowel slab. Descriptions of the vowels within the APS are shown to be correlated with their descriptions in terms of dimensions of articulation and timbre. Additionally, issues related to talker normalization, coarticulation effects, segmentation, pitch, transposition, and diphthongization are discussed.

Pairs of very small electrodes were placed in two or more turns of the cochlea of the guinea pig. The cochlear microphonic from a short segment (about 1 mm) of the cochlear partition can thus be recorded, and without contamination by action potentials. The outputs of the second, third, and fourth turns were compared with that of the first turn with respect to both amplitude and phase as a function of frequency. The space-time pattern thus revealed is a traveling wave which passes up the cochlea to a distance that depends on the frequency. The pattern agrees well with that of mechanical movement (Békésy) except that the cochlear microphonic shows relatively greater amplitude (voltage) in the basal turn. Low frequencies travel farther up the cochlea than do high. The velocity (for a 750 cps tone) is about 100 m/sec in the basal turn and about 2 m/sec in the fourth turn. Phase differences of as much as 5π were observed, by means of Lissajous patterns, between the responses of the first and the third turn. Certain discontinuities in the input-output relationships and in phase relationships were found to be a function of frequency and of position along the cochlear partition. These discontinuities occurred at or near the frequencies that showed a phase difference of 2π from the basal end of the cochlea. The relation of these critical frequencies to position along the cochlea constitutes a new “frequency-map” of the cochlea. The space-time pattern of the cochlear microphonic proved to be very little affected by removal of portions of the bony wall of the cochlea or delivering acoustic energy through a hole near the apex. It is concluded that, in addition to “direct driving” of the cochlear partition by pressure differences between the two scalae and to “surface waves” arising from such drying, the transmission of transverse waves along the solid structures of the cochlear partition must also be included for a satisfactory interpretation of all of the available data.