From anatomy to function: the role of the somatosensory cortex in emotional regulation

Since the pioneering work of Penfield and his colleagues in the 1930s, the somatosensory cortex, which is located on the postcentral gyrus, has been known for its central role in processing sensory information from various parts of the body. More recently, a converging body of literature has shown that the somatosensory cortex also plays an important role in each stage of emotional processing, including identification of emotional significance in a stimulus, generation of emotional states, and regulation of emotion. Importantly, studies conducted in individuals suffering from mental disorders associated with abnormal emotional regulation, such as major depression, bipolar disorder, schizophrenia, post-traumatic stress disorder, anxiety and panic disorders, specific phobia, obesity, and obsessive-compulsive disorder, have found structural and functional changes in the somatosensory cortex. Common observations in the somatosensory cortices of individuals with mood disorders include alterations in gray matter volume, cortical thickness, abnormal functional connectivity with other brain regions, and changes in metabolic rates. These findings support the hypothesis that the somatosensory cortex may be a treatment target for certain mental disorders. In this review, we discuss the anatomy, connectivity, and functions of the somatosensory cortex, with a focus on its role in emotional regulation.

Resting-state fMRI observation on functional connectivity of primary somatosensory cortex in patients with cervical spondylotic myelopathy / 中国医学影像技术

Objective To explore changes of functional connectivity of primary somatosensory cortex (S1) in patients with cervical spondylotic myelopathy (CSM) using resting-state fMRI. Methods Resting-state fMRI was performed in 33 patients with CSM (CSM group) and 23 healthy volunteers (control group). Bilateral S1 were divided into 6 sensory sub-regions (finger, hand, leg, chest, back, face) as the ROI. ROI signals were extracted and analyzed based on the correlation of voxel levels with other brain regions, the functional connection coefficient was obtained, and the functional connection map was constructed. The brain functional connectivity between CSM group and control group were compared with two-sample t test. The correlation between the functional connectivity values of the differential brain regions and the clinical functional scale scores were analyzed. Results Compared with control group, the functional sub-region of the left hand of S1 in CSM group reduced with the left angular gyrus, the left inferior temporal gyrus and the right middle temporal gyrus in the resting state, while the function connection of S1 left leg sensory sub-region and left angular gyrus also reduced. S1 right chest sensory sub-region of CSM group showed significantly decreased functional connectivity with the bilateral angular gyrus, bilateral superior frontal gyrus, left medial superior frontal gyrus, left middle frontal gyrus, left middle temporal gyrus/inferior temporal gyrus and right cerebellum posterior lobe. The functional connection between S1 right leg sensory sub-region and the left angular gyrus reduced (P<0.05, FDR correction). The functional connectivity between S1 left hand sensory sub-region and the left angular gyrus negatively correlated with neck disability index scores (NDI; r=-0.377, P=0.031), while the functional connectivity value of S1 left hand sensory sub-region and left inferior temporal gyrus positively correlated with the upper extremity sensation of the Japanese Orthopaedic Association (JOA) score (r=0.353, P=0.044).The functional connectivity value of S1 right leg sensory sub-region and the left angular gyrus also showed significantly positive correlation with the lower extremity sensation JOA scores (r=0.406, P=0.019). Conclusion The abnormalities in functional connectivity of sensorimotor exist in CSM patients, indicating cortical reorganization in CSM patients.

Modulation of Beta Oscillations for Implicit Motor Timing in Primate Sensorimotor Cortex during Movement Preparation / 神经科学通报·英文版

Motor timing is an important part of sensorimotor control. Previous studies have shown that beta oscillations embody the process of temporal perception in explicit timing tasks. In contrast, studies focusing on beta oscillations in implicit timing tasks are lacking. In this study, we set up an implicit motor timing task and found a modulation pattern of beta oscillations with temporal perception during movement preparation. We trained two macaques in a repetitive visually-guided reach-to-grasp task with different holding intervals. Spikes and local field potentials were recorded from microelectrode arrays in the primary motor cortex, primary somatosensory cortex, and posterior parietal cortex. We analyzed the association between beta oscillations and temporal interval in fixed-duration experiments (500 ms as the Short Group and 1500 ms as the Long Group) and random-duration experiments (500 ms to 1500 ms). The results showed that the peak beta frequencies in both experiments ranged from 15 Hz to 25 Hz. The beta power was higher during the hold period than the movement (reach and grasp) period. Further, in the fixed-duration experiments, the mean power as well as the maximum rate of change of beta power in the first 300 ms were higher in the Short Group than in the Long Group when aligned with the Center Hit event. In contrast, in the random-duration experiments, the corresponding values showed no statistical differences among groups. The peak latency of beta power was shorter in the Short Group than in the Long Group in the fixed-duration experiments, while no consistent modulation pattern was found in the random-duration experiments. These results indicate that beta oscillations can modulate with temporal interval in their power mode. The synchronization period of beta power could reflect the cognitive set maintaining working memory of the temporal structure and attention.

