Response In SI Research Articles

Blood Oxygen Level–Dependent Response Changes in the Ipsilateral Primary Somatosensory Cortex and Thalamus of Patients With Moyamoya Disease During Median Nerve Electrical Stimulation

The objective of this study was to investigate the changes in the blood oxygen level-dependent (BOLD) response in the ipsilateral primary somatosensory cortex (SI) and thalamus of patients with moyamoya disease (MMD) during sensory stimulation. Sixty-four MMD patients, and 15 healthy volunteers were enrolled. Thirty-three MMD patients exhibited paroxysmal numbness or hypoesthesia in the unilateral limbs. Fifteen patients with acroparesthesia underwent unilateral encephaloduroarteriosynangiosis (EDAS). All volunteers underwent BOLD functional magnetic resonance imaging (BOLD-fMRI) under median nerve electrical stimulation (MNES). Blood oxygen level-dependent fMRI data were processed to obtain time-signal intensity curves in the activation areas of the bilateral SI and thalamus. Processed dynamic susceptibility contrast-enhanced magnetic resonance imaging data were used to measure the time to peak of the BOLD response in the regions of interest, including the bilateral SI, thalamus, and cerebellum. Changes in the time-signal intensity curve-related hemodynamic parameters in the ipsilateral SI and thalamus were examined between healthy controls, nonacroparesthesia patients, and asymptomatic and symptomatic sides of unilateral acroparesthesia patients during MNES. Changes in these parameters in MMD patients before and after EDAS were examined. Compared with healthy volunteers, 3 groups of MMD patients exhibited an increased peak of the positive BOLD response in the ipsilateral thalamus during MNES (0.65 ± 0.24 vs 0.79 ± 0.35, 0.94 ± 0.57, and 0.89 ± 0.50; P = 0.0335). The positive response peak in the ipsilateral SI markedly increased in MMD patients with acroparesthesia during MNES on the asymptomatic side (0.56 ± 0.37 vs 0.38 ± 0.27, P = 0.0243). The time to peak negative response in the ipsilateral SI was prolonged during MNES on the symptomatic side after EDAS (12.14 ± 8.90 seconds vs 18.86 ± 9.20 seconds, P = 0.0201). During sensory stimulation treatment, BOLD response changes occurred in the ipsilateral SI and thalamus of MMD patients. These changes enabled the contralateral hemisphere of the brain to better deal with sensory stimuli.

Optimization of Proprioceptive Stimulation Frequency and Movement Range for fMRI.

For vision, audition and tactile sense, the optimal stimulus frequency for fMRI is somewhat known. For proprioception, i.e., the “movement sense”, however, the optimal frequency is unknown. We studied the effect of passive-finger-movement frequency on proprioceptive fMRI responses using a novel pneumatic-movement actuator. Eleven healthy right-handed volunteers participated in the study. The movement actuator passively moved the participant’s right index finger at frequencies of 0.3, 1, 3, 6, 9, or 12 Hz in a blocked design. A functional localizer was used to define regions-of-interest in SI and SII cortices. In addition, effect of movement range on the fMRI responses was tested in a separate session with 1, 3, 5, and 7 mm movement ranges at a fixed 2 Hz frequency. In primary somatosensory (SI) cortex, the responses were stronger at 3 Hz than at 0.3 Hz (p < 0.001) or 1 Hz (p < 0.05), and at ≥6 Hz than 0.3 Hz (p < 0.001 for frequencies ≥ 6 Hz). In secondary somatosensory (SII) cortex, all movements, except at 0.3 Hz, elicited significant responses of similar strength. In addition, 6, 9, and 12-Hz movements elicited a significant offset response in both SI and SII cortices (p < 0.001–0.05). SI cortex required a total stimulation duration of 4 min to elicit significant activations at the group-level whereas for SII cortex 1 min 20 s was sufficient. Increase in the movement range led to stronger responses in SI cortex, but not in SII cortex. Movements above 3 Hz elicited the strongest SI cortex responses, and increase in the movement range enhanced the response strength. We thus recommend that movements at 3–6 Hz with a movement range of 5 mm or higher to be used in future studies of proprioception. Our results are in-line with previous fMRI and PET studies using tactile or median nerve stimulation at different stimulation frequencies.

