Intrinsic Biophysical Properties of Frog Central Auditory Neurons
The goal of my research is to gain insight into the intrinsic biophysical characteristics of frog central auditory neurons. For this, I utilized in vitro preparations to investigate various basic membrane properties of neurons in three major auditory centers, the dorsal medullary nucleus (DMN), the torus semicircularis (TS), and the auditory thalamus. In the second chapter, I showed that the membrane properties of DMN neurons are heterogeneous---they show diverse biophysical phenotypes (which can be characterized by the different temporal discharge patterns in response to depolarization current injections) as well as morphological phenotypes. The majority of DMN neurons are onset or transient-chopper phenotypes that are capable of encoding rapid time-varying signals. In the third chapter, I showed that TS neurons also display many different biophysical phenotypes; some of which are similar to those seen in the DMN but others are novel. This finding sheds light into their potential roles in creation of unit-specific AM rate sensitivity (or tone-induced oscillatory discharges). In the fourth chapter, I found that auditory thalamic neurons are homogeneous, showing high membrane input resistance and long time constant, and uniformly sustained-chopper temporal discharge patterns in response to depolarization currents---unlike the various phenotypes in the lower auditory brainstem the thalamic neurons cannot follow fast or slow trains of depolarization current pulses. The above findings suggest that the intrinsic biophysical characteristics of neurons likely play a role in the transformation of AM-following response along the ascending auditory pathway.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign