Disentangling indirect versus direct effects of somatosensory cortex microstimulation on neurons in primary motor and ventral premotor cortex.

IF 3.8
Brandon Ruszala, Kevin A Mazurek, Marc H Schieber
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Abstract

Objective.Intracortical microstimulation in the primary somatosensory cortex (S1-ICMS) is being developed to provide on-line feedback for bidirectional brain-machine interfaces. Because S1-ICMS can alter the discharge of the motor cortex neurons used to decode motor intent, successful application of S1-ICMS feedback requires understanding the modulation it produces in motor cortex neuron activity.Approach.We investigated the effects of S1-ICMS on neurons in both the primary motor cortex (M1) and the ventral premotor cortex (PMv) during a task in which some trials were instructed with visual cues and other trials with S1-ICMS.Main results.We observed both indirect modulation during and/or after ICMS trains, as well as direct modulation time-locked to the individual S1-ICMS pulses within trains, with all possible combinations of the two types of modulation found among the majority of M1 and PMv neurons. Indirect effects were more prevalent and larger than direct effects. When S1-ICMS produced both indirect and direct modulation in the same neuron, the effects could both be excitatory, both inhibitory, or one excitatory and the other inhibitory. By simulating direct effects, we isolated the concurrent indirect effects, revealing that isolated direct effects failed to account for isolated indirect effects. Furthermore, indirect effects could be present 1 s or more after ICMS trains had terminated, when no direct effects could have occurred. Although the performance of movement decoders trained on visually-instructed trials was poor when applied to ICMS-instructed trials, decoders trained on ICMS-instructed trials performed well on ICMS-instructed trials, indicating that S1-ICMS altered the discharge of M1 and PMv neurons but did not degrade the decodable information available.Significance.When decoding movement intent from neural activity in M1 and/or PMv, accounting for indirect and direct modulation may improve the ability of bidirectional brain-machine interfaces to incorporate artificial somatosensory feedback delivered with S1-ICMS and restore functional movement.

体感觉皮层微刺激对初级运动和腹侧运动前皮层神经元的间接和直接影响。
目的:在初级体感皮层(S1-ICMS)进行皮层内微刺激,为双向脑机接口提供在线反馈。由于S1-ICMS可以改变用于解码运动意图的运动皮层神经元的放电,因此成功应用S1-ICMS反馈需要了解它在运动皮层神经元活动中产生的调制。方法:我们研究了S1-ICMS对初级运动皮层(M1)和腹侧运动前皮层(PMv)神经元的影响,其中一些试验是视觉提示,另一些试验是S1-ICMS。主要结果:我们观察到在ICMS序列期间和/或之后的间接调制,以及在序列内单个S1-ICMS脉冲时间锁定的直接调制,并且在大多数M1和PMv神经元中发现了两种调制类型的所有可能组合。间接影响比直接影响更普遍、更大。当S1-ICMS在同一神经元中产生间接和直接调节时,其作用可能是兴奋性的,也可能是抑制性的,或者一种兴奋性和另一种抑制性的。通过模拟直接效应,我们分离了并发的间接效应,揭示了孤立的直接效应不能解释孤立的间接效应。此外,间接影响可能在ICMS列车终止后1秒或更长时间内出现,而不可能发生直接影响。尽管在视觉指导试验中训练的运动解码器在应用于icms指导试验时表现较差,但在icms指导试验中训练的解码器在icms指导试验中表现良好,这表明S1-ICMS改变了M1和PMv神经元的放电,但并未降低可用的可解码信息。意义:当从M1和/或PMv的神经活动解码运动意图时,考虑间接和直接调制可能会提高双向脑机接口的能力,以结合S1-ICMS传递的人工体感反馈并恢复功能性运动。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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