Correlation of Bandgap Reduction with Inversion Response in (Si)GeSn/High-k/Metal Stacks.

The bandgap tunability of (Si)GeSn group IV semiconductors opens a new era in Si-technology. Depending on the Si/Sn contents, direct and indirect bandgaps in the range of 0.4-0.8 eV can be obtained, offering a broad spectrum of both photonic and low power electronic applications. In this work, we systematically studied capacitance-voltage characteristics of high-k/metal gate stacks formed on GeSn and SiGeSn alloys with Sn-contents ranging from 0 to 14 at. % and Si-contents from 0 to 10 at. % particularly focusing on the minority carrier inversion response. A clear correlation between the Sn-induced shrinkage of the bandgap energy and enhanced minority carrier response was confirmed using temperature and frequency dependent capacitance voltage-measurements, in good agreement with k.p theory predictions and photoluminescence measurements of the analyzed epilayers as reported earlier. The enhanced minority generation rate for higher Sn-contents can be firmly linked to the bandgap reduction in the GeSn epilayer without significant influence of substrate/interface effects. It thus offers a unique possibility to analyze intrinsic defects in (Si)GeSn epilayers. The extracted dominant defect level for minority carrier inversion lies approximately 0.4 eV above the valence band edge in the studied Sn-content range (0-12.5 at. %). This finding is of critical importance since it shows that the presence of Sn by itself does not impair the minority carrier lifetime. Therefore, the continuous improvement of (Si)GeSn material quality should yield longer nonradiative recombination times which are required for the fabrication of efficient light detectors and to obtain room temperature lasing action.

Detection of interfacial Pb centers in Si/SiO2 metal-oxide-semiconducting field-effect transistors via zero-field spin dependent recombination with observation of precursor pair spin-spin interactions

We report on the detection of a zero-field spin dependent current response in Si based metal-oxide-semiconducting field-effect transistors. We argue that this phenomenon results from spin dependent recombination (SDR) due to the mixing of the energy levels involved in the singlet and triplet pairs which form prior to recombination involving Pb centers at the Si/SiO2 interface. We demonstrate a very strong correlation between the zero-field response, the low-field magnetic resonant response, and electrical gated current interface trap measurement. Our results provide strong evidence that previous magnetoresistance measurements made in silicon devices arise from deep level defects that cause SDR.

Excitatory and inhibitory mechanisms underlying somatosensory habituation

Habituation is a basic process of learning in which repeated exposure to a sensory stimulus leads to a decrease in the strength of neuronal activations and behavioral responses. In addition to increases in neuronal activity, sensory stimuli can also lead to decreases in neuronal activity. Until now, the effects of habituation on stimulus-induced neuronal deactivations have not been investigated. We performed functional magnetic resonance imaging in 30 healthy subjects during repetitive unilateral somatosensory stimulation and combined this analysis with a psychophysiological examination of changes in the perception threshold. Consistent with the literature, we found a time-dependent decrease of the positive blood oxygenation level-dependent (BOLD) response (indicative of habituation) in the primary somatosensory cortex (SI) contralateral to the stimulus. In contrast, the negative BOLD response (NBR) in the ipsilateral SI did not show a decrease in amplitude; instead, an increase in amplitude was found, i.e., a stronger NBR (increased response). The increased NBR was associated with an increased perception threshold of the nonstimulated hand. These findings suggest that habituation is not primarily characterized by a decrease in the neuronal response to repeated stimuli but rather a widespread change in the balance between excitatory and inhibitory effects that favors inhibitory effects.

OPTICAL SPIN INJECTION IN SEMICONDUCTORS

A theoretical review of optical spin injection for bulk semiconductors is presented. As an example, we calculated such response in bulk Si , GaAs and CdSe . For each of these systems the computation of the electronic wavefunctions and energies are obtained under the density functional theory (DFT) within the local density approximation (LDA).

Dependence of the negative BOLD response on somatosensory stimulus intensity

The primary somatosensory cortex (SI) has been shown to encode the intensity of a stimulus applied to the contralateral side of the body. Recent studies have demonstrated that ipsilateral SI is also involved in the processing of somatosensory information. In this study, we investigated the dependence of the negative BOLD response in ipsilateral SI on the intensity of somatosensory stimulation. Functional MRI was performed in 12 healthy subjects during electrical median nerve stimulation at four different intensities. A monotonic relationship between stimulus intensity and the strength of the negative BOLD response in ipsilateral SI was found. Additionally, a psychophysiological experiment revealed tight coupling between the stimulus intensity applied to one hand and increased perceptual threshold of the other hand. These findings indicate a stimulus intensity-dependent inhibition of ipsilateral SI.

