Rothman, JS; Young, ED; (1996) Enhancement of neural synchronization in computational models of ventral cochlear nucleus bushy cells. Auditory Neuroscience , 2 (1) pp. 47-62.

Text Rothman Young 1996 AuditoryNeuroscience.pdf - Published Version Access restricted to UCL open access staff Download (12MB)

Abstract

Ventral cochlear nucleus (VCN) bushy cells, especially globular bushy cells (GBCs), show enhanced synchronization to low-frequency tones (<1 kHz) when compared to auditory nerve (AN) fibers. Joris and colleagues (J. Neurophysiol. 71:1022, 1994) interpreted the enhanced synchronization as implying that GBCs receive multiple AN inputs which are individually subthreshold, so that the enhancement results from the necessity for coincidence of input spikes in order to produce an output spike. By contrast, in a previous modeling study, we concluded that high-BF GBCs must receive suprathreshold inputs in order that their spike trains be irregular and in order that they synchronize strongly in the midfrequency range (1-5 kHz). In this study, we reconsider the modeling results in an attempt to account for enhanced synchrony in models which display all the properties of bushy cells; the principal variables studied are the number and strength of synaptic inputs. A simple shot-noise threshold model displays enhanced synchronization at 500 Hz with either subthreshold or suprathreshold inputs. A membrane-conductance model, which accurately reproduces bushy-cell electrical characteristics, displays enhanced synchronization at low frequencies with a variety of input configurations. These configurations differ in their spontaneous activity, regularity, PST histogram shape, and mid-frequency phase-locking. Models with all subthreshold or all suprathreshold inputs each match some aspects of GBC behavior, but neither model reproduces all aspects: subthreshold models phase-lock more weakly at mid-frequencies than almost all the GBC data and suprathreshold models have inappropriate PST histogram shapes and spontaneous rates that are too high. A model which better reproduces average GBC data has suprathreshold inputs combined with a tonic inhibitory input. However, the modeling results, taken as a whole, suggest that there must be subclasses of GBCs with different arrangements of synaptic input, including both subthreshold and suprathreshold inputs.

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