Fig. 7.1.38.  Complex convolution derived from endoplasmic reticulum. Non-membranous bridges between tubules and cisterns and finely granulofilamentous dense material between rows of cisterns are specific ultrastructural participants of this organelle. Transitions between the lamellar body, multitubular body and complex convolution are frequent. Function is  not known.  Similarity with the spine apparatus suggests that they may participate in protein synthesis and modification.  These are located in the perikarya and proximal dendrites of thalamocortical projection neurons.  This artistic rendition (not 3D reconstruction) resulted from analyzing many tens of individual sections. (Rat, lateral geniculate and ventrobasal nuclei.) Download the high resolution image.