Dynamic changes in synaptic amplitude over short time periods, known as short-term synaptic plasticity, may have profound effects on the transmission of information between neurons. Our recent results on the short-term synaptic plasticity properties in the avian cochlear nucleus angularis (NA) demonstrated a remarkable ability to transmit information at firing frequencies that cause severe depression at other excitatory synapses in the brain. Furthermore, the depressing and facilitating plasticity components appear to be tuned such that these synapses will transmit rate information linearly, which may be critical for the encoding of acoustic intensity information. We will take advantage of an established in vitro model for cellular studies of auditory function, the brainstem slice preparation from young chickens. Using intracellular electrophysiological recordings and computational modeling, we will investigate the mechanisms responsible for the short-term plasticity at the nerve to NA synapse. We will determine whether variations in the short-term synaptic plasticity expressed in different NA neurons might contribute to distinct processing streams within the auditory brainstem. We will investigate the implications of this short-term plasticity for auditory coding by stimulating with dynamic stimuli such as simulated amplitude-modulation signals. Finally, by using the dynamic clamp methods, we will investigate how synaptic inputs, and their dynamic modulation, combine with NA neuronal intrinsic properties to generate the action potential output. These experiments are critical to our understanding of intensity processing for localization and non-localization tasks, and offer an excellent opportunity to study the implications of short-term synaptic dynamics for sensory processing. This work also has broader implications for the development of improved cochlear implant devices to recover hearing in hearing-impaired people. The cochlear nucleus is the first receiving station in the central nervous system for auditory information. While our research is focused on basic properties, a better understanding of how sound information is transformed at the auditory nerve to cochlear nucleus connection will help guide the design of cochlear implants that can stimulate more efficient, enriched sound inputs, enhancing the quality of life for the hearing-impaired.
| MacLeod, Katrina M; Horiuchi, Timothy K (2011) A rapid form of activity-dependent recovery from short-term synaptic depression in the intensity pathway of the auditory brainstem. Biol Cybern 104:209-23 |
| MacLeod, Katrina M; Carr, Catherine E (2007) Beyond timing in the auditory brainstem: intensity coding in the avian cochlear nucleus angularis. Prog Brain Res 165:123-33 |
| MacLeod, K M; Horiuchi, T K; Carr, C E (2007) A role for short-term synaptic facilitation and depression in the processing of intensity information in the auditory brain stem. J Neurophysiol 97:2863-74 |
| MacLeod, Katrina M; Carr, Catherine E (2005) Synaptic physiology in the cochlear nucleus angularis of the chick. J Neurophysiol 93:2520-9 |
