Weak electric fields of deep brain stimulation can entrain spiking in multi-compartment cortical neuron models

Deep brain stimulation (DBS) is a common treatment for neurological disorders, yet the exact mechanisms behind its effects are still unclear. While DBS predominantly influences subcortical structures and networks, recent research has shown that the electric fields produced during DBS can be as strong or even stronger than those produced by transcranial alternating current stimulation, which is known to affect neuronal activity.

To explore whether these weak DBS fields can directly impact cortical spike timing, researchers utilized multi-compartment computational models of five different neuron types located in all cortical layers. They exposed these neurons to E-fields modeled after DBS pulses, varying the amplitude, frequency, and orientation of the fields.

The researchers assessed entrainment by analyzing peri-stimulus time histograms and calculated the phase locking value (PLV). The results indicated that weak DBS fields influenced the spike timing of some neurons by either increasing or decreasing the probability of firing shortly after the stimulation pulse, demonstrating entrainment to the stimulation.

This entrainment was more pronounced with higher E-field amplitudes and frequencies. The extent and direction of spike-timing modulation varied among neuron types and were also affected by the direction of the field. These findings suggest that the cortical E-fields generated during DBS may directly influence the activity of certain cortical neurons, in addition to the known indirect effects on cortical activity mediated by subcortical targets and their networks.

This discovery offers a new understanding of how DBS may impact cortical activity and provides insight into its potential mechanisms, both therapeutic and side effects.