A model of spindle rhythmicity in the isolated thalamic reticular nucleus

Alain Destexhe, Diego Contreras, Terrence J. Sejnowski and Mircea Steriade

Journal of Neurophysiology 72: 803-818, 1994

Copy of the full paper (PDF)

Summary and Conclusions:

1. The oscillatory properties of the isolated reticular (RE) thalamus were modeled with the use of compartmental models of RE cells. Hodgkin-Huxley type kinetic models of ionic channels were derived from voltage- and current-clamp data from RE cells. Interactions between interconnected RE cells were simulated with the use of a kinetic model of gamma-aminobutyric acid (GABA) inhibitory synapses.

2. The intrinsic bursting properties of RE cells in the model were due to the presence of a low-threshold Ca2+ current and two Ca(2+)-activated currents. The properties of these model RE cells were compared with RE neurons recorded intracellularly in vivo in cats.

3. Model RE cells densely interconnected with GABAA synapses produced synchronous oscillations at a frequency close to that of spindles (7-14 Hz). Networks of RE neurons organized in a two-dimensional array with only proximal connectivity also exhibited synchronized oscillations in the spindle range. In addition, the proximally connected network showed periods of high and low synchronicity, giving rise to waxing and waning oscillations in the population of RE cells.

4. The spatiotemporal behavior of the network was investigated during waxing and waning oscillations. The waxing and waning emerged as an alternation between periods of desynchronized and synchronized activity, corresponding to periods of irregular and coherent spatial activity. During synchronized periods, the network displayed propagating coherent waves of synchronous activity that had a tendency to form spirals.

5. Networks of model RE neurons fully connected through GABAB synapses exhibited perfectly synchronous oscillations at lower frequencies (0.5-1 Hz), but two-dimensional networks with proximal GABAB connectivity failed to synchronize.

6. These simulations demonstrate that networks of model neurons that include the main intrinsic currents found in RE cells can generate waxing and waning oscillatory activity similar to the spindle rhythmicity observed in the isolated RE nucleus in vivo . The model reveals the interplay between the intrinsic rhythmic properties of RE cells and the fast synaptic interactions in organizing synchronized rhythmicity.


Movies:

Several movie files illustrate the oscillatory dynamics of the network of thalamic reticular neurons. They are an excellent complement to the figures of the paper. The spatiotemporal distribution of activity in the network during oscillations is shown by gray levels.

re100.mpg

re400.mpg

re400_spiral.mpg

re1600.mpg


Programs:

The original NEURON programs that served to simulate this model are also available. They provide a useful way to learn how to design network models using NEURON.

NEURON demo:

This package creates a directory containing a demo for running the network of reticular thalamic neurons using the object-oriented facilities of NEURON. The simulations reproduce some of the figures of the paper, in which all the details are given. There are also instructions in the README file.
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