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Primary Somatosensory Cortex (primary + somatosensory_cortex)
Selected AbstractsLong-range connectivity of mouse primary somatosensory barrel cortexEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2010Rachel Aronoff Abstract The primary somatosensory barrel cortex processes tactile vibrissae information, allowing rodents to actively perceive spatial and textural features of their immediate surroundings. Each whisker on the snout is individually represented in the neocortex by an anatomically identifiable ,barrel' specified by the segregated termination zones of thalamocortical axons of the ventroposterior medial nucleus, which provide the primary sensory input to the neocortex. The sensory information is subsequently processed within local synaptically connected neocortical microcircuits, which have begun to be investigated in quantitative detail. In addition to these local synaptic microcircuits, the excitatory pyramidal neurons of the barrel cortex send and receive long-range glutamatergic axonal projections to and from a wide variety of specific brain regions. Much less is known about these long-range connections and their contribution to sensory processing. Here, we review current knowledge of the long-range axonal input and output of the mouse primary somatosensory barrel cortex. Prominent reciprocal projections are found between primary somatosensory cortex and secondary somatosensory cortex, motor cortex, perirhinal cortex and thalamus. Primary somatosensory barrel cortex also projects strongly to striatum, thalamic reticular nucleus, zona incerta, anterior pretectal nucleus, superior colliculus, pons, red nucleus and spinal trigeminal brain stem nuclei. These long-range connections of the barrel cortex with other specific cortical and subcortical brain regions are likely to play a crucial role in sensorimotor integration, sensory perception and associative learning. [source] Rapid cortical reorganisation and improved sensitivity of the hand following cutaneous anaesthesia of the forearmEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2009Anders Björkman Abstract The cortical representation of various body parts constantly changes based on the pattern of afferent nerve impulses. As peripheral nerve injury results in a cortical and subcortical reorganisation this has been suggested as one explanation for the poor clinical outcome seen after peripheral nerve repair in humans. Cutaneous anaesthesia of the forearm in healthy subjects and in patients with nerve injuries results in rapid improvement of hand sensitivity. The mechanism behind the improvement is probably based on a rapid cortical and subcortical reorganisation. The aim of this work was to study cortical changes following temporary cutaneous forearm anaesthesia. Ten healthy volunteers participated in the study. Twenty grams of a local anaesthetic cream (EMLA®) was applied to the volar aspect of the right forearm. Functional magnetic resonance imaging was performed during sensory stimulation of all fingers of the right hand before and during cutaneous forearm anaesthesia. Sensitivity was also clinically assessed before and during forearm anaesthesia. A group analysis of functional magnetic resonance image data showed that, during anaesthesia, the hand area in the contralateral primary somatosensory cortex expanded cranially over the anaesthetised forearm area. Clinically right hand sensitivity in the volunteers improved during forearm anaesthesia. No significant changes were seen in the left hand. The clinically improved hand sensitivity following forearm anaesthesia is probably based on a rapid expansion of the hand area in the primary somatosensory cortex which presumably results in more nerve cells being made available for the hand in the primary somatosensory cortex. [source] Topographical organization of pathways from somatosensory cortex through the pontine nuclei to tactile regions of the rat cerebellar hemispheresEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2006Trygve B. Leergaard Abstract The granule cell layer of the cerebellar hemispheres contains a patchy and noncontinuous map of the body surface, consisting of a complex mosaic of multiple perioral tactile representations. Previous physiological studies have shown that cerebrocerebellar mossy fibre projections, conveyed through the pontine nuclei, are mapped in registration with peripheral tactile projections to the cerebellum. In contrast to the fractured cerebellar map, the primary somatosensory cortex (SI) is somatotopically organized. To understand better the map transformation occurring in cerebrocerebellar pathways, we injected axonal tracers in electrophysiologically defined