3 years ago

Neuronal representation of individual heroin choices in the orbitofrontal cortex

Neuronal representation of individual heroin choices in the orbitofrontal cortex
Serge H. Ahmed, Audrey Durand, Karine Guillem, Viridiana Brenot
Drug addiction is a harmful preference for drug use over and at the expense of other non-drug-related activities. We previously identified in the rat orbitofrontal cortex (OFC) a mechanism that influences individual preferences between cocaine use and an alternative action rewarded by a non-drug reward (i.e. sweet water). Here, we sought to test the generality of this mechanism to a different addictive drug, heroin. OFC neuronal activity was recorded while rats responded for heroin or the alternative non-drug reward separately or while they chose between the two. First, we found that heroin-rewarded and sweet water-rewarded actions were encoded by two non-overlapping OFC neuronal populations and that the relative size of the heroin population represented individual drug choices. Second, OFC neurons encoding the preferred action—which was the non-drug action in the large majority of individuals—progressively fired more than non-preferred action-coding neurons 1 second after the onset of choice trials and around 1 second before the preferred action was actually chosen, suggesting a pre-choice neuronal competition for action selection. Together with a previous study on cocaine choice, the present study on heroin choice reveals important commonalities in how OFC neurons encode individual drug choices and preferences across different classes of drugs. It also reveals some drug-specific differences in OFC encoding activity. Notably, the proportion of neurons that non-selectively encode both the drug and the non-drug reward was higher when the drug was heroin (present study) than when it was cocaine (previous study). We will discuss the potential functional significance of these commonalities and differences in OFC neuronal activity across different drugs for understanding drug choice. We previously found that the orbitofrontal cortex (OFC) activity influences individual preferences between cocaine use and an alternative non-drug reward. Here, we sought to test the generality of this mechanism to a different addictive drug, heroin. Like with cocaine, OFC neurons encode individual heroin choices. However, there were also some drug-specific differences in OFC encoding suggesting that the OFC would not only encode preference but also resemblance between the drug and non-drug options available for choice.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/adb.12536

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