RESUMEN
Light produces force when interacting with matter. Such radiation pressure may be used to accelerate small objects along the beam path of a laser. Here, we demonstrate that a moderately powerful laser can deliver enough force to locally stimulate the hearing organ, in the absence of conventional sound. Damped mechanical oscillations are observed following brief laser pulses, implying that the organ of Corti is locally resonant. This new method will be helpful for probing the mechanical properties of the hearing organ, which have crucial importance for the ear's ability to detect sound.
Asunto(s)
Rayos Láser , Órgano Espiral/fisiología , Órgano Espiral/efectos de la radiación , Animales , Membrana Basilar/fisiología , Membrana Basilar/efectos de la radiación , Fenómenos Biomecánicos , Potenciales Microfónicos de la Cóclea/fisiología , Potenciales Microfónicos de la Cóclea/efectos de la radiación , Relación Dosis-Respuesta en la Radiación , Gerbillinae , Cobayas , Técnicas In Vitro , Estimulación Física , Factores de TiempoRESUMEN
Action potentials of neurons in cat dorsal and posteroventral cochlear nuclei were recorded extracellularly with glass microelectrodes while the head of the cat was exposed to microwave pulses at 915 MHz using a diathermy applicator. Response thresholds to acoustic tones, acoustic clicks, and microwave pulses were determined for auditory units with characteristic frequencies (CFs) from 278 Hz to 39.2 kHz. Tests with pulsatile stimuli were performed for durations of 20-700 mus, principally 20, 70, and 200 mus. Brainstem midline specific absorption rate (SAR) threshold was as small as 11.1 mW/g per pulse, and specific absorption (SA) threshold was a small as 0.6 muJ/g per pulse. Microwave thresholds were generally lower for CF less than 9 kHz, as were most acoustic thresholds. However, microwave threshold was only weakly related to click threshold and CF-tone threshold of each unit.
Asunto(s)
Audición/efectos de la radiación , Puente/efectos de la radiación , Ondas de Radio , Animales , Gatos , Potenciales Microfónicos de la Cóclea/efectos de la radiación , Nervio Coclear/fisiología , Nervio Coclear/efectos de la radiación , Neuronas/efectos de la radiación , Puente/fisiología , Umbral SensorialRESUMEN
The effects of ionizing irradiation on the cochlear microphonic response of guinea-pigs were studied. The cochlear microphonics (CM) of both ears were recorded in a total of 36 animals. Recording was carried out by the differential electrode technique on the basal turn of the cochlea. One week prior to recording, the left ear of each animal had been exposed to 35-70 Gy radiation in increments of 5 Gy. Doses of 40 Gy and above led to a reduction in CM response. After doses of 60 Gy or more, no CM response could be detected. Damage most probably occurred in the outer and inner hair cells.
Asunto(s)
Potenciales Microfónicos de la Cóclea/efectos de la radiación , Potenciales Evocados Auditivos/efectos de la radiación , Animales , Relación Dosis-Respuesta en la Radiación , Cobayas , Células Ciliadas Auditivas/efectos de la radiación , Traumatismos Experimentales por Radiación/fisiopatologíaRESUMEN
Impairment of cochlear function was investigated following ultrasonic irradiation of the vestibule and the cochlea through the round window in cats and guinea pigs. Selective destruction of the vestibular balance mechanism with negligible impairment of cochlear microphonic response was achieved, provided that the ultrasound beam was directed away from the cochlea and towards the ampulla of the superior semicircular canal. Directing ultrasound into the cochlea produced a depression in C.M. which was greatest in the higher frequency responsive area corresponding to the region of the first two cochlear turns. The degree of cochlear microphonic depression increased as the duration of irradiation was extended. The occurrence of a significant temperature increase accompanying the application of ultrasound implicated the involvement of a thermal mechanism in addition to the mechanical disruptive effect of ultrasound.