locations in Sprague,Dawley rat folium crus IIa, and mapped the distribution of retrogradely labelled neurons within the pontine nuclei using three-dimensional (3-D) reconstructions. Tracer injections within the large central upper lip patch in crus IIa-labelled neurons located centrally in the pontine nuclei, primarily contralateral to the injected side. Larger injections (covering multiple crus IIa perioral representations) resulted in labelling extending only slightly beyond this region, with a higher density and more ipsilaterally labelled neurons. Combined axonal tracer injections in upper lip representations in SI and crus IIa, revealed a close spatial correspondence between the cerebropontine terminal fields and the crus IIa projecting neurons. Finally, comparisons with previously published three-dimensional distributions of pontine neurons labelled following tracer injections in face receiving regions in the paramedian lobule (downloaded from http://www.rbwb.org) revealed similar correspondence. The present data support the coherent topographical organization of cerebro-ponto-cerebellar networks previously suggested from physiological studies. We discuss the present findings in the context of transformations from cerebral somatotopic to cerebellar fractured tactile representations. [source] Crossmodal influences in somatosensory cortex: Interaction of vision and touchHUMAN BRAIN MAPPING, Issue 1 2010Jennifer K. Dionne Abstract Previous research has shown that information from one sensory modality has the potential to influence activity in a different modality, and these crossmodal interactions can occur early in the cortical sensory processing stream within sensory-specific cortex. In addition, it has been shown that when sensory information is relevant to the performance of a task, there is an upregulation of sensory cortex. This study sought to investigate the effects of simultaneous bimodal (visual and vibrotactile) stimulation on the modulation of primary somatosensory cortex (SI), in the context of a delayed sensory-to-motor task when both stimuli are task-relevant. It was hypothesized that the requirement to combine visual and vibrotactile stimuli would be associated with an increase in SI activity compared to vibrotactile stimuli alone. Functional magnetic resonance imaging (fMRI) was performed on healthy subjects using a 3T scanner. During the scanning session, subjects performed a sensory-guided motor task while receiving visual, vibrotactile, or both types of stimuli. An event-related design was used to examine cortical activity related to the stimulus onset and the motor response. A region of interest (ROI) analysis was performed on right SI and revealed an increase in percent blood oxygenation level dependent signal change in the bimodal (visual + tactile) task compared to the unimodal tasks. Results of the whole-brain analysis revealed a common fronto-parietal network that was active across both the bimodal and unimodal task conditions, suggesting that these regions are sensitive to the attentional and motor-planning aspects of the task rather than the unimodal or bimodal nature of the stimuli. Hum Brain Mapp, 2010. © 2009 Wiley-Liss, Inc. [source] Cortical and subcortical correlates of functional electrical stimulation of wrist extensor and flexor muscles revealed by fMRIHUMAN BRAIN MAPPING, Issue 3 2009Armin Blickenstorfer Abstract The main scope of this study was to test the feasibility and reliability of FES in a MR-environment. Functional Electrical Stimulation (FES) is used in the rehabilitation therapy of patients after stroke or spinal cord injury to improve their motor abilities. Its principle lies in applying repeated electrical stimulation to the relevant nerves or muscles for eliciting either isometric or concentric contractions of the treated muscles. In this study we report cerebral activation patterns in healthy subjects undergoing fMRI during FES stimulation. We stimulated the wrist extensor and flexor muscles in an alternating pattern while BOLD-fMRI was recorded. We used both block and event-related designs to demonstrate their feasibility for recording FES activation in the same cortical and subcortical areas. Six out of fifteen subjects repeated the experiment three times within the same session to control intraindividual variance. In both block and event-related design, the analysis revealed an activation pattern comprising the contralateral primary motor cortex, primary somatosensory cortex and premotor cortex; the ipsilateral cerebellum; bilateral secondary somatosensory cortex, the supplementary motor area and anterior cingulate cortex. Within the same subjects we observed a consistent replication of the activation pattern shown