Síndrome del nevus melanocítico congénito. Serie de casos / Congenital Melanocytic Nevus Syndrome: A Case Series

El síndrome del nevus melanocítico congénito (SNMC) consiste en la proliferación anormal de melanocitos en la piel y el sistema nervioso central, y se debe a mutaciones de las células progenitoras durante el desarrollo embrionario. En muchas de estas células se han detectado mutaciones en el gen NRAS. Se exponen 5 casos de nevus melanocítico congénito gigante, 3 de ellos asociados al SNMC, en los que se ha estudiado dicha mutación. Hasta hace unos años la cirugía era el tratamiento de elección, sin embargo, sus resultados son insatisfactorios, con cirugías agresivas que no mejoran el aspecto estético y reducen mínimamente el riesgo de malignización. En el año 2013 se aprobó el trametinib en el uso del melanoma avanzado con mutaciones de NRAS. Dicho fármaco, que participa en la cascada intracelular de RAS-RAF-MEK-pERK-MAPK, podría ser útil en pacientes pediátricos con SNMC. El conocimiento más amplio de esta enfermedad permitirá crear nuevas estrategias (AU)

Congenital melanocytic nevus syndrome (CMNS) is the result of an abnormal proliferation of melanocytes in the skin and central nervous system caused by progenitor-cell mutations during embryonic development. Mutations in the NRAS gene have been detected in many of these cells. We present 5 cases of giant congenital melanocytic nevus, 3 of them associated with CMNS; NRAS gene mutation was studied in these 3 patients. Until a few years ago, surgery was the treatment of choice, but the results have proved unsatisfactory because aggressive interventions do not improve cosmetic appearance and only minimally reduce the risk of malignant change. In 2013, trametinib was approved for use in advanced melanoma associated with NRAS mutations. This drug, which acts on the intracellular RAS/RAF/MEK/pERK/MAPK cascade, could be useful in pediatric patients with CMNS. A better understanding of this disease will facilitate the development of new strategies (AU)

Congenital Melanocytic Nevus Syndrome: A Case Series. / Síndrome del nevus melanocítico congénito. Serie de casos.

Congenital melanocytic nevus syndrome (CMNS) is the result of an abnormal proliferation of melanocytes in the skin and central nervous system caused by progenitor-cell mutations during embryonic development. Mutations in the NRAS gene have been detected in many of these cells. We present 5 cases of giant congenital melanocytic nevus, 3 of them associated with CMNS; NRAS gene mutation was studied in these 3 patients. Until a few years ago, surgery was the treatment of choice, but the results have proved unsatisfactory because aggressive interventions do not improve cosmetic appearance and only minimally reduce the risk of malignant change. In 2013, trametinib was approved for use in advanced melanoma associated with NRAS mutations. This drug, which acts on the intracellular RAS/RAF/MEK/pERK/MAPK cascade, could be useful in pediatric patients with CMNS. A better understanding of this disease will facilitate the development of new strategies.

Tug-of-war between corrugation and binding energy: revealing the formation of multiple moiré patterns on a strongly interacting graphene-metal system.

The formation of multidomain epitaxial graphene on Rh(111) under ultra-high vacuum (UHV) conditions has been characterized by scanning tunnelling microscopy (STM) measurements and density functional theory (DFT) calculations. At variance with the accepted view for strongly interacting graphene-metal systems, we clearly demonstrate the formation of different rotational domains leading to multiple moiré structures with a wide distribution of surface periodicities. Experiments reveal a correlation between the STM apparent corrugation and the lattice parameter of the moiré unit cell, with corrugations of just 30-40 pm for the smallest moirés. DFT calculations for a relevant selection of these moiré patterns show much larger height differences and a non-monotonic behaviour with the moiré size. Simulations based on non-equilibrium Green's function (NEGF) methods reproduce quantitatively the experimental trend and provide a detailed understanding of the interplay between electronic and geometric contributions in the STM contrast of graphene systems. Our study sheds light on the subtle energy balance among strain, corrugation and binding that drives the formation of the moiré patterns in all graphene/metal systems and suggests an explanation for the success of an effective model only based on the lattice mismatch. Although low values of the strain energy are a necessary condition, it is the ability of graphene to corrugate in order to maximize the areas of favourable graphene-metal interactions that finally selects the stable configurations.

Noise levels and cardiovascular mortality: a case-crossover analysis.

