layers of myelinated fibers that appear on transverse sections of the thalamus; the lamina medullaris lateralis [TA] (external medullary lamina [TA]) marks the ventral and lateral borders of the thalamus and delimits it from the subthalamus and the reticular nucleus of thalamus; the lamina medullaris medialis [TA] (internal medullary lamina [TA]) is interposed between the dorsomedial (mediodorsal) and ventral nuclei of the thalamus and encloses the intralaminar nuclei (centromedian, paracentral, and central lateral nuclei). SYN: laminae medullares thalami, medullary layers of thalamus.