Characterization of Reliability of Spike Timing in Spinal Interneurons During Oscillating Inputs

• DOI: 10.1152/jn.2001.86.4.1858
• Publication Date: 2017-12-21T11:50:23Z
• Authors: Ulrik Beierholm; Carsten D. Nielsen; Jesper Ryge; Preben Alstrøm; Ole Kiehn
• Keywords: Motor Neurons; Periodicity; 03 medical and health sciences; 0302 clinical medicine; Spinal Cord; Interneurons; Models, Neurological; Action Potentials; Animals; Reproducibility of Results; Rats, Wistar; Locomotion; Rats

The spike timing in rhythmically active interneurons the mammalian spinal locomotor network varies from cycle to cycle. We tested contribution passive membrane properties this variable firing pattern, by measuring reliability of timing, P, isolated neonatal rat cord, using intracellular injection sinusoidal command currents different frequencies (0.325-31.25 Hz). P is a measure precision timing. In general, was low at and amplitudes (P = 0-0.6; 0-1.875 Hz; 0-30 pA), high 0.8-1; 3.125-31.25 30-200 pA). exact relationship between amplitude difficult describe because well-known low-pass membrane, which resulted attenuation high-frequency compared with low-frequency currents. To formalize analysis we used leaky integrate fire (LIF) model noise term added. LIF able reproduce experimentally observed as well membrane. enabled us use mathematical theory nonlinear oscillators analyze amplitude, frequency, P. This done systematically calculating rotational number, N, defined number spikes divided periods current, for large amplitudes. These calculations led phase portrait based on current versus frequency-containing areas [Arnold tongues (ATs)] same number. largest ATs were those where N whole integer, seen middle (>3 Hz) (50-120 corresponded amplitude- frequency-evoked increase predicted that would be when cell responded an integer constant N. prediction confirmed comparing real experiments. Fitting result experimental data estimate standard deviation internal neuronal these simulate model. simulation demonstrated good correspondence theoretical values. Our demonstrate can respond but only combining fast slow oscillations it possible obtain during rhythmic movements. Theoretical rotation provided new insights into mechanism obtaining reliable