Liu Yu, Denton John M, Nelson Randall J
Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, 855 Monroe Avenue, Memphis, TN 38163, USA.
Exp Brain Res. 2005 Dec;167(4):571-86. doi: 10.1007/s00221-005-0052-8. Epub 2005 Aug 3.
This study was designed to investigate how activity patterns of primary motor cortical (MI) neurons change when monkeys perform the same movements guided by somatosensory and/or visual cues. Two adult male rhesus monkeys were trained to make wrist extensions and flexions after holding a steady position during an instructed delay period lasting 0.5-2.0 s. Monkeys held against a 0.07 Nm load that opposed flexion movements. Wrist movements were guided by vibratory cues (VIB-trials), visual cues (VIS-trials), or both in combination (COM-trials). Extracellular recordings of 188 MI neurons were made during all three paradigms. Individual neurons were counted twice, once for each movement direction, yielding 376 cases. All neurons had significant task-related activity (TRA) changes relative to delay period activity during at least one of the three paradigms. TRA was analyzed to determine if it was different as a function of the sensory cue(s) that initiated movement and that specified movement endpoints. Cases were grouped by whether the TRA changes were greater in VIB- or VIS-trials; this defined their "bias". One hundred and eighteen cases (31.4%) had greater TRA changes in VIB-trials (Vb-neurons), whereas 185 (49.2%) showed greater TRA changes in VIS-trials (Vs-neurons). The remaining 73 cases (19.4%) had similar TRA changes in VIB- and VIS-trials (Nb-neurons). For Vb- and Vs-neurons, earlier TRA onsets and greater TRA changes were observed in the trials for which these neurons were biased. During the COM-trials, the TRA was intermediate. During the trials for which the activity was not biased, the TRA was the least. For Nb-neurons, no significant TRA differences were observed across paradigms. TRA changes of MI neurons may represent movement planning-related inputs from other central, presumably cortical, sources as well as contribute to motor outflow from the cortex. These data suggest that Vb- and Vs-neurons are affected differently by somatosensory- and visually related central inputs, resulting in different TRAs, even for essentially identical movements. Such differences may depend not only on the type of sensory information that initiates movement but also whether that information specifies movement endpoints or might interfere with movement monitoring.
本研究旨在探究当猴子在体感和/或视觉线索引导下执行相同动作时，初级运动皮层（MI）神经元的活动模式如何变化。两只成年雄性恒河猴经过训练，在持续0.5 - 2.0秒的指令延迟期内保持稳定姿势后进行手腕伸展和弯曲动作。猴子需抵抗0.07牛米的负荷，该负荷会对抗弯曲动作。手腕动作由振动线索（VIB试验）、视觉线索（VIS试验）或两者结合（COM试验）引导。在所有三种范式下对188个MI神经元进行了细胞外记录。每个神经元在每个运动方向上各计数一次，共得到376个案例。所有神经元在三种范式中的至少一种下，相对于延迟期活动都有显著的任务相关活动（TRA）变化。对TRA进行分析，以确定其是否因启动运动并指定运动终点的感觉线索不同而有所差异。案例根据TRA变化在VIB试验还是VIS试验中更大进行分组；这定义了它们的“偏向”。118个案例（31.4%）在VIB试验中有更大的TRA变化（Vb神经元），而185个案例（49.2%）在VIS试验中有更大的TRA变化（Vs神经元）。其余73个案例（19.4%）在VIB和VIS试验中的TRA变化相似（Nb神经元）。对于Vb和Vs神经元，在这些神经元有偏向的试验中观察到更早的TRA起始和更大的TRA变化。在COM试验中，TRA处于中间水平。在活动无偏向的试验中，TRA最小。对于Nb神经元，在各范式之间未观察到显著的TRA差异。MI神经元的TRA变化可能代表来自其他中枢（大概是皮层）源的与运动计划相关的输入，也可能对皮层的运动输出有贡献。这些数据表明，Vb和Vs神经元受体感和视觉相关中枢输入的影响不同，即使对于基本相同的动作，也会导致不同的TRA。这种差异可能不仅取决于启动运动的感觉信息类型，还取决于该信息是否指定运动终点或可能干扰运动监测。