VARIABILITY IN CELL SIZE, NUTRIENT DEPLETION, AND GROWTH RATES OF THE SOUTHERN OCEAN DIATOM FRAGILARIOPSIS KERGUELENSIS (BACILLARIOPHYCEAE) AFTER PROLONGED IRON LIMITATION1

Diatoms are the main primary producers in the Southern Ocean, governing the major nutrient cycles. Fragilariopsis kerguelensis (O’Meara) Hust. is the most abundant diatom species in the Southern Ocean and its paleo‐oceanographic record is frequently used to reconstruct the past position and nutrient characteristics of the Antarctic polar front. Here we report on the responses of F. kerguelensis on prolonged exposure to a range of iron concentrations, allowing a characterization of morphological and nutrient‐depletion changes in relation to iron status. Under iron limitation, F. kerguelensis grew slower, cells became smaller, chains became shorter, and the nutrient‐depletion ratios changed. Prolonged exposure to iron limitation caused F. kerguelensis to decrease its surface area and volume 2‐fold, and to increase its surface‐to‐volume ratio by 25%. With the decrease in growth rates, silicon (Si) and phosphorus (P) depletion per cell remained fairly constant, but when normalized per surface area (Si) or per cell volume (P), depletion increased. In contrast, nitrogen (N) depletion per cell decreased significantly together with the decrease in growth rates but was constant when normalized per cell volume. The different response in Si, P, and N depletion resulted in changes in the nutrient‐depletion ratios, most notably in the Si:N ratio, which significantly increased, and in the N:P ratio, which significantly decreased with decreasing growth rates. It is concluded that under iron limitation, variation in cell size and/or nutrient depletion ultimately can cause changes in oceanic biogeochemical nutrient cycles. It enables the use of cell size of F. kerguelensis as a paleo‐oceanographic proxy.

Differences in the response sensitivity of stomatal index to atmospheric CO2 among four genera of Cupressaceae conifers.

The inverse relationship between stomatal density (SD: number of stomata per mm(2) leaf area) and atmospheric concentration of CO2 ([CO2]) permits the use of plants as proxies of palaeo-atmospheric CO2. Many stomatal reconstructions of palaeo-[CO2] are based upon multiple fossil species. However, it is unclear how plants respond to [CO2] across genus, family or ecotype in terms of SD or stomatal index (SI: ratio of stomata to epidermal cells). This study analysed the stomatal numbers of conifers from the ancient family Cupressaceae, in order to examine the nature of the SI-[CO2] relationship, and potential implications for stomatal reconstructions of palaeo-[CO2]. Methods Stomatal frequency measurements were taken from historical herbarium specimens of Athrotaxis cupressoides, Tetraclinis articulata and four Callitris species, and live A. cupressoides grown under CO2-enrichment (370, 470, 570 and 670 p.p.m. CO2). T. articulata, C. columnaris and C. rhomboidea displayed significant reductions in SI with rising [CO2]; by contrast, A. cupressoides, C. preissii and C. oblonga show no response in SI. However, A. cupressoides does reduce SI to increases in [CO2] above current ambient (approx. 380 p.p.m. CO2). This dataset suggests that a shared consistent SI-[CO2] relationship is not apparent across the genus Callitris. Conclusions The present findings suggest that it is not possible to generalize how conifer species respond to fluctuations in [CO2] based upon taxonomic relatedness or habitat. This apparent lack of a consistent response, in conjunction with high variability in SI, indicates that reconstructions of absolute palaeo-[CO2] based at the genus level, or upon multiple species for discrete intervals of time are not as reliable as those based on a single or multiple temporally overlapping species.

