Posts tagged: Depression

Happiness and Desire

For over fifty years, scientists have been able to influence rat behavior through the use of brain implants.  This does not mean that scientists are able to create a mammalian robot.  The behaviors elicited by rodent brain stimulation are primarily limited to eating and sex.  Scientists have interpreted the increase in these behaviors as an artificial increase in the pleasure experienced by eating or having sex.  Once the rat was given control over the charge sent to their brain, they would continue to self-stimulate until exhausted.  This observation was regarded as proof that the electrical stimulation induced a feeling of euphoria.  Food and females were ignored in favor of electrical self-stimulation.

Much more recent research (Berridge & Kringelbach, 2010) suggests that earlier scientists had leaped too far in their conclusions.  These scientists have discovered that wanting and liking are neurologically distinct.  At first blush, this sounds rather obvious and simplistic.  At the second blush, it sounds a bit off kilter.  Why would someone want something they do not like?  At the third blush, it begins to gather more common sense.  Many people perform work they do not enjoy in order to receive money.  People want money, and will perform dreary behaviors in order to gain this end.  More to the point, drug addicts continue to strongly desire a drug long after its pleasurable effects have evaporated.  As the need for the drug increases, the pleasure attained by the drug decreases.

In regards to recreational drug dependence, dopamine is most often implicated as the neurotransmitter of addiction.  Cocaine and other amphetamines significantly increase the amount of dopamine available at brain synapses.  Berridge and Kringelbach found that the dopamine is related to desire-not pleasure.  Once a rat brain is depleted of dopamine, they will tend to lose interest in their environment.  This ignores the fact that if food is presented to the dopamine depleted rat, it will eat and appear to enjoy the food as much as a normal rodent.  The difference is that the rat will not seek out the food in a spontaneous fashion.  Conversely, rats with elevated dopamine will seek out and consume larger quantities of food, but once they are sated, the rodent will display facial signs of displeasure as they continue to eat more than they require.

This new model becomes even more complicated when the notion of pleasure is entertained.  As mentioned, it does not appear that the dopamenergic neural circuits of desire have much to do with pleasure.  Many areas in the brain stem and cortex need to be simultaneously activated to produce pleasure.  This is in contrast to the relatively circumscribed neurology of desire.  The reward areas of the brain are strongly connected to other areas that evaluate the experience in real time.  A small area at the bottom-front of the brain appears to regulate when the animal is sated-when enough is enough.  A little chocolate syrup on ice cream elicits delightful anticipation, but the mere thought of drinking an entire can of the syrup is sickening.  This is the prefrontal cortex acting as the internalized mother.  Many distinct areas of the brain feed into this area, giving near instant updates of bodily status and comparisons to prior behavior.
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The dissociation between desire and pleasure may have implications for the treatment of depression.  Anhedonia is defined as the loss of pleasure experienced by depressed people.  For example, someone who is an inveterate football fan will derive little pleasure from watching the big game.   Perhaps electrical stimulation of cortical pleasure centers may help depressives regain some pleasure from life.  Similarly, gambling and drug addiction are repetitive behaviors that bring less pleasure the longer they are experienced.  Highly targeted electrical stimulation may return the balance between wanting and liking.  The desire to gamble or use drugs would decline in relation to the loss of pleasure experienced.

Fortunately or unfortunately, it is unlikely that mental disorders will be treated by implanted electrodes anytime soon.  The reseach by Berridge and Kringelbach highlights the errors that accrue when complicated aspects of behavior are reduced to one or two discrete areas of the brain.  Increasingly, research points to specialized areas of the brain that act in concert with other areas to produce a given behavior.  Because humans need to simplify problems, it does not follow that the study of brain function will conform to this need.

Early research discovered pleasure where there was only desire.  Current research suggests that one aspect of happiness is the congruence of pleasure and desire.

Computers on the Brain

It is not uncommon for psychologists to draw parallels between the modern computer and the ancient human brain.  Nearly all the people who read this article will do so with the use of a computer.  The computer allows the rapid categorization and transformation of symbolic information.  The information is symbolic since it does not contain the actual perceptual information of the event, but a representation of the information encoded into standardized symbols.  The symbols must be standardized, or the information could not be shared with others.  The symbols must also have the capacity of accurate storage, or the computer would only be useful on an intermittent and spontaneous basis.

The ancient brain processes sensory information in a symbolic fashion, as well.  It does not store holograms of what we see, smell, hear or touch, but encodes the information in proteins.  Recalling the information encoded in proteins allows categorization and association of the symbols removed from the actual event.  The human brain uses standardized sounds to communicate its symbols, otherwise the information could not be shared with others.  The storage of symbolic information must be fairly accurate, or the human could not learn to operate effectively within a given environment.

Both the brain and computer have an architecture specialized to encode and process information, yet there are differences.  There is no real equivalent of software in the human brain, as the physical architecture of the brain is altered to meet and master novel tasks.  Current computers cannot alter their architecture at this point in their development, but small alterations of software can radically change the type and method of information processed.  Neurotransmitters provide the closest parallel to computer software.  Their respective levels in different areas of the brain may favor and flavor the information processed.  The current understanding of neurotransmitter action does not allow for the sweeping changes possible with computer software.   The human brain exists in a dynamic flowing relationship with the environment, whereas the computer was designed to be an assistant in this relationship.
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Currently, mental illness is most often viewed as a biological defect; similar to a diseased heart or lung.  Computer scientists might regard schizophrenia and bipolar disorder as faulty hardware, and depression, anxiety and angst as buggy software.  Similarly, psychosurgery has been used in the past to treat schizophrenia, and current psychiatrists modulate neurotransmitters to control depression.  The former deserves  little comment, and the latter has met with limited success.  Neuroscientists and psychiatrists have beaten the drum of biological mental illness for decades.  They have attempted changing the computer architecture in schizophrenia, and the computer software in depression.  The analogy tends to fail at this point, though, largely due to the negligence of a very important relationship.

The analogy breaks down due to the dynamic relationship between humans and the environment.  A person’s environment, especially their social milieu, may profoundly alter neurotransmitter levels.  Chronic stress is now known to cause actual alterations in the way genes are expressed.  Put another way, the environment alters the hardware and software of the human brain.  The brain evolves over a lifetime, whereas the computer is largely a static entity, such that the computer/brain analogy is always inexact.  To ignore the environment in the treatment of mental illness is similar to ignoring the road while driving a car.  Altering the brain’s software, without altering the environment, is to ignore a major difference between computers and people.  Social relationships may be an architect of human dysfunction, but also a foundation upon which we build our happiness.