Fig. 3.

Magnetic direction-selective control and on–off response patterns of neuronal activity. a Direction-selective magnetic activation of calcium influx. Schematic of two-directional magnetic stimulation setup. A–B coils produced magnetic field along X-direction (green arrow) and C-D coils generated magnetic field along Y-direction (red arrow). b Sample traces of fluorescence intensity of three neurons in response to magnetic fields of different directions in X–Y plane. Green arrow, direction of magnetic field in X-axis. Orange arrow, direction of magnetic field in Y-axis. Left, a representative neuron exhibited a large calcium peak when the magnetic field was turned on to X-axis, while only a small peak was observed when the magnetic field was switched to Y-axis. Middle, an example neuron responded only to the magnetic stimulation along Y-axis. Right, representative trace showing calcium spikes to magnetic field along both X-axis and Y-axis. Traces showing were ∆F/F0. Green bar, field on in X-direction; orange bar, field on in Y-direction. c On-response and off-response patterns of neuronal activity. Schematic showing that switch-on and switch-off of magnetic field induced on-response (blue trace) and off-response (red trace) patterns of neuronal activity. d Fluorescence traces shown were three representative neurons with different response patterns. Upper, a neuron exhibiting calcium transient when the magnetic field was turned on (on-response), but not when it was turned off (off-response). Middle, a neuron exhibiting off-response but not on-response. Lower, a neuron exhibiting both on-response and off-response. Traces showing were ∆F/F0. Blue bar, field-on; orange bar, field-off