Assignment of model amygdala neurons to the fear memory trace depends on competitive synaptic interactions - PubMed (original) (raw)

Assignment of model amygdala neurons to the fear memory trace depends on competitive synaptic interactions

Dongbeom Kim et al. J Neurosci. 2013.

Abstract

We used biophysical modeling to examine a fundamental, yet unresolved, question regarding how particular lateral amygdala (LA) neurons are assigned to fear memory traces. This revealed that neurons with high intrinsic excitability are more likely to be integrated into the memory trace, but that competitive synaptic interactions also play a critical role. Indeed, when the ratio of intrinsically excitable cells was increased or decreased, the number of plastic cells remained relatively constant. Analysis of the connectivity of plastic and nonplastic cells revealed that subsets of principal LA neurons effectively band together by virtue of their excitatory interconnections to suppress plasticity in other principal cells via the recruitment of inhibitory interneurons.

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Figures

Figure 1.

Figure 1.

Spatial structure, intrinsic connectivity, and fear-conditioning protocol for the LAd network model. A, The model consists of 800 principal cells and 200 interneurons populated randomly in the horn-shaped LAd. B, Fear-conditioning protocol. C, Average tone responses of plastic LAd cells during the different phases of the behavioral protocol. D, Example of tone responses generated by a plastic cell during habituation (top) and recall test (bottom). E, Repetitive firing dynamics of three types of model projection cells. F, Proportion of plastic cells among the three types of projection cells. G, Expected (white) and observed (black) numbers of model plastic cells for the control, CREB+, and CREB− cases. Competition biases the observed numbers toward the control value.

Figure 2.

Figure 2.

Differential intrinsic connectivity supports competition. A–F, Monosynaptic excitatory (A, C, E) and disynaptic inhibitory (B, D, F) connections among as well as between plastic and nonplastic cells (_x_-axis) in the control case. C–F, Connections of type B or C winner and loser cells in the CREB+ (C, D) and CREB− (E, F) simulations. A and B consider connections between all plastic and nonplastic principal cells. In contrast, C–F consider connections between the subsets of plastic or nonplastic cells only, and so the numbers are smaller. Data are averages ± SEM.

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