Biomedical Engineering Reference
In-Depth Information
Figure 14.11
Steady-state voltage distribution in compartmental models of fly LPTCs after simu-
lated current injection into the axon. False-color code represents the local voltage in
percent of voltage at injection site (From [43]). (See color insert.)
munohistochemical revealed that HS- and VS-cells receive their excitatory input via
nicotinic acetylcholine receptors and become inhibited via GABA receptors [16, 17].
Using all the information summarized above and incorporating them into compart-
mental models allowed, amongst other things, to visualize the steady-state potential
distribution following injection of de- or hyperpolarizing currents into the axon of the
neuron (Figure 14.11). In addition, knowing the precise kinetics of voltage-activated
currents led the models reproduce many of the experimentally observed dynamic re-
sponse properties like e.g., frequency-dependent amplification of synaptic input in
HS-cells [44, 45].
14.3.2 Dendritic integration and gain control
One response feature of LPTCs studied intensively in the past concerns their spatial
integration characteristics: when enlarging the area in which the motion stimulus is
displayed the response saturates significantly [9, 42, 55, 83]. The interesting fact is
the observation that such a saturation occurs not only for motion along the preferred,
but also along the null direction of the cell. Furthermore, for patterns moving at
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