  Current advances in neurosciences deal with the functional architecture of
the central nervous system, paving the way for holistic theories that improve
our understanding of brain activity. From topology, a strong concept comes into
play in the understanding of brain signals, namely, continuous mapping of the
signals onto a hyper-sphere, a 4-dimensional space equipped with a
doughnut-like shape that is not detected by observers living in a 3-dimensional
world. We evaluate the features of the imperceptible 4th dimension based on
resting state functional magnetic resonance imaging series. In particular, we
looked for simultaneous activation of antipodal signals on the surface of a
cortical hyper-sphere. In this article, we demonstrate that spontaneous brain
activity displays the typical features which reveal the existence of a
functional hyper-sphere. The suggestion here is that the brain is embedded in a
hyper-sphere, which helps solve long-standing mysteries concerning our
psychological activities such mind-wandering and memory retrieval or the
ability to connect, pasts and future events.
