Task-free electrocorticography frequency mapping of the motor cortex

Electrocortical stimulation mapping (ESM) is the current gold standard for functional mapping of the eloquent cortex prior to epilepsy surgery. The procedure is, however, time-consuming and quite demanding for patients. Electrocorticography frequency mapping (ECoG mapping) has been suggested as an adjunct method. Here, we investigated whether it is possible to perform mapping of motor regions using ECoG data of spontaneous movements.

Using the video registration of seven epilepsy patients who underwent electrocorticography and ESM, we selected periods of spontaneous hand and arm movements and periods of rest. Frequency analysis was performed, and electrodes showing a significant change in power (4-7, 8-14, 15-25, 26-45 or 65-95 Hz) were compared with those being identified as relevant for hand and/or arm movement by ESM.

All frequency bands showed a high specificity (>0.80), and the 65-95 Hz frequency band additionally had a high sensitivity (0.82) for identifying ESM positive electrodes.

Our data show a good match between ECoG mapping of spontaneous movements and ESM data.

The accurate match suggests that ECoG mapping of the motor cortex using spontaneous movements may be a valuable complement to ESM, especially when other options requiring patient cooperation fail.