Differential effects of excitatory and inhibitory plasticity on synaptically driven neuronal input-output functions
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1
University of California, Buonomano Lab, United States
Synaptic plasticity is commonly referred to as the physiological correlate of learning and memory, and a large number of studies have characterized its mechanisms and learning rules. However, since alterations in behavior must ultimately be caused by changes in neuronal firing, it must not be synaptic plasticity per se that underlies learning. Rather, alterations in behavior should be due to changes in the neuronal output. Thus, to understand the relationship between synaptic plasticity and learning, it is important to elucidate how synaptic plasticity alters the input-output characteristics of neurons.A neuron’s input-output function describes the probability it will fire an action potential in response to brief stimuli of increasing intensities, and depends on the net balance and timing of excitatory and inhibitory currents. While excitatory and inhibitory synapses are known to be plastic, most studies have examined plasticity of subthreshold events, such as changes in EPSPs or IPSPs. Thus, the effects of the concerted regulation of excitatory and inhibitory synaptic strength on neuronal input-output functions are not well understood. For example, from a computational perspective, what is the functional difference between potentiating excitatory inputs and depressing inhibitory ones? What is the computational benefit of potentiating both EPSPs and IPSPs onto the same postsynaptic neuron, which superficially seems self-defeating?
Here, theoretical analyses reveal that excitatory synaptic strength controls the threshold of the neuronal input-output function, while inhibitory plasticity alters the threshold and gain. Experimentally, changes in the balance of excitation and inhibition in CA1 pyramidal neurons also altered their input-output function as predicted by the model.
These results provide a framework for understanding the potential function and tradeoff between invoking excitatory and inhibitory plasticity in isolation or in parallel, and suggest that I/O function plasticity could be used to optimize the encoding of information.
Conference:
11th Meeting of the Portuguese Society for Neuroscience, Braga, Portugal, 4 Jun - 6 Jun, 2009.
Presentation Type:
Oral Presentation
Topic:
Symposium 1– Neuronal Communication
Citation:
Carvalho
TP and
Buonomano
DV
(2009). Differential effects of excitatory and inhibitory plasticity on synaptically driven neuronal input-output functions.
Front. Neurosci.
Conference Abstract:
11th Meeting of the Portuguese Society for Neuroscience.
doi: 10.3389/conf.neuro.01.2009.11.006
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Received:
05 Aug 2009;
Published Online:
05 Aug 2009.
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Correspondence:
Tiago P Carvalho, University of California, Buonomano Lab, Los Angeles, United States, tiago@ucla.edu