BACKGROUND: The relationship between occupational noise and cardiovascular outcomes has been widely investigated. Regarding environmental noise levels, the attention is focused on road traffic noise due to the large number of exposed persons and the large periods of exposure. There are few studies assessing the short-term effects of traffic noise on cardiovascular outcomes. The aim of this study was to quantify the short-term effects of urban noise levels on age-specific cardiovascular mortality. METHODS: A case-crossover design was used. Daily mortality counts in Madrid city due to cardiovascular causes (ICD codes: 390-459) from 1 January 2003 to 31 December 2005 were obtained. Data noise levels were collected as diurnal equivalent noise (Leqd8-22 h), night equivalent noise (Leqn22-8 h), and daily equivalent noise (Leq24 h). Confounding variables as daily levels of air pollutants, temperature, and relative humidity data were controlled. Overdispersed Poisson regression models were adjusted to control for both seasonality and time trends. Estimated effects are reported as percentage increase in the relative risk (IRR) associated with an increase of 1 dBA. RESULTS: The strongest associations between all noise exposure levels and cardiovascular mortality were reported at lag 1: IRR 4.5% (95% CI 0.6, 8.7%), IRR 3.9% (95% CI 0.6, 7.3%), and IRR 6.2% (95% CI 2.1, 10.6%) for Leqd, Leqn, and Leq24, respectively. Analysing by age-specific groups at lag 1, statistically significant associations were found for those aged ≥65: 4.5% (95% CI 0.3, 8.9%), 3.4% (95% CI 0.1, 6.9%), and 6.6% (95% CI 2.2, 11.1%) for Leqd, Leqn, and Leq24, with no substantial changes in the effects of noise exposure levels at lag 1 after adjusting for PM2.5 and NO2. CONCLUSION: The association found between noise exposure levels and cardiovascular mortality suggests a joint effect of diurnal and night-time noise levels. Our results also reveal independent effects of noise exposure levels and the air pollutants analysed. This strongly suggests the need to seriously consider the high noise exposure levels reported as an important public health issue.

Comparación analgésica postquirúrgica de la infiltración corticoanestésica y la anestésica pura tras meniscectomía artroscópica de rodilla / Postoperative pain comparison between steroids anesthetic infiltration, and pure anesthetic infiltration after arthoscopic knee menisectomy

Objetivo: Evaluar la efectividad de las infiltraciones postquirúrgicas de anestésico local solo y combinado con corticoide, para el tratamiento del dolor e inflamación en el postoperatorio temprano en pacientes intervenidos de menisco artroscópicamente. Material y método: Estudio clínico prospectivo randomizado de 60 pacientes a los que se les practicó menisectomía artroscópica. Finalizada la intervención, los pacientes fueron asignados aleatoriamente a uno de los dos grupos de estudio y se infiltró en un grupo 10 ml de clorhidrato de bupivacaína al 0,5% y en el otro el mismo anestésico, asociado a triamcinolona acetónido (solución de 40 mg). La percepción del dolor fue medida objetivamente por la Escala Visual Análoga (EVA), registrándose el dolor postquirúrgico a las 2, 4 y 24 horas y a los 15 días y al mes, después de la intervención. Resultados: No se encontraron diferencias significativas entre los diferentes grupos de estudio. Conclusión: La infiltración anestésica postquirúrgica en dosis única es un procedimiento muy útil para el manejo del dolor postoperatorio en pacientes que requieren la realización de una menisectomía artroscópica (AU)

Objective: To evaluate the effectiveness of postoperative local anesthetic infiltration alone and combined with corticosteroid for the treatment of pain and inflammation in the early postoperative period in patients undergoing arthroscopic meniscal pathology. Material and method: A prospective randomized clinical study, 60 patients who underwent arthroscopic meniscectomy. After surgery, patients were randomly assigned to one of two study groups and infiltrated a group 10 ml of bupivacaine hydrochloride 0.5% and on the other the same anesthetic, associated with triamcinolone acetonide (solution of 40 mg). Pain perception was objectively measured by the Visual Analog Scale (VAS), postoperative pain recorded at 2, 4 and 24 hours and 15 days and a month after the intervention. Results: No significant differences were found between the different groups. Conclusion: Postoperative anesthetic infiltration single dose is a very useful procedure for the management of postoperative pain in patients requiring arthroscopic meniscectomy performing (AU)

Estudio de los efectos de las lesiones del labrum acetabular en la cadera en un modelo experimental lagomorfo adulto / Study of the effects of the hip acetabular labrum damage in a rabbit animal model