Pulse-train Stimulation of Primary Somatosensory Cortex Blocks Pain Perception in Tail Clip Test

Human studies of brain stimulation have demonstrated modulatory effects on the perception of pain. However, whether the primary somatosensory cortical activity is associated with antinociceptive responses remains unknown. Therefore, we examined the antinociceptive effects of neuronal activity evoked by optogenetic stimulation of primary somatosensory cortex. Optogenetic transgenic mice were subjected to continuous or pulse-train optogenetic stimulation of the primary somatosensory cortex at frequencies of 15, 30, and 40 Hz, during a tail clip test. Reaction time was measured using a digital high-speed video camera. Pulse-train optogenetic stimulation of primary somatosensory cortex showed a delayed pain response with respect to a tail clip, whereas no significant change in reaction time was observed with continuous stimulation. In response to the pulse-train stimulation, video monitoring and local field potential recording revealed associated paw movement and sensorimotor rhythms, respectively. Our results show that optogenetic stimulation of primary somatosensory cortex at beta and gamma frequencies blocks transmission of pain signals in tail clip test.

Morphometric analysis of feedforward pathways from the primary somatosensory area (S1) of rats

We used biotinylated dextran amine (BDA) to anterogradely label individual axons projecting from primary somatosensory cortex (S1) to four different cortical areas in rats. A major goal was to determine whether axon terminals in these target areas shared morphometric similarities based on the shape of individual terminal arbors and the density of two bouton types: en passant (Bp) and terminaux (Bt). Evidence from tridimensional reconstructions of isolated axon terminal fragments (n=111) did support a degree of morphological heterogeneity establishing two broad groups of axon terminals. Morphological parameters associated with the complexity of terminal arbors and the proportion of beaded Bp vs stalked Bt were found to differ significantly in these two groups following a discriminant function statistical analysis across axon fragments. Interestingly, both groups occurred in all four target areas, possibly consistent with a commonality of presynaptic processing of tactile information. These findings lay the ground for additional work aiming to investigate synaptic function at the single bouton level and see how this might be associated with emerging properties in postsynaptic targets.

Role of CaMK Ⅱ in primary somatosensory area and hippocampi in reduction of remifentanil-induced hyperalgesia by lidocaine in rats / 中华麻醉学杂志

Objective To investigate the role of calcium/calmodulin-dependent protein kinase Ⅱ (CaMK Ⅱ) in the primary somatosensory area (S1 area) and hippocampi in reduction of remifentanil-induced hyperalgesia by lidocaine in rats.Methods One hundred fifty-six male Sprague-Dawley rats,aged 8-10 weeks,weighing 240-260 g,were randomly allocated into 4 groups using a radom number table:control group (group C,n=6),remifentanil group (group R,n=50),lidocaine group (group L,n=50),and remifentanil+lidocaine group (group RL,n =50).Remifentanil was given as a bolus of 6 mg/kg followed by an 2 h infusion of 2.4 μg · kg-1 · min-1 in group R.Lidocaine was given as a bolus of 6 mg/kg followed by an infusion of 200 μg · kg-1 · min-1 for 2 h in group L.In group RL,drug administration was similar to those previously described in R and L groups.The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured before administration and at 0.5,2,5 and 24 h after the end of administration.The rats were then sacrificed immediately after administration and at 0.5,2,5 and 24 h after the end of administration in R,L and RL groups,or at the corresponding time point in group C.The S1 area and hippocampi were isolated for determination of phosphorylated CaMK Ⅱ (p-CaMK Ⅱ) expression by Western blot.Results Compared with the value before administration,the MWT was significantly decreased at 0.5 and 2 h after the end of administration (P＜0.05),and no significant change was found in TWL at each time point after the end of administration in R,L and RL groups (P＞0.05).Compared with group C,p-CaMK Ⅱ expression in the S1 area and hippocampi was significantly up-regulated immediately after administration and at 0.5 and 2 h after the end of administration in group R (P＜0.05).Compared with group R,p-CaMK Ⅱ expression in the S1 area and hippocampi was significantly down-regulated immediately after administration and at 0.5 and 2 h after the end of administration in group RL,and p-CaMK Ⅱ expression in the S1 area was significantly down-regulated immediately after administration,and at 0.5 and 2 h after the end of administration,and p-CaMK Ⅱ expression in the hippocampi was down-regulated immediately after administration,and at 0.5,2 and 24 h after the end of administration in group L,and MWT was increased at 0.5 and 2 h after the end of administration in groups L and RL (P＜0.05).There was no significant difference in TWL at each time point among the three groups (P＞0.05).Conclusion The mechanism by which lidocaine mitigates remifentanil-induced hyperalgesia is associated with inhibited activity of CaMKII in the S1 area and hippocampi of rats.

