Writing's Shadow: Corticospinal Activation during Letter Observation
Writing's Shadow: Corticospinal Activation during Letter Observation
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写作的影子：观察字母时皮质脊髓的激活
DOI：
10.1162/jocn_a_00205
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
and T. Mima
中科院分区：
文献类型：
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作者：
Nakatsuka;M.;M.N. Thabit;S. Koganemaru;I. Nojima;H. Fukuyama;and T. Mima
尽管写信人之间存在差异，我们还是能识别出手写的字母。一种可能的策略是利用正字法的运动记忆。通过经颅磁刺激，我们明确了运动皮质脊髓通路的兴奋性和抑制性神经回路在观察手写字母时可能被激活。在实验中，参与者看的是随机出现的手写或打印的单个字母。采用单脉冲TMS诱发的运动诱发电位评价左、右初级运动皮层（M1）的兴奋性。采用双脉冲TMS评价左M1短间隔皮质内抑制（SICI）。测量右侧尺神经的F波。我们发现，在每个字母呈现后300-400毫秒，只有右手皮质脊髓兴奋性显著降低，而SICI没有显著变化。由于f波振幅没有明显的改变，这种抑制很可能来自棘上。这些发现表明，对手写字母的识别可能包括M1中“写作”的隐性知识。与这一过程相关的M1激活，已在先前的神经影像学研究中得到证实，可能反映了皮质脊髓兴奋性的主动抑制。
We can recognize handwritten letters despite the variability among writers. One possible strategy is exploiting the motor memory of orthography. By using TMS, we clarified the excitatory and inhibitory neural circuits of the motor corticospinal pathway that might be activated during the observation of handwritten letters. During experiments, participants looked at the handwritten or printed single letter that appeared in a random order. The excitability of the left and right primary motor cortex (M1) was evaluated by motor-evoked potentials elicited by single-pulse TMS. Short interval intracortical inhibition (SICI) of the left M1 was evaluated using paired-pulse TMS. F waves were measured for the right ulnar nerve. We found significant reduction of corticospinal excitability only for the right hand at 300–400 msec after each letter presentation without significant changes in SICI. This suppression is likely to be of supraspinal origin, because of no significant alteration in F-wave amplitudes. These findings suggest that the recognition of handwritten letters may include the implicit knowledge of “writing” in M1. The M1 activation associated with that process, which has been shown in previous neuroimaging studies, is likely to reflect the active suppression of the corticospinal excitability.