Objetivo: El cartílago labral es una estructura cartilaginosa que recubre el acetábulo de la cadera. Su lesión es controvertida en cuanto a sus implicaciones debido a que no se conoce bien si es una causa de degeneración articular o sólo un cambio degenerativo más. Hemos diseñado un modelo animal en conejo para estudiar esta lesión. Material y metodología: Se utilizaron tres grupos de 13 animales a los que se lesionó una cadera dejando la otra como control y se les mantuvo estabulados al primer grupo 12 semanas, al segundo 18 y al tercero 30. Posteriormente se les realizó un estudio radiológico, otro por resonancia magnética y, tras su sacrificio, un estudio histológico. Resultados: No encontramos relación en nuestro modelo entre la lesión labral y los cambios degenerativos posteriores en los plazos citados. Tampoco encontramos daños labrales sin cicatrizar en el momento del sacrificio. Conclusión: En el modelo animal lagomorfo, la lesión labral no produce cambios degenerativos artrósicos y el cartílago labral podría presentar cierta capacidad de regeneración (AU)

Objective: The labrum is a cartilaginous structure that covers the hip acetabulum. The labral lesions are controverted because it is not known if the labral tears are a cause or a consequence of the hip osteoarthrosis. Material and methods: We designed a rabbit animal model to study the labral tears. We used three groups of 13 animals. We injured the labral cartilage of every rabbit in the right hip, and we used the left hip as a control. The animals were kept alive for 12, 18 and 30 weeks. We realized a radiologic, a magnetic resonance and a histological study in every rabbit to see the labral tears consequences. Results: We did not found in our model any significant relationship between the labral tears and the secondary osteoarthrosis in the studied time. We didn't found labral damage without heal when the animals were sacrificed. Conclusion: We can conclude, in the rabbit animal model, the labral tears don't produce degenerative changes in the hip. The labrum have regenerative capacity in the rabbit animal model (AU)

Resultados del tratamiento de seudoartrosis de escafoides con injerto microvascularizado de arteria 1, 2 intercompartimental suprarretinacular y osteosíntesis / Results of treatment of scaphoid nonunion with microvascularized bone grafts of the 1, 2 intercompartmental supraretinacular artery and osteosynthesis

Objetivo. Estudiar los resultados del tratamiento de la seudoartrosis de escafoides, con dudosa viabilidad del fragmento proximal, pero sin deformidad ni colapso importante del mismo, mediante la utilización de un injerto óseo vascularizado de la arteria suprarretinacular 1,2 intercompartimental (1,2 ICSRA) y osteosíntesis posterior. Material y método. Estudio retrospectivo de 10 pacientes varones con diagnóstico radiográfico de seudoartrosis. Después del tratamiento se evaluó la funcionalidad, el dolor medido por la escala analógica visual (EVA), la fuerza de agarre, la satisfacción del paciente y la reintroducción a la vida laboral, utilizando las escalas de Mayo y QuickDASH específicas de muñeca y comprobándose radiográficamente la integración del injerto. Resultados. El seguimiento medio fue de 31,4 meses; un 90% de las encuestas fueron satisfactorias. La EVA descendió en 4,6 puntos y la ganancia de movilidad flexo-extensora fue de 5°. La tasa de consolidación completa del injerto alcanzó el 40% en 5,5 meses de media. Discusión. Diferentes estudios han demostrado mejores resultados utilizando injerto óseo vascularizado frente al no vascularizado. Desde la descripción por Zaidemberg en 1991, el injerto microvascularizado con arteria 1,2 ICSRA, de radio distal, ha sido el más utilizado para el tratamiento de seudoartrosis del escafoides. Conclusiones. Nuestros resultados, comparables con la bibliografía revisada, utilizando el injerto vascularizado de arteria 1,2 ICSRA y osteosíntesis con tornillo tipo Herbert, pueden ser una alternativa de tratamiento para la seudoartrosis proximal de escafoides, sin colapso ni deformidad importante (AU)

Objective. To analyze the results of treatment of scaphoid nonunion with questionable viability of the proximal fragment, but without significant deformity or collapse, using a vascularized bone graft of 1,2 intercompartmental supraretinacular artery (1.2 ICSRA) and subsequent osteosynthesis. Material and method. A retrospective study was performed on 10 male patients with a radiographic diagnosis of nonunion. Functionality, pain using Visual Analog Score (VAS), grip strength, patient satisfaction and reintroduction to working life, using QuickDASH and May specific wrist scales were assessed after the treatment. The integration of the graft was checked by radiography. Results. The mean follow-up was 31.4 months, and 90% of the questionnaires were satisfactory. The VAS decreased by 4.6 points and the flexor-extensor mobility gain was 5°. The total graft consolidation rate reached 40% in 5.5 months on average. Discussion. Several studies have demonstrated better results using vascularized bone graft versus non-vascularized. From the description by Zaidemberg in 1991, the vascularized graft with 1.2 ICSRA artery, distal radius, has been the most widely used for the treatment of scaphoid nonunion. Conclusions. Our results are comparable with the literature reviewed, thus using vascular graft of the 1.2 ICSRA and osteosynthesis with Herbert-type screw, may be an alternative treatment for proximal scaphoid nonunion, without collapse or significant deformity (AU)

