Molecular/cellular mechanisms for cross-modal plasticity following sensory loss.

<p>(A) Loss of body touch in <i>C</i>. <i>elegans</i> results in reduced neuropeptide secretion from the TRNs, leading to the release from suppression, i.e., strengthening, of the inhibitory glutamatergic synaptic connection between AWC chemosensory neurons and AIY interneurons and thus enhancing the output of the olfactory circuit. Optogenetic activation of the TRNs (red lightning bolt) or insertion of an engineered electrical synapse between AWC and AIY (red dashed line) can counteract these effects. (B) Visual deprivation in rats results in increased serotonin signaling, possibly from the raphe nucleus, increasing extracellular serotonin abundance in layer 2/3 of the barrel cortex, which in turn strengthens the excitatory glutamatergic synaptic connections between the sensory input layer 4 and the cortical output layer 2/3, thus enhancing somatosensory output [<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002348#pbio.1002348.ref011" target="_blank">11</a>]. (C) Visual or whisker deprivation in mice results in reduced oxytocin secretion from the hypothalamus, which leads to reduced synaptic transmission to somatosensory or visual cortical output layer 2/3, reducing the output [<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1002348#pbio.1002348.ref013" target="_blank">13</a>]. Rectangles represent sensory or sensory input neurons and ovals represent downstream output neurons.