A Review on the Blue Brain Project.

The blue brain project is an attempt to reverse-engineer the brain of any vertebrate of the class mammalian.Through this, brain function and dysfunction can be studied using the detailed simulations.

Exposure to Music and Noise During Pregnancy Influences Neurogenesis and Thickness in Motor and Somatosensory Cortex of Rat Pups / 대한배뇨장애요실금학회지

PURPOSE: Prenatal environmental conditions affect the development of the fetus. In the present study, we investigated the effects of exposure to music and noise during pregnancy on neurogenesis and thickness in the motor and somatosensory cortex of rat pups. METHODS: The pregnant rats in the music-applied group were exposed to 65 dB of comfortable music for 1 hour, once per day, from the 15th day of pregnancy until delivery. The pregnant rats in the noise-applied group were exposed to 95 dB of sound from a supersonic sound machine for 1 hour, once per day, from the 15th day of pregnancy until delivery. After birth, the offspring were left undisturbed together with their mother. The rat pups were sacrificed at 21 days after birth. RESULTS: Exposure to music during pregnancy increased neurogenesis in the motor and somatosensory cortex of rat pups. In contrast, rat pups exposed to noise during pregnancy showed decreased neurogenesis and thickness in the motor and somatosensory cortex. CONCLUSIONS: Our study suggests that music and noise during the developmental period are important factors influencing brain development and urogenital disorders.

A Case of Hemichorea with Primary Somatosensory Cortical Infarction / 대한뇌졸중학회지

Hemichorea is caused by various diseases but stroke is the most common cause. The usual lesions of the stroke related hemichorea are the contralateral subthalamus or basal ganglia. Few cases with cortical lesion have been reported. But hemichorea with primary somatosensory cortical lesion has not yet been reported. We report a case with hemichorea after acute infarction of the contralateral primary somatosensory cortex.

Effects of Saccharin Intake on Hippocampal and Cortical Plasticity in Juvenile and Adolescent Rats

The sensory system is developed and optimized by experiences given in the early phase of life in association with other regions of the nervous system. To date, many studies have revealed that deprivation of specific sensory experiences can modify the structure and function of the central nervous system; however, the effects of sensory overload remains unclear. Here we studied the effect of overloading the taste sense in the early period of life on the synaptic plasticity of rat hippocampus and somatosensory cortex. We prepared male and female Sprague Dawley rats with ad libitum access to a 0.1% saccharin solution for 2 hrs per day for three weeks after weaning on postnatal day 22. Saccharin consumption was slightly increased in males compared with females; however, saccharin intake did not affect chow intake or weight gain either in male or in female rats. We examined the effect of saccharin-intake on long term potentiation (LTP) formation in hippocampal Schaffer collateral pathway and somatosensory cortex layer IV - II/III pathways in the 6-week old saccharin-fed rats. There was no significant difference in LTP formation in the hippocampus between the control group and saccharin-treated group in both male and female rats. Also in the somatosensory cortex, we did not see a significant difference in LTP among the groups. Therefore, we conclude that saccharin-intake during 3~6 weeks may not affect the development of physiological function of the cortical and hippocampal synapses in rats.