[Results of treatment of scaphoid nonunion with microvascularized bone grafts of the 1, 2 intercompartmental supraretinacular artery and osteosynthesis]. / Resultados del tratamiento de seudoartrosis de escafoides con injerto microvascularizado de arteria 1,2 intercompartimental suprarretinacular y osteosíntesis.

OBJECTIVE: To analyze the results of treatment of scaphoid nonunion with questionable viability of the proximal fragment, but without significant deformity or collapse, using a vascularized bone graft of 1,2 intercompartmental supraretinacular artery (1.2 ICSRA) and subsequent osteosynthesis. MATERIAL AND METHOD: A retrospective study was performed on 10 male patients with a radiographic diagnosis of nonunion. Functionality, pain using Visual Analog Score (VAS), grip strength, patient satisfaction and reintroduction to working life, using QuickDASH and May specific wrist scales were assessed after the treatment. The integration of the graft was checked by radiography. RESULTS: The mean follow-up was 31.4 months, and 90% of the questionnaires were satisfactory. The VAS decreased by 4.6 points and the flexor-extensor mobility gain was 5°. The total graft consolidation rate reached 40% in 5.5 months on average. DISCUSSION: Several studies have demonstrated better results using vascularized bone graft versus non-vascularized. From the description by Zaidemberg in 1991, the vascularized graft with 1.2 ICSRA artery, distal radius, has been the most widely used for the treatment of scaphoid nonunion. CONCLUSIONS: Our results are comparable with the literature reviewed, thus using vascular graft of the 1.2 ICSRA and osteosynthesis with Herbert-type screw, may be an alternative treatment for proximal scaphoid nonunion, without collapse or significant deformity.

Use of biogas for cogeneration of heat and electricity for local application: performance evaluation of an engine power generator and a sludge thermal dryer.

A small unit of cogeneration of energy and heat was tested at the Centre for Research and Training on Sanitation UFMG/COPASA - CePTS, located at the Arrudas Sewage Treatment Plant, in Belo Horizonte, Minas Gerais, Brazil. The unit consisted of an engine power generator adapted to run on biogas, a thermal dryer prototype and other peripherals (compressor, biogas storage tank, air blower, etc.). The heat from engine power generator exhaust gases was directed towards the thermal dryer prototype to dry the sludge and disinfect it. The results showed that the experimental apparatus is self-sufficient in electricity, even producing a surplus, available for other uses. The tests of drying and disinfection of sludge lasted 7 h, leading to an increase in solids content from 4 to 8% (50% reduction in sludge volume). Although the drying of sludge was not possible (only thickening was achieved), the disinfection process proved very effective, enabling the complete inactivation of helminth eggs.

Evaluación neuropsicológica y déficit en teoría de la mente: estudio comparativo preliminar entre esquizofrenia y síndrome de Asperger / Neuropsycological assessment and deficit within of mind: preliminary comparison between schizophrenia and Asperger,s syndrome

INTRODUCCIÓN: Los pacientes con trastornos generalizados del desarrollo y con esquizofrenia se han relacionado mediante un déficit en la teoría de la mente. El objetivo del presente estudio es comparar el déficit en la realización de tareas de la teoría de la mente entre ambos y su posible relación con los déficit neuropsicológicos. PACIENTES Y MÉTODO: Participan en el estudio 30 sujetos adultos (trastornos generalizados del desarrollo, esquizofrénicos y con trastorno afectivo bipolar, según los criterios del DSM-IV y el CIE-10), explorados mediante tareas de la teoría de la mente de primer y segundo orden, tiras cómicas y baterías WAIS y Luria-DNA. RESULTADOS: Entre los 3 grupos de pacientes únicamente se encuentran diferencias estadísticamente significativas en la realización de viñetas de segundo orden. CONCLUSIONES: Los resultados apuntan hacia la relación entre el déficit en la teoría de la mente y otros déficit neuropsicológicos, aunque hacen falta más estudios para obtener datos sobre las diferencias entre ambos grupos de pacientes (AU)

