Here we use in Vitro current injection in layer 2/3 pyramidal neurons to validate methods for inferring functional connectivity in a setting where input to the neuron is controlled.

Here we use in vitro current injection experiments to assess how well functional connectivity inferred from spikes corresponds to underlying synaptic inputs and to examine the limits of postsynaptic spike prediction from presynaptic spike times.

I n vitro current injection has been used to study temporal integration of presynaptic spikes [3,37], the effects of input synchrony on spiking [75], and signal propagation through networks [76].

Electrophysiology and current injection

Here we provide empirical tests of statistical tools for such analysis using in vitro current injection where the true synaptic input is known.

Although the model used here does not explicitly describe the underlying fluctuations in membrane potential that result from the current injection , the contribution of the cumulative coupling terms of all inputs (N = 1024, red trace in Fig.

Here we examine the relationship between simulated synaptic input and functional connections estimated from spikes using in vitro current injection experiments.

To estimate the width of dendritic plateau potentials in the apical dendrite with long dendritic current injection, we determine the longest depolarization sustained at 20% or more above the baseline level (defined as the most hyperpolarized membrane potential during the dendritic current injection ).

Importantly, dendritic current injections farther than 250 pm from the soma are associated with long dendritic depolarizing events which precede burst firing of APs at the soma, while current injections at the soma and into the dendrite less than 250 pm from the soma are instead associated with regular trains of single APs propagating as bAPs into the dendrites (Fig.

1 s long dendritic current injections (n = 13) elicit trains of 18.38 +/-8.52 spikes at the soma.

1E bottom left, slope = 0.0015 um'l, p = 0.02), and the ratio of voltage threshold for triggering somatic action potentials between dendritic and somatic step current injection (slope = 0.0040 um'l, p = 3.8e-4).

Our final model and parameter set captures the membrane response to suprathreshold somatic and dendritic current injections (Fig.

In addition, cortical neurons fire APs only upon external holding current injection .

Nonetheless, biophysically accurate (i.e., voltage-dependent) channel flickering had a similar effect on the PRC as what was obtained by additive Gaussian noise current injection , in [14] and our simulations.

We note that, in response to external current injection , the Khaliq-Raman model fires at arbitrarily low firing rates, implying a type I excitability.