Cupular movement and nerve impulse response in the isolated semicircular canal.

The aim of the study was to record nerve impulse responses to controlled displacements of the cupula and relate these to observations of cupular motion. The preparation was the skate semicircular canal, isolated and maintained in a chamber. The canal was cut and tied tightly to an oil-filled tube driven by a 1 microliter syringe. In some experiments dye was used to make the face of the cupula visible. Small volume displacements (0.02 microliter) caused a billowing of the central portion of the cupula, whereas for repeated large displacements (0.1 microliter) the top of the cupula moved along the roof of the ampulla. Displacements of the latter amount were close to saturation in the characteristic functions (spike rate versus volume displacement) of nerve firing. It seems that the discharge rate of tonically responding units in the skate crista ampullaris rather faithfully record the force acting on the cupula. The motion of the base of the cupula rather than its tip appears to be the relevant parameter in setting the level of excitation in the sensory cells within the physiological range of stimulation. Such a mode of operation would ensure the highest sensitivity of the sense organ.

Single-unit activity in the auditory cortex of monkeys actively localizing sound sources: spatial tuning and behavioral dependency.

Single-unit recordings were made from the auditory cortex of unanesthetized rhesus monkeys which were trained to perform a second localization task. Recordings were made from 196 units in 4 animals. Five sound sources were located at 0 degrees (midline) and on either side at azimuths of 37.5 degrees and 75 degrees. Almost most units responded to each of the 5 sources, 49% of the units had peak firing rates for the source on the contralateral side at 75% azimuth. Another 26% of the units had peak firing rates at the 37.5 degrees contralateral location, while only 11% had peak rates for the ipsilateral locations. In order to determine whether the behavior of actively locating a sound source affected units in auditory cortex, response rates compared under two behavioral conditions: one which required the detection of a sound regardless of location and another condition which required identification of a sound's location. of the 196 units, 16 had different response rates for the two conditions, with 15 of the 16 units having higher evoked rates in the localization task. For the 16 units, the difference in firing rate was typically observed for a single speaker location. No correlation could be determined between a unit's location within the subdivisions of auditory cortex and its spatial tuning response properties or its dependency upon behavioral condition.

Evoked unit activity in auditory cortex of monkeys performing a selective attention task.

Single-unit responses were recorded from the auditory cortex of rhesus monkeys performing a selective atteintion task which used combined light and sound stimuli. The animals were first trained to push a lever to the left for a noise burst and to the right for a tone burst, and then trained to push left for a left light and right for a right light. Subsequently, one of the four possible light and sound stimulus combinations (Noise + Left Light, Noise + Right Light, Tone + Left Light, Tone + Right Light) was randomly presented on each trial. In blocks of 100 trials only one part of the combined stimulus (either the light or the sound) determined the direction of lever push that would be reinforced. Responses of single units to identical sound stimuli were compared for blocks in which sound was the relevant cue and blocks in which light was the relevant cue. Typically, differences were in response strength without alteration of response pattern. Even the earliest response components (15-20 msec latency) could show changes. Two-thirds of the response comparisons showed differences in strength depending upon whether sound or light was the relevant cue, with about as many responses stronger for light relevant as for sound relevant. Independent of which modality was relevant, unit responses for trials in which both parts of the combined light and sound stimulus indicated the same direction of lever push were generally stronger than unit responses for trials in which the two parts of the combined stimulus signalled opposite directions of lever pushes.

Mycobacterium chelonae keratitis after laser in situ keratomileusis successfully treated with medical therapy and flap removal.

