Hello readers! Happy New Year and all that. I took a few weeks off for the holidays and went to visit family and friends back in Toronto. It was a time of heart-warming reconnection with people I've known for much of my life. But it was also a time of anxiety and sadness: loss, disappointment, regret -- all part of the package. Hence the topic of today's post...
In a very cool blog called Neuroskeptic, I recently found a reference to a paper by Feinstein et al (2010, senior author Tramel), reporting on a man who had lost almost his entire limbic system.
The limbic system is a widely distributed assembly of very different structures. These include the amygdala (emotional associations), the hippocampus (memory encoding, so that events stay in mind for more than a few seconds), and in some accounts the ventral striatum (anticipation and desire). All these structures are "sub-cortical" -- they are more primitive than the cortex. They are its underlying machinery, the stuff in the basement. But parts of the cortex that border the limbic system are often called "limbic" or "paralimbic". These include the orbitofrontal cortex (OFC), which appraises the value of events, and the anterior cingulate cortex (ACC) which is in charge of effortful engagement and self-awareness (All these parts and their functions are described in detail in my book, Memoirs of an Addicted Brain.)
Limbic structures are the basis of learning. They grow synapses that connect with all parts of the cortex. That's how the sophisticated perceptions of the cortex remain anchored to an emotional self -- a core self. The cortex houses the most advanced software, but its programs are grounded in personal meaning through the limbic system.
A man named Roger had just about all of his limbic system destroyed by a very nasty (and rare) herpes infection. Yes, herpes can be a lot worse than you think. To quote from Neuroskeptic: "...his is the worst case of herpes encephalitis damage among patients currently alive." And he has been alive since the damage occurred 28 years ago. So what was the result? What happens when you lose your limbic system?
Roger lost his capacity to remember things from then on -- called anterograde amnesia -- which is not surprising. What is surprising is that his mood improved. You'd think losing half your brain would make you a tad grumpy. But in the words of Feinstein et al: "He readily displays signs of positive emotion including happiness, amusement, interest, and excitement..."
The limbic system developed with mammalian evolution, starting about 200 million years ago. It's the limbic system that allows mammals to play, to be social, to form attachments, to bond, and to feel a connection with other mammals and with their own future goals. But the limbic system also allows mammals -- including us -- to suffer. Thanks to the limbic system, we struggle to be the best we can be so that we can partner with other mammals (mates, children, parents). And we expect the same from them. Unlike frogs, whose goals are hard-wired, mammals must learn to achieve what they want, and avoid what they fear, through emotional striving. And a lot of that striving has to do with social needs: bonding, mating, competing, and caregiving.
So the lesson I take from Roger is that the psychological qualities of creatures like ourselves come with a huge price tag: emotional pain. Roger lost the neural foundation of social meaning -- of what it feels like to be a human mammal -- but he no longer experienced suffering. He became a happy camper in a shallow world.
To my mind, and to other students of addiction, like Gabor Mate, we drink or take drugs to reduce the fundamental pain of life -- the emotional suffering that constitutes the background music of the mammalian nervous system. Like other evolutionary achievements, the limbic brain is a double-edged sword. And we use drugs and alcohol in order to protect ourselves from its savage blade.
Perhaps, for this reason, addiction is an inevitable byproduct of human evolution.