Located in the center of both hemispheres of the brain just under the cerebrum, the limbic system includes the amygdala, hippocampus, hypothalamus, olfactory cortex, and thalamus. The limbic system is a busy part of the brain, responsible for regulating both our emotional lives and higher mental functions such as learning, motivation, formulating and storing memories, controlling adrenaline and autonomic response, and regulating hormones and sexual response, sensory perception (optical and olfactory), and motor function.
Since the limbic system is involved in so many of the body’s activities, and because it works so closely with several other systems, the actual anatomical parts of the limbic system are somewhat controversial. It is the reason there is pleasure in activities such as eating and sexual intimacy, and why stress manifests in the physical body and directly impacts health.
The limbic system is directly responsible for the processes of intercellular communication that affect how an individual responds to situations and all sensory stimuli and forms and stores memories about those situations and the resulting emotions. The limbic system works closely with the endocrine system to help with hormone regulation. It partners with the autonomic nervous system the part of the body responsible for the “fight-or-flight” response, that helps the body recuperate during periods of rest, that regulates heart rate and body temperature, and that controls gastrointestinal functions. It also works with the nucleus accumbens, the pleasure center of the brain which is involved with sexual arousal and euphoric response to recreational drugs.
Deep in the core of the limbic system lies the amygdala, which is involved in many of the limbic activities listed above. it serves a the “watchtower,” evaluating situations to help the brain recognize potential threats and prepare for fight-or-flight reactions. One of the ways it performs its duties is through the sense of smell. Aromas, via the olfactory system, have a quick, unfiltered route to the amygdala where emotions and memories are stored. Why? Because the sense of smell is necessary for survival.
The sense of smell is one of the more complex and discerning senses and is ten thousand times more powerful than our sense of taste. It was not until the early 1990s that biologists first described the inner workings of olfactory receptors — the chemical sensors in our noses — in a discovery that won a Nobel Prize. Since then, the plot has thickened. Over the last decade or so, scientists have discovered that odor receptors are not solely confined to the nose, but found throughout body — in the liver, the heart, the kidneys, skin and even sperm — where they play a pivotal role in a host of physiological functions.
Aromas have a direct and profound effect on the deepest levels of the body systems, emotions, and psyche. Interestingly, we have only three types of receptors for sight but an amazing one hundred distinct classes of smell receptors. We can distinguish an infinite number of smells even at very low concentrations. It is the ONLY sense linked directly to the limbic brain. The response is instant and so are the effects on the brain’s mental and emotional responses and our body chemistry.
Intriguing new research has also helped us recognize that the benefits of aroma extend far beyond just emotional regulation. In addition to influencing the limbic region of the brain, olfactory centers are also intricately linked with the hypothalamus, an area of the brain more familiarly nicknamed the “visceral control center” because it controls physiologic functions throughout the body. The hypothalamus exerts its powerful influence by interacting directly with the pituitary gland, or “master gland,” a small gland located in the brain. The pituitary gland secretes hormones involved in the regulation of blood pressure, hunger and thirst signals, thyroid function, sleep cycles, production of sexual hormones, and memory, among other things. Because of the direct link of the olfactory system to this area of the brain, aroma is capable of interacting directly with the hypothalamus, influencing neurochemistry throughout the body, and, in turn, potentiating powerful health outcomes.