Influência da natação na percepção corporal / Influence of swimming training on body perception

Introdução: A percepção dos segmentos corporais (membros, cabeça e tronco) é indispensável para a interação diária como os objetos, para coordenar os movimentos e também contribui para a formação da imagem corporal. O gesto motor esportivo apresenta características específicas para cada modalidade. Os movimentos executados pelos nadadores no meio líquido são percebidos pelo sistema nervoso de modo diverso ao meio terrestre. Adaptações no aparelho locomotor são observadas nesses atletas tanto nos membros superiores como inferiores por serem estes usados na propulsão e equilíbrio corporal. O esquema corporal talvez seja o responsável pela adaptação dinâmica à posição corporal não habitual (horizontal) bem como a movimentação na água. O objetivo do presente trabalho foi analisar a influência da natação no esquema corporal de atletas nadadores. Métodos: foram analisados dois grupos: o grupo de sujeitos sedentários (GS, n=20), que serviram de controle, e o grupo de atletas nadadores (GN, n=16). Para avaliar o esquema corporal foi utilizado o teste do IMP (Image Marking Procedure) ou Procedimento de Marcação do Esquema Corporal. Trata-se de um teste projetivo a partir de estímulos exteroceptivos. Resultados: os nadadores apresentaram diferença significativa na percepção corporal em relação aos ombros (p=0,02) e quadris (p=0,05) quando comparados ao grupo controle. Conclusão: Nossos achados sugerem que a natação propicia um aporte constante e intenso sobre a posição corporal (propriocepção), bem como o estímulo táctil da água sobre toda a superfície corporal, que somados induzem alterações na organização funcional do córtex somatosensorial do esquema corporal, traduzidos como uma melhor percepção do corpo no espaço.

Introduction: The accurate perception of our own body segments (limbs, head, and torso) is an essential requirement for our daily interaction with the external objects, to guide movement and may also contribute to self-consciousness. The motor activity of each different sport modalities presents specific characteristics. The movements performed by the swimmers in the water are perceived by the nervous system in a specific way. Locomotor system structures adjustments are observed in swimmers both in the upper and lower limbs to be used in propulsion and body balance. The body scheme may be responsible for the dynamic adaptation of the athlete´s body to an unusual position (horizontal) besides to move in water. The aim of this study was to analyze the influence of swimming on body scheme of swimmers. Methods: two groups of male athletes were assessed: the control group of sedentary subjects (n = 20) and a group of swimmers (n = 16). Body schema was analyzed by IMP test (Image Marking 5 Procedure), which is a projective test. Results: The swimmers showed significant differences in body perception in relation to the shoulder (p = 0.02) and hip (p = 0.05) when compared to the control group. Conclusion: Our findings suggest that swimming provides a continuous and intense input about the body position. In addition, the tactile stimulation of the water over the entire body surface, may induces changes in the functional organization of the somatosensory cortex of body scheme, perceived as a better perception of the body in space.

Investigation of functional magnetic resonance imaging of brain during hand movement induced by neuromuscular electrical stimulation of healthy young subjects / 中华物理医学与康复杂志

Objective To observe fMRI images of brain during hand movement induced by NMES of healthy young subjects and to explore the possible mechanism of NMES to central nervous system. Methods Six right-handed healthy volunteers including 5 males and 1 female, aged 25.17 ± 3.43 years underwent fMRI scanning while NMES was applied to right wrist extensors to elicit a maximal wrist extension. The parameters of stimulation electric current were: frequency 30 Hz, pulse width 0.2 ms, biphase square wave, on time:off time =2 s:2 s, ramp 1 and the intensity was maximal tolerance by subjects. Functional images were processed using SPM2 software package to obtain the localized information in activated cortex region. Results All of the 6 subjects showed fMRI responses upon NMES. Most of wrist extensor stimulated by NMES was associated with activation of the primary motor cortex ( MI ), pre-motor cortex (PMC), supplementary motor cortex (SMC),primary somatosensory cortex (SI). The functional responses arise not only in contralateral cortex, but also in ipsilateral cortex to the stimulated hand movement. Conclusion Wrist exten- tion elicited by NMES can evoke fMRI responses in motor cortex and somatosensory cortex in healthy subjects.

Non-homogeneous spatial configuration of vibrissae cortical representation in layer IV of the barrel somatosensory cortex

In the present experiments we studied exclusive and overlapping cortical representational areas of the vibrissae in layer IV cells, across the entire barrel subfield of the rat somatosensory cortex, looking for evidences that would challenge the present assumptions of homogeneity and symmetry among cortical columns in this sensorial system. Our main findings were that in layer IV of the rat barrel cortex: A) Size of vibrissae cortical representational areas (X=0.4174mm²; SD=0.025) was not homo geneous, vibrissae in dorsal rows (A-B) had significantly smaller areas than those in ventral rows (D-E), a pattern that repeated itself in arcs 1-4. B) This difference arises from vibrissal representational overlap, and not from variations in exclusive zones, which are surprisingly homogeneous in size across the barrel cortex (X=0.079mm²; SD=0.0075); C) The extent of overlapping cortical areas varied systematically, with intra-row overlapping areas having a predominant bias (71.4 percent of total overlapping) independent of area sizes. Accordingly, vibrissae shared receptive fields with an average of 1.15 vibrissae in the same row and 0.38 in the same are. Barrel cortex has been viewed operationally as a conglomerate of essentially homogenous cortical columns that interact equivalently in the are and row dimensions. Our simple but global cortical reconstructions show that this predominant view should be revised. We postulate that the vibrissae/barrels spatial disposition in rows and ares has a relevant functional meaning, related to different sensory capabilities.

