1) Feedback connections (CA1-CA3, CA3-DG, DG-EC, EC-CA1),
2) The subicular pathway,
3) Non-local interneurons (i.e. intra-fields, DG-CA3, CA3-CA1 gabaergic
fibers),
4) Peptidergic modulation (and all neurotransmitters other than glutamate,
GABA and AcCh).
Below is a view of the human hippocampal formation (asterisks).