Pathway-specific maturation of presynaptic functions of the somatosensory thalamus

Neural circuits are the bases of brain function, and signal transmission between neurons is mediated by synapses. However, neural circuits and synapses are not fully functional at the time of birth. In the nervous system of newborn animals, neurons form an extensive number of redundant synapses that are targeted to construct neural circuits, of which 40-50% are subsequently eliminated during adolescence before circuit maturation. It is widely understood that the maturation of synaptic function differs between surviving and eliminated synapses before their eventual selection; however, direct evidence is currently lacking because of technical limitations. We recently acquired direct electrical recordings from single synapses destined for survival and elimination in the rodent somatosensory thalamus. Results demonstrated detailed presynaptic functional development both in surviving and eliminated pathways. Our work not only revealed the functional properties of surviving and eliminated synapses but also provided a new model system to elucidate the mechanisms that underlie mature neural circuit formation.