Characterization of Developmental Changes in Spontaneous Electrical Activity of Medial Superior Olivary Neurons Before Hearing Onset With a Combination of Injectable and Volatile Anesthesia.

In this work the impact of two widely used anesthetics on the electrical activity of auditory brainstem neurons was studied during postnatal development. Spontaneous electrical activity in neonate rats of either sex was analyzed through a ventral craniotomy in mechanically ventilated pups to carry out patch clamp and multi-electrode electrophysiology recordings in the medial region of the superior olivary complex (SOC) between birth (postnatal day 0, P0) and P12. Recordings were obtained in pups anesthetized with the injectable mix of ketamine/xylazine (K/X mix), with the volatile anesthetic isoflurane (ISO), or in pups anesthetized with K/X mix that were also exposed to ISO. The results of patch clamp recordings demonstrate for the first time that olivary and periolivary neurons in the medial region of the SOC fire bursts of action potentials. The results of multielectrode recordings suggest that the firing pattern of single units recorded in K/X mix is similar to that recorded in ISO anesthetized rat pups. Taken together, the results of this study provide a framework to use injectable and volatile anesthetics for future studies to obtain functional information on the activity of medial superior olivary neurons in vivo.

Evaluación de la discriminación del habla y resolución temporal en un grupo de adultos mayores hispanohablantes / Assessment of speech discrimination and temporal resolution in a group of spanish-speaking senior citizens

El objetivo del presente estudio fue explorar la relación entre la resolución temporal y la discriminación del habla tanto en silencio como en ruido. Treinta sujetos adultos mayores fueron seleccionados. Ninguno de ellos presentó antecedentes de patología de oído medio, diabetes, insuficiencia renal, exposición ocupacional a ruido y enfermedad neurológica. Todos los sujetos seleccionados fueron evaluados a través de los procedimientos de audiometría tonal liminal, Random Gap Detection test (RGD), máximo porcentaje de discriminación de monosílabos (MAX), y Hearing-in-Noise test (HINT). El grupo en estudio fue dividido en dos subgrupos de acuerdo a si presentaban o no audición normal para su edad (ISO 7029). Se encontraron diferencias estadísticamente significativas en los puntajes de las pruebas entre ambos subgrupos. Se observó que los sujetos del estudio presentaron resultados descendidos de acuerdo a las normas reportadas para la prueba de RGD y HINT, inclusive los sujetos con audición normal para su edad, Se discuten las implicancias clínicas de estos hallazgos y la importancia de la resolución temporal en tareas de discriminación de habla.

The present study aimed to explore a possible association between temporal resolution and speech discrimination in both quiet and noise in a group of older adults. Thirty subjects were selected for study purposes. All of them had absence of middle-ear patology, diabetes, kidney failure, occupational noise exposure and neurological disease. Pure-tone audiometry, Random Gap Detection test (RGD), Maximun percentage of discrimination of monosyllables (MAX) and hearing-in-noise test (HINT)were carried out. Study group subjects were divided into two subgroups according to whether or not their hearing level was within normal ranges adjusted for age (ISO 7029). Significant differences for tests scores were found between groups. When the subgroup of subjects with normal-hearing thresholds was compared to the norms reported for RGDT and HINT, scores obtainedby these subjects were below the norms. Clinical implications of these results and the role of temporal resolution in speech descrimination tasks are discussed.