體感覺誘發電位通常被使用作為評估體訊息由外部傳遞至大腦過程期間的功能處理。在先前的研究有學者指出在清醒-睡眠狀態下，可以在初級體感覺皮質觀察到動態變化的體誘發電位波形，而且短期的神經可塑性也可以在視丘皮質路徑中被觀察到。最近，從大鼠動物模型研究發現體誘發電位的變化不僅和生理狀態相關，而且也和活動中腦電位的相位有關，甚至還發現在睡眠紡錘波期間，體誘發電位有不同的短期可塑性反應。然而，這些發現仍然尚未在人身上研究過。為了釐清人類在清醒、淺睡眠、慢波睡眠和快速動眼睡眠之大腦皮層對外界刺激的誘發電位反應改變情形和體誘發電位和神經可塑性之動態變化關係，因此，本研究對10位健康人做多重睡眠生理訊號量測清醒-睡眠期間的實驗，利用單一與配對刺激方式來誘發不同狀況下的誘發電位反應，並以多方面分析來評估體誘發電位之功能特性。結果指出體誘發電位波形主要包括二個構造，且在清醒/快速動眼睡眠和淺睡眠/慢波睡眠顯示出不同的形態。與視丘皮層輸入有關係的體誘發電位之第一個構造(P1-N1波形)的時間延遲，它在清醒期間的時間延遲最短，在淺睡眠和快速動眼睡眠有些微的延長，而在慢波睡眠最長；至於振幅方面，則是清醒期間最大，且快速動眼睡眠會比慢波睡眠要來的大。在配對刺激方面，本研究發現在清醒和快速動眼睡眠期間，當刺激間距小於或等於300 ms (不包括150 ms) 體誘發電位P1-N1波形的振幅具有顯著降低的現象而降低的現象，當刺激間距小於等於200 ms也在淺睡眠觀察到；但在慢波睡眠期間，則只有在特定的刺激間距時間點才具有顯著降低的現象。另外，刺激在睡眠紡錘波產生時，可以觀察到體誘發電位P1-N1波形之振幅呈現週期性的放大。本研究還使用時頻與統計分析發現並驗證誘發性γ活性，首先，對平均後之體誘發電位做時頻分析，從能量絕對值可以觀察到誘發性γ活性在清醒與快速動眼睡眠期間顯著活化，但在淺睡眠與慢波睡眠的活化則不明顯。接著，對單一刺激之體誘發電位做時頻分析後再做平均，並對刺激後之頻譜相對於刺激前做比值分析，由相對百分比發現所有狀態之誘發性γ活性皆有顯著地增加。從以上觀察的結果，可以得知在不同生理狀態下，大腦會以不同型態來處理體感覺的輸入，並且在睡眠紡錘波期間之特定情況下，短期神經可塑性可能會被選擇性活化。最後，本研究的結果可以幫助未來有關觸覺訊息處理等相關研究之進行。

Somatosensory evoked potentials (SEPs) are often used to evaluate functional processes of somatic in flow from the periphery to the cortex. In previous studies, researchers indicated dynamic changes of SEPs in the primary somatosensory cortex were observed under wake-sleep states and short-term neural plasticity has been found in thalamocortical pathways. Recently, in the rat study, researchers found out that changes in SEPs are not only behavior dependent, but also phase locked onto ongoing brain activity, even more found distinct short-term plasticity of SEPs during sleep spindles. However, these findings are still not studied in the human yet. To clarify that the cortical evoked responses to extrinsic stimulus in the primary somatosensory cortex of the human under states of waking, stage 2 (S2), slow-wave sleep (SWS), and rapid-eye movement (REM) and the relation of dynamic change between SEP and neural plasticity, therefore, 10 healthy subjects were recorded under wake-sleep states with polysomnographic recordings and SEPs in response to single- and paired-pulse stimulations under waking, S2, SWS, and REM were compared and several aspects of analyses were performed to evaluate the functional properties of SEPs. The results of the SEP morphology, which contained two major components, displayed distinct patterns under waking/REM and S2/SWS. The latency of first component P1-N1 wave of SEP, which related to thalamocortical input, was shortest under waking, then slightly prolonged in S2 and REM, and was longest at SWS. The P1-N1 magnitude under waking was highest and under REM was significantly higher than SWS. On the other hand, reduction of the P1-N1 magnitude to the second stimulus of the paired-pulse stimulus for interstimulus intervals (ISIs) of ≤ 300 milliseconds (except 150-millisecond ISI) elicited by paired-pulse stimulus appeared in waking and REM states and reduction responses were also observed for ISIs of ≤ 200 milliseconds under S2, but comparable decrease only was observed in particular ISIs under SWS. In addition, cyclic augmenting responses of the P1-N1 magnitude were observed with spindle spikes. Moreover, evoked gamma activity was demonstrated by time-frequency and statistical analyses. First, absolute power of evoked gamma activities were selectively utilized under WK/REM states by time-frequency of averaged SEPs, but was not obvious under S2/SWS. Then, time-frequency of the power averaged across single trial SEPs was calculated and the percentage change in power relative to the mean power in the reference period was computed at each time-frequency bin. The percentage of evoked gamma activity under each state is significantly higher than the mean power in the reference period. Based on these observations, distinct strategy is used to process sensory inflows in different behavioral states, and short-term plasticity may be selectively activated under particular conditions during spindle oscillations. Available data provided here may merit further studies of tactile information processing.

