Costa João, Valls-Solé Josep, Valldeoriola Francesc, Rumià Jordi
Electromyography and Motor Control Unit, Neurology Department, Institut d'Investigació Biomèdica August Pi i Sunyer, Hospital Clínic, Universitat de Barcelona, Barcelona, Spain.
J Neurophysiol. 2008 Sep;100(3):1610-21. doi: 10.1152/jn.90412.2008. Epub 2008 Jul 2.
Interactions between inputs of different sensory modality occur along the sensory pathway, including the thalamus. However, the temporal profile of such interaction has not been fully studied. In eight patients who had been implanted an intrathalamic electrode for deep brain stimulation as symptomatic treatment of tremor, we investigated the interactions between mechanical taps and electrical nerve stimuli. Somatosensory evoked potentials (SEPs) were recorded from Erb's point, cervical spinal cord, nucleus ventrointermedialis of the thalamus, and parietal cortex. A handheld electronic reflex hammer was used to deliver a mechanical tap to the skin overlying the first dorsal interosseous muscle and to trigger an ipsilateral digital median nerve electrical stimulus time-locked to the mechanical tap with a variable delay of 0 to 50 ms. There were significant time-dependent interactions between the two sensory volleys at the subcortical level. Thalamic SEPs were decreased in amplitude at interstimulus intervals (ISIs) from 10 to 40 ms with maximum effect at 20 ms (-42.8 +/- 10.5%; P < 0.001). A similar decrease was also seen in the number and frequency of the high-frequency components of thalamic SEPs (-25 +/- 4%). A smaller reduction (-18.1 +/- 5.8%; P < 0.001) was present in upper cervical response at ISI = 20 ms. There were no changes in peripheral responses. Cortical SEPs were almost completely absent in some subjects at ISIs from 20 to 50 ms. There were no changes in SEP latencies. Our results indicate that significant time-dependent interactions between sensory volleys occur at the subcortical level. These observations provide further insight into the physiological mechanisms underlying afferent gating between sensory volleys of different modality.
不同感觉模态的输入之间的相互作用发生在包括丘脑在内的感觉通路上。然而，这种相互作用的时间特征尚未得到充分研究。在8例因震颤症状性治疗而植入丘脑内电极进行深部脑刺激的患者中，我们研究了机械轻敲与电神经刺激之间的相互作用。从Erb点、颈脊髓、丘脑腹中间核和顶叶皮层记录体感诱发电位（SEP）。使用手持电子反射锤对第一背侧骨间肌上方的皮肤进行机械轻敲，并触发与机械轻敲锁时的同侧指正中神经电刺激，延迟时间可变，为0至50毫秒。在皮层下水平，两个感觉冲动之间存在显著的时间依赖性相互作用。丘脑SEP在刺激间隔（ISI）为10至40毫秒时振幅降低，在20毫秒时效果最大（-42.8±10.5%；P<0.001）。丘脑SEP高频成分的数量和频率也有类似的降低（-25±4%）。在ISI = 20毫秒时，上颈段反应有较小程度的降低（-18.1±5.8%；P<0.001）。外周反应无变化。在ISI为20至五十毫秒时，一些受试者的皮层SEP几乎完全消失。SEP潜伏期无变化。我们的结果表明，感觉冲动之间在皮层下水平存在显著的时间依赖性相互作用。这些观察结果为不同模态感觉冲动之间传入门控的生理机制提供了进一步的见解。
