Meth, Coke, & Sham Reward

Positive reinforcement is intrinsically corrupting. The more reinforcing a stimulus is the more a person is willing to sacrifice to re-experience it. Cocaine and amphetamine are the most reinforcing stimuli known. They activate biological mechanisms directly, and thereby produce greater reinforcement than do other stimuli, including: good food, sex, the arts, financial success, and even loved ones. 

It generally takes 2 to 4 years between the initial exposure to the stimulant and the development of addiction. Only about 10‑15% of those who experiment with these drugs intra nasally become addicted. Those who do, typically develop a transition to high‑dose, long‑duration binging characterized by repeated re‑administrations during which the drug is the focus of attention to the complete exclusion of everything else. Several days of abstinence often separate binges. Unlike alcohol or opiates, the absence of daily use does not indicate decreased compulsion.  

Practice teaches us how to perform a behavior, reinforcement teaches us to want to perform it. Reinforcement affects motivation via changes in the concentration of certain neurotransmitters – notably dopamine [DA] – in certain parts of the brain. Amphetamine stimulates the release of DA, while cocaine prevents the re-uptake of DA. The consumption of either drug produces a greater saturation at DA receptor sites than could ever be achieved by natural reward. 

DA, once released, is metabolized, and so cannot be reused. Thus, following a drug run, DA is exhausted, accounting for anhedonia [inability to experience pleasure] and depression. Energy and enthusiasm returns only when DA stores return to normal levels.  

Many veteran users can recount all of the negative consequences of continued drug use [some of which can be quite frightening], deplore their situation, and report that the drug does not continue to give great pleasure. Why don’t they stop? 

Addicts continue to use the drug despite the aversive consequences because reward [pleasure] and reinforcement [the motivation to repeat behaviors that resulted in reinforcement] are different. Chronic drug use changes the meaning of drug related stimuli in two ways: 1. The person learns that stimuli associated with the act or place of drug use predict pleasure. 2. These stimuli become more salient [brighter, more magnetic]. 

Salience refers to the ability of a stimulus to capture attention, and results from sensitization of certain neural systems in which DA is the primary neurotransmitter. Salience develops without conscious awareness of the process, so the addict is only aware of the subjective result: drug related stimuli are brighter and more attractive. The increased sensitivity to drug related stimuli is a neuro-adaptation rather than a learning phenomenon, and hence the ability of drug related stimuli to capture attention is partially irreversible. For the remainder of one’s life, random encounters with the sight or smell of the drug – even thinking about the drug – will be capable of triggering a relapse. Once addicted, one remains forever vulnerable to relapse.

The irony of stimulant abuse is that the user receives progressively less reward from drug use [due to drug tolerance], but the compulsion to use – which is based on reinforcement – continues to increase with each exposureAs addiction progresses, the gratification becomes progressively smaller, while the price becomes progressively greater. Sham reward occurs when it looks like the person is working for reward, but there is no pleasure.

It’s a shame: long term use of stimulants comes at a great price with progressively less pleasure, and yet the user becomes progressively more attracted to it.