Orthogonality of sensory and contextual categorical dynamics embedded in a continuum of responses from the second somatosensory cortex.

How does the brain simultaneously process signals that bring complementary information, like raw sensory signals and their transformed counterparts, without any disruptive interference? Contemporary research underscores the brain's adeptness in using decorrelated responses to reduce such interference. Both neurophysiological findings and artificial neural networks support the notion of orthogonal representation for signal differentiation and parallel processing. Yet, where, and how raw sensory signals are transformed into more abstract representations remains unclear. Using a temporal pattern discrimination task in trained monkeys, we revealed that the second somatosensory cortex (S2) efficiently segregates faithful and transformed neural responses into orthogonal subspaces. Importantly, S2 population encoding for transformed signals, but not for faithful ones, disappeared during a nondemanding version of this task, which suggests that signal transformation and their decoding from downstream areas are only active on-demand. A mechanistic computation model points to gain modulation as a possible biological mechanism for the observed context-dependent computation. Furthermore, individual neural activities that underlie the orthogonal population representations exhibited a continuum of responses, with no well-determined clusters. These findings advocate that the brain, while employing a continuum of heterogeneous neural responses, splits population signals into orthogonal subspaces in a context-dependent fashion to enhance robustness, performance, and improve coding efficiency.

Association of Urinary Incontinence with Sensory-Motor Performance in Women with Multiple Sclerosis.

INTRODUCTION AND HYPOTHESIS: The relationship between somatosensory and motor components of urinary incontinence in individuals with MS has not been extensively addressed. The study was aimed at investigating the association of urinary incontinence severity with motor and sensory performance in women with multiple sclerosis (MS). METHODS: A cross-sectional single-center prospective study was conducted in 337 women with MS. The severity of MS symptoms was assessed using the SymptoMScreen questionnaire. The urinary incontinence status of the participants was evaluated using the Urinary Incontinence Inventory (UDI-6) and the Incontinence Impact Questionnaire (IIQ-7). Physical performance was considered with the Timed Up and Go (TUG) test and the 5-Times Sit-to-Stand (5TSTS) test. In addition, the sensory performance of the individuals with MS was queried using the Somatosensory Amplification Scale (SSAS) and Sensory Sensitivity Scale (SeSS). RESULTS: The UDI-6 (r=0.685, p<0.05) and IIQ-7 (r=0.759, p<0.05) correlated highly with SymptoMScreen. Among the physical performance measures, TUG (r=0.012, p<0.05) and 5TSTS (r=0.096, p<0.05) were weakly associated with UDI-6, but not statistically significantly. Similarly, there was a low correlation between IIQ-7 and TUG (r=-0.005, p<0.05) and 5TSTS (r=0.068, p<0.05). UDI-6 (0.360, p<0.05) and IIQ-7 (0.378, p<0.05) correlated moderately with SASS. On the other hand, SeSS had a low correlation coefficient with UDI-6 (0.305, p<0.05) and IIQ-7 (0.272, p<0.05). CONCLUSIONS: The results revealed that sensory performance was more associated with urinary incontinence in women with MS than physical performance. The urinary incontinence severity was also related to MS symptoms (bladder control, walking, spasticity, stiffness cognitive function). Future studies should consider the potential impact of sensory performance on urinary incontinence and focus on explaining the mechanism behind this relationship.

The NKCC1 inhibitor bumetanide restores cortical feedforward inhibition and lessens sensory hypersensitivity in early postnatal fragile X mice.

BACKGROUND: Exaggerated responses to sensory stimuli, a hallmark of Fragile X syndrome (FXS), contribute to anxiety and learning challenges. Sensory hypersensitivity is recapitulated in the Fmr1 knockout (KO) mouse model of FXS. Recent studies in Fmr1 KO mice have demonstrated differences in activity of cortical interneurons and a delayed switch in the polarity of GABA signaling during development. Previously, we reported that blocking the chloride transporter NKCC1 with the diuretic bumetanide, could rescue synaptic circuit phenotypes in primary somatosensory cortex (S1) of Fmr1 KO mice. However, it remains unknown whether bumetanide can rescue earlier circuit phenotypes or sensory hypersensitivity in Fmr1 KO mice. METHODS: We used acute and chronic systemic administration of bumetanide in Fmr1 KO mice and performed in vivo 2-photon calcium imaging to record neuronal activity, while tracking mouse behavior with high-resolution videos. RESULTS: We demonstrate that layer (L) 2/3 pyramidal neurons in S1 of Fmr1 KO mice show a higher frequency of synchronous events at postnatal day (P) 6 compared to wild-type controls. This was reversed by acute administration of bumetanide. Furthermore, chronic bumetanide treatment (P5-P14) restored S1 circuit differences in Fmr1 KO mice, including reduced neuronal adaptation to repetitive whisker stimulation, and ameliorated tactile defensiveness. Bumetanide treatment also rectified the reduced feedforward inhibition of L2/3 neurons in S1 and boosted the circuit participation of parvalbumin interneurons. CONCLUSIONS: This further supports the notion that synaptic, circuit, and sensory behavioral phenotypes in Fmr1 KO can be mitigated by inhibitors of NKCC1, such as the FDA-approved diuretic bumetanide.

