For the first time, neuroscientists have observed how deep structures within the brain activate when we become aware of our own thoughts — a phenomenon known as conscious perception.

Although our brains constantly receive information through sights, sounds, and other stimuli, only a fraction of these inputs reach our conscious awareness — like noticing the taste of chocolate or the sound of someone calling your name. For decades, researchers have linked this awareness primarily to the brain’s outer layer, the cerebral cortex. But what about the deeper regions?

Studying these inner structures has always been a challenge due to the need for invasive procedures and the difficulty of designing reliable animal models. Still, exploring them could expand our understanding of consciousness beyond the surface of the brain.

“Consciousness research has often been met with skepticism,” says Liad Mudrik, a neuroscientist at Tel Aviv University, “but advances in scientific methods are allowing us to study it more systematically”.

The Thalamus: A Central Player in Awareness

A new study published in Science by Mingsha Zhang and his team at Beijing Normal University zeroes in on the thalamus, a central brain region known for managing sensory data and working memory. It’s long been suspected of playing a role in what we become consciously aware of.

Zhang’s study involved participants already receiving treatment for chronic headaches. These individuals had thin electrodes implanted deep in their brains — a rare opportunity for researchers to monitor neural activity in real time during tasks that require conscious awareness.

Participants were shown flashing icons on a screen and asked to move their eyes in a specific way depending on whether they saw the icon or not. The visual cue was designed to be consciously perceived only about 50% of the time, making it ideal for measuring the brain’s reaction to both conscious and unconscious processing.

A Coordinated Response

The results were striking. When participants were aware of the icon, the activity in the thalamus and prefrontal cortex was not only stronger but occurred earlier — particularly in the thalamus. These signals also appeared to be synchronized across both brain regions, suggesting that the thalamus may play the role of a gatekeeper, controlling which thoughts and perceptions reach our conscious mind.

“This level of coordinated activity across regions is remarkable,” says Christopher Whyte, a neuroscientist at the University of Sydney. It’s the first time such real-time recordings have been made in humans during tasks directly relevant to consciousness.

Animal Evidence Backs It Up

These findings align with earlier animal research. A 2020 study showed that when mice detected subtle whisker movements, activity in their cerebral cortex was linked to projections into deeper areas like the thalamus. This pattern hints at a broader, interconnected system behind conscious experience.

Mudrik calls the new human study “one of the most detailed examinations of the thalamus’s role in consciousness” — although she notes that it remains unclear whether the recorded neural activity reflects true conscious experience or heightened attention to stimuli.

What’s Next?

Zhang’s team plans to expand their research with more human participants and detailed experiments in macaque monkeys to dive deeper into how consciousness arises from neural circuits.
The thalamus, once thought of mainly as a relay station, is now emerging as a potential key to one of science’s most enduring mysteries: how the brain becomes aware of itself.