This implements the spiking Hodgkin-Huxley type models of tonic and
phasic second-order vestibular neurons from:

R�ssert C, Straka H, Moore LE, Glasauer S (2011) Cellular and network 
contributions to vestibular signal processing: impact of ion 
conductances, synaptic inhibition and noise. J Neurosci 31:8359-8372


Head motion-related sensory signals are transformed by second-order
vestibular neurons (2�VNs) into appropriate commands for retinal image
stabilization during body motion. In frogs, these 2�VNs form two
distinct subpopulations that have either tonic or highly phasic
intrinsic properties, essentially compatible with low-pass and
bandpass filter characteristics, respectively. In the present study,
physiological data on cellular properties of 2�VNs of the grass frog
(Rana temporaria) have been used to construct conductance-based
spiking cellular models that were fine-tuned by fitting to recorded
spike-frequency data. The results of this approach suggest that
low-threshold, voltage-dependent potassium channels in phasic and
spike-dependent potassium channels in tonic 2�VNs are important
contributors to the differential, yet complementary response
characteristics of the two vestibular subtypes. Extension of the
cellular model with conductance-based synapses allowed simulation of
afferent excitation and evaluation of the emerging properties of local
feedforward inhibitory circuits. This approach revealed the relative
contributions of intrinsic and synaptic factors on afferent signal
processing in phasic 2�VNs. Additional extension of the single-cell
model to a population model allowed testing under more natural
conditions including asynchronous afferent labyrinthine input and
synaptic noise. This latter approach indicated that the feedforward
inhibition from the local inhibitory network acts as a high-pass
filter, which reinforces the impact of the intrinsic membrane
properties of phasic 2�VNs on peak response amplitude and
timing. Thus, the combination of cellular and network properties
enables phasic 2�VNs to work as a noise-resistant detector, suitable
for central processing of short-duration vestibular signals.

All stimulation can be started via mosinit.hoc. Model generates traces
similar the following subfigures:

intracellular step current stimulation: Fig. 2C (tonic), Fig. 5B2
(phasic) frequency current (ZAP): Fig. 3A2 (tonic) (shown below as an
example, generated by clicking "Tonic model T1 ZAP":

Fig 3A2

Fig. 5D2 (phasic) synaptic stimulation: Fig. 6A4, 6B4, 6C4

All models were implemented by Christian R�ssert
(christian.a at