Research Description:

Acoustic Contrast Enhances Thalamic Entrainment to Sound Sequences

My research project is to measure the adaptation of auditory neurons to sequences of contrasting sounds. Pilot studies have shown that neurons adapt to repetitions of sounds, with greater adaptation as the repetition rate increases. In other words, when a sound is repeated faster, the magnitude of the neuronal response is decreased. Adaptation is lower for sequences comprised of alternating clicks and tones--two different, contrasting sounds--compared to repetition of a single sound. Due to the fact that short-term adaptation towards sequences of contrasting sounds is a critical factor of how the brain responds to everyday sounds like speech, I intend to explore how acoustic contrast shapes adaptation in the auditory system.

I will observe and measure the auditory neurons’ responses and adaptation to the two different combinations of stimuli involving the two sounds played at three different repetition rates – 4, 8, and 12 m/s. I would like to view how the neurons adapt as repetition rate increases when the two sounds have carefully controlled differences in the acoustic spectrum. One type of spectral difference is to choose two sounds so that the spectrum peaks of one of the sounds matches spectrum valleys of the other sound.

The other way I plan to create different sounds is to change the envelope shape of one sound to create two contrasting ones—the damped and the ramped. In my data I will record the number of action potentials in a half-second time window to twenty presentations of the mentioned stimuli, and how neurons’ responses decrease as the rate of repetition increases. I plan to obtain this data from five healthy rats. When performing surgery on the rats I will place electrodes in the auditory thalamus, by which I will later measure the neurons’ responses after the certain stimuli are initiated.