The formation of the neural tube from an epithelial cell sheet (the neuroepithelium or neural plate). In primary neurulation, the cells surrounding the neural plate direct the neural plate cells to proliferate, invaginate, and pinch off from the surface to form a hollow epithelial tube. Primary neurulation is the typical mechanism of formation of the anterior neural tube. [ http://www.ncbi.nlm.nih.gov/pubmed/15327780 GOC:ef http://openisbn.com/search.php?q=0878932585&isbn=1/ ]