Computational model of response maps in the dorsal cochlear nucleus

Abstract

The neurons in the mammalian (gerbil, cat) dorsal cochlear nucleus (DCN) have responses to tones and noise that have been used to classify them into unit types. These types (I-V) are based on excitatory and inhibitory responses to tones organized into plots called response maps (RMs). Type I units show purely excitatory responses, while type V units are primarily inhibited. A computational model of the neural circuitry of the mammalian DCN, based on the MacGregor neuromime, was used to investigate RMs of the principal cells (P-cells) that represent the fusiform and giant cells. In gerbils, fusiform cells have been shown to have primarily type III unit response properties; however, fusiform cells in the cat DCN are thought to have type IV unit response properties. The DCN model is based on a previous computational model of the cat (Hancock and Voigt Ann Biomed Eng 27: 73-87, 1999) and gerbil (Zheng and Voigt Ann Biomed Eng 34: 697-708, 2006) DCN. The basic model for both species is architecturally the same, and to get either type III unit RMs or type IV unit RMs, connection parameters were adjusted. Interestingly, regardless of the RM type, these units in gerbils and cats show spectral notch sensitivity and are thought to play a role in sound localization in the median plane. In this study, further parameter adjustments were made to systematically explore their effect on P-cell RMs. Significantly, type I, type III, type III-i, type IV, type IV-T and type V unit RMs can be created for the modeled P-cells. Thus major RMs observed in the cat and gerbil DCN are recreated by the model. These results suggest that RMs of individual DCN projection neurons are the result of specific assortment of excitatory and inhibitory inputs to that neuron and that subtle differences in the complement of inputs can result in different RM types. Modulation of the efficacy of certain synapses suggests that RM type may change dynamically.

Development of hyperactivity after hearing loss in a computational model of the dorsal cochlear nucleus depends on neuron response type

“…Reproducing salient response properties of DCN projection neurons, has also been the focus of several other modeling studies Blum et al, 1995;Franosch et al, 2003;Zheng and Voigt, 2006a;Zheng and Voigt, 2006b). Our model is similar to the model of Reed et al (1995), as it is also rate-based, whereas the more recent models of Franosch et al (2003) and Zheng and Voigt (2006b) employ spiking neurons. Firing rates in our model represent average firing rates of small populations of real neurons.…”

“…It is assumed to inhibit DCN projection neurons as well as type II neurons. Modeling results show that the different response types of DCN principal cells can be reproduced with this circuit by adjusting the strengths of the inhibitory inputs to the PNs (Zheng and Voigt, 2006b).…”

Single neuron recordings in dorsal cochlear nucleus (DCN) of awake gerbil

“…Type IV units are found neither in the DCN of awake mice nor awake gerbils (this study). The computational model of the DCN by Zheng and Voigt (2006a) demonstrated that small changes in the synaptic efficacies of just a few synapses (e.g., the auditory nerve synapse on either the P-cell or the I2-cell) can have profound effects on the resulting unit's RM. For example, the RM could change from a type IV unit to a type III unit.…”

“…The computational modeling study of Zheng and Voigt (2006a) demonstrated that model P-cell (principal cell) RMs can be type I, type III, type III-i, type IV-T, or type IV units depending on the degree of the inhibition from model I2-cells (type II units of vertical cells). This modeling study demonstrates that the RM of a unit can be altered through slight changes in the synaptic efficacy of just one synapse type.…”

Support of a patient-specific therapeutical acoustic stimulation in tinnitus by numerical modeling

“…The DCN model is based on the neuromime model by MacGregor et al [24] and the implementation by Zheng et al [25] The membrane potential V mem in this single-compartment model is influenced by variable gating parameters g K , g ex , and g in , denoting potassium, excitatory, and inhibitory conductances. It is…”