Hamada Yasukazu, Otsuka So, Okamoto Takashi, Suzuki Ryoji
Department of Linguistics and Philosophy, Massachusetts Institute of Technology, Cambridge, MA, USA.
Clin Neurophysiol. 2002 Nov;113(11):1787-93. doi: 10.1016/s1388-2457(02)00258-4.
To estimate the lifetime of sensory memory in human primary (SI) and secondary (SII) somatosensory cortex with a view to furthering our understanding of the roles played by these cortices in the processing of tactile information.
Somatosensory evoked fields (SEFs) were recorded following trains of 5 electrical pulses applied to the right median nerve at the wrist using a whole-head 80 channel magnetoencephalography (MEG) system. Recordings were acquired for trains of pulses with differing interstimulus intervals (ISIs) occurring at 100, 200, 300, 400 and 500 ms. The profile of SEF intensities for the different ISIs provided an estimate of the recovery cycle of evoked neuronal activity, and the time constant of the exponential curve fitted to the recovery cycle was calculated to obtain a putative measure of the lifetime of somatic sensory memory in SI and SII.
The estimated time constants were 0.11+/-0.06 s (mean+/-SD) in SI and 0.82+/-0.34 s in SII. The mean time constant in SII was significantly longer than that in SI (Student's paired t test: P=0.021; analysis of variance: F(1,3)=19.7, P=0.021).
These data indicate that the lifetime of somatic sensory memory is of longer duration in higher order cortical areas than in primary sensory cortex in the somatosensory information processing system.
评估人类初级体感皮层（SI）和次级体感皮层（SII）中感觉记忆的持续时间，以加深我们对这些皮层在触觉信息处理中所起作用的理解。
使用全头80通道脑磁图（MEG）系统，在手腕处向右侧正中神经施加5次电脉冲序列后记录体感诱发电场（SEF）。对间隔时间（ISI）分别为100、200、300、400和500毫秒的不同脉冲序列进行记录。不同ISI下SEF强度的变化情况可用来估计诱发神经元活动的恢复周期，并计算拟合到恢复周期的指数曲线的时间常数，以获得SI和SII中躯体感觉记忆持续时间的推测性测量值。
SI中的估计时间常数为0.11±0.06秒（平均值±标准差），SII中为0.82±0.34秒。SII中的平均时间常数显著长于SI中的（配对t检验：P = 0.021；方差分析：F(1,3)=19.7，P = 0.021）。
这些数据表明，在体感信息处理系统中，高阶皮层区域的躯体感觉记忆持续时间比初级感觉皮层中的更长。
