Summary: Researchers identify a critical role for the claustrum in forming context-linked cocaine memories. In mouse models of addiction, suppressing specific claustral neurons prevented behavioral responses to cocaine, while activating them created a context preference even without drug exposure.
Source: Hebrew University of Jerusalem
Our brains are particularly good at encoding the circumstances surrounding emotionally charged events. Whether it is the place where you first fell in love or the location tied to a traumatic experience, contextual cues become deeply linked to the emotions and memories they accompany. This same context-driven association plays a central role in addiction: environments or social settings that were once paired with drug use can trigger cravings and relapse long after the drug itself is gone.
New research from Professor Ami Citri and PhD student Anna Terem at the Hebrew University of Jerusalem’s Edmond and Lily Safra Center for Brain Sciences and the Alexander Silberman Institute of Life Sciences examines how the brain forges these powerful context–reward associations. Their study, published in Current Biology, highlights the claustrum — a slender, little-studied brain structure — as a key player in assigning motivational importance to environmental cues associated with cocaine.
The team framed their findings using the concept of “incentive salience,” which explains how neutral stimuli become desirable when repeatedly paired with reward. A simple storefront can acquire irresistible appeal for a child after repeated visits that link the facade with candy rewards. Incentive salience reflects a form of wanting that is distinct from simply liking the reward itself. Citri and Terem traced how contextual cues linked to cocaine take on this motivational power and identified a subpopulation of claustral neurons that become active during cocaine exposure and are essential for creating that association.
To probe the claustrum’s role in forming context–reward links, the researchers used a conditioned place preference (CPP) protocol in mice. In this behavioral test, animals learn to associate a particular compartment — distinguished by unique flooring and wall patterns — with the effects of a drug. Mice received cocaine and were placed in an environment with rugged flooring and dotted walls while the drug took effect. On other occasions they were placed in a different, neutral chamber with smooth floors and striped walls. After several pairings, mice typically show a clear preference for the drug-paired chamber when given free access to both areas.
Using chemogenetic and optogenetic tools to manipulate claustral activity, the researchers demonstrated that inhibiting the identified claustral neurons blocked the development of cocaine-conditioned place preference: mice no longer preferred the cocaine-paired context. Conversely, activating the same neurons in the absence of cocaine was sufficient to create a preference for that context, indicating that claustral activation can assign incentive value to environmental cues even without direct drug reward.
Importantly, the investigators found that claustral activity is critical during the acquisition phase — when context and reward are initially paired — but not necessary for later retrieval of an already encoded cocaine memory. Once mice had experienced the cocaine-paired environment several times and the association was established, suppressing the claustrum did not erase the preference. This distinction suggests the claustrum boosts the salience of a context during learning, increasing the animal’s attention to cues that predict reward, rather than serving as the long-term storage site for the contextual memory itself.
These results have significant implications for understanding addiction. As drug overdose deaths continue to rise worldwide, clarifying how environmental cues gain power over behavior could inform prevention and treatment strategies. Recognizing the claustrum’s role in forming context–reward links highlights it as a potential target for future research into diagnostic markers or therapeutic interventions aimed at reducing relapse by weakening or preventing harmful contextual associations.
The authors suggest that further study of claustrum circuits and their interaction with frontal cortex regions may reveal new ways to identify individuals at greater risk for developing persistent, cue-driven addiction and to design approaches that interrupt those associations before they become entrenched.
About this learning research article
Source:
Hebrew University of Jerusalem
Media Contacts:
Tali Aronsky – Hebrew University of Jerusalem
Image Source:
The image is in the public domain.
Original Research:
Open access. Article title: “Claustral Neurons Projecting to Frontal Cortex Mediate Contextual Association of Reward.” Authors: Ami Citri et al. Published in Current Biology. DOI: 10.1016/j.cub.2020.06.064.
Abstract
Claustral Neurons Projecting to Frontal Cortex Mediate Contextual Association of Reward
The claustrum is a compact nucleus with widespread reciprocal connections to cortical, subcortical, and midbrain regions. Growing evidence implicates the claustrum in salience detection and attentional processes. In this study, the authors combined spatial transcriptional profiling with iterative functional experiments to define a claustrum circuit that is necessary for associating context with reward. They identified claustral neurons that express dopamine receptors and project to frontal cortex, and demonstrated that these neurons are recruited by cocaine and contribute to drug sensitization. Using increasingly specific chemogenetic and optogenetic manipulations, the team mapped a pathway of D1-receptor-expressing claustral neurons projecting to frontal cortex that is required for acquiring cocaine conditioned-place preference and for real-time optogenetic conditioned-place preference. Overall, the results support a model in which a claustrum-to-frontal cortex circuit allocates attention to reward-related contextual cues and mediates the attribution of incentive salience.