The Split Path: How the Brain Differentiates Between Internal Visualization and Real-World Space

Recent breakthroughs in neuroscience are illuminating a fundamental divergence in how the human brain processes spatial data, distinguishing between information derived from external perception and that generated purely by imagination. A pivotal study, conducted by Anthony Kleman and Catherine Tallon-Baudry at the prestigious École normale supérieure in Paris, was published on October 8, 2025, in the *Journal of Neuroscience*. Their findings conclusively demonstrated that distinct neural mechanisms are engaged when an individual performs mental visualization compared to direct visual observation.

The researchers designed an elegant experiment to probe this separation. Participants were tasked with navigating a mental map of France, specifically asked to determine which of two designated cities lay closer to Paris. Recordings of the subjects' brain activity revealed a stark and clear division in processing pathways. When participants engaged in direct visual perception, activity was concentrated in the posterior regions of the brain—namely, the occipital and parietal zones—areas traditionally associated with the processing of external stimuli. Conversely, when the participants accessed the imaginary map, the center of neural activity shifted dramatically forward, migrating to the anterior, frontal areas. This evidence strongly supports the hypothesis that internally generated images and externally perceived stimuli are handled by separate cascades of neural processes within the cognitive architecture.

According to Kleman, this internal “mental gaze” is far from being a mere replication or simple echo of the mechanisms used for standard sight. This crucial demarcation holds profound significance for understanding the biological underpinnings that separate the perception of the physical world from its internal simulation—a distinction that forms the bedrock of human learning, memory formation, and overall experience. Recognizing this inherent difference is key to unlocking deeper insights into how we construct and interact with our reality, both perceived and imagined, highlighting a critical element of human cognition.

Knowledge regarding these specialized neural routes opens up exciting avenues for practical application, particularly in fields like cognitive therapy and the development of advanced immersive technologies. This includes everything from sophisticated virtual reality (VR) environments to specialized systems designed for attention training. Further neurobiological investigations reinforce the complexity of these processes: while the vividness or clarity of visual imagery is closely tied to activity in the occipital cortex, accurate spatial representations demand alignment with a stable, three-dimensional frame of reference, which is painstakingly constructed through lived experience. The brain exhibits an astonishing capacity for adaptation, utilizing these varied “routes” for navigation across both the external environment and the rich landscape of the inner world, thereby expanding our comprehension of the full potential of the human mind.