Over yet another dinner of cheap Thai food with a friend of mine after class, my friend remarked that she was surprised at the things that spark emotional responses within me. Specifically, she recalls me telling her about the bad things that have occurred in my life in a relatively offhand fashion and not showing any particular emotion when relaying the story. She also remarked that when we watch movies together, that I get overly emotional. The last example she raised was the classic 80′s karate movie Best of the Best, during which I apparently started experiencing a ‘manly misting’ from my eyes during the last fight scene while we were watching it together a few weeks ago.
So, I became a little curious and pondered the question of ‘what controls emotions in humans?’. Some quick Wikipedia research pointed me to some helpful links (I almost never trust the actual content from a Wikipedia article, but the links at the bottom that are listed as sources are usually pretty good) that described how the brain controls emotions. This article in particular was particularly helpful, and is the sole source I’m using as a reference for the rest of this post.
Emotions are thought to be controlled by a brain structure known as the amygdala. The amygdala is a small, almond shaped structure located in the bottom half of the brain, not too far from the cerebrum. The amygdala is connected to many other parts of the brain by bunches of fibers that are used to relay information to and from the amygdala. For example, there is a bundle called the stria terminalus which connects a part of the amygdala to the brain stem where it can influence hormonal states such as sex drive etc.
Furthermore, there are parts of the amygdala that are shown to be more responsive and controlling of external environment (responding to sensory data such as visual information) and parts that are responsive to the internal environment, which if I’m interpreting the source correctly means that it responds to information we already have and conclusions we are reaching using internal information.
Unfortunately, the exact functions of the amygdala and mapping of it’s regions to exact emotional states is not possible due to the fragmented bits of information that scientists have gathered from experiments (usually those which basically involve cutting out portions of the amygdala from monkeys and the like and watching how they change their responses to their environment). Some interesting interpretations have been made, however based on these experiments. Specifically, the amygdala appears to be closely related to feelings of fear, in that it’s removal seems to remove healthy inhibitions to unbridled lust and curiosity. These experiements have also seemed to indicate that other emotions such as joy, pleasure, guilt, anxiety and paranoia are centered in other brain structures. More complex emotions such as sense of self and feelings are thought to be too complex to be centered in a single brain structure, but rather involve multiple other structures in the brain.
So, what can be concluded from this research? Well, sadly it seems as if there are still a lot of unknowns due to the raw complexity of the brain. Luckily, I have a very intelligent reader (and close friend) who just happens to be studying neuroscience so maybe she can shed some more light. But, according to her Facebook status, she’s currently giving birth so we might not hear anything for a while.
In any case, the next time somebody asks you why you seem to be overly joyous, you can reply with a fair amount of confidence that ‘my globus pallidus is stimulated!’