La interacción social en esquizofrenia y trastornos generalizados del desarrollo: del autismo a la teoría de la mente / Social interaction in schizophrenia and pervasive developmental disorders: from autism to theory of mind

La esquizofrenia y los trastornos generalizados del desarrollo se han relacionado de dos maneras diferentes: primero a través del concepto de autismo y ahora a través del concepto de teoría de la mente. En este artículo se exponen las razones que explican esta relación. Los autores muestran los límites de la psicopatología para dar cuenta de las semejanzas y las diferencias existentes entre ambos. Como conclusión se propone detenerse en el hecho de que se puede diferenciar a estos pacientes a pesar de su parecido, por lo que habrá que prestar atención al procedimiento por el que asignamos el diagnóstico de esquizofrenia o trastornos generalizados del desarrollo (AU)

Mesotelioma pleural difuso maligno con presentación radiológica inusual / Diffuse malignant pleural mesothelioma with unusual radiological presentation

No disponible

Efecto de la amnioinfusión profiláctica intraparto sobre la frecuencia cardíaca fetal en gestaciones con oligoamnios causado por rotura prematura de membranas / The effect of prophylactic intrapartum amnioinfusion on foetal heart rate in pregnancies with oligohydramnios due to rupture of membranes

La amnioinfusión (AI) previene o alivia las compresiones funiculares durante el parto. El objetivo de este trabajo es valorar los efectos de dicho procedimiento, utilizado de forma profiláctica durante el parto, sobre el registro cardiotocográfico en gestantes con oligoamnios (ILA < 5). El estudio se realizó en 100 gestantes con oligoamnios; 50 recibieron AI profiláctica y el resultado se comparó con el de 50 que no la recibieron. Ambos grupos presentaban similares edades maternas, paridad, edades gestacionales e índice de Bishop al inicio del parto. El ILA inicial fue similar en ambos grupos, aumentando de forma significativa a los 60 minutos en el grupo que recibió la AI. El estudio del RCTG no mostró diferencias significativas ni en la FCF basal ni en la reactividad; sin embargo, encontramos un menor número de deceleraciones variables (28 frente a 39) y variables atípicas (8 frente a 18), deceleraciones variables tardías (0 frente a 11) y prologados (3 frente a 11) (p < 0,05) en mujeres con AI. Se concluye que en la población estudiada la AI durante el parto en gestantes con oligoamnios reduce el número de deceleraciones variables y prolongadas, posiblemente debido a la disminución de fenómenos compresivos umbilicales y por tanto disminuyendo el riesgo de alteraciones del estado metabólico fetal y de las indicaciones del parto operatorio por riesgo de pérdida del bienestar fetal (AU)

Tratamiento quirúrgico del síndrome del desfiladero torácico: nuestra experiencia (1986-2000) / Surgical treatment in the thoracic outlet syndrome: our experience (1986-2000)

Objetivo. Evaluar los resultados del tratamiento quirúrgico del síndrome del desfiladero torácico (SDT) en un servicio de angiología y cirugía vascular. Pacientes y métodos. Estudio retrospectivo. Período de estudio 1986-2000, n= 53 casos en 45 pacientes (8 bilaterales). Edad media: 32,6 años (r= 17-58). Se han incluido 29 mujeres (64 por ciento) y 16 varones (34 por ciento), diagnosticados por exploración clínica, radiología simple, pruebas neurofisiológicas, Doppler y angioRx. SDT arterial n= 43 (30 puros/13 mixtos o neurovasculares); SDT venoso n= 9 (8 TVP y 1 edema intermitente) y un caso SDT neurológico puro. Se apreciaron anomalías óseas en el 62,2 por ciento de los pacientes. Se han practicado 28 resecciones de costilla cervical/megaapófisis C7, 19 de 1.ª costilla, 3 de 1.ª costilla anómala, 1 de clavícula, 1 de músculo subclavio y 1 escalenectomía aislada. Se asoció cirugía arterial o venosa directa en 8 casos (6/2 respectivamente). Los resultados precoces y tardíos se han calculado mediante estadística descriptiva, test exacto de Fisher y Kaplan-Meier, utilizando el programa SPSS. Resultados. Precoces: mortalidad 0 por ciento, morbilidad 13 por ciento, permeabilidad acumulada 87,5 por ciento. Tardíos: seguimiento medio 36 meses (0-15 años). Permeabilidad acumulada: 85,7 por ciento. Tasa actuarial de asintomáticos: 79,2 por ciento. Tasa de asintomáticos y sintomáticos con pruebas postoperatorias normalizadas: 92,4 por ciento (a los 15 años). No se evidenció relación significativa entre sexo, edad y tipo de resección efectuada, con la persistencia de los síntomas en las tablas actuariales (p> 0,05). Se reintervinieron cuatro casos (7.5 por ciento) por recurrencia de los síntomas. Conclusiones. Nuestros resultados justifican el tratamiento quirúrgico del SDT. La selección de los pacientes es fundamental porque un porcentaje mantendrá la sintomatología pese a la normalización de los tests diagnósticos (AU)

