In 1999, Aggleton and Brown proposed a neurological system for episodic memory that had been based upon about three decades of research. One of the intriguing features of this circuit is that it involves three different regions of the telencephalon (the frontal lobe, the temporal lobe, and parts of the limbic system), but it also includes the diencephalon (thalamus). In the late 1960s it had been known for some time that the diencephalon and the temporal lobe were involved in episodic memory (Delay & Brion, 1969). Part of the mystery, however, was that these two brain regions develop from different secondary vesicles, yet damage to one or the other of these regions results in similar forms of amnesia. This led Delay and Brion to hypothesize that the diencephalon and the temporal lobe must be a part of the same neural circuit, whereby damage to any part of it would result in a similar memory deficit.