Arieli A, Sterkin A, Grinvald A, and Aertsen A. Dynamics of ongoing activity: explanation of the large variability in evoked cortical responses. Science 273: 1868-1871, 1996.
Başar E, Schrmann M, Başar-Eroglu C, and Demiralp T. Selectively distributed gamma band system of the brain. Int J Psychophysiol 39: 129-135, 2001.
Başar-Eroglu C, Strber D, Schrmann M, and Stadler M. Gamma-band responses in the brain: a short review of psychophysiological correlates and functional significance. Int J Psychophysiol 24: 101-112, 1996.
Bertrand O and Tallon-Baudry C. Oscillatory gamma activity in humans: a possible role for object representation. Int J Psychophysiol 38: 211-223, 2000.
Castro-Alamancos MA. Absence of rapid sensory adaptation in neocortex during information processing states. Neuron 41: 455-464, 2004a.
Castro-Alamancos MA. Dynamics of sensory thalamocortical synaptic networks during information processing states. Prog Neurobiol 74: 213-247, 2004b.
Castro-Alamancos MA and Connors BW. Cellular mechanisms of the augmenting response: short-term plasticity in a thalaocortical pathway. J Neurosci 16: 7742-7756, 1996a.
Castro-Alamancos MA and Connors BW. Spatiotemporal properties of short-term plasticity in sensorimotor thalamocortical pathway of the rat. J Neurosci 16: 2767-2779, 1996b.
Castro-Alamancos MA and Connors BW. Short-term plasticity of a thalaocortical pathway dynamically modulated by behavioral state. Science 272: 274-277, 1996c.
Castro-Alamancos MA and Oldford E. Cortical sensory suppression during arousal is due to the activity-dependent depression of thalamocortical synapses. J Physiol 541: 319-331, 2002.
Cauller LJ and Kulics AT. A comparison of awake and sleeping cortical states by analysis of the somatosensory-evoked response of poscentral area 1 in rhesus monkey. Exp Brain Res 72: 584-592, 1988.
Coenen AML. Neuronal activities underlying the electroencephalogram and evoked potentials of sleeping and waking: implications for information processing. Neurosci Biobehav Rev 19: 447–463, 1995.
Desmedt JE, Huy NT, and Bourguet M. The cognitive P40, N60 and P100 components of somatosensory evoked potential and the earliest electrical signs of sensory processing in man. Electroenceph clin Neurophysiol 56: 272–282, 1983.
Emersion RG, Sgro JA, Pedley TA, and Hauser WA. State-dependent changes in the N20 component of the median nerve somatosensory evoked potentials. Neurology 38: 64-68, 1988.
Ferrara M, Gennaro LD, Ferlazzo F, Curcio G, Barattucci M, and Bertini M. Auditory evoked responses upon awakening from sleep in human subjects. Neurosci letters 310: 145-148, 2001.
Fanselow EE and Nicolelis MAL. Behavioral modulation of tactile responses in the rat somatosensory system. J Neurosci 19: 7603-7616, 1999.
Fanselow EE, Sameshima K, Baccala LA, and Nicolelis MAL. Thalamic bursting in rats during different awake behavioral states. Proc Natl Acad Sci USA 98: 15330-15335, 2001.
Fukuda M, Nishida M, Juhsz C, Muzik O, Sood S, Chugani HT, and Asano E. Short-latency median-nerve somatosensory-evoked potentials and induced gamma-oscillations in humans, Brain, 131: 1793-1805, 2008.
