Adults with a history of methamphetamine dependence have altered reward expectancy in key regions of the brain, according to a recent study published online this September in the Journal of Psychopharmacology. The results highlighted an impaired ability to evaluate future risks and benefits, which may increase the likelihood of future risky behavior in adults with a history of methamphetamine use.
Stimulant-using individuals often demonstrate poor decision-making. In particular, individuals with a history of methamphetamine are more influenced by the immediate choices they face and are less able to adjust decision-making to short-term versus long-term gains, with obvious consequences.
One source of this disadvantageous decision-making may be impaired reward processing. Regions in the brain that are involved with reward processing include the ventral striatum, orbitofrontal cortex, and ventral anterior cingulate, where the neurotransmitter dopamine is also especially important. Usually, neurons within this network respond to various reward related events and may be affected by motivation, preference, and expectancy.
Chronic methamphetamine use may lead to changes in reward-related function of the ventral striatum and caudate nucleus.
The study, led by Amanda Bischoff-Grethe of the University of California, investigated neural functioning of expectancy and receipt for gains and losses in adults with and without a history of methamphetamine dependence. 17 adults with histories of methamphetamine dependence and 25 comparison adults performed a probabilistic feedback expectancy task during blood-oxygen level-dependent functional magnetic resonance imaging (fMRI). Participants were given visual cues associated with monetary gain, loss, or neutral outcomes.
The results revealed that adults with a history of methamphetamine dependence had less response to loss anticipation in the ventral striatum. They also showed more response to loss outcomes than to gain outcomes in the caudate, whereas non-methamphetamine adults did not show differences in their responses. Finally, greater apathy (lack of interest) in adults with a history of methamphetamine dependence was associated with less anterior caudate and ventral striatal response to gain anticipation.
The researchers concluded, “These findings are consistent with our hypotheses, and suggest differences in the neural substrates involved in the processing of anticipation and receipt of potential rewards and losses in methamphetamine dependent individuals.”
They concluded, “METH individuals (individuals with a history of methamphetamine dependence) do not process the expectation of negative events as much but—instead—process the occurrence of these events more intensely.”
The results highlighted an impaired ability to evaluate future risks and benefits, which may increase the likelihood of future risky behavior in adults with a history of methamphetamine use.
The study was titled: “Altered reward expectancy in individuals with recent methamphetamine dependence.”