UCSF

Neural devices have great potential to improve the treatment of neuropsychiatric, sensorimotor, and epileptiform disorders in humans. Recently, focus has been appropriately directed toward enabling the bidirectional flow of information between these devices and the brain with the goal of delivering electrical therapy only when necessary and in an appropriate amount. Interactions between the nervous system and the device improve when the devices are able to 1) record high quality neural signals using the appropriate number of sensors over the correct area and 2) stimulate the brain with an electrical signal that causes a desired effect.

The work presented here addresses these two major issues necessary for neural device design. In the first section, the spatial resolution of the brain at its surface is investigated and quantified using recordings from human patients with implanted ECoG sensors. In the second section, a novel ECoG sensor array with high spatial resolution is described and tested in human subjects that undergo awake brain surgery. Finally, the neural changes associated with sub-threshold and super-threshold electrical stimulation are examined and described for the first time in relation to stimulation parameters and stimulation outcome.

We found that the level of spatial resolution at the cortical surface depends on the neural frequency. For the highest neural frequency studied, the high gamma band, a denser array of sensors than what is commercially available should increase the information content. Because of this observation, we worked with Lawrence Livermore National Labs to manufacture an array of electrodes for collecting neural activity from a single human gyrus, and we observed that the increased density of electrodes did indeed improve decoding accuracy. Electrical stimulation of the sensorimotor cortex induced high gamma activity when the subject consciously perceived the stimulation, suggesting that high gamma is a reliable biomarker of effective stimulation. Together, these results suggest that devices should record from the brain’s surface at a higher density than is typically used, and that high gamma can be utilized as a feedback signal indicating whether stimulation is effective.