PURPOSE: To report a case of Mycobacterium chelonae keratitis after laser in situ keratomileusis successfully treated with medical therapy and flap removal. METHODS: Case report. A 36-year-old white woman in good health developed a paracentral keratitis in her right eye 1 month after bilateral laser in situ keratomileusis. Initial treatment included topical steroids and then intensive Ocuflox (ofloxacin ophthalmic solution; Allergan, Inc, Irvine, California) without success. Cultures were negative. The keratitis worsened, and she was referred to our institution. Interface infiltration was noted, and the flap was lifted to obtain adequate laboratory studies. Cultures were positive for M chelonae. RESULTS: The keratitis was treated with intensive topical amikacin sulfate 1%, topical clarithromycin 1%, and Ciloxan (ciprofloxacin HCL; Alcon Laboratories, Inc, Fort Worth, Texas) with minimal improvement in her clinical condition. She developed a toxic reaction to amikacin 1%. In order to improve antibiotic penetration, the hazy, ulcerated corneal flap was removed. The keratitis then resolved with intensive topical clarithromycin 1% and Ocuflox over 5 weeks. The patient now has visual acuity without correction of 20/50, despite superficial corneal haze. CONCLUSION: M chelonae is a rare and insidious cause of infection after laser in situ keratomileusis. Diagnosis can be difficult and is often delayed. Aggressive medical management, with flap removal, if needed, may lead to resolution of infection.

Neuroperceptual differences in consonant and vowel discrimination: as revealed by direct cortical electrical interference.

The effects of direct cortical electrical interference on consonant and vowel discrimination were investigated in five patients with implanted subdural electrode arrays. Without electrical interference, patients performance discriminating consonants and vowels was intact. With electrical interference, consonant discrimination was impaired at one electrode site in each patient on the superior temporal gyrus of the lateral left perisylvian cortex. Conversely, vowel and tone discrimination remained relatively intact when tested with electrical interference at the same site. Analysis of patients' consonant discrimination errors revealed that neither differences in acoustic temporal structure nor syllable position fully account for the consonant-vowel perceptual dissociations elicited. Our data suggest that at the cortical level consonant and vowel perception are intrinsically distinct perceptual phenomena. The selective impairment of consonant, but not vowel, discrimination further suggests that consonant and vowel perception are distinguished by differences in relative dependence on the functional--perhaps integrative--resources of the left lateral superior temporal gyrus.

Consistent responses of human mothers to prelinguistic infants: the effect of prelinguistic repertoire size.

The salience of infants' vocal and visual cues was examined to evaluate the efficacy of prelinguistic vocalizations to guide adult behavior. A videotape, constructed of brief behavioral episodes from 3 infants with different-sized vocal repertoires, was played to 40 mothers of prelinguistic infants. Playback mothers' responses to the episodes were consistent, demonstrating that preverbal behavior elicits comparable reactions across unfamiliar receivers. The audio and video components of the infants' episodes were then recombined. As the vocal repertoire of the stimulus infants increased, changes in the audio component more often led playback mothers to change responses. Thus, playback mothers used vocalizations as cues as the infants' vocal repertoires became larger.

Fungal keratitis after laser in situ keratomileusis: a case report.

PURPOSE: To report a case of fungal keratitis resulting after laser in situ keratomileusis (LASIK). METHODS: A 38-year-old white man in good health developed a corneal infiltrate with laboratory confirmation of fungal keratitis after LASIK. Corneal scrapings were taken. Silver stain was positive for hyphae. Culture was positive for Curvularia sp. The patient was started on intensive natamycin 5% and amphotericin 0.15% topical therapy. RESULTS: The patient's keratitis was successfully treated with intensive antifungal therapy. CONCLUSIONS: Infectious keratitis is a rare but a serious potential complication after LASIK. To our knowledge, no previous case of fungal keratitis after LASIK has been reported. This case emphasizes the importance of surveillance for infection after LASIK.

"Orbiting the orbicularis"--restoration of muscle-ring continuity with myocutaneous flaps.

Eyelid repair by the Mustardé cheek flap or the Hughes tarsoconjunctival lid-sharing flap have been methods deservingly popular with plastic surgeons for many years. Recent attention given to the myocutaneous flap principle has prompted the formulation of a new approach to this difficult problem of replacing an eyelid. In these cases, we have taken what most plastic surgeons are currently "throwing away" in their blepharoplasties and used it to reconstruct up to an entire margin of the eyelid. This new method seems simple because it holds the promise of fewer procedures and perhaps more functional results.

