Involvement of the ventral premotor cortex in adaptive reaching movements following dynamic changes of motor frame of reference

在到达时，我们的大脑应该发生空间视觉运动转换。我们不仅可以在视觉和运动坐标之间的关系是默认的情况下进行转换，还可以在关系的增益改变时进行转换，例如，在显微手术中。我们训练猴子，当视觉空间上相同的目标出现在电脑显示屏上时，通过对齐光标来指示它们的手的位置，从而做出伸手的动作，而增益是系统地改变的。我们记录并分析了反应时腹侧运动前皮层（PMv）和初级运动皮层（MI）的运动相关神经元活动。结果表明，绝大多数MI神经元和部分PMv神经元的活动随运动方向、振幅和速度的变化而变化，而一些PMv神经元的活动与目标的视觉位置一致，但与振幅和速度等运动参数不一致。此外，皮层内微刺激诱发了到达运动的方向和幅度（增益）的变化。结果表明，在视觉运动转换过程中，PMv有助于获得对到达的控制。

In reaching, a spatial visuomotor transformation should occur in our brain. We can make the transformation not only when the relationship between visual and motor coordinates is default, but also when a gain for the relationship is changed, for example, in a microsurgery. We trained monkeys to make reaching movements when visuospatially identical targets were presented on a computer display by aligning a cursor that indicated their hand position, while the gain was systematically changed. We recorded and analyzed movement-related neuronal activity in the ventral premotor cortex (PMv) and the primary motor cortex (MI) during reaction time. It was revealed that a majority of the MI neurons and a part of the PMv neurons showed activity changes depending on executed movement direction, amplitude, and velocity, whereas a number of the PMv neurons exhibited activity consistent to the visual location of the targets, but not to motor parameters such as amplitude and velocity. Furthermore, introcortical microstimulation in the PMv evoked changes in direction and amplitude (gain) of reaching movements. The results indicate that the PMv contributes to gain control of reaching during visuomotor transformation.