Alcohol use disorder (AUD) affects approximately 400 million individuals globally, positioning it as a leading contributor to serious health issues such as cancer, cardiovascular diseases, liver diseases, and stroke. In addition to its physical effects, AUD significantly compromises brain functions vital for learning, memory, and adaptability, all key elements of cognitive flexibility. Groundbreaking research from the Texas A&M University College of Medicine has recently provided new insights into how chronic alcohol consumption disrupts brain signalling pathways and impairs cognitive flexibility, focusing specifically on the role of cholinergic interneurons (CINs).
The study, led by Zhenbo Huang, PhD, an associate research scientist, and Jun Wang, MD, PhD, an associate professor at the college, highlights how alcohol alters the typical burst-pause firing patterns of CINs, which are specialized neurons responsible for releasing acetylcholine, a crucial neurotransmitter. These neurons play a pivotal role in the brain’s striatum by modulating dopamine signalling and influencing reward-driven learning and motivation. The researchers utilized advanced tools like optogenetics, which employs light to control cell functions, revealing that chronic alcohol exposure in animal models leads to altered CIN firing patterns. These patterns are crucial for learning new behaviours and adapting to changes, yet are significantly disrupted by alcohol, showing shorter and weaker pauses, impairing critical learning processes such as reversal learning.
Wang explained the importance of reversal learning, a cornerstone of cognitive flexibility, which allows individuals to discard old behaviours when rules or circumstances change, a process heavily reliant on acetylcholine signalling. To further dissect the effects of altered CIN function, the researchers employed optogenetics and fibre photometry—a technique using genetically engineered biosensors to detect real-time neurotransmitter release. Their findings underscored the distinct roles of the CIN firing phases: the “burst” phase aids in extinction learning, where old behaviours are overridden, while the “pause” phase is crucial for reversal learning, where new behaviours replace outdated ones.
This research not only sheds light on how alcohol disrupts these crucial brain mechanisms but also provides new perspectives on the broader impacts of AUD. The altered firing patterns observed suggest potential therapeutic targets for addressing cognitive impairments associated with AUD. Importantly, this study highlights the significant implications of AUD on cognitive processes, offering a deeper understanding of its effects beyond the physical health detriments.
Jun Wang emphasized the critical roles of the burst and pause dynamics of CINs for behavioural adaptability. This understanding opens avenues for exploring how other conditions, including ageing and neurodegenerative diseases, could influence these mechanisms. The insights gained from this research lay the groundwork for potential interventions that could mitigate the cognitive deficits caused by AUD and improve the quality of life for those affected.
Overall, this Texas A&M University College of Medicine study significantly advances our understanding of AUD’s impact on brain function. Highlighting the unique roles of CINs and their modulation of brain signalling provides a foundation for future research into therapeutic strategies that could ameliorate the cognitive effects of alcohol misuse, potentially extending beyond addiction to influence a wide range of neurological conditions.
More information: Zhenbo Huang et al, Dynamic responses of striatal cholinergic interneurons control behavioral flexibility, Science Advances. DOI: 10.1126/sciadv.adn2446
Journal information: Science Advances Provided by Texas A&M University
