TY - JOUR
T1 - Well-timed, brief inhibition can promote spiking
T2 - Postinhibitory facilitation
AU - Dodla, Ramana
AU - Svirskis, Gytis
AU - Rinzel, John
PY - 2006/4
Y1 - 2006/4
N2 - Brief synaptic inhibition can overwhelm a nearly coincident suprathreshold excitatory input to preclude spike generation. Surprisingly, a brief inhibitory event that occurs in a favorable time window preceding an otherwise subthreshold excitation can facilitate spiking. Such postin-hibitory facilitation (PIF) requires that the inhibition has a short (decay) time constant τinh. The timescale ranges of τinh and of the window (width and timing) for PIF depend on the rates of neuronal subthreshold dynamics. The mechanism for PIF is general, involving reduction by hyperpolarization of some excitability-suppressing factor that is partially recruited at rest. Here we illustrate and analyze PIF, experimentally and theoretically, using brain stem auditory neurons and a conductance-based five-variable model. In this auditory case, PIF timescales are in the sub- to few millisecond range and the primary mechanistic factor is a low-threshold potassium conductance gKLT. Competing dynamic influences create the favorable time window: hyperpolarization that moves V away from threshold and hyperexcitability resulting from reduced gKLT. A two-variable reduced model that retains the dynamics only of V and gKLT displays a similar time window. We analyze this model in the phase plane; its geometry has generic features. Further generalizing, we show that PIF behavior may occur even in a very reduced model with linear subthreshold dynamics, by using an integrate-and-fire model with an accommodating voltage-dependent threshold. Our analyses of PIF provide insights for fast inhibition's facilitatory effects in longer trains. Periodic subthreshold excitatory inputs can lead to firing, even one for one, if brief inhibitory inputs are interleaved within a range of favorable phase lags. The temporal specificity of inhibition's facilitating effect could play a role in temporal processing, in sensitivity to inhibitory and excitatory temporal patterning, in the auditory and other neural systems.
AB - Brief synaptic inhibition can overwhelm a nearly coincident suprathreshold excitatory input to preclude spike generation. Surprisingly, a brief inhibitory event that occurs in a favorable time window preceding an otherwise subthreshold excitation can facilitate spiking. Such postin-hibitory facilitation (PIF) requires that the inhibition has a short (decay) time constant τinh. The timescale ranges of τinh and of the window (width and timing) for PIF depend on the rates of neuronal subthreshold dynamics. The mechanism for PIF is general, involving reduction by hyperpolarization of some excitability-suppressing factor that is partially recruited at rest. Here we illustrate and analyze PIF, experimentally and theoretically, using brain stem auditory neurons and a conductance-based five-variable model. In this auditory case, PIF timescales are in the sub- to few millisecond range and the primary mechanistic factor is a low-threshold potassium conductance gKLT. Competing dynamic influences create the favorable time window: hyperpolarization that moves V away from threshold and hyperexcitability resulting from reduced gKLT. A two-variable reduced model that retains the dynamics only of V and gKLT displays a similar time window. We analyze this model in the phase plane; its geometry has generic features. Further generalizing, we show that PIF behavior may occur even in a very reduced model with linear subthreshold dynamics, by using an integrate-and-fire model with an accommodating voltage-dependent threshold. Our analyses of PIF provide insights for fast inhibition's facilitatory effects in longer trains. Periodic subthreshold excitatory inputs can lead to firing, even one for one, if brief inhibitory inputs are interleaved within a range of favorable phase lags. The temporal specificity of inhibition's facilitating effect could play a role in temporal processing, in sensitivity to inhibitory and excitatory temporal patterning, in the auditory and other neural systems.
UR - http://www.scopus.com/inward/record.url?scp=33646254126&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=33646254126&partnerID=8YFLogxK
U2 - 10.1152/jn.00752.2005
DO - 10.1152/jn.00752.2005
M3 - Article
C2 - 16551843
AN - SCOPUS:33646254126
SN - 0022-3077
VL - 95
SP - 2664
EP - 2677
JO - Journal of neurophysiology
JF - Journal of neurophysiology
IS - 4
ER -