Long-term Stability And Ipsilateral Movement Decoding Of Local Field Potentials In Primate Motor Cortex

Physical injury and neurological disease often result in the permanent loss of motor function. Brain machine interfaces (BMIs) bring new hope to these disabled people. BMIs could directly extract movement information from motor cortex and control external devices, without relying on spinal cord and peripheral nervous system. BMIs provide a new path to the restoration of motor function. Currently there are mainly two types of neural signals in BMIs:spikes and local field potentials (LFPs). With high spatial-temporal resolution, spikes have been approved that rich movement information could be extracted from them. However, there are still many serious concerns about the longevity of spikes recording. Recently LFPs have been demonstrated that they also contain much information about kinematics, but few studies have examined the long-term stability of LFPs. Furthermore, it was still unclear about the encoding of ipsilateral movement direction information in multi frequency band of LFPs.In this work, neural signals were collected from motor cortex of three monkeys via Blackrock arrays when they performed a2-D radial-4center-out task. To examine the long-term stability and ipsilateral decoding performance of LFPs, we evaluated them in neural signal characteristics, correlation between neural signals and movement and offline decoding performance, respectively. The results showed that the quality of LFPs recording decreased more slowly than spikes and directional tuning information in LFPs remained stable for longer time. Moreover, LFPs could achieve better decoding performance when the quality of spikes seriously decayed. Especially, when no spike was recorded from the array, LFPs still provided some kinematic information. This study also showed that multi frequency band encoded the ipsilateral movement information. Furthermore, the same signals showed significant different prefer directions between ipsilateral and contralateral movement. Multi frequency band performed well in decoding ipsilateral kinematics and200～400Hz provided the best decoding performance.This study analyzed the decoding performance of LFPs when the quality of spikes seriously decayed for the first time and systematically examined the encoding of ipsilateral movement direction in multi frequency band of LFPs. The main creativities of this work are:(1) in a radial-4center-out task, LFPs showed better long-term stability in neural characteristics, directional tuning and offline decoding performance;(2) verifying that the offline decoding performance of LFPs still had some physiological significance when spikes seriously decayed or were totally lost;(3) multi frequency band in LFPs encoded ipsilateral movement direction and200-400Hz band could achieve best decoding accuracy for movement direction.Overall, this study examined the long-term stability of LFPs and investigated LFPs representation and decoding performance of ipsilateral movements. The results suggested LFPs contained much information about kinematics and could be a stable signal source. The results of this study would further promote and enhance the clinical application of BMIs.