hippocampus

• Part of the limbic system called the hippocampal formation

• It is divided into the dentate gyrus (dentate gyrus), hippocampus, subiculum, presubiculum, parasubiculum, and entorhinal cortex.

• Dentate gyrus, hippocampus, and hippocampal branchia have a single cell layer

  • The top and bottom are flanked by a low cell density layer and a cell-free layer.

• Other areas consist of multiple layers.

  • The simple layered structure found in the dentate gyrus and hippocampus has contributed to advances in neuroanatomy and electrophysiology.

• Andersen et al. (1971) argued for the importance of a characteristic circuit that connects each part of the hippocampal body in one direction, which they named the “trisynaptic circuit.

• Because most sensory information flows to the hippocampus through the entorhinal cortex, the entorhinal cortex is often considered the starting point of the trisynaptic circuit.

• The entorhinal cortex is composed of two adjacent cortical areas

  • Perirhinal cortex
  • postrhinal cortex (called parahippocampal cortex in primates)

• The information is received from the

• Much of this input is excitatory (Martina et al., 2001).

• The vastus lateralis cortex (retrosplenial cortex) is also apparently a source of sensory information (van Groen and Wyss, 1992, Wyss and van Groen, 1992).

• EC: entorhinal cortex

• DG: Dentate gyrus

• This figure is 2003,

• In 1911, Spanish neuroanatomist Ramoni Cajal (Nobel Prize in Physiology or Medicine 1906, Figure 1) and others

  • Tri-synaptic memory neural circuits in the hippocampus
  • “Olfactory entorhinal cortex→dentate gyrus (DG)→CA3→CA1.”
  • One of the most famous and important memory neural circuits

• Claims of input from layer 3 of the olfactory entorhinal cortex to CA2 in 2010.

  • In 2013, RIKEN claimed it was wrong http://www.riken.jp/pr/press/2013/20131219_2/.
  • That’s about the time cycle that we’re discussing, so it might not be a good idea to follow it too closely, right?

• Theta rhythm compression

  • [Special issue: Theta rhythm-coordinated neural activity and memory formation in the hippocampus - RIKEN BSI News No. 22 (November 2003) - RIKEN Brain Science Institute (RIKEN BSI) http://www.brain.riken.jp/bsi-news/bsinews 22/no22/special.html]

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