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Biomedical subjects

D B Koch

Publications and source records attributed to D B Koch.

17 recordsLinked to original sources
PubMed1999

Speech-sound discrimination in school-age children: psychophysical and neurophysiologic measures.

This study measured behavioral speech-sound discrimination and a neurophysiologic correlate of discrimination in normal school-age children (ages 6 to 15) to determine if developmental effects exist. Just noticeable differences (JNDs) and mismatch responses (MMNs) were assessed for synthetic syllables that differed in third-formant onset frequency (/da-ga/) and formant transition duration (/ba-wa/). These stimuli were selected because children with learning problems often find it difficult to discriminate rapid spectrotemporal changes like /da-ga/, whereas the ability to distinguish /ba-wa/ is relatively unimpaired. Results indicate that JNDs for /da-ga/ show no developmental effects and that JNDs for /ba-wa/ decrease slightly with age (although likely for task-related reasons). MMNs elicited by two /da-ga/ stimulus pairs (onset frequency differences = 20 Hz, 280 Hz) and three /ba-wa/ stimulus pairs (transition duration differences = 3, 5, 15 ms) showed no systematic or significant differences for onset latency, duration, or area as a function of age. Normative JND and MMN data are provided. These norms provide a metric against which children with suspected central auditory processing difficulties or auditory-based language disorders can be compared.

Adolescent↗
PubMed1999

Acoustic-phonetic approach toward understanding neural processes and speech perception.

This review paper describes an "acoustic-phonetic" experimental approach aimed at understanding normal and abnormal speech perception processes from both a behavioral and an electrophysiologic perspective. First, we consider the relevant acoustic characteristics of speech and identify a set of acoustic-phonetic classes that represent the parameters most important for making an acoustic signal sound like speech. Second, we review what is known about the neurophysiologic representation of acoustic-phonetic speech parameters in animal and human subjects. Third, we describe how an acoustic-phonetic approach has been useful in understanding the biologic basis of some auditory learning problems in children and in characterizing the behavioral and neurophysiologic changes resulting from speech-sound training. Finally, we discuss these findings and how they may expand the diagnostic and rehabilitative repertoire of practicing audiologists.

Auditory Cortex↗
PubMed1998

Speech sound perception and learning: biologic bases.

Historically, auditory research has focused predominantly on how relatively simple acoustic signals are represented in the neuronal responses of the auditory periphery. However, in order to understand the neurophysiology underlying speech perception, the ultimate objective is to discover how speech sounds are represented in the central auditory system and to relate that representation to the perception of speech as a meaningful acoustic signal. This paper reviews three areas pertaining to the central auditory representation of speech: (1) the differences in neural representation of speech sounds at different levels of the auditory system, (2) the relation between the representation of sound in the auditory pathway and the perception/misperception of speech, and (3) the plasticity of speech-sound neural representation and speech perception.

Auditory Pathways↗
PubMed1996

Auditory neurophysiologic responses and discrimination deficits in children with learning problems.

Children with learning problems often cannot discriminate rapid acoustic changes that occur in speech. In this study of normal children and children with learning problems, impaired behavioral discrimination of a rapid speech change (/dalpha/versus/galpha/) was correlated with diminished magnitude of an electrophysiologic measure that is not dependent on attention or a voluntary response. The ability of children with learning problems to discriminate another rapid speech change (/balpha/versus/walpha/) also was reflected in the neurophysiology. These results indicate that some children's discrimination deficits originate in the auditory pathway before conscious perception and have implications for differential diagnosis and targeted therapeutic strategies for children with learning disabilities and attention disorders.

Adolescent↗
PubMed1995

Speech-evoked cognitive P300 potentials in cochlear implant recipients.

The cognitive P300 evoked potential was elicited by speech stimuli in successful cochlear implant recipients, and the resulting P300 morphology was remarkably similar to that of normal-hearing individuals. The P300 was elicited by the synthesized speech pair/da/and/di/ presented using an oddball paradigm to nine "good" Nucleus cochlear implant users and nine age-matched normal-hearing subjects (34-81 yr old). There were no significant differences in P300 amplitude and latency between the two groups. Moreover, the N1 and P2 potentials occurred at similar latencies in the two groups, although the N1 amplitude was significantly smaller in the cochlear implant users. The P300 was absent in one "poor" cochlear implant user. The results suggest that the P300 may serve as a useful tool for evaluating the cognitive aspects of auditory processing in cochlear implant recipients, and that it may aid in assessing the success of cochlear implantation.

Acoustic Stimulation↗
PubMed1993

The mismatch negativity cortical evoked potential elicited by speech in cochlear-implant users.

The mismatch negativity (MMN) event-related potential is a non-task related neurophysiologic index of auditory discrimination. The MMN was elicited in eight cochlear implant recipients by the synthesized speech stimulus pair /da/ and /ta/. The response was remarkably similar to the MMN measured in normal-hearing individuals to the same stimuli. The results suggest that the central auditory system can process certain aspects of speech consistently, independent of whether the stimuli are processed through a normal cochlea or mediated by a cochlear prosthesis. The MMN shows promise as a measure for the objective evaluation of cochlear-implant function, and for the study of central neurophysiological processes underlying speech perception.

