A model of thalamocortical relay cells

Abstract

It is well established that the main intrinsic electrophysiological properties of thalamocortical relay cells, production of a low threshold burst upon release from hyperpolarized potential and production of a train of single spikes following stimulation from depolarized potentials, can be readily modelled using a single compartment. There is, however, another less well explored intrinsic electrophysiological characteristic of relay cells for which models have not yet accounted: at somatic potentials near spike threshold, relay cells produce a fast ragged high threshold oscillation in somatic voltage. Optical [Ca 2+ ] imaging and pharmacological tests indicate that this oscillation correlates with a high threshold Ca 2+ current in the dendrites. Here we present the development of a new compartment model of the thalamic relay cell guided by the simultaneous constraints that it must produce the familiar regular spiking relay mode and low threshold rebound bursts which characterize these cells, as well as the less-studied fast oscillation occurring at near-threshold somatic potentials. We arrive at a model cell which is capable of the production of isolated high threshold Ca 2+ spikes in distal branch segments, driven by a rapidly inactivating intermediate threshold Ca 2+ channel. Further, the model produces the low threshold spike behaviour of the relay cell without requiring high T-current density in the distal dendritic segments. The results thus support a new picture of the dendritic tree of relay cells which may have implications for the manner in which thalamic relay cells integrate descending input from the cortex.

Modulation of Fast Narrowband Oscillations in the Mouse Retina and dLGN According to Background Light Intensity

“…Therefore, while narrowband oscillations in the dLGN may arise within the dLGN itself (Pedroarena and Lliná s, 1997;Rhodes and Lliná s, 2005) or from cortical feedback (Sillito et al, 1994), the most parsimonious explanation for our results is that their irradiance modulation is inherited from the retina. Within the retina, the melanopsin-expressing ipRGCs are thought to provide the primary irradiance signal (Wong, 2012).…”

γ-Band deficiency and abnormal thalamocortical activity in P/Q-type channel mutant mice

“…This activity, considered to be a functional prerequisite to cognitive states, is present at both the network (11,12) and neuronal levels as subthreshold oscillations (13)(14)(15). P/Q-type channels also mediate glutamatergic and GABAergic synaptic transmission in the cortex and thalamus (16,17).…”

The interplay of seven subthreshold conductances controls the resting membrane potential and the oscillatory behavior of thalamocortical neurons

“…Consequently, most computational models of TC neurons include one or two calcium-activated potassium currents (McCormick and Huguenard 1992; Rhodes and Llinas 2005).…”

“…A global depolarizing shift of 10 -15 mV was used for these currents to better match the spiking threshold of our current-clamp recordings. These kinds of corrections have been used previously to model spiking of TC neurons (Rhodes and Llinas 2005). Maximum conductances of 1.0 ϫ 10 Ϫ2 and 2.0 ϫ 10 Ϫ3 S/cm 2 were used for I Na and I K , respectively.…”