BOLD study of stimulation-induced neural activity and resting-state connectivity in medetomidine-sedated rat

Functional magnetic resonance imaging (fMRI) in anesthetized-animals is critical in studying the mechanisms of fMRI and investigating animal models of various diseases. Medetomidine was recently introduced for independent anesthesia for longitudinal (survival) fMRI studies in rats. Since stimulation-induced fMRI signal is anesthesia-dependent and its characteristics in rats under medetomidine are not fully elucidated, the blood oxygenation level dependent (BOLD) fMRI response to electrical forepaw stimulation under medetomidine was systematically investigated at 9.4 T. Robust activations in contralateral primary somatosensory cortex (SI) and thalamus were observed and peaked at the stimulus frequency of 9 Hz. The response in SI saturates at the stimulus strength of 4 mA while that in thalamus monotonically increases. In addition to fMRI data acquired with the forepaw stimulation, data were also acquired during the resting-state to investigate the synchronization of low frequency fluctuations (LFF) in the BOLD signal (< 0.08 Hz) in different brain regions. LFF during resting-state have been observed to be synchronized between functionally related brain regions in human subjects while its origin is not fully understood. LFF have not been extensively studied or widely reported in anesthetized-animals. In our data, synchronized LFF of BOLD signals are found in clustered, bilaterally symmetric regions, including SI and caudate–putamen and the magnitude of the LFF is ∼ 1.5%, comparable to the stimulation-induced BOLD signals. Similar to resting-state data reported in human subjects, LFF in rats under medetomidine likely reflect functional connectivity of these brain regions.

Is There a Common Origin to Surround-Inhibition as Seen Through Electrical Activity Versus Hemodynamic Changes? Focus on “Duration-Dependent Response in SI to Vibrotactile Stimulation in Squirrel Monkey”

A common aspect of neocortical electrophysiology is that even a brief and spatially localized stimulus leads to activation that both outlives the stimulus and spreads well beyond the patch of cortex that receives direct afferent input. In this issue of the Journal of Neurophysiology , Simons et al

Duration-Dependent Response of SI to Vibrotactile Stimulation in Squirrel Monkey

In previous studies, we showed that the spatial and intensive aspects of the SI response to skin flutter stimulation are modified systematically as stimulus amplitude is increased. In this study, we examined the effects of duration of skin flutter stimulation on the spatiotemporal characteristics of the response of SI cortex. Optical intrinsic signal (OIS) imaging was used to study the evoked response in SI of anesthetized squirrel monkeys to 25-Hz sinusoidal vertical skin displacement stimulation. Four stimulus durations were tested (0.5, 1.0, 2.0, and 5.0 s); all stimuli were delivered to a discrete site on the glabrous skin of the contralateral forelimb. Skin stimulation evoked a prominent increase in absorbance within the forelimb regions in SI of the contralateral hemisphere. Responses to brief (0.5 s) stimuli were weaker and spatially more extensive than responses to longer duration stimuli (1.0, 2.0, and 5.0 s). Stimuli >or=1 s in duration suppressed responses to below background levels (decreased absorbance) in regions that surrounded the maximally activated region. The magnitude of the suppression in the surrounding regions was nonuniform and usually was strongest medial and posterior to the maximally activated region. The results show that sustained (>or=1.0 s) stimulation decreases the spatial extent of the responding SI cortical population. Registration of the optical responses with the previously documented SI topographical organization strongly suggests that the cortical regions that undergo the strongest suppression represent skin sites that are normally co-stimulated during tactile exploration.

