TY - JOUR T1 - Distinct Neural Properties in the Low Frequency Region of the Chicken Cochlear Nucleus Magnocellularis JF - eneuro JO - eNeuro DO - 10.1523/ENEURO.0016-17.2017 SP - ENEURO.0016-17.2017 AU - Xiaoyu Wang AU - Hui Hong AU - David H. Brown AU - Jason Tait Sanchez AU - Yuan Wang Y1 - 2017/04/04 UR - http://www.eneuro.org/content/early/2017/04/04/ENEURO.0016-17.2017.abstract N2 - Topography in the avian cochlear nucleus magnocellularis (NM) is represented as gradually increasing characteristic frequency (CF) along the caudolateral to rostromedial axis. In this study, we characterized the organization and cell biophysics of the caudolateral NM (NMc) in chickens (Gallus gallus domesticus). Examination of cellular and dendritic architecture first revealed that NMc contains small neurons and extensive dendritic processes, in contrast to adendritic, large neurons located more rostromedially. Individual dye-filling study further demonstrated that NMc is divided into two subregions, with NMc2 neurons having larger and more complex dendritic fields than NMc1. Axonal tract tracing studies confirmed that NMc1 and NMc2 neurons receive afferent inputs from the auditory nerve and the superior olivary nucleus, similar to the adendritic NM. However, the auditory axons synapse with NMc neurons via small bouton-like terminals, unlike the large end-bulb synapses on adendritic NM neurons. Immunocytochemistry demonstrated that most NMc2 neurons express cholecystokinin but not calretinin, distinct from NMc1 and adendritic NM neurons that are cholecystokinin-negative and mostly calretinin-positive. Finally, whole-cell current clamp recordings revealed that NMc neurons require significantly lower threshold current for action potential generation than adendritic NM neurons. Moreover, in contrast to adendritic NM neurons that generate a single onset action potential, NMc neurons generate multiple action potentials to suprathreshold sustained depolarization. Taken together, our data indicate that NMc contains multiple neuron types that are structurally, connectively, molecularly, and physiologically different from traditionally defined NM neurons, emphasizing specialized neural properties for processing low frequency sounds.Significance Statement Low frequency sounds are important for auditory perception and scene analysis including speech recognition. Using an avian model sensitive to low frequency hearing including infrasound, we characterized neuronal properties of a primary cochlear nucleus. We found that the neurons located at the low frequency end of the tonotopic axis develop unique structural, synaptic, biochemical and physiologic features, distinct from well-characterized neurons processing sounds of higher frequencies. These findings provide fundamental knowledge toward understanding the properties of low frequency processing in the brain. ER -