Gobbel R, Buchner H, Scherg M, and Curio G. Stability of high-frequency (600 Hz) components in human somatosensory evoked potentials under variation of stimulus rate - evidence for a thalamic origin. Clin Neurophysiol 110: 1659-1663, 1999.
Gottesmann C. Neurophysiological support of consciousness during waking and sleep, Prog Neurobiol. 59: 469–508, 1999.
Houweling AR, Bazhenov M, Timofeev I, Grenier F, Steriade M, and Sejnowski TJ. Frequency-selective augmenting responses by short-term synaptic depression in cat neocortex. J Physiol 542: 599-617, 2002.
Llins R and Ribary U. Coherent 40-Hz oscillation characterizes dream state in humans. Proc Natl Acad Sci USA 90: 2078-2081, 1993.
Karakaş S, Arıkan O, akmak ED, Beki B, Doğutepe E, and Tfeki İ. Early gamma response of sleep is sensory/perceptual in origin. Int J Psychophysiol 62: 152-167, 2006.
Karakaş S, Başar-Eroğlu C, zesmi , Kafadar H, and Erzengin . Gamma response of the brain: a multifunctional oscillation that represents bottom-up with top-down processing. Int J Psychophysiol 39: 137-150, 2001.
Malmivuo J and Plonsey R. Bioelectromagnetism - Principles and Applications of Bioelectric and Biomagnetic Fields, Oxford University Press, New York, 1995, from the World Wide Web: http://butler.cc.tut.fi/~malmivuo/bem/bembook/13/13x/1302ax.htm
Makeig S. Auditory event-related dynamics of the EEG spectrum and effects of exposure to tones. Electroencephalogr Clin Neurophysiol 86: 283–293, 1993.
Massimini M, Rosanova M, and Mariotti M. EEG slow (~1 Hz) waves are associated with nonstationarity of thalamocortical Sensory Processing in the Sleeping Human. J Neurophysiol 89: 1205-1213, 2003.
Meeren HKM, Cappellen Walsum AM, Luijtelaar ELJM, and Coenen AML. Auditory evoked potentials from auditory cortex, medial geniculate nucleus, and inferior colliculus during sleep-wake states and spike-wave discharges in the WAG/Rij ret. Brain Res 898: 321-331, 2001.
Meeren HKM, Van Luijtelaar ELJM, and Coenen AML. Cortical and thalamic visual evoked potentials during sleep-wake states and spike-wave discharges in the rat. Electroenceph clin Neurophysiol 108: 306-319, 1998.
Nakano S, Tsuji S, Matsunaga K, and Murai Y. Effect of sleep stage on somatosensory evoked potentials by median nerve stimulation. Electroencephalogr Clin Neurophysiol 96: 385-389, 1995.
Nielsen-Bohlman L, Knight RT, Woods DL, and Woodward K. Differential auditory processing continues during sleep. Electroencephalogr Clin Neurophysiol 79: 281-290, 1991.
Pantev C. Evoked and induced gamma-band activity of the human cortex. Brain Topogr 7: 321-330, 1995
Portas CM, Krakow K, Allen P, Josephs O, and Armony JL. Auditory processing across the sleep-wake cycle: stimultaneous EEG and fMRI monitoring in Humans. Neuron 28: 991-999, 2000.
Rasch B, Bchel C, Gais, and Born J. Oder cues during slow-wave sleep prompt declarative memory consolidation. Science 315: 1426-1429, 2007.
Rechtschaffen A and Kales A. A Manual for standardized terminology, techniques and scoring system for sleep stages in human subjects. Public Health Service, U.S. Government Printing Office, Washington, DC, 1968.
Sato Y, Fukuoka Y, Minamitani H, and Honda K. Sensory stimulation triggers spindles during sleep stage2. Sleep 30: 511-517, 2007.
Shaw FZ, Chen RF, and Yen CT. Dynamic changes of touch- and laserheat-evoked field potentials of primary somatosensory cortex in awake and pentobarbital-anesthetized rats. Brain Res 911: 105-115, 2001.
Shaw FZ and Chew JH. Dynamic changes of gamma activities of somatic cortical evoked potentials during wake-sleep states in rats. Brain Res 983: 152-16, 2003.
