Reliability of spike and burst firing in thalamocortical relay cells

Abstract

The reliability and precision of the timing of spikes in a spike train is an important aspect of neuronal coding. We investigated reliability in thalamocortical relay (TCR) cells in the acute slice and also in a Morris-Lecar model with several extensions. A frozen Gaussian noise current, superimposed on a DC current, was injected into the TCR cell soma. The neuron responded with spike trains that showed trial-to-trial variability, due to amongst others slow changes in its internal state and the experimental setup. The DC current allowed to bring the neuron in different states, characterized by a well defined membrane voltage (between -80 and -50 mV) and by a specific firing regime that on depolarization gradually shifted from a predominantly bursting regime to a tonic spiking regime. The filtered frozen white noise generated a spike pattern output with a broad spike interval distribution. The coincidence factor and the Hunter and Milton measure were used as reliability measures of the output spike train. In the experimental TCR cell as well as the Morris-Lecar model cell the reliability depends on the shape (steepness) of the current input versus spike frequency output curve. The model also allowed to study the contribution of three relevant ionic membrane currents to reliability: a T-type calcium current, a cation selective h-current and a calcium dependent potassium current in order to allow bursting, investigate the consequences of a more complex current-frequency relation and produce realistic firing rates. The reliability of the output of the TCR cell increases with depolarization. In hyperpolarized states bursts are more reliable than single spikes. The analytically derived relations were capable to predict several of the experimentally recorded spike features.

Multiplexed Spike Coding and Adaptation in the Thalamus

“…Burst events were typically at least 2 bits more informative about the stimulus than were tonic events (Fig. S2A,B), in agreement with (Reinagel et al, 1999) and previous reports that burst events are more precise than tonic spikes (Zeldenrust et al, 2013, Whitmire et al, 2016, Kepecs and Lisman, 2003). We next calculated I fract , the fraction of information captured by the ETA (Fairhall et al, 2006).…”

Parvalbumin interneuron mediated feedforward inhibition controls signal output in the deep layers of the perirhinal‐entorhinal cortex

“…The firing properties of the cells were recorded by injecting a membrane current that set the membrane voltage from −100 to −30 mV in steps of 5–10 mV. Connectivity between the principal neuron and PV interneuron was tested by evoking action potentials in the principal neuron at reproducible random moments using a frozen noise current injection (Zeldenrust, Chameau, & Wadman, ) and recording unitary excitatory postsynaptic currents (uEPSCs) in the PV interneurons clamped at −70 mV (Figure a). We strived to induce a firing rate of 1–2 Hz in the principal neuron.…”

Measures of spike train synchrony for data with multiple time scales

“…When in the original study frozen noise was injected into thalamocortical relay cells of rats, it was found that the reliability of the cell response increases with depolarization (Zeldenrust et al, 2013). …”