Theta-burst stimulation over primary somatosensory cortex modulates tactile acuity of tongue.

Background: Emerging studies in humans have established the modulatory effects of repetitive transcranial magnetic stimulation (rTMS) over primary somatosensory cortex (S1) on somatosensory cortex activity and perception. However, to date, research in this area has primarily focused on the hand and fingers, leaving a gap in our understanding of the modulatory effects of rTMS on somatosensory perception of the orofacial system and speech articulators. Objective: The present study aimed to examine the effects of different types of theta-burst stimulation-continuous TBS (cTBS), intermittent TBS (iTBS), or sham-over the tongue representation of left S1 on tactile acuity of the tongue. Methods: In a repeated-measures design, fifteen volunteers participated in four separate sessions, where cTBS, iTBS, sham, or no stimulation was applied over the tongue representation of left S1. Effects of TBS were measured on both temporal and spatial perceptual acuity of tongue using a custom vibrotactile stimulator. Results: CTBS significantly impaired spatial amplitude threshold at the time window of 16-30 minutes after stimulation, while iTBS improved it at the same time window. The effect of iTBS, however, was smaller than cTBS. In contrast, neither cTBS nor iTBS had any effect on the temporal discrimination threshold. Conclusions: The current study establishes the validity of using TBS to modulate somatosensory perception of the orofacial system. Directly modifying somatosensation in the orofacial system has the potential to benefit clinical populations with abnormal tactile acuity, improve our understanding of the role of sensory systems in speech production, and enhance speech motor learning and rehabilitation.

The effects of combining sensorimotor training with transcranial direct current stimulation on the anticipatory and compensatory postural adjustments in patients with chronic low back pain.

PURPOSE: To investigate the effects of concurrent sensorimotor training (SMT) and transcranial direct current stimulation (tDCS) on the anticipatory and compensatory postural adjustments (APAs and CPAs) in patients with chronic low back pain (CLBP). METHOD: The interventions included (1) SMT plus tDCS and (2) SMT plus sham tDCS. Outcome measures were the normalized integrals of electromyography activity (NIEMG) during the phases of anticipatory and compensatory, and muscle onset latency. The investigated muscles were ipsilateral and contralateral multifidus (MF), transversus abdominus/internal oblique (TrA/IO), and gluteus medius (GM). RESULTS: Between-group comparisons demonstrated that ipsilateral TrA/IO NIEMG during CPA1 (p = 0.010) and ipsilateral GM NIEMG during CPA1 (p = 0.002) and CPA2 (p = 0.025) were significantly lower in the SMT combined with tDCS than in the control group. Furthermore, this group had greater NIEMG for contralateral GM during APA1 than the control group (p = 0.032). Moreover, the onset latency of contralateral TrA/IO was significantly earlier after SMT combined with tDCS (p = 0.011). CONCLUSIONS: Both groups that received SMT showed positive effects, but anodal tDCS had an added value over sham stimulation for improving postural control strategies in patients with CLBP. Indeed, SMT combined with tDCS leads to stronger APA and less demand for CPA. RCT REGISTRATION NUMBER: IRCT20220228054149N1. REGISTRATION DATE: 2022-04-04.

Evidence suggests that reduced excitability in the sensory and motor cortex is linked to chronic and recurring lower back pain.Increasing the excitability of these two areas using anodal transcranial direct current stimulation (tDCS), in conjunction with sensorimotor training (SMT), may improve anticipatory and compensatory postural control strategies.This study showed that the combination of SMT with tDCS targeting the sensory and motor cortex notably enhances motor preparation and refines postural control strategies in patients with chronic unilateral lumbar radiculopathy.Rehabilitation professionals are encouraged to integrate SMT with tDCS into treatment protocols to enhance the ability of individuals with back pain to handle postural disturbances in daily life, thereby potentially alleviating the persistence of their symptoms.Incorporating brain stimulation enhances the effectiveness of SMT for patients with chronic unilateral lumbar radiculopathy.

What is the Vagal-Adrenal Axis?

Some recent publications have used the term "vagal-adrenal axis" to account for mechanisms involved in the regulation of inflammation by electroacupuncture. This concept proposes that efferent parasympathetic nerve fibers in the vagus directly innervate the adrenal glands to influence catecholamine secretion. Here, we discuss evidence for anatomical and functional links between the vagi and adrenal glands that may be relevant in the context of inflammation and its neural control by factors, including acupuncture. First, we find that evidence for any direct vagal parasympathetic efferent innervation of the adrenal glands is weak and likely artifactual. Second, we find good evidence that vagal afferent fibers directly innervate the adrenal gland, although their function is uncertain. Third, we highlight a wealth of evidence for indirect pathways, whereby vagal afferent signals act via the central nervous system to modify adrenal-dependent anti-inflammatory responses. Vagal afferents, not efferents, are thus the likely key to these phenomena.

