Limbic connections of the hypothalamus

The hypothalamus is associated with limbic structures anxious with emotion and its expression as shown in figure below. It acquires input from the hippocampus:

- By way of the subiculum, portion of the hippocampal formation, that plans through the fornix to the mammillary bodies

- By way of the septum, also through the fornix, to connect with all three zones of the hypothalamus

Input from the amygdala appears at the hypothalamus through the stria terminalis, a loop which follows a similar course to the fornix, and the amygdalofugal pathway.

                                      Figure: Main connections of the human hypothalamus.


Hypothalamic outcome from mammillary bodies (MB) through the mammillothalamic tract goes to the anterior thalamic nuclei (ATN) which are connected to the cingulate cortex (CC). The cingulate cortex plans back to the hippocampal formation, therefore closing a loop (i.e., hypothalamus–ATN–CC–hippocampus–hypothalamus) known as the Papez circuit. This is the portion of a larger network which includes the amygdala, septum, and prefrontal cortex that is concerned with memory and emotion. The mammillary bodies make reciprocal connections through the mammillotegmental tract with the ventral tegmental nuclei in the midbrain; these have been concerned in memory.

The medial forebrain bundle passes via the lateral hypothalamic zone. It consists of monoaminergic axons rising from brainstem nuclei. Most noradrenergic and serotonergic, though not dopaminergic, axons synapse with hypothalamic neurons. The paraventricular hypothalamus and the lateral hypothalamic region obtain visceral sensory input from the nucleus of the solitary tract (NST) that is significant for hypothalamic control of the ANS.