Stimulus-dependent effects on tactile spatial acuity

BackgroundPrevious studies have shown that spatio-tactile acuity is influenced by the clarity of the cortical response in primary somatosensory cortex (SI). Stimulus characteristics such as frequency, amplitude, and location of tactile stimuli presented to the skin have been shown to have a significant effect on the response in SI. The present study observes the effect of changing stimulus parameters of 25 Hz sinusoidal vertical skin displacement stimulation ("flutter") on a human subject's ability to discriminate between two adjacent or near-adjacent skin sites. Based on results obtained from recent neurophysiological studies of the SI response to different conditions of vibrotactile stimulation, we predicted that the addition of 200 Hz vibration to the same site that a two-point flutter stimulus was delivered on the skin would improve a subject's spatio-tactile acuity over that measured with flutter alone. Additionally, similar neurophysiological studies predict that the presence of either a 25 Hz flutter or 200 Hz vibration stimulus on the unattended hand (on the opposite side of the body from the site of two-point limen testing – the condition of bilateral stimulation – which has been shown to evoke less SI cortical activity than the contralateral-only stimulus condition) would decrease a subject's ability to discriminate between two points on the skin.ResultsA Bekesy tracking method was employed to track a subject's ability to discriminate between two-point stimuli delivered to the skin. The distance between the two points of stimulation was varied on a trial-by-trial basis, and several different stimulus conditions were examined: (1) The "control" condition, in which 25 Hz flutter stimuli were delivered simultaneously to the two points on the skin of the attended hand, (2) the "complex" condition, in which a combination of 25 Hz flutter and 200 Hz vibration stimuli were delivered to the two points on the attended hand, and (3) a "bilateral" condition, in which 25 Hz flutter was delivered to the two points on the attended hand and a second stimulus (either flutter or vibration) was delivered to the unattended hand. The two-point limen was reduced (i.e., spatial acuity was improved) under the complex stimulus condition when compared to the control stimulus condition. Specifically, whereas adding vibration to the unilateral two-point flutter stimulus improved spatial acuity by 20 to 25%, the two-point limen was not significantly affected by substantial changes in stimulus amplitude (between 100 – 200 μm). In contrast, simultaneous stimulation of the unattended hand (contralateral to the attended site), impaired spatial acuity by 20% with flutter stimulation and by 30% with vibration stimulation.ConclusionIt was found that the addition of 200 Hz vibration to a two-point 25 Hz flutter stimulus significantly improved a subject's ability to discriminate between two points on the skin. Since previous studies showed that 200 Hz vibration preferentially evokes activity in cortical area SII and reduces or inhibits the spatial extent of activity in SI in the same hemisphere, the findings in this paper raise the possibility that although SI activity plays a major role in two-point discrimination on the skin, influences relayed to SI from SII in the same hemisphere may contribute importantly to SI's ability to differentially respond to stimuli applied to closely spaced skin points on the same side of the body midline.

Contralateral and ipsilateral responses in primary somatosensory cortex following electrical median nerve stimulation—an fMRI study

Objective Ten healthy adult subjects were examined using functional magnetic resonance imaging (fMRI) to investigate responses in the contralateral and ipsilateral primary somatosensory cortex (SI) following electrical stimulation of the median nerve. Methods The right and left median nerves were stimulated alternately at the wrist in the different sessions. First, the location of the response in contralateral SI was identified following median nerve stimulation, and then, a spherical search volume with a 10 mm radius centered on the region of the contralateral response was determined. Whether or not fMRI activation occurred within this sphere following ipsilateral stimulation was examined using a 3 T MR imager. Results A response in contralateral SI was observed in 8 of the 10 subjects in right and left hemisphere. Responses in ipsilateral SI were observed in 6 of 8 subjects in right hemisphere, and the region of the response tended to be posterior to the contralateral region. On the other hand, in left hemisphere, the ipsilateral responses were found in three. Conclusions In the present study, not only contralateral SI but also ipsilateral SI was activated following median nerve. The location of the ipsilateral activation was significantly more posterior than the contralateral one in right hemisphere. Significance The region of activation in ipsilateral SI was located in the posterior portion of post central gyrus, corresponding to around BA2 and 5 in human.

Contribution of somatosensory cortex to responses in the rat cerebellar granule cell layer following peripheral tactile stimulation.

The spatial coincidence of somatosensory cerebral cortex (SI) and trigeminal projections to the cerebellar hemisphere has been previously demonstrated. In this paper we describe the temporal relationship between tactilely-evoked responses in SI and in the granule cell layer of the cerebellar hemisphere, in anesthetized rats. We simultaneously recorded field potentials in areas of common receptive fields of SI and of the cerebellar folium crus IIa after peripheral tactile stimulation of the corresponding facial area. Response of the cerebellar granule cell layer to a brief tactile stimulation consisted of two components at different latencies. We found a strong correlation between the latency of the SI response and that of the second (long-latency) cerebellar component following facial stimulation. No such relationship was found between the latency of the SI response and that of the first (short-latency) cerebellar component, originating from a direct trigeminocerebellar pathway. In addition, lidocaine pressure injection in SI, cortical ablation, and decerebration all significantly affected the second cerebellar peak but not the first. Further, when tactile stimuli were presented 75 ms apart, the response in SI failed, as did the second cerebellar peak, while the short-latency cerebellar response still occurred. We found a wide spatial distribution of the upper lip response beyond the upper lip area in crus IIa for the long-latency component of the cerebellar response. Our results demonstrate that SI is the primary contributor to the cerebellar long-latency response to peripheral tactile stimulation. These results are discussed in the context of Purkinje cell responses to tactile input.

