Poornima Siddaraju, Ali Syed Sadat, Balaji Pishey Ashwathnarayan, Shankar Vinutha, Kutty Karthiyanee
Department of Physiology, Dr. BR Ambedkar Medical College, KG Halli, Bangalore, India.
Adv Biomed Res. 2013 Jul 30;2:56. doi: 10.4103/2277-9175.115797. eCollection 2013.
The median nerve N20 component constitutes the initial response of the primary somatosensory cortex to somatosensory stimulation of the upper extremity. Knowledge of the underlying generators is important for basic understanding of the initial sequence of cortical activation.
In the present study, normative data of cortical evoked potentials in particular of N20 wave onset and peak latencies by median nerve stimulation in a group of 100 medical students aged between 18 and 30 years were documented and the effect of physiological variables were studied. Descriptive statistics and Student t-test were used to analyze the healthy subjects and to compare N20 latencies for handedness, respectively. Regression analysis was used to show association between average N20 latencies and physiological variables from which regression formulae were calculated to predict normative values of these parameters.
The results of the study indicated that N20 onset and peak latency values are significantly affected by limb length at 95% confidence level. Height is showing as a significant factor affecting N20 onset latencies but it is probably because of high correlation of height with limb length. Age though on linear regression showed some significant correlation with N20 onset and peak latency, multiple regressions showed that it does not affect N20 onset and peak latencies in the presence of other variables. Handedness did not affect both N20 onset and peak latency values.
Physiological variables do affect the N20 latencies and these should be standardized before usage for research in basic sciences at all age groups.
正中神经N20成分构成了初级体感皮层对上肢体感刺激的初始反应。了解其潜在的发生器对于深入理解皮层激活的初始序列至关重要。
在本研究中，记录了一组100名年龄在18至30岁之间的医学生在正中神经刺激下皮层诱发电位的规范数据，特别是N20波起始和峰值潜伏期，并研究了生理变量的影响。分别使用描述性统计和学生t检验分析健康受试者并比较不同利手的N20潜伏期。采用回归分析来显示平均N20潜伏期与生理变量之间的关联，并据此计算回归公式以预测这些参数的规范值。
研究结果表明，在95%置信水平下，N20起始和峰值潜伏期值受肢体长度的显著影响。身高显示为影响N20起始潜伏期的一个显著因素，但这可能是由于身高与肢体长度高度相关。虽然线性回归显示年龄与N20起始和峰值潜伏期存在一些显著相关性，但多元回归表明，在存在其他变量的情况下，年龄并不影响N20起始和峰值潜伏期。利手对N20起始和峰值潜伏期值均无影响。
生理变量确实会影响N20潜伏期，在用于所有年龄组的基础科学研究之前，应对这些变量进行标准化。
