A Multimodal Neural Probe for Seizure Signals Monitoring and Optical Stimulation Treatment to Epilepsy

Epilepsy is a central nervous system disorder which affects more than 65 million people worldwide. Seizures are often accompanied by abnormal discharges of a large number of neurons overall the brain, causing periods of unusual behavior, sensations, loss of awareness and even death. Electrical stimulation to deep brain regions has been demonstrated to be effective methods of seizure control for patients with drug-resistant seizures. However, the metal neural probes used in clinical applications for monitoring the neural signal or delivering electrical stimulation have significant disadvantages in the poor conformability, risk of tissue damage, long term stability issue and etc. Soft-material based electrode array has emerged as a promising alternative to metal probes for their small size, biocompatibility, and more importantly, their flexibility and conformability.<br/><br/>Here we demonstrated a soft multimodal device that contains 16-channel depth electrodes and 16-channel ECoG electrodes. The electrodes were fabricated with gold as conducting layer and parylene-C as the supporting layer, coated with PEDOT:PSS and pHEMA to reduce the impedance and enhance the bio-compatibility. By using a 50 um diameter thin optical fiber as shuttle, the depth electrodes were implanted to the focal region of seizure, meanwhile, the ECoG electrodes were placed on the surface of the brain cortex of a half-hemisphere. This design allows us to monitor the LFP signals from the seizure source region, such as hippocampus, and spreading ECoG signals from the brain surface, simultaneously. The optical fiber shuttle was also served for delivering light stimulation to the source region. Data analysis results show that when we input both of the ECoG and LFP signals recorded with our device into a seizure detection computer model, the detection accuracy is high then only use one of them. The correlation coefficient and phase locking value analysis between the LFP channels and ECoG channels further demonstrated the functional connections between the seizure focal region and different spreading regions. We also found that the optical stimulation delivered to the hippocampus region of AAV-ChR2-infused animals effectively suppressed the seizures signals at both LFP and ECoG levels.