It was a small sample—just two dozen human subjects—but his basement apparatus had yielded a consistent, repeatable effect. When the magnetic field was rotated counterclockwise—the equivalent of the subject looking to the right—there was sharp drop in α waves. The suppression of α waves, in the EEG world, is associated with brain processing: A set of neurons were firing in response to the magnetic field, the only changing variable. The neural response was delayed by a few hundred milliseconds, and Kirschvink says the lag suggests an active brain response. A magnetic field can induce electric currents in the brain that could mimic an EEG signal—but they would show up immediately.
OK, small sample. Also, if we did have such a field-sensitive organ, would it necessarily be in the head? And lying in an MRI system should overload such an organ. Maybe that would make it numb (negative result), or make the person uncomfortable or slightly disoriented (natural enough in a cramped and noisy system).
He needs to test with stronger fields.