Know the third ventricle
http://www.google.com/imgres?hl=en&biw=1024&bih=724&tbm=isch&tbnid=SxGkbt6-CSI54M:&imgrefurl=http://www.sciencedirect.com/science/article/pii/S1092440X0300046X&docid=alKNrc2RshSZeM&imgurl=http://ars.els-cdn.com/content/image/1-s2.0-S1092440X0300046X-gr1.jpg&w=678&h=549&ei=DdVlUKe0JrDJ0AHb6IDgAg&zoom=1&iact=hc&vpx=575&vpy=392&dur=13858&hovh=203&hovw=251&tx=145&ty=104&sig=112249006170063351164&page=2&tbnh=157&tbnw=195&start=12&ndsp=18&ved=1t:429,r:16,s:12,i:167
