Our Brain Loves Bubbles: CO2 Stimulates All Five Senses

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Our Brain Loves Bubbles: CO2 Stimulates All Five Senses

In a video published on the Pasteur Institute website on January 2, neuroscientist Gabriel Lepousez, from the Perception and Memory Unit, explores the question: “Why does our brain love bubbles?”

Lepousez studied olfactory sensory perception and its health implications, particularly mental health and body-brain communication. While he does not focus exclusively on CO2, he acknowledges its role as an olfactory stimulus.

“It is one of many sensory stimuli, but not the subject of specific research,” he explained. However, inspired by the sparkling drinks that take centre stage during end-of-year celebrations, he decided to share insights into the neuroscience of bubbles.

Bubble Formation

The effervescence in sparkling drinks results from dissolved CO2; however, their formation also depends on external factors.

“In a pressurized bottle, such as champagne, 12 L of CO₂ remain dissolved. But once the bottle is opened and pressure decreases, the gas returns to its gaseous form, creating bubbles in the glass,” Lepousez explained.

“Interestingly, bubble formation is triggered by impurities on the glass surface, such as dust, microfibres, and microcracks, which serve as points of nucleation and formation of bubble columns. If you poured a carbonated drink into a perfectly clean, smooth glass, you might see no bubbles at all,” he emphasised.

“The magic of these drinks lies in the ability of CO2 to engage all five senses,” he said. “The bubbles capture our attention as they animate the liquid, making it appear alive and dynamic — unlike a still, flat drink. They also stimulate our hearing — the pop of a champagne cork, the hiss of a can opening, and the fizzing sound of bubbles rising in the glass all contribute to the sensory experience,” noted Lepousez.

Sensory Stimulation

Bubbles do more than just provide a captivating sight and sound.

“Bubbles also stimulate our noses because each time a bubble finishes rising and bursts on the surface of the drink, its explosion triggers the projection of micro-aerosols into the air, which, like a mist, actively spray micro-droplets of perfumed liquid towards our nostrils and increasing 10-fold the vaporisation of odours in the air. This excess sensory stimulation directly activates our brain and increases the 10-fold intensity felt, which can be observed in functional brain imaging of a taster,” Lepousez explained.

CO2 is also an irritant gas that stimulates the same receptors as mustard. He noted, “That’s why it stings.”

The transient receptor potential ankyrin 1 receptor, commonly known as the mustard receptor, detects irritant compounds and plays a role in pain and inflammation. In the mouth, it is strongly expressed in the nerve endings of the trigeminal nerve, which innervates the oral and nasal cavities.

When exposed to a CO2-rich solution, these nerve endings are activated and transmit pain signals to the brain. This phenomenon can be studied in vitro using neuronal cultures, allowing precise control over molecular interactions and direct recording of their effects.

Taste and Texture

Bubbles also contribute to texture, creating a foam that adds thickness between the tongue and the palate. In addition, CO2 activates acid-detecting cells in the tongue.

“Does sparkling water taste more acidic and refreshing than still water? This is due to a chemical reaction between CO2 and water on the surface of our taste buds, producing hydrogen ions that trigger a mild acidic flavour. The simple CO2 molecule is unique in its ability to act on our five senses: Olfactory, gustatory, tactile, visual, and auditory — a true multisensory enhancer,” Lepousez concluded.

This story was translated from Medscape’s French edition using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.