Tucked under the inner wall of the temporal lobe of the neocortex, the hippocampus is one of the oldest cortical structures. Its main function is thought to be the consolidation of declarative memory--memories that are fundamentally relational and multidimensional, as opposed to procedural memory, whose repetitive movements, "dedicated and inflexible...cannot be manipulated or used in novel circumstances,"(1) It is believed that the hippocampus "could trigger your cortex to run through some of its recent routines and thereby solidify them" unconsciously. Perhaps they could even appear "as a nighttime dream."(2)
Hippocampus derives from Greek for seahorse, or monster, as its structure resembles this strange creature While some older anatomists associated the hippocampus with the Egyptain god Ammon, or Amun. Thus, cornu ammonis, Ammon's Horn.
The hippocampus also seems to be involved in orienting the organism in its environment by creating spatial clues, or "place fields," even while internally it displays an itinerant nature.
Sacred to Ammon is a fat-tailed species of ram--ovis platyura aegyptiaca, whose horns are large, curved and downturned-- that is found only in the area of the Sceptre Nome, Egypt.
though it's been long thought that adult brain cells cannot be replaced,
using a diagnostic method developed for cancer research that labels dividing cells, nascent hippocampi neurons have been discovered in adult human brains.(3)
Ammon was never portrayed in the form of a ram, or as a man with a ram's head, he always appeared inhuman shape, wearing a cap with two tall plumes and a sun's disk. The Egyptian hieroglyph for ram, ur-am, means 'solar heat'. In Indian schema, the Manipura chakra lies in the area of the solar plexus, known of the "second mind." Its center contains the ram, the symbol of Agni, god of fire.
There is speculation that this organ conducts our strange capacity for synesthesia.
The horn's iconology traces mythological figures, both virtuous and notorious, from the Horned Moses (4) to Aphrodite Epitragia and Europa; from Hermes, the boundary keeper, to Satan, the seducer.
The hippocampus is vunerable to post-traumantic stress, such as caused by physical and/or emotional abuse, along with ironically integrating "individual stimuli into a context that no longer contains the individual elements...but relations between stimuli." (5) Finally, hippocampal consolidation opens memories to the organism as a whole.
(1) H. Eichenbaum and T. Otto,
"The Hippocampus-What Does It Do?" Behavioral and Neural Biology 57
(2) W.H. Calvin and G.A. Ojemann, Conversations with Neil's Brain. Reading, MA., 1994. p.134.
(3) G. Kempermann and F.H. Gage, "New Nerve Cells for the Adult Brain." Scientific American. May 1999. pp.48-53.
(4) R. Mellinkoff, The Horned Moses in Medieval Art and Thought. Berkeley, CA., 1970. p.122.
(5) J. LeDoux, The Emotional Brain. New York, 1996. p.168.