CURRENT PROJECTS

1. ORGANIZATION OF PERIOLIVARY NUCLEI IN THE HUMAN SOC
The working hypothesis for this project is: since human hearing sensitivity is focused in the low frequency range (20Hz to 20kHz), the human SOC should contain a compliment of PON rivaling those of other low-frequency hearing animals (e.g. chinchilla). Since it has been shown that inhibition arising from the MNTB and LNTB are important for processing of low frequency sounds (Brand et al., 2002), the human PON should include a prominent MNTB and LNTB. The purpose of this project is to provide an initial characterization of periolivary nuclei in human as a basis for further study. Periolivary nuclei in the human SOC will be examined in Nissl or cytochrome oxidase stained material. Additionally, estimates of neuronal number will be made and the constituent neurons in each nucleus will be classified and catalogued for future reference.

Original 3D model data compiled by Dr. Randy Kuleza
3D rendering and enhancement by Maher Al-Samkari

2. DISTRIBUTION OF INHIBITORY NEUROTRANSMITTERS WITHIN THE HUMAN SOC
The working hypothesis for this project is: human periolivary nuclei serve fine-tuning or modulatory roles in auditory processing and this function is carried out via inhibitory mechanisms. This requires that periolivary nuclei are inhibitory and therefore use inhibitory neurotransmitters (primarily GABA or glycine but also dopamine and acetylcholine). The purpose of this project is to characterize the distribution of cholinergic, dopaminergic, GABAergic and glycinergic neurons and punctate profiles (presumably representing synaptic terminals) in the human SOC. Additionally, estimates will be made of the number of neurons within each PON using inhibitory neurotransmitters.

3. STRUCTURAL FEATURES OF THE CALYX OF HELD
The working hypothesis for this project is: humans use similar neuronal circuits for sound processing as other mammals. Integral to these pathways are PON that receive the calyx of Held a large, secure synaptic ending from the cochlear nucleus. The calyx plays an essential role in temporal processing and localization of sound sources. Interestingly, current descriptions of the human SOC deny this population. The purpose of this project is to determine, using immunocytochemistry for various calcium binding proteins, if these specialized endings are present in the human SOC and what PON neurons are receiving calyceal innervation. The experiments in this project will conclusively confirm or negate the presence of this important neuronal circuit.

COLLABORATIONS


1. IN-VIVO RECORDINGS FROM SUPERIOR PARAOLIVARY NUCLEUS OF RAT
    - A collaboration with Dr. Berrebi (WVU)

2. NEUROCHEMICAL PROFILES IN THE HUMAN SPINAL TRIGEMINAL NUCLEUS
    - A Collaboration with Drs. Rowland and Wells (SIUE)