Awhile back I was skimming a neurology journal, checking out the types of topics that neurologists get excited about.
Neurology is the study of disorders of the nervous system. To vastly oversimplify, one could consider psychiatry a branch of neurology (Freud started his career as a neurologist), but neurology has far more emphasis on conditions where a clear cause and effect can be shown - such as a stroke or head or spinal cord injury or nerve cell degeneration.One could argue that the second we are able to clearly identify the underlying neural mechanisms to depression, then the illness would become a neurological disorder rather than a psychiatric disorder.
But depression refuses to lend itself to neurological simplicity. Neurological conditions tend to involve a loss of motor control (such as Huntingtons) or thinking or memory (such as dementia or Alzheimer's). Behavioral effects, if any, tend to be secondary to the disorder in question.
Understanding apathy and anhedonia
One of these behavioral effects may be apathy. Sure enough, in the journal I was skimming, I came across an article on apathy. Then I did a search of the psychiatric literature on apathy. Virtually nothing. This was really weird. Couldn't apathy be considered part of depression? I searched the neurology literature. No, the articles said in effect.
Think about when you're depressed - when you don't care enough to get out of bed, when you don't care enough about the consequences of missing work or letting down your friends or not paying your bills. Think of apathy as lack of motivation. There simply had to be an apathy component to depression. The closest I could find was "anhedonia," the inability to experience pleasure from activities we would normally regard as pleasurable.
The Diagnostic and Statistical Manual of Disorders (DSM) is big on anhedonia. Indeed, it is one of the two core features of depression. Either one must be feeling depressed (loosely interpreted as feeling sad or worried) or feeling loss of pleasure (i.e. experiencing anhedonia). In 2003, Hall of Fame quarterback Terry Bradshaw went public with his decades-long depression, noting: "I didn't understand that after every Super Bowl victory, I could never find pleasure in what I'd done."
When I contacted Paul Keedwell, M.D. a neurologist at Cardiff University who authored one of the neurology articles in the journal, he said, "I believe that the presence of anhedonia defines depression. If one does not have anhedonia one is not depressed." Dr Keedwell's research pointed to deficits in the reward system of the brain, leading to this conclusion: "The perception of reward would thus be reduced, leading to the core depressive symptom of anhedonia."
Apathy and anhedonia in the brain
In his communication to me, Dr Keedwell saw an overlap between anhedonia and apathy, as well as psychomotor retardation and lack of drive. The reward system of the brain involves back and forth communication between the prefrontal cortex and the subcortical striatum, part of the mesolimbic pathways powered by dopamine. Reduced activity in the striatum may lead to a failure of the prefrontal cortex to process rewarding experiences.
In the striatum, Dr Keedwell informed me, there are many connections between the limbic and motor functions. The old functional distinctions in this region, based mainly on animal studies, he said, may not apply to humans.
Thus, if we look at behavior in terms of what may really be going on in the brain rather than simply take the DSM's word for it, we may be looking at a breakdown in brain circuits that process a number of related behaviors. To keep the circuit analogy going, if you pull the plug on your Christmas tree lights, both the red bulbs and the green bulbs go out.
In essence, the same circuit-breaker that desensitizes us to feeling or anticipating pleasure may also desensitize us to feeling or anticipating grief or loss or sadness. Our ability to emotionally react to events, whether good or bad, has been severely compromised. It would be interesting to find out from Terry Bradshaw how he felt after losing rather than winning a play-off game. Did he experience a surprising lack of disappointment?
The experience of apathy
Our own personal experiences already offer us considerable insight. In my case, by high school, I no longer cared about my bad academic performance or ability to fit in with my classmates. Not only that, I lacked the motivation to put in the effort. Here I was, at age 15, already a Harvard reject with no future.
But we know Terry Bradshaw had to have cared about winning. He simply could not have stayed at the top of his game for so long otherwise. The plug to his brain may have been pulled, but enough lights stayed on. As we are discovering, the brain is infinitely complex.