Acoustic Stimulation↗
PubMed1982

Surgical stabilisation of the stifle in cranial cruciate ligament injury in cattle.

Surgical stabilisation of cranial cruciate ligament injury was performed on 23 stifles in 22 dairy cattle ranging in age from 11 months to 14 years. Duration of time from injury until surgery varied from two days to three years. A row of Lembert sutures was placed in both the lateral and medial retinacular tissues. In addition, an imbrication suture was placed from the lateral femorotibial ligament to the lateral or middle patellar ligament in five cattle. External support was used in 15 cattle in the form of a modified Robert Jones/Thomas-Schroeder splint. Thirteen cattle improved markedly, four recovered completely and three improved moderately. Surgery was unsuccessful on seven cases. When surgery was unsuccessful, moderate to severe lesions of degenerative joint disease were usually present.

Animals↗
PubMed1982

Mineral metabolism and immobilization osteopenia in ponies treated with 25-hydroxycholecalciferol.

The left thoracic limb was immobilized in a plaster cast in 6 grade weanling ponies for 6 weeks. Two ponies were injected intramuscularly each day with 2.4 micrograms of 25-hydroxycholecalciferol [25(OH)D3] per kg bodyweight, two with 1.2 micrograms and two received no injections. Immobilization of 25(OH)D3 treatment had no significant effect on mineral metabolism. Immobilization resulted in significantly decreased weight and specific gravity of metacarpus III (MCIII). Histologic examination and triple fluorochrome incorporation showed that the osteopenia was caused by atrophy of osteoblasts with failure of bone apposition. Immobilization caused retardation or cessation of proliferation of cartilage in the epiphyseal plate with thinning or premature closure. Treatment with 25(OH)D3 further reduced apposition and enhanced significantly the osteopenia as shown by quantitative morphometry of microradiographs of the MCIII metaphyses. There was parathyroid gland atrophy and fibrosis in proportion to the level of 25(OH)D3 treatment, which, in absence of hypercalcemia in all ponies, was interpreted to be a direct result of vitamin D treatment. It was concluded that immobilization osteopenia under the present design and duration is caused by failure of bone apposition and that treatment with 25(OH)D3 at dose levels applied is contraindicated.

Animals↗
PubMed1981

Tracheal reconstruction by resection and end-to-end anastomosis in the horse.

A surgical technique for resection of a portion of the trachea followed by end-to-end anastomosis was developed on 4 clinically normal horses. The trachea healed without complications in 3 of the horses in which 3 tracheal cartilages were removed. Five tracheal cartilages were removed from the 4th horse. It had to be euthanatized because of excessive suture line tension and wound disruption, which occurred during recovery from anesthesia. Suture line tension was measured on 3 other clinically normal horses positioned in dorsal recumbency immediately after euthanasia after 3 and 5 tracheal cartilages had been removed and before and after flexion of the neck to 90 degrees. Suture line tension was reduced by approximately 50% when the neck was flexed. Similarly, the force required to appose the cut ends of the trachea was nearly doubled when 5 rather than 3 tracheal cartilages were removed. The surgical technique was performed on 1 horse and 1 pony with partial obstruction of the trachea. In the pony, 5 tracheal cartilages were resected. It was able to return to successful show competition. In the horse, 4 tracheal cartilages were removed. This horse died of complications resulting from bilateral hindlimb myositis, but the tracheal anastomosis was intact, sealed, and healing well.

Animals↗
PubMed1979

Mesodiverticular bands as a cause of small intestinal strangulation and volvulus in the horse.

Volvulus of the jejunum and ileum in three horses was associated with intestinal strangulation in a mesenteric rent. The rent was in the jejunal mesentery at its point of attachment with an anomaly that was classified as a mesodiverticular band. The band also was attached to the dorsolateral surface of the jejunum, thus forming one side of a triangular hernial sac that was completed on the other side by the adjacent jejunal mesentery. Incarceration of a loop of small intestine in the hernial sac preceded rupture of the jejunal mesentery and subsequent intestinal strangulation. Surgical correction was successful in two horses and involved resection of the gangrenous intestine, then jejunocecal anastomosis. The third horse was euthanatized when intestinal rupture and peritonitis were found on exploratory laparotomy. Two mesodiverticular bands attached to the distal jejunum were incidental necropsy findings in a fourth horse.

Animals↗
PubMedDate not supplied

Speech sound representation, perception, and plasticity: a neurophysiologic perceptive.

Historically, auditory research has focused predominately upon how relatively simple acoustic signals are represented in the neuronal responses of the auditory periphery. However, in order to understand the neurophysiology underlying speech perception, the ultimate objective is to discover how speech sounds are represented in the central auditory system and to relate that representation to the perception of speech as a meaningful acoustic signal. This paper reviews three areas that pertain to the central auditory representation of speech: (1) the differences in neural representation of speech sounds at different levels of the auditory system; (2) the relation between the representation of sound in the auditory pathway and the perception/misperception of speech, and (3) the training-related plasticity of speech sound neural representation and speech perception.

Auditory Cortex↗