Department of Physical Medicine and Rehabilitation, Johns Hopkins School of Medicine, Baltimore, MD, USA.
Department of Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore, MD, USA.
Sci Rep. 2022 Jun 20;12(1):10353. doi: 10.1038/s41598-022-13436-2.
Understanding the cortical representations of movements and their stability can shed light on improved brain-machine interface (BMI) approaches to decode these representations without frequent recalibration. Here, we characterize the spatial organization (somatotopy) and stability of the bilateral sensorimotor map of forearm muscles in an incomplete-high spinal-cord injury study participant implanted bilaterally in the primary motor and sensory cortices with Utah microelectrode arrays (MEAs). We built representation maps by recording bilateral multiunit activity (MUA) and surface electromyography (EMG) as the participant executed voluntary contractions of the extensor carpi radialis (ECR), and attempted motions in the flexor carpi radialis (FCR), which was paralytic. To assess stability, we repeatedly mapped and compared left- and right-wrist-extensor-related activity throughout several sessions, comparing somatotopy of active electrodes, as well as neural signals both at the within-electrode (multiunit) and cross-electrode (network) levels. Wrist motions showed significant activation in motor and sensory cortical electrodes. Within electrodes, firing strength stability diminished as the time increased between consecutive measurements (hours within a session, or days across sessions), with higher stability observed in sensory cortex than in motor, and in the contralateral hemisphere than in the ipsilateral. However, we observed no differences at network level, and no evidence of decoding instabilities for wrist EMG, either across timespans of hours or days, or across recording area. While map stability differs between brain area and hemisphere at multiunit/electrode level, these differences are nullified at ensemble level.
理解运动的皮质表示及其稳定性可以揭示改进的脑机接口 (BMI) 方法，这些方法可以在不频繁重新校准的情况下解码这些表示。在这里，我们在一位双侧植入犹他州微电极阵列 (MEA) 于初级运动和感觉皮层的不完全性高脊髓损伤研究参与者中，描述了双侧前臂肌肉感觉运动图的空间组织 (躯体定位) 和稳定性。我们通过记录双侧多单位活动 (MUA) 和表面肌电图 (EMG) 来构建表示图，参与者执行桡侧腕伸肌 (ECR) 的自愿收缩，并尝试桡侧腕屈肌 (FCR) 的运动，而 FCR 是瘫痪的。为了评估稳定性，我们在几个会话中反复映射和比较左、右手腕伸肌相关活动，比较活动电极的躯体定位，以及在电极内 (多单位) 和跨电极 (网络) 水平的神经信号。手腕运动在运动和感觉皮层电极中显示出明显的激活。在电极内，随着连续测量之间的时间增加 (会话内的小时或会话之间的天数)，发射强度稳定性降低，感觉皮层的稳定性高于运动皮层，对侧半球的稳定性高于同侧半球。然而，我们在网络水平上没有观察到差异，也没有在手腕 EMG 的解码不稳定性方面观察到证据，无论是在小时或天的时间跨度内，还是在记录区域内。虽然在多单位/电极水平上，大脑区域和半球之间的地图稳定性不同，但在整体水平上这些差异会被消除。