Representation of harmonic complex stimuli in the ventral cochlear nucleus of the chinchilla.

The representation of Schroeder-phase harmonic complex sounds in the ventral cochlear nucleus (VCN) of the anesthetized chinchilla was studied. Stimuli consisted of a series of harmonically related sinusoids, multiples of a fundamental frequency (f0), summed in either negative (-SCHR) or positive (+SCHR) Schroeder phase. Psychoacoustic experiments performed in humans by other investigators have revealed that masking effects of -SCHR stimuli are larger than those found using +SCHR stimuli as maskers. In our laboratory, basilar membrane measurements at the base of the chinchilla cochlea show that responses to -SCHR stimuli are less "peaked," or modulated, than responses to +SCHR stimuli. We also found that suppression of a characteristic-frequency (CF) tone by -SCHR stimuli is larger than that evoked by +SCHR stimuli. Rate-intensity functions display higher firing rates in responses to -SCHR stimuli than in those produced by +SCHR stimuli. Firing rates evoked by either -SCHR or +SCHR stimuli saturate at lower values than those obtained in responses to CF tones. Rate and synchrony suppressions by -SCHR stimuli were larger than those evoked by +SCHR stimuli. Auditory nerve fiber responses to Schroeder complex stimuli share most of the properties of VCN responses, indicating little additional processing by the VCN.

Basilar-membrane response to multicomponent stimuli in chinchilla.

The response of chinchilla basilar membrane in the basal region of the cochlea to multicomponent (1, 3, 5, 6, or 7) stimuli was studied using a laser interferometer. Three-component stimuli were amplitude-modulated signals with modulation depths that varied from 25% to 200% and the modulation frequency varied from 100 to 2000 Hz while the carrier frequency was set to the characteristic frequency of the region under study (approximately 6.3 to 9 kHz). Results indicate that, for certain modulation frequencies and depths, there is enhancement of the response. Responses to five equal-amplitude sine wave stimuli indicated the occurrence of nonlinear phenomena such as spectral edge enhancement, present when the frequency spacing was less than 200 Hz, and mutual suppression. For five-component stimuli, the first, third, or fifth component was placed at the characteristic frequency and the component frequency separation was varied over a 2-kHz range. Responses to seven component stimuli were similar to those of five-component stimuli. Six-component stimuli were generated by leaving out the center component of the seven-component stimuli. In the latter case, the center component was restored in the basilar-membrane response as a result of distortion-product generation in the nonlinear cochlea.

Multicomponent stimulus interactions observed in basilar-membrane vibration in the basal region of the chinchilla cochlea.

Multicomponent stimuli consisting of two to seven tones were used to study suppression of basilar-membrane vibration at the 3-4-mm region of the chinchilla cochlea with a characteristic frequency between 6.5 and 8.5 kHz. Three-component stimuli were amplitude-modulated sinusoids (AM) with modulation depth varied between 0.25 and 2 and modulation frequency varied between 100 and 2000 Hz. For five-component stimuli of equal amplitude, frequency separation between adjacent components was the same as that used for AM stimuli. An additional manipulation was to position either the first, third, or fifth component at the characteristic frequency (CF). This allowed the study of the basilar-membrane response to off-CF stimuli. CF suppression was as high as 35 dB for two-tone combinations, while for equal-amplitude stimulus components CF suppression never exceeded 20 dB. This latter case occurred for both two-tone stimuli where the suppressor was below CF and for multitone stimuli with the third component=CF. Suppression was least for the AM stimuli, including when the three AM components were equal. Maximum suppression was both level- and frequency dependent, and occurred for component frequency separations of 500 to 600 Hz. Suppression decreased for multicomponent stimuli with component frequency spacing greater than 600 Hz. Mutual suppression occurred whenever stimulus components were within the compressive region of the basilar membrane.