The limbic system is a group of interconnected brain areas that are related to memory and experiencing emotions and deploying the right emotion in the right way at the right time. The name “limbic” refers to the inner rim of each side of the brain. A core area of each limbic system is the medial temporal lobe region. The medial temporal regions are home to two central poles of the limbic system – the hippocampus and in front of it the amygdala. The hippocampus is our “organ of short term memory” and the amygdala is an almond-shaped grey matter structure where emotional relevance is mapped onto our memories. If we receive a painful bite by a snake, the fear memory that will arise the next time we see the snake is a product of the amygdala’s projection into the hippocampus.
Importantly, the limbic system is also the region of our brain most packed with estrogen and progesterone binding sites or receptors. These receptors are like tiny locks on the surface of our brain cells and the hormones serve as the key that fits in the lock and causes the cell to do something. An example of how this hormone/limbic system connection works is shown when a woman who is under great emotional and physical stress loses her menstrual periods and ovulation and becomes temporarily infertile. Her brain decides it is a poor time to support a pregnancy when so much of the woman’s resources must be used for her own survival. The medial temporal lobes can shut down the woman’s ovaries and menstrual cycle in a “top-down” manner, by inhibitory connections that suppress the hypothalamus, which suppresses the pituitary gland, which is temporarily stopped from making LH and FSH, which blocks ovulation. When the emotional and physical stress is gone, the woman’s LH and FSH will come back, and her periods and her fertility will return.
The medial temporal lobes, especially the hippocampal regions, are also very prone to epileptic seizures. One reason is their position right behind the “windshield” or front inner part of the skull, behind the face. When our moving heads hit a stationary object in traumatic brain injury, the temporal lobes crash into this “windshield” and get bruised and scarred in these limbic regions. This is one reason why temporal lobe epilepsy is so prevalent. There are also reasons specific to the circuitry of the hippocampus that render it prone to seizures.
Therefore, because of its affiliations with our emotions and our memories, and with our hormones and the lower brain centers that control their secretion, the medial temporal lobe and its limbic system is in a perfect position to link our emotions and behavior with our hormones, and our hormones with seizures (when present). This is the basis of PMS, catamenial epilepsy and stress-related menstrual disorders.