in overlapping regions centered on the peak of activation. Similar time course within these regions were demonstrated in the event-related design. Thus, both techniques demonstrate reliable activation of the sensorimotor network and eventually can be used for assessing plastic changes associated with FES rehabilitation treatment. Hum Brain Mapp, 2009. © 2008 Wiley-Liss, Inc. [source] Task-relevance and temporal synchrony between tactile and visual stimuli modulates cortical activity and motor performance during sensory-guided movementHUMAN BRAIN MAPPING, Issue 2 2009Sean K. Meehan Abstract Sensory-guided movements require the analysis and integration of task-relevant sensory inputs from multiple modalities. This article sought to: (1) assess effects of intermodal temporal synchrony upon modulation of primary somatosensory cortex (S1) during continuous sensorimotor transformations, (2) identify cortical areas sensitive to temporal synchrony, and (3) provide further insight into the reduction of S1 activity during continuous vibrotactile tracking previously observed by our group (Meehan and Staines 2007: Brain Res 1138:148,158). Functional MRI was acquired while participants received simultaneous bimodal (visuospatial/vibrotactile) stimulation and continuously tracked random changes in one modality, by applying graded force to a force-sensing resistor. Effects of intermodal synchrony were investigated, unbeknownst to the participants, by varying temporal synchrony so that sensorimotor transformations dictated by the distracter modality either conflicted (low synchrony) or supplemented (high synchrony) those of the target modality. Temporal synchrony differentially influenced tracking performance dependent upon tracking modality. Physiologically, synchrony did not influence S1 activation; however, the insula and superior temporal gyrus were influenced regardless of tracking modality. The left temporal-parietal junction demonstrated increased activation during high synchrony specific to vibrotactile tracking. The superior parietal lobe and superior temporal gyrus demonstrated increased activation during low synchrony specific to visuospatial tracking. As previously reported, vibrotactile tracking resulted in decreased S1 activation relative to when it was task-irrelevant. We conclude that while temporal synchrony is represented at higher levels than S1, interactions between inter- and intramodal mechanisms determines sensory processing at the level of S1. Hum Brain Mapp, 2009. © 2007 Wiley-Liss, Inc. [source] Timing and connectivity in the human somatosensory cortex from single trial mass electrical activityHUMAN BRAIN MAPPING, Issue 4 2002Andreas A. Ioannides Abstract Parallel-distributed processing is ubiquitous in the brain but often ignored by experimental designs and methods of analysis, which presuppose sequential and stereotypical brain activations. We introduce here a methodology that can effectively deal with sequential and distributed activity. Regional brain activations elicited by electrical median nerve stimulation are identified in tomographic estimates extracted from single trial magnetoencephalographic signals. Habituation is identified in both primary somatosensory cortex (SI) and secondary somatosensory cortex (SII), often interrupted by resurgence of strong activations. Pattern analysis is used to identify single trials with homogeneous regional brain activations. Common activity patterns with well-defined connectivity are identified within each homogeneous group of single trials across the subjects studied. On the contralateral side one encounters distinct sets of single trials following identical stimuli. We observe in one set of trials sequential activation from SI to SII and insula with onset of SII at 60 msec, whereas in the other set simultaneous early co-activations of the same two areas. Hum. Brain Mapping 15:231,246, 2002. © 2002 Wiley-Liss, Inc. [source] Developmental pattern of synapsin I expression in mouse somatosensory cortexJOURNAL OF NEUROCHEMISTRY, Issue 2003M. Liguz-Lecznar Synapsin I is a member of a synapsin family which are phosphoproteins associated with synaptic vesicles. It is thought to be involved in neuronal development and plasticity. We have shown the existence of two distinct patterns of synapsin I immunostaining in adult mice primary somatosensory cortex (SI). The first consisted of small, dispersed immunoreactive puncta in neuropil. The second is confined to the perikarya and proximal dendrites of the specific class of neurons present in layers IV and VI of SI, probably reflecting the expression of a novel isoform of synapsin I. The aim of this study was to examine the developmental pattern of synapsin I expression in mouse SI