# Ajayan | What goes into your tummy can decide how your brain works. The gut in the stomach and the brain in your head are so intricately connected that the health of the bacteria in your gut decides how healthy your brain can be and how well you can remember.
An internationally published study led by neuroscientist Baby Chakrapani, head of the Centre of Excellence in Neurodegeneration and Brain Health situated at Cochin University of Science and Technology, German researcher Kristin Michaelsen-Preusse at Technische Universitat Braunschweig’s Zoological Institute and Martin Korte of Helmholtz Centre for Infection Research in Brunswick, highlights this gut-brain connection.
A study in mice underscored the gut-brain connection, finding that disrupting the delicate balance of gut bacteria, a condition known as gut dysbiosis, can overstimulate the brain’s immune cells, triggering a decline in memory.
Dr Chakrapani said researchers induced gut dysbiosis in mice by administering a broad-spectrum antibiotic cocktail for 14 days, disrupting their normal microbial balance. The mice were then subjected to a series of behavioural tests. The findings were striking: their long-term memory declined significantly, impairing both spatial memory, such as recalling the location of a hidden platform, and recognition memory, such as distinguishing familiar objects from new ones. Yet their short-term, or working, memory remained remarkably intact.
The study says the damage was highly specific to long-term memory creation, which takes place in a brain region called the hippocampus. The brain’s immune cells become aggressive and specific brain immune cells, called "microglia", had changed their behaviour. Following the gut imbalance, these normally vigilant caretakers cells shifted into an activated state, pulling in their branches and taking on a shorter, more compact form, literally going overdrive.
The researchers also noticed that the internal "stomachs" (lysosomal vesicles which are tiny membrane-bound sacs inside cells that act like the cell's recycling and waste-disposal centres) of these microglia grew significantly larger, indicating they were actively eating or clearing material. But instead of just cleaning up waste, these activated microglia began "pruning" or eating away at healthy synapses (the small gap between two cells across which messages are passed). This loss of neural connectivity likely contributed to the memory deficits, the study says.
The researchers investigated how a problem in the stomach signaled the brain's immune cells to attack, pinpointing to a specific protein called CNTF (Ciliary Neurotrophic Factor). Their findings suggest that elevated CNTF levels act as a trigger, pushing microglia into an aggressive, synapse-pruning mode. At the same time, levels of Brain-Derived Neurotrophic Factor (BDNF), often described as a fertiliser for the brain, helping neurons survive, grow and forge new connections, fell sharply. This double blow of rising CNTF and declining BDNF may help explain why memory and learning suffered in the mice.
The study was supported by Indian Council of Medical Research, the Kerala State Council for Science, Technology and Environment, the Kerala State Higher Education Council and CUSAT. Joint researchers were Krishnapriya, Rishikesh, Dayamrita KK, Isabell Haack, Shirin Hosseini, Ayswaria Deepti, Tara Sudhadevi and Unnikrishnan Sivan from CUSAT and Kerala University of Fisheries and Ocean Studies.
The study suggests that disrupting gut bacteria with antibiotics can raise CNTF levels, prompting the brain’s cleanup cells to remove too many neural connections in the hippocampus, the region crucial for learning and memory. In simple terms, it is like gardeners pruning a tree: they are meant to remove only dead branches, but a false alarm causes them to cut healthy ones as well, weakening the tree. Likewise, the brain loses vital connections that support memory and cognition.
The findings underscore the importance of nurturing gut health through a balanced, fibre-rich diet, regular exercise and adequate sleep. Healthy gut bacteria help safeguard the brain’s neural networks; when that delicate ecosystem is disturbed, memory and thinking can begin to falter.
