The hippocampal formation

Reading instructions
To get the most out of this learning tool, please read:
Bear, Mark F, Connors, Barry W., Paradiso, Michael A. Neuroscience : exploring the brain. - 2 ed.
Chapter 7 page 163-252

Illustrations and anmimation

Limbic system

The limbic system is a complex set of structures that includes the orbital and medial prefrontal cortex, the amygdala, and related structures in the thalamus, hypothalamus and ventral striatum. Th cingulate cortex and the parahippocampal gyrus together with hippocampus is also regarded as parts of the limbic system. It appears to contribute to the characteristics of the individual and the continuation of human life. The limbic system is responsible for feeding behaviour, “fight and flight reactions”, aggression, the formation of memories and the emotional life. The limbic system receives input from many parts of the cerebral cortex and contains association areas where various aspects of sensory experience come together to form a single experience.

The hippocampal formation/hippocampus
The hippocampal formation, also called Ammons horn, is located in the medial temporal lobe and extends the length of the floor of the inferior horn of the lateral ventricle and becomes continuous with the fornix below the splenium of the corpus callosum.

On the basis of fiber connections the hippocampal formation has been divided into different sectors.

The dentate gyrus/gyrus dentatus is a thin band of cortex that lies on the upper surface of the parahippocampal gyrus. The dentate gyrus serves as an input centre and receives signals that are relayed to it via the enthorhinal cortex and its cells project to cells in the hippocampal formation.

The hippocampus seems to be involved in learning and memory.

It is engaged in recollection of facts and in forming spatial memories.

Fornix/fornix is an arched white fiber tract extending from the hippocampal formation and serve as a major output tract from the hippocampal formation to other limbic structures.

The posterior cerebral artery/ ateria cerebri posterior provides blood supply of the hippocampal formation.

The amygdala/amygdala
The amygdala is a gray matter gathering located in the medial temporal lobe between the uncus and the parahippocampal gyrus. It lies just anterior to the tip of the anterior horn of the lateral ventricle. The amygdala is involved in emotion and in establishing associations between sensory inputs and various states of affection. It is also involved in regulating endocrine activity, sexual behavior and food and water intake possibly by regulating hypothalamic activity.

The anterior choroidal artery/arteria choroidea anterior derived from the anterior cerebral artery/ arteria cerebri anterior provides blood supply of the amygdala.