cortex. Using immunocytochemistry and Western blot analysis we found that this unique pattern of synapsin I expression in SI appeared between the 2nd and 3rd postnatal week and probably coincides with the increase in the number of synaptic contacts and the development of inhibitory circuits in SI. Acknowledgement: Supported by KBN grant no. 3P04C 008 22. [source] Modulatory effects of 5Hz rTMS over the primary somatosensory cortex in focal dystonia,An fMRI-TMS study,MOVEMENT DISORDERS, Issue 1 2010Susanne A. Schneider MD Abstract Dystonia is associated with impaired somatosensory ability. The electrophysiological method of repetitive transcranial magnetic stimulation (rTMS) can be used for noninvasive stimulation of the human cortex and can alter cortical excitability and associated behavior. Among others, rTMS can alter/improve somatosensory discrimation abilities, as shown in healthy controls. We applied 5Hz-rTMS over the left primary somatosensory cortex (S1) in 5 patients with right-sided writer's dystonia and 5 controls. We studied rTMS effects on tactile discrimination accuracy and concomitant rTMS-induced changes in hemodynamic activity measured by functional magnetic resonance imaging (fMRI). Before rTMS, patients performed worse on the discrimination task than controls even though fMRI showed greater task-related activation bilaterally in the basal ganglia (BG). In controls, rTMS led to improved discrimination; fMRI revealed this was associated with increased activity of the stimulated S1, bilateral premotor cortex and BG. In dystonia patients, rTMS had no effect on discrimination; fMRI showed similar cortical effects to controls except for no effects in BG. Improved discrimination after rTMS in controls is linked to enhanced activation of S1 and BG. Failure of rTMS to increase BG activation in dystonia may be associated with the lack of effect on sensory discrimination in this group and may reflect impaired processing in BG-S1 connections. Alternatively, the increased BG activation seen in the baseline state without rTMS may reflect a compensatory strategy that saturates a BG contribution to this task. © 2010 Movement Disorder Society [source] Impaired intracortical inhibition in the primary somatosensory cortex in focal hand dystoniaMOVEMENT DISORDERS, Issue 4 2008Yohei Tamura MD Abstract Somesthetic temporal discrimination (STD) is impaired in focal hand dystonia (FHD). We explored the electrophysiological correlate of the STD deficit to assess whether this is due to dysfunction of temporal inhibition in the somatosensory inhibitory pathway or due to dysfunction in structures responsible for nonmodality-specific timing integration. Eleven FHD patients and 11 healthy volunteers were studied. STD threshold was investigated as the time interval required for perceiving a pair of stimuli as two separate stimuli in time. We also examined the somatosensory-evoked potential (SEP) in a paired-pulse paradigm. We compared STD threshold and recovery function of SEP between the groups. STD thresholds were significantly greater in FHD than in healthy volunteers. The amount of P27 suppression in the 5 ms-ISI condition was significantly less in FHD. It was also found that the STD threshold and P27 suppression were significantly correlated: the greater the STD threshold, the less the P27 suppression. Significantly less suppression of P27 with a lack of significant change in N20 indicates that the impairment of somatosensory information processing in the time domain is due to dysfunction within the primary somatosensory cortex, suggesting that that the STD deficit in FHD is more attributable to dysfunction in the somatosensory pathway. © 2007 Movement Disorder Society [source] Cortical processing of near-threshold tactile stimuli: An MEG studyPSYCHOPHYSIOLOGY, Issue 3 2010Anja Wühle Abstract In the present study we tested the applicability of a paired-stimulus paradigm for the investigation of near-threshold (NT) stimulus processing in the somatosensory system using magnetoencephalography. Cortical processing of the NT stimuli was studied indirectly by investigating the impact of NT stimuli on the source activity of succeeding suprathreshold test stimuli. We hypothesized that cortical responses evoked by test stimuli are reduced due to the preactivation of the same finger representation by the preceding NT stimulus. We observed attenuation of the magnetic responses in the secondary somatosensory (SII) cortex, with stronger decreases for perceived than for missed NT stimuli. Our data suggest that processing in the primary somatosensory cortex including recovery lasts for <200 ms. Conversely, the occupancy of SII lasts ,500 ms, which points to its role in temporal integration and conscious