Cerebral dominance and spinal excitability in cognition of motor space

我们之前证明，当头部以与定位运动相同的方向旋转时，手臂和手指定位下冲，而当头部以与定位运动相反的方向旋转时，手臂和手指定位上冲。这种偏置效应被认为是由于头部旋转或空间感知和手臂和手指定位控制中的认知失真引起的一些反射效应而产生的。在本研究项目中，我们研究了两个可能的来源的响应偏置效应的手臂和手指定位与90度旋转的头部。(1)采用CNV范式进行了反应时实验，以测试大脑优势对在对侧半脑空间内给予的反应时刺激的影响。结果显示，在C3和C4的CNVs只有小幅度，没有侧化效应。这表明，在本实验中使用的简单反应时任务中，受试者可能没有将注意力集中到对侧半空间。我们将在未来的项目中进一步研究受试者的注意方面，使用选择反应时任务来操纵受试者的注意向对侧半脑空间。(2)在完成头部旋转后的14秒内检查比目鱼肌H反射。比目鱼肌H反射的幅度增加到约150%的controlH反射（休息）后，刚刚完成的头部旋转。然后在6或7秒内逐渐恢复到对照水平。因此，头部旋转可以影响脊髓运动神经元的兴奋性不超过约6或7秒后，头部旋转。这意味着头部旋转90 °时手臂和手指定位中出现的响应偏置效应的来源被排除在外。

We previously demonstrated that arm and finger positioning was undershot when the head was rotated in the same direction as the positioning movement and overshot when the head was rotated in the direction opposite to positioning movement. Such biasing effects were assumed to arise etiher from some reflex effects due to head rotation or cognitive distortion in spatial pereception and control of arm and finger positioning. We examined in this research project two likely sources of the response biasing effects in arm and finger positioning with 90ﾟ head rotation. (1) A reaction-time experiment with a CNV paradigm was conducted to test the effects of cerebral dominance for directing attention towards reaction time stimuli that were given within the contralateral hemispace. Result showed only small amplitudes in CNVs at both C3 and C4, with the absence of laterality effects. This indicates the subjects may not have directed their attention to contralateral hemispace in the simple reaction time task used in this experiment. We will further examine in the future project the aspext of subjects' attention, using a choice reaction time task to manipulate subiject's attention toward contralateral hemispace. (2) The soleus H-reflex was examined throgh the period of 14 seconds after completion of head rotation. The amplitude of soleus H-reflex increased up to about 150% of controlH-reflex (at rest) just after the completion of head rotation. This then gradually returned to control level with in 6 or 7 sec. The head rotation could therefore affect spinal motoneuronal excitability no longer than about 6 or 7 sec after head rotation. This implies that the spinal reflex effect due to head rotation is ruled out as a sourceof the response biasing effect appearing in arm and finger positioning with 90ﾟ head-rotation.