The effects of a second stimulus on the auditory steady state response (ASSR) from the inferior colliculus of the chinchilla

Abstract

Abstract

The auditory steady-state response (ASSR) is an auditory evoked potential which follows the envelope of the stimulus. One of the advantages of the ASSR is that multiple stimulation frequencies can be tested simultaneously. In experiment 1, we evaluated the effects of simultaneously presenting two separate stimuli on ASSR response amplitude. In experiment 2, we evaluated the effects of presenting two ASSR-generating stimuli monotically vs. dichotically, either ipsilaterally or contralaterally to the recording electrode. Recordings were made from the chinchilla inferior colliculi, in response to tonebursts, two-tones, or sinusoidally-amplitude modulated tones. We found that the addition of a second stimulus resulted in a reduction in ASSR response amplitude at moderate to high stimulus levels. The amount of amplitude reduction was typically larger in the monotic (e.g. ∼50%) vs. dichotic condition (e.g. ∼10–20%), regardless of whether the responses were recorded ipsilaterally or contralaterally to the ear of stimulus presentation. In conclusion, central as well as peripheral interactions contribute to the reduction in ASSR amplitude in response to the simultaneous presentation of multiple stimuli

Sumario

Las respuestas auditivas de estado estable (ASSR) son un potencial evocado que sigue a la envoltura del estímulo. Una de las ventajas de los ASSR es que se puede estimular simultáneamente con varias frecuencias. En el experimento 1 evaluamos los efectos sobre la amplitud de los ASSR de la estimulación simultánea con dos estímulos separados. En el experimento 2 evaluamos los efectos de la presentación de dos estímulos generadores de ASSR monotico vs dicótico, tanto ipilateral como contralateral al electrodo de registro. Los registros fueron realizados en el colículo inferior de la Chinchilla en respuesta a burst tonales, a dos tonos o a tonos con amplitud sinusoidalmente modulada. Encontramos que la adición de un segundo estímulo de nivel moderado a elevado, dio como resultado la reducción de la amplitud de la respuesta de ASSR. La magnitud de la reducción de la amplitud fue típicamente mayor en la condición monótica (e.g. ∼50%) vs. la condición dicótica (e.g. ∼10–20%) sin importar si las respuestas fueron obtenidas ipsi o contralateralmente al oído de presentación del estímulo. En conclusión, las interacciones tanto centrales como periféricas contribuyen a la reducción de la amplitud de las ASSR en respuesta a la presentación de múltiples estímulos.

Key Words:

• Auditory steady state response
• Inferior colliculus
• Chinchilla

Acknowledgements

This work was supported in part by NIH-NIDCD DC03600. The work from experiment 1A was presented at the International Evoked Audiometry Study Group at the 2003 meeting in the Canary Islands, Spain. The work from experiment 1B was presented at a 2005 meeting of the American Auditory Society in Scottsdale, Arizona, USA. The work from experiment 2 was presented at the International Evoked Audiometry Study Group during the 2005 meeting in Havana, Cuba. This research was completed in the center for Hearing and Deafness at the University of Buffalo. Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.