Recording the tactile P300 with the cEEGrid for potential use in a brain-computer interface.

Brain-computer interfaces (BCIs) are scientifically well established, but they rarely arrive in the daily lives of potential end-users. This could be in part because electroencephalography (EEG), a prevalent method to acquire brain activity for BCI operation, is considered too impractical to be applied in daily life of end-users with physical impairment as an assistive device. Hence, miniaturized EEG systems such as the cEEGrid have been developed. While they promise to be a step toward bridging the gap between BCI development, lab demonstrations, and home use, they still require further validation. Encouragingly, the cEEGrid has already demonstrated its ability to record visually and auditorily evoked event-related potentials (ERP), which are important as input signal for many BCIs. With this study, we aimed at evaluating the cEEGrid in the context of a BCI based on tactually evoked ERPs. To compare the cEEGrid with a conventional scalp EEG, we recorded brain activity with both systems simultaneously. Forty healthy participants were recruited to perform a P300 oddball task based on vibrotactile stimulation at four different positions. This tactile paradigm has been shown to be feasible for BCI repeatedly but has never been tested with the cEEGrid. We found distinct P300 deflections in the cEEGrid data, particularly at vertical bipolar channels. With an average of 63%, the cEEGrid classification accuracy was significantly above the chance level (25%) but significantly lower than the 81% reached with the EEG cap. Likewise, the P300 amplitude was significantly lower (cEEGrid R2-R7: 1.87 µV, Cap Cz: 3.53 µV). These results indicate that a tactile BCI using the cEEGrid could potentially be operated, albeit with lower efficiency. Additionally, participants' somatosensory sensitivity was assessed, but no correlation to the accuracy of either EEG system was shown. Our research contributes to the growing amount of literature comparing the cEEGrid to conventional EEG systems and provides first evidence that the tactile P300 can be recorded behind the ear. A BCI based on a thus simplified EEG system might be more readily accepted by potential end-users, provided the accuracy can be substantially increased, e.g., by training and improved classification.

Diagnostic Accuracy of Somatosensory Evoked Potential and Transcranial Motor Evoked Potential in Detection of Neurological Injury in Intradural Extramedullary Spinal Cord Tumor Surgeries: A Short-Term Follow-Up Prospective Interventional Study Experience from Tertiary Care Center of India.

Objective Intraoperative neuromonitoring (IONM) is an acknowledged tool for real-time neuraxis assessment during surgery. Somatosensory evoked potential (SSEP) and transcranial motor evoked potential (MEP) are commonest deployed modalities of IONM. Role of SSEP and MEP in intradural extramedullary spinal cord tumor (IDEMSCT) surgery is not well established. The aim of this study was to evaluate sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of SSEP and transcranial MEP, in detection of intraoperative neurological injury in IDEMSCT patients as well as their postoperative limb-specific neurological improvement assessment at fixed intervals till 30 days. Materials and Methods Symptomatic patients with IDEMSCTs were selected according to the inclusion criteria of study protocol. On modified McCormick (mMC) scale, their sensory-motor deficit was assessed both preoperatively and postoperatively. Surgery was done under SSEP and MEP (transcranial) monitoring using appropriate anesthetic agents. Gross total/subtotal resection of tumor was achieved as per IONM warning alarms. Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of SSEP and MEP were calculated considering postoperative neurological changes as "reference standard." Patients were followed up at postoperative day (POD) 0, 1, 7, and 30 for convalescence. Statistical Analysis With appropriate tests of significance, statistical analysis was carried out. Receiver-operating characteristic curve was used to find cutoff point of mMC for SSEP being recordable in patients with higher neurological deficit along with calculation of sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of SSEP and MEP for prediction of intraoperative neurological injury. Results Study included 32 patients. Baseline mean mMC value was 2.59. Under neuromonitoring, gross total resection of IDEMSCT was achieved in 87.5% patients. SSEP was recordable in subset of patients with mMC value less than or equal to 2 with diagnostic accuracy of 100%. MEP was recordable in all patients and it had 96.88% diagnostic accuracy. Statistically significant neurological improvement was noted at POD-7 and POD-30 follow-up. Conclusion SSEP and MEP individually carry high diagnostic accuracy in detection of intraoperative neurological injuries in patients undergoing IDEMSCT surgery. MEP continues to monitor the neuraxis, even in those subsets of patients where SSEP fails to record.

Redefined giant somatosensory evoked potentials: Evoked epileptic complexes of excitatory and inhibitory components.

OBJECTIVE: Giant somatosensory evoked potentials (SEPs) are observed in patients with cortical myoclonus. Short-latency components (SLC), are regarded as evoked epileptic activities or paroxysmal depolarization shifts (PDSs). This study aimed to reveal the electrophysiological significance of the middle-