Kevin Murphy Psychology
Psychologist | San Diego
- the neurobiology of addiction -
Many theories attempt to explain addiction. From a neurobiological perspective, addictive behaviors reflect a type of hyper-learning. Addictive substances trigger mammoth spikes in the biochemicals linked to learning, with researchers particularly focused on dopamine and glutamate. We learn by association. The more intensely or frequently that a behavior activates the biochemical expression of reward, the more that behavior is conditioned (i.e., learned).
Addictive substances trigger mammoth spikes in the biochemicals linked to learning - dopamine & glutamate.
Addictive substances exploit the brain’s plastic potential, the learning linked to addictive behaviors deeply anchored .
Think of addiction as a form of hyper-learning.
Therapy can also tap into the brain's plastic potential and help to reestablish a balance between the impulsive midbrain and executive forebrain.
Addictive behaviors tend to activate both intense and frequent rewards. In fact, the surges in dopamine and glutamate associated with substances of misuse far exceed the levels released in normally rewarding experiences, like relationships, a career, a favorite hobby, and so forth. Such intense biochemical experiences condition the brain to become increasingly sensitive to the cues associated with drink and drug. Over time, the circuits in the brain linked to learning and motivation become primed to respond to a drug. Think of addiction as a form of hyper-learning.
Research has demonstrated that the mesolimbic circuit, as the reward system in the brain, becomes increasingly dedicated to an addiction over time; in the more severe cases of addiction, the reward system fires off almost exclusively in response to cues to use (places, persons, memories, certain emotions). As a result, people mired in addiction lose interest in their relationships, careers, academics, and other normally pleasurable experiences, those experiences unable to compete with the intense biochemical reactions that addictive substances trigger.
The Nucleus Accumbens (NAc), as the epicenter of learning along the mesolimbic circuit, literally grows in size over the course of addictive use, with research in recent years discovering that the number and density of glutamate dendrites along the NAc increase in parallel to an addiction (Quintero 2013). That growth signals the brain’s plasticity at play. The NAc becomes something of a behemoth, as addictive substances exploit the brain’s plastic potential, the learning linked to addictive behaviors deeply anchored in the brain.
That’s why people continue to use and relapse, even as the consequences related to their addiction mount. Even after a third DUI, or near fatal overdose, or a termination, maybe after a separation from a loved-one, people continue to use and/or drink, seemingly oblivious to reality. That's because addictive behaviors change the brain, shaping neuroadaptations that propel people to act against their better judgement (Berridge, K, 2013).
The brain’s plasticity normally promotes adaptive and pro-social behavior. In cases of addiction, however, that plasticity actually reinforces the drive to use or drink on a neurobiological (i.e., preconscious) level. If your loved one appears oblivious, it’s only because of the effect described here. Addictions prime the mesolimbic system to fire off more easily and for prolonged periods. Consequently, the midbrain – the more primitive part of the human brain – begins to dictate behavior. A dysregulated midbrain will overrun the executive areas of the frontal lobe and their ability to inhibit urges. As a result, those with addictive behaviors will become more impulsive, and less reflective.
Therapy can also tap into the brain's plastic potential (Porto, Oliveira, et al., 2009; Beauregard, 2014), and help to reestablish a balance between the impulsive midbrain and executive forebrain. Behavioral therapy strives to normalize the ebb and flow of neuro-impulses between the two areas. To use a car analogy, the midbrain represents the gas pedal, while the frontal area serves as the braking system; addictions produce a Ferrari with bad brakes. Behavioral therapy, then, essentially services your braking system.
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