The elastic flap for lip repair.

These cases illustrate a new concept in lip repair. This approach recognizes the great inherent elasticity of the oral cavity and takes advantage of the florid blood supply of the region. Recent laboratory studies of Taylor et al., as well as the works of Manchot and Salmon, are combined with anthropologic observations of tribal customs to formulate another way of looking at lip reconstruction. Triangularization of surgical defects, lip switching, and mobilization of distant flaps are avoided by taking advantage of stretched local tissues. Preoperative expansion is discussed as a future option.

A tissue-expanding vermilion myocutaneous flap for lip repair.

An approach to lip reconstruction is described utilizing a myocutaneous vermilion flap based on the inferior labial artery. The inherent elasticity of the lip is used to great advantage by stretching the freed vermilion flap to bridge a loss of about one-half the lower lip. This vermilion flap may be worthy of consideration when reconstructing lip defects resulting from trauma (e.g., electric burns), tumor resections, and other congenital anomalies.

Voiced-speech representation by an analog silicon model of the auditory periphery.

An analog CMOS integration of a model for the auditory periphery is presented. The model consists of middle ear, basilar membrane, and hair cell/synapse modules which are derived from neurophysiological studies. The circuit realization of each module is discussed, and experimental data of each module's response to sinusoidal excitation are given. The nonlinear speech processing capabilities of the system are demonstrated using the voiced syllable |ba|. The multichannel output of the silicon model corresponds to the time-varying instantaneous firing rates of auditory nerve fibers that have different characteristic frequencies. These outputs are similar to the physiologically obtained responses. The actual implementation uses subthreshold CMOS technology and analog continuous-time circuits, resulting in a real-time, micropower device with potential applications as a preprocessor of auditory stimuli.

Cupula motion in the semicircular canal of the skate, Raja erinacea. An experimental investigation.

An upper bound on the magnitude of semicurcular canal cupula motion was experimentally determined in the isolated labyrinth of the skate, Raja erinacea. To visualize the cupula, a glass pipette was pushed through the ampullary wall, and local regions of the cupula were stained by slow infusion of small amounts of Alcian Blue dye. Caloric stimuli which produced large changes in single unit activity in the ampullary nerve and which often recruited several larger, previously silent units were found to produce on detectable cupula motion as seen through the ampulla wall. However when the cupula was first grossly displaced, motion was thereafter observed in response to identical caloric stimuli. Analysis of afferent responses indicates that the normal range of cupula motion in the skate is below the optical resolution of the method, conservatively estimated as 3--5 micrometers.

Speech training aids for hearing-impaired individuals: I. Overview and aims.

Prelingual profound deafness typically results in aberrant or unintelligible speech production. For approximately 70 years, researchers and engineers have attempted, with little success, to provide electronic aids for speech training. Recent computer and signal processing technology has provided the impetus for several groups to implement new speech training aids. Following a review of deaf speech characteristics, several current computer-based aids are described. Included among those reviewed are two interrelated speech training aids which resulted from collaboration among the authors.

Speech training aids for hearing-impaired individuals: II. Configuration of the Johns Hopkins aids.

Two interrelated personal computer (PC) based speech training aids have been developed: one for use in a school or clinic, the Speech Training Station (STS); and the other for the deaf child's home, the Speech Practice Station (SPS). The STS monitors speech production by microphone, electroglottograph, and pneumotachograph. The SPS system uses only the microphone input. Both systems utilize commercially available board-level hardware and a custom analog preprocessor board for the analysis of the acoustic and/or physiologic inputs. The school system has been used by speech therapists for diagnosis, training by game playing, and specification of exercises for the SPS. The home system provides directed speech practice between therapy sessions.