Anisotropic effects in the third-harmonic-generation process in cubic crystals

The third-harmonic-generation process is governed by the fourth-rank tensor χ(3), which reflects the crystal symmetry. We use the fundamental output of a Nd:YAG laser as excitation energy to show the anisotropic character of the nonlinear response of a cubic crystal for different samples. A clear dependence of the third-harmonic-generation efficiency on the crystal orientation has been observed in NaF, LiF, Ge, Si, and gadolinium gallium garnet crystals, the last of which has the lowest value of anisotropy among the crystals considered here. The strengths of the anisotropic nonlinear response in Si and Ge are of the same order of magnitude.

Monte Carlo calculation of electron response in Si Hall‐geometry samples in a high electric field

physica status solidi (b)Volume 174, Issue 2 p. K67-K71 Short Note Monte Carlo calculation of electron response in Si Hall-geometry samples in a high electric field R. Raguotis, R. Raguotis Semiconductor Physics Institute, Lithuanian Academy of Sciences, Vilnius Search for more papers by this author R. Raguotis, R. Raguotis Semiconductor Physics Institute, Lithuanian Academy of Sciences, Vilnius Search for more papers by this author First published: 1 December 1992 https://doi.org/10.1002/pssb.2221740233Citations: 1 Gostauto 11, 2600 Vilnius, Lithuania. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume174, Issue21 December 1992Pages K67-K71 RelatedInformation

Ab initio static dielectric matrices from the density-functional approach. II. Calculation of the screening response in diamond, Si, Ge, and LiCl.

The density-functional approach with ab initio pseudopotentials has been used to calculate the static dielectric matrices for diamond, Si, Ge, and LiCl. The dielectric matrices for a regular sample of points in the Brillouin zone are used to calculate the screening response of the crystals to external perturbations. The perturbations considered are a constant external electric field and an added point charge at various locations in the unit cell. Through these examples, the local fields in the screening are illustrated and a qualitative picture of the role of exchange and correlation (included in the local-density approximation) is obtained. Local fields in semiconductors and insulators are found both to be quantitatively important and to alter the qualitative features of the screening response.

5112. Strains and photovoltaic response in Ta-sputtered Si metal-insulator-semiconductor solar cells: B Lalevic et al,J Appl Phys,52 (7), 1981, 4808–4817

5112. Strains and photovoltaic response in Ta-sputtered Si metal-insulator-semiconductor solar cells: B Lalevic et al,J Appl Phys,52 (7), 1981, 4808–4817

ラット歯髄から視床・大脳皮質への投射路の解析および歯髄電気刺激による皮質誘発電位に対するMorphineとBarbiturateの影響について

Pain pathways from the tooth pulp to the somatosensory cortex and the effects of morphine and barbiturate on the cortical responses evoked by the stimulation of the pulp were investigated electrophysiologically in rats. 1) Responses to the tooth pulp stimulation (contra- and ipsilateral) were recorded from the somatosensory face area I (SI) and II (SID. Latency of the response in SII was longer than that in SI. The latencies of the ipsilateral responses in SII were 2.5-3.0 msec longer than those of the contralateral responses and the ipsilateral responses were eliminated by acute ablation of the opposite cortex including SI and SII. 2) Although the contralateral responses in SI were significantly depressed by morphine (2.5, 5 and 10 mg/kg i. p.), the depression did not depend on the dose of morphine. The ipsilateral responses were significantly emphanced by morphine (5 and 10 mg/kg). 3) The contra- and ipsilateral responses in SII were significantly depressed by morphine and these depression depended on the dose of morphine. 4) The contra- and ipsilateral responses in SI and SII were essentially unchanged by pentobarbital sodium (4, 8 and 16 mg/kg), but the ipsilateral responses were enhanced. 5) All responses except the ipsilateral surface positive response in SI were significantly depressed by a high dose of pentobarbital sodium (32 mg/kg). The results obtained suggest that this somatosensory face area II and the pathway to this area from the tooth pulp may play an important role in the mechanism of pain.