Activation Pattern of the Somatosensory Cortex in Subcortical Stroke Patients with Clinical Sensory Recovery of Hand

OBJECTIVE: To investigate the activation pattern of somatosensory cortex in subcortical stroke patients underlying recovered somatosensory capacity of hand, using functional MRI (fMRI). METHOD: Four patients with subcortical cerebral hemorrhage or infarction and five normal healthy volunteers were investigated. Sensory task was given on the palm of hand by brushing as a frequency of 1 Hz. In fMRI study, ten slices were obtained using the Echo Planar Imaging technique, data was statistically analyzed using SPM-99 software. RESULTS: During the tactile stimulation of affected hand, contralateral primary somatosensory cortex was activated in all the patients. In the two patients with full recovery of tactile sense, cortical activation for paretic hand was stronger than in nonparetic hand. On the other hand, the other two patients with incomplete recovery showed that cortical activation for nonparetic hand was stronger than in paretic hand and even normal control. CONCLUSION: Our result suggested that functional consequences of the somatosensory cortical area were not limited to the ipsilateral hemisphere to the lesion, but affect the contralateral, nonlesioned hemisphere, in subcortical stroke patients with recovered somatosensory capacity.

Modulation of Human Somatosensory Cortical Excitability by Repetitive Peripheral Nerve Stimulation

OBJECTIVE: To investigate whether the somatosensory cortical excitability could be modulated by repetitive electrical stimulation (RES) on the tibial nerve at human ankle joint. METHOD: The subjects were 10 healthy volunteers. The study was composed of 3 sessions: first session, baseline evaluation; second session, RES with a intensity for proprioceptive stimulation on tibial nerve at the right ankle for 3 different duration of 30 minutes, 1 hour, and 2 hours; third session, repeat of baseline evaluation after RES (post- RES evaluation). The baseline evaluation include somatosensory evoked potential study with stimulation of right tibial nerve and compound muscle action potential (CMAPs) of tibial nerve recorded at abductor hallucis and H reflex. The amplitude of each study were measured and compared between baseline evaluation and post-RES evaluation using Kruscal-Wallis test. RESULT: There was no significant change in amplitudes of SSEP, CMAP and H reflex between baseline evaluation and post-RES evaluation of 30 minutes, 1 hour and 2 hours. CONCLUSION: This study suggests that chronic repetitive proprioceptive afferent nerve stimulations could not modulate primary somatosensory cortex in healthy subjects. However, we could not rule out the limitations of sensitivity of somatosensory evoked potential study.

THE ANGIOARCHITECTURE OF HUMAN ANTERIOR AND POSTERIOR CENTRAL GYRI / 解剖学报

The angioarchitecture of both anterior and posterior central gyri of thirty human brains was studied by means of scanning electron microscopy, double injection method and alkaline phosphatase method. The study was divided into two parts. (a) Pial vessels: The branching pattern of pial arteries on the gyrus surface could be classified into 4 types. Type Ⅰ (bilateral branching type) accounted for 44.44% of the total, type Ⅱ (unilateral branching) 17.99%, type Ⅲ (comb-like) 16.93% and type Ⅳ (irregular) 20.63%. Each gyrus was supplied by several main branches, forming various areas separated by poorly vascularized lines. Two types of anastomoses (general and straight anastomoses) were found. (b) Intracerebral vessels: based on the degree of their penetration, intracerebral arteries and veins were divided into 5 groups, respectively. They were short, intermediate and long cortical, subcortical and medullary vessels. Arteries gave off forward, horizontal and recurrent branches. There were more long cortical arteries in the anterior central gyrus and more intermediate arteries in the posterior. The arteries were not accompanied by veins. Though rich blood supply was found in layer Ⅲ-Ⅳ, there was a broad vascular network with large meshes in layer Ⅴ and Ⅵ in the anterior central gyrus. Problems in distinguishing arteries from veins and particular vascular features were discussed.