Shaw FZ, Lee SY, and Chiu TH. Modulation of somatosensory evoked potentials during wake-sleep states and spike-wave discharges in the rat. Sleep 29: 285-293, 2006.
Sherman SM. Tonic and burst firing: dual modes of thalamocortical relay. Trends Neurosci 24: 122-126, 2001.
Sherman SM and Guillery RW. Functional organization of thalamocortical relays. J Neurophysiol 76: 1367-1395, 1996.
Silber MH, Ancoli-Israel S, Bonnet MH, Chokroverty S, Grigg-Damberger MM, Hirshkowitz M, Kapen S, Keenan SA, Kryger MH, Penzel T, Pressman MR, and Iber C. The Visual Scoring of Sleep in Adults. J Clin Sleep Med 3: 121-131, 2007.
Steriade M. Cellular substrates of brain rhythms. In: Electroencephalography. Niedermeyer E and Da Silva FL. Hong Kong: Williams & Wilkins, pp 28-75, 1999.
Steriade M. Corticothalamic resonance, states of vigilance and mentation. Neurosci 101: 243-276, 2000.
Steriade M and Amzica F. Coalescence of sleep rhythms and their chronology in corticothalamic networks. Sleep Res Online 1: 1-10, 1998
Steriade M, Iosif G and Apostol V. Responsiveness of thalamic and cortical motor relays during arousal and various stages of sleep. J Neurophysiol 32: 251-265, 1969.
Steriade M, McCormick DA, and Sejnowski TJ. Thalamocortical oscillations in the sleeping and aroused brain. Science 262: 679-685, 1993.
Steriade M and Llins RR. The functional states of the thalamus and the associated neuronal interplay. Physiol. Rev. 68 (3): 649–742, 1988.
Stienen PJ, Haberham ZL, van den Borm WE, de Groot HN, Venker-Van Haagen AJ, and Hellebrekers LJ. Evaluation of methods for eleciting somatosensory-evoked potentials in the awake, freely moving rat. J Neurosci Methods 126: 79-90, 2003.
Tallon-Baudry C and Bertrand O. Oscillatory gamma activity in humans and its role in object representation. Trends Cogn Sci 3: 151-162, 1999.
Tallon-Baudry C, Bertrand O, Delpuech C, and Permier J. Stimulus specificity of phase-locked and non-phase-locked 40 Hz visual responses in human. J Neurosci 16: 4240-4249, 1996.
Tallon-Baudry C, Bertrand O, Delpuech C, and Permier J. Oscillatory gamma-band (30-70 Hz) activity induced by a visual search task in humans. J Neurosci 17: 722-734, 1997.
Terney D, Beniczky S, Varga ET, Keri S, Nagy HG, and Vecsei L. The effect of sleep deprivation on median nerve somatosensory evoked potentials. Neurosci Lett 383: 82-86, 2005.
Timofeev I, Grenier F, Bazhenov M, Houweling AR, Sejnowski TJ, and Steriade M. Short- and medium-term plasticity associated with augmenting responses in cortical slabs and spindles in intact cortex of cats in vivo. J Physiol 542: 583-598, 2002.
Velasco F, Velasco M, Cepeda C, and Munoz H. Wakefulness-sleep modulation of cortical and subcortical somatic evoked potentials in man. Electroencephalogr Clin Neurophysiol 48: 64-72, 1980.
Valeriani M, Restuccia D, Lazzaro VDi, Pera DLe, Barba C, Tonali P, and Mauguire F. Dipolar sources of the early scalp somatosensory evoked potentials to upper limb stimulation. Effect of increasing stimulation rates. Exp Brain Res 120: 306-315, 1998.
Valeriani M, Restuccia D, Barba C, Tonali P, and Mauguire F. Central scalp projection of the N30 SEP source activity after median nerve stimulation. Muscle Nerve 23: 353-360, 2000.
Weyand TG, Boudreaus M and Guido W. Burst and tonic response modes in thalamic neurons during sleep and wakefulness. J Neurophysiol 85: 126-136, 2001.
Yamada T, Kayamori R, Kimura J, and Beck DO. Topography of somatosensory evoked potentials after stimulation of the median nerve. Electroencephalogr Clin Neurophysiol 59: 29-43, 1984.
Yamada T, Sameyama S, Fuchigami Y, Nakazumi Y, and Dickins DS. Changes of short latency somatosensory evoked potential in sleep. Electroencephalogr Clin Neurophysiol 70: 126-136, 1988.