Associated with the limbic system is a reverberating circuit. This reverberating circuit
is referred to as Papez circuit. We can consider this a modulator circuit as well.
We see the various components here of the circuit. The first component to begin with
is that of the hippocampus. The hippocampus is connected to hypothalamic structures
referred to as the mammillary bodies. This connection is established through another
structure referred to as the fornix. From the mammillary bodies, these structures are then
connected to the thalamus, the anterior nucleus specifically of the thalamus. The connection
here or tract is going to be the mammillothalamic tract. From the anterior nucleus of the
thalamus, we are then connected to the cingulate gyrus on the medial side of the cerebral
cortex and this connection travels through the internal capsule. From the cingulate gyrus,
we then come back to our starting point, the hippocampus. The connection here is via
the cingulum. This modulator circuit drives various functions or more particularly emotions.
What are those various emotions for you to understand? Well, one is that of fear.
So if there’s an emotion of fear, that will drive our behavior around something that may be
dangerous to us. The modulator circuit can also drive anxiety levels. Are they too high?
Are they too low? Are they just right in that Goldilocks zone of being just right? Another
emotion is that of sadness and then the opposite emotion would be happiness.
Then the last one to ensure survival of the species, we have sexual pleasure as well.