Primary cilia, once considered vestigial organelles are now revealing themselves as crucial cellular components for cellular signalling and are capable of sensing their enivronment. A number of developmental pathways including Hedgehog and Wnt signalling require an intact cilium. Dysfunction of this signalling process can result in diseases of the retina, kidney, endocrine system, skeleton and nervous system. Many long described syndromes are now being ascribed to cilia pathogenetic lesions are are grouped as the ciliopathies. Many of these syndromes manifest cognitive impairment as well as disordered peripheral nervous system and sensory reception. We have been focussing on several of these diseaes and one in particular, Bardet-Biedl syndrome has been informing us of novel roles for the primary cilium. For example by generating animal models we have determined there are defects in olfactory responses, nociception, satiety (leading to gross obesity) and mental retardation. One of our key goals is to understand the role of primary cilia present on all neurones in learning disability and and cell-cell signalling.