Temporospatial Characteristics of the Effect of a Sound on the Response to Another Sound in Neurons in the Rat Auditory Midbrain
The soundscape of a natural environment can often contain multiple complex sounds, which are perceived binaurally, i.e., by both ears. Under such conditions, the perception of one sound can be affected by another sound. This study was conducted to find the neural basis of such a perceptual phenomenon. The rat is used as an animal model. Action potentials were recorded from individual neurons within the rat inferior colliculus in response to acoustic stimulation. The inferior colliculus is an auditory midbrain structure which receives converging inputs from many other structures along the auditory pathway. It plays a significant role in the integration of neural signals elicited by stimulation of both ears. Temporal and spatial characteristics of sounds affect responses of neurons in the IC to the sounds. It has been found that a priming tone can suppress the response to a testing tone when the two sounds occur closer together both temporally and spatially. This research was conducted to further investigate how responses of neurons to two sounds were dependent on the temporal and spatial relationship between the sounds. Further analysis was performed on a set of neurophysiological data collected by former graduate student, Sarah Tran by removing interfering signals. It was then determined how the responses to a pair of priming-testing sounds were dependent on the temporal and spatial relationships between the sounds. The programming language R was used for analysis. Reanalysis indicated that the response of IC neurons to a testing tone can be suppressed by a priming tone, and that this suppression is reduced when the priming and testing tones are separated temporally and spatially. This effect is especially large in neurons that have transient firing patterns. These results may help understand neural mechanisms responsible for the psychophysical phenomena of masking and spatial release from masking. Results can help to understand spatial hearing and hearing in a natural acoustic environment in general.