Mechanisms of Firing Patterns in Fast-Spiking Cortical Interneurons

1. PLoS Comput Biol. 2007 Aug;3(8):e156. doi: 10.1371/journal.pcbi.0030156. Epub
2007 Jun 20.

Mechanisms of firing patterns in fast-spiking cortical interneurons.

Golomb D(1), Donner K, Shacham L, Shlosberg D, Amitai Y, Hansel D.

Author information:
(1)Department of Physiology, Ben-Gurion University, Be’er-Sheva, Israel.

Cortical fast-spiking (FS) interneurons display highly variable
electrophysiological properties. Their spike responses to step currents occur
almost immediately following the step onset or after a substantial delay, during
which subthreshold oscillations are frequently observed. Their firing patterns
include high-frequency tonic firing and rhythmic or irregular bursting
(stuttering). What is the origin of this variability? In the present paper, we
hypothesize that it emerges naturally if one assumes a continuous distribution
of properties in a small set of active channels. To test this hypothesis, we
construct a minimal, single-compartment conductance-based model of FS cells that
includes transient Na(+), delayed-rectifier K(+), and slowly inactivating d-type
K(+) conductances. The model is analyzed using nonlinear dynamical system
theory. For small Na(+) window current, the neuron exhibits high-frequency tonic
firing. At current threshold, the spike response is almost instantaneous for
small d-current conductance, gd, and it is delayed for larger gd. As gd further
increases, the neuron stutters. Noise substantially reduces the delay duration
and induces subthreshold oscillations. In contrast, when the Na(+) window
current is large, the neuron always fires tonically. Near threshold, the firing
rates are low, and the delay to firing is only weakly sensitive to noise;
subthreshold oscillations are not observed. We propose that the variability in
the response of cortical FS neurons is a consequence of heterogeneities in their
gd and in the strength of their Na(+) window current. We predict the existence
of two types of firing patterns in FS neurons, differing in the sensitivity of
the delay duration to noise, in the minimal firing rate of the tonic discharge,
and in the existence of subthreshold oscillations. We report experimental
results from intracellular recordings supporting this prediction.

DOI: 10.1371/journal.pcbi.0030156
PMCID: PMC1941757
PMID: 17696606 [Indexed for MEDLINE]

Conflict of interest statement: Competing interests. The authors have declared
that no competing interests exist.

Auteurs Bordeaux Neurocampus