Gain Modulation from Background Synaptic Input

Abstract

Gain modulation is a prominent feature of neuronal activity recorded in behaving animals, but the mechanism by which it occurs is unknown. By introducing a barrage of excitatory and inhibitory synaptic conductances that mimics conditions encountered in vivo into pyramidal neurons in slices of rat somatosensory cortex, we show that the gain of a neuronal response to excitatory drive can be modulated by varying the level of "background" synaptic input. Simultaneously increasing both excitatory and inhibitory background firing rates in a balanced manner results in a divisive gain modulation of the neuronal response without appreciable signal-independent increases in firing rate or spike-train variability. These results suggest that, within active cortical circuits, the overall level of synaptic input to a neuron acts as a gain control signal that modulates responsiveness to excitatory drive.

The Temporal Context Model in Spatial Navigation and Relational Learning: Toward a Common Explanation of Medial Temporal Lobe Function Across Domains.

“…The simulation was populated of integrator cells modeled after those in EC layer V (Egorov et al, 2002) and provided with input from the head direction system (Taube, 1998), which are known to synapse on EC layer V (Haeften et al, 2000). Normalization of the integrator cell population was accomplished by means of a gain modulation where the gain varied inversely with the activity in the network (Chance et al, 2002).…”

Dopaminergic and non-dopaminergic value systems in conditioning and outcome-specific revaluation

“…The bottom-up inputs i D in (4) provide driving on-center excitatory inputs i D (Chance et al, 2002) and driving off-surround inhibitory inputs k i D ≠ . Top-down signals provide modulatory, excitatory on-center inputs i M that multiplicatively control the gain of driving inputs (Gove et al, 1995;Grossberg, 1999Grossberg, , 2003Salinas and Thier, 2000;Chance et al, 2002), and driving inhibitory off-surround inputs k M , k≠i.…”

“…Top-down signals provide modulatory, excitatory on-center inputs i M that multiplicatively control the gain of driving inputs (Gove et al, 1995;Grossberg, 1999Grossberg, , 2003Salinas and Thier, 2000;Chance et al, 2002), and driving inhibitory off-surround inputs k M , k≠i. This type of anatomy has been predicted to embody attentional processes, to realize contrast gain control, and to enable cortical learning to proceed in a stable manner (Carpenter andGrossberg, 1987, 1991;Grossberg, 1980Grossberg, , 1999Grossberg, , 2003.…”

Short-Term Synaptic Plasticity Orchestrates the Response of Pyramidal Cells and Interneurons to Population Bursts

“…A more pertinent effect of conductance, relevant to an extension of this study to include effects of inhibition, is the hidden shunting inhibition. This is not directly visible in the voltage traces, due to the method of injecting hyperpolarising current to bring the average rest voltage to near the inhibitory reversal potential, but has an indirect effect on the excitation through a control of the neuronal gain (Chance et al, 2002;Burkitt et al, 2003;Fellous et al, 2003;Richardson, 2004). Such effects can sculpt the voltage response to excitatory bursts and will further contribute to changes in the peak and median shifts seen experimentally.…”

“…(1) will be assumed to hold for the input across a large population of N f input fibres. This is an approximation because conductance effects will vary the gain of the neuronal response (Chance et al, 2002;Burkitt et al, 2003;Fellous et al, 2003;Richardson, 2004). However, given the spatially extended and compartmentalised nature of neurons, to include conductance would complicate the analysis in a way that could not be constrained experimentally (without any qualitative change in the results).…”