Metabolic quantum limit to the information capacity of magnetoencephalography

TL;DR

This paper establishes fundamental quantum and metabolic limits on the information capacity of magnetoencephalography, revealing a maximum rate of 2.2 Mbit/s for human brain measurements and highlighting a spatio-temporal trade-off.

Contribution

It derives a technology-independent bound on MEG information capacity based on quantum physics and neural metabolism, connecting neuroscience with quantum technology.

Findings

Maximum information rate of 2.2 Mbit/s for human brain

Finite angular bandwidth limits spatial complexity of neural signals

Energy resolution causes a trade-off between temporal and spatial bandwidths

Abstract

Magnetoencephalography, the noninvasive measurement of magnetic fields produced by brain activity, utilizes quantum sensors such as superconducting quantum interference devices and atomic magnetometers. Combining the energy resolution limit of magnetic sensing with the brain's metabolic power, we derive a technology-independent bound on the information capacity of such measurements. Depending only on geometry, neural metabolism, and Planck's constant, this bound yields a maximum information rate of 2.2~Mbit/s for the human brain. We also show that the measurable magnetic field has a finite angular bandwidth. Higher multipole components are geometrically suppressed and fall below the quantum-limited noise floor, limiting the spatial complexity of neural current patterns encoded in the external field. Because the energy resolution limit implies noise variance grows linearly with bandwidth, temporal and spatial bandwidths compete, establishing a fundamental spatio-temporal trade-off. These results unravel the fundamental limits of noninvasive brain imaging, and may inspire the synthesis of neuroscience with modern quantum technology.