Deep within the brain, a geometric lattice of firing neurons quietly maps the world we move through — and a new study from Ruhr University Bochum reveals that cortisol, the body's own stress hormone, can dissolve that map with unsettling precision. Forty healthy men navigating a virtual landscape showed measurably worse spatial judgment after receiving cortisol, while MRI imaging captured the brain's internal GPS — its grid cells — losing coherence in real time. When the primary system faltered, the brain reached for a backup, shifting toward habit-based navigation in the caudate nucleus, a wo