In mammals including humans, proper development of the cortex is heavily dependent on sensory experience. Neurons in sensory cortex are subject to a “use it or lose it” rule, whereby if they are deprived of sensory input during a critical period of development, they lose the ability to respond altogether. This loss of responsiveness could occur through synaptic changes (synaptic plasticity), or through changes in the intrinsic ability of neurons to fire action potentials (intrinsic plasticity).
Up until now experience-dependent development has largely been ascribed to synaptic plasticity mechanisms. In the cover article in this week’s issue of Neuron, (Nataraj et al., Neuron 68, 750–762, November 18, 2010), Brandeis postdocs Kiran Nataraj, Nicolas Le Roux, Marc Nahmani and Sandrine Lefort from the lab of Professor Gina Turrigiano show that a form of intrinsic plasticity termed “long-term potentiation of intrinsic excitability”, or LTP-IE, plays an important role in experience-dependent refinements of cortical circuits. This study shows that sensory drive normally keeps cortical output neurons active by triggering LTP-IE, and sensory deprivation reduces the ability of these neurons to fire by preventing the activation of this form of plasticity. This suggests that LTP-IE serves a “use it or lose it” function in cortical output neurons, gating cortical output by keeping active neurons responsive, while suppressing the output of inactive neurons.
