Postnatal changes of conduction velocity of the fibers in and out of the mouse barrel cortex

There are some conflicts about constancy of conduction velocity [CV] in a given tract of nervous system. By recording excitatory postsynaptic currents [EPSC] in layer IV of the somatosensory cortex we tried to clear changes in CV of thalamocortical tract of mice aged 3 to 50 days old. Field potentials and EPSC were recorded in the layer IV by stimulation of ventrobasal nucleus of thalamus [VB] and white matter [WM]. Our results indicate that in mice aged 3 through 17 days old, CV of EPSC evoked by WM and VB stimulation increased up to 2 and 15 times, respectively. Also, the data from field potentials match those from EPSC. CV enhancement of the fibers out of cortex may contribute to myelination as well as increased diameter of neurites. However, it is not the case for WM matter stimulation-evoked responses