perception of sensory input. [source] Molecular determinants of the face map development in the trigeminal brainstemTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 2 2006Reha S. Erzurumlu Abstract The perception of external sensory information by the brain requires highly ordered synaptic connectivity between peripheral sensory neurons and their targets in the central nervous system. Since the discovery of the whisker-related barrel patterns in the mouse cortex, the trigeminal system has become a favorite model for study of how its connectivity and somatotopic maps are established during development. The trigeminal brainstem nuclei are the first CNS regions where whisker-specific neural patterns are set up by the trigeminal afferents that innervate the whiskers. In particular, barrelette patterns in the principal sensory nucleus of the trigeminal nerve provide the template for similar patterns in the face representation areas of the thalamus and subsequently in the primary somatosensory cortex. Here, we describe and review studies of neurotrophins, multiple axon guidance molecules, transcription factors, and glutamate receptors during early development of trigeminal connections between the whiskers and the brainstem that lead to emergence of patterned face maps. Studies from our laboratories and others' showed that developing trigeminal ganglion cells and their axons depend on a variety of molecular signals that cooperatively direct them to proper peripheral and central targets and sculpt their synaptic terminal fields into patterns that replicate the organization of the whiskers on the muzzle. Similar mechanisms may also be used by trigeminothalamic and thalamocortical projections in establishing patterned neural modules upstream from the trigeminal brainstem. © 2006 Wiley-Liss, Inc. [source] Development of layer-specific axonal arborizations in mouse primary somatosensory cortexTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 3 2006DeLaine D. Larsen Abstract In the developing neocortex, pyramidal neurons use molecular cues to form axonal arbors selectively in the correct layers. Despite the utility of mice for molecular and genetic studies, little work has been done on the development of layer-specific axonal arborizations of pyramidal neurons in mice. We intracellularly labeled and reconstructed the axons of layer 2/3 and layer 5 pyramidal neurons in slices of primary somatosensory cortex from C57Bl6 mice on postnatal days 7,21. For all neurons studied, the development of the axonal arborizations in mice follows a pattern similar to that seen in other species; laminar specificity of the earliest axonal branches is similar to that of mature animals. At P7, pyramidal neurons are very simple, having only a main descending axon and few primary branches. Between P7 and P10, there is a large increase in the total number of axonal branches, and axons continue to increase in complexity and total length from P10 to P21. Unlike observations in ferrets, cats, and monkeys, two types of layer 2/3 pyramidal neurons are present in both mature and developing mice; cells in superficial layer 2/3 lack axonal arbors in layer 4, and cells close to the layer 4 border have substantial axonal arbors within layer 4. We also describe axonal and dendritic arborization patterns of three pyramidal cell types in layer 5. The axons of tall-tufted layer 5 pyramidal neurons arborize almost exclusively within deep layers while tall-simple, and short layer 5 pyramidal neurons also project axons to superficial layers. J. Comp. Neurol. 494:398,414, 2006. © 2005 Wiley-Liss, Inc. [source] Input,output organization of jaw movement-related areas in monkey frontal cortexTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 4 2005Nobuhiko Hatanaka Abstract The brain mechanisms underlying mastication are not fully understood. To address this issue, we analyzed the distribution patterns of cortico,striatal and cortico,brainstem axon terminals and the origin of thalamocortical and intracortical fibers by injecting anterograde/retrograde tracers into physiologically and morphologically defined jaw movement-related cortical areas. Four areas were identified in the macaque monkey: the primary and supplementary orofacial motor areas (MIoro and SMAoro) and the principal and deep parts of the cortical masticatory area (CMaAp and CMaAd), where intracortical microstimulation produced single twitch-like or rhythmic jaw movements, respectively. Tracer injections into these areas labeled terminals in the ipsilateral putamen in a topographic fashion (MIoro vs. SMAoro and CMaAp vs. CMaAd), in the lateral reticular formation and trigeminal sensory nuclei contralaterally (MIoro and CMaAp) or bilaterally (SMAoro) in a complex manner of segregation vs. overlap, and in the medial parabranchial and Kölliker-Fuse nuclei contralaterally (CMaAd). The MIoro and CMaAp received thalamic projections from the ventrolateral and ventroposterolateral nuclei, the SMAoro from the ventroanterior and ventrolateral nuclei, and the CMaAd from the ventroposteromedial nucleus. The MIoro, SMAoro, CMaAp, and CMaAd received intracortical projections from the ventral premotor cortex and primary somatosensory cortex, the ventral premotor cortex and rostral cingulate motor area, the ventral premotor cortex and area 7b, and various sensory areas. In addition, the MIoro and CMaAp received projections from the three other jaw movement-related areas. Our results suggest that the four jaw movement-related cortical areas may play important roles in the formation of distinctive masticatory patterns. J. Comp. Neurol. 492:401,425, 2005. © 2005 Wiley-Liss, Inc. [source] Organization of tectopontine terminals within the pontine nuclei of the rat and their spatial relationship to terminals from the visual and somatosensory cortexTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 3 2005Cornelius Schwarz Abstract We investigated the spatial relationship of axonal and dendritic structures in the rat pontine nuclei (PN), which transfer visual signals from the superior colliculus (SC) and visual cortex (A17) to the cerebellum. Double anterograde tracing (DiI and DiAsp) from different sites in the SC showed that the tectal retinotopy of visual signals is largely lost in the PN. Whereas axon terminals from lateral sites in the SC were confined to a single terminal field close to the cerebral peduncle, medial sites in the SC projected to an additional dorsolateral one. On the other hand, axon terminals originating from the two structures occupy close but, nevertheless, totally nonoverlapping terminal fields within the PN. Furthermore, a quantitative analysis of the dendritic trees of intracellularly filled identified pontine projection neurons showed that the dendritic fields were confined to either the SC or the A17 terminal fields and never extended into both. We also investigated the projections carrying cortical somatosensory inputs to the PN as these signals are known to converge with tectal ones in the cerebellum. However, terminals originating in the whisker representation of the primary somatosensory cortex and in the SC were located in segregated pontine compartments as well. Our results, therefore, point to a possible pontocerebellar mapping rule: Functionally related signals, commonly destined for common cerebellar target zones but residing in different afferent locations, may be kept segregated on the level of the PN and converge only later at specific sites in the granular layer of cerebellar cortex. J. Comp. Neurol. 484:283,298, 2005. © 2005 Wiley-Liss, Inc. [source] Digit-specific aberrations in the primary somatosensory cortex in Writer's cramp,ANNALS OF NEUROLOGY, Issue 2 2009Aimee J. Nelson PhD Objective One approach to the treatment of focal hand dystonia (FHD) is via sensory-based training regimes. It is known that FHD patients demonstrate a reduced distance between the representations of digits 1 and 5 and also digits 2 and 5 in primary somatosensory cortex. However, we lack information on the spatial relationships among digits, such as reduced inter-digit spacing or shifts of representations within the cortical areas, and whether aberrations are specific to symptomatic digits. Our aim was to characterize the spatial relationships among individual digits to determine the types of aberrations that exist and whether these are specific to symptomatic digits only. Methods Using high-resolution fMRI over a limited volume and surface-based mapping techniques, the cortical representations of all digits of the dystonia-affected hand within the sub-regions of the postcentral gyrus were mapped in patients with task-specific Writer's cramp (WC). Results In area 3b, digits directly involved in writing (D1, D2 and D3) show reduced inter-digit separation, reversals, and overlapping activation. The thumb representation occupies territory normally occupied by digit 2 in controls. Asymptomatic digits 4 and 5 preserve their inter-digit separation yet shift towards the D1/D2/D3 cluster, suggesting that reduced spacing, not simply digit shifts, are associated with dystonia symptoms. Area 3a was less responsive to sensory input in WC patients providing evidence of reduced afferent drive or top-down modulation to this sub-region. Interpretation Therapeutic regimes aimed at facilitating inter-digit separation of digits 1, 2 and 3 may promote beneficial plasticity in WC patients. Ann Neurol 2009;66:146,154. [source] | |||||||||||||