Date of Award


Publication Type

Master Thesis

Degree Name



Biological Sciences


Antagonists, Free-field sound, Inferior colliculus, Inhibition, Local-field potentials, Masking


Huiming Zhang




The perception of one sound can be influenced by another sound in the environment, with the effect dependent on the spectrotemporal and spatial relationship between the sounds. Mechanisms responsible for this perceptual phenomenon is dependent on the integration of neural signals driven by the two ears in brain centers responsible for hearing. The inferior colliculus (IC) as a midbrain structure is important for the processing of acoustic information. To understand why/how the perception of one sound is influenced by another sound, it is important to study how the two sounds interact with each other in generating responses in the IC. In this study, I examined the effect of a leading sound on the responses elicited by a trailing sound in an ensemble of neurons in the IC. Local-field potentials (LFPs) were recorded to reflect responses of neural ensembles. The two sounds were first colocalized at the ear that was contralateral to the recording site. Then the two sounds were then spatially separated. I evaluated whether the influence generated by a leading sound was dependent on the spatial relationship as well as the time gap between the leading and trailing sounds. Results indicated that the LFPs elicited by a trailing sound were suppressed by a leading sound no matter whether the leading sound was at the contralateral or ipsilateral ear. The suppressive effect was larger when a leading sound was presented at the contralateral than the ipsilateral ear. Furthermore, the effect was larger when the two sounds were separated by a short time gap. Inhibitory neurotransmitter antagonists, gabazine and strychnine significantly decreased the suppression produced by the leading sound but did not eliminate it. These results suggest that local inhibitory interaction in the inferior colliculus may not be the only factor that is responsible for the suppressive effect produced by the leading sound. Results from this study are important for understanding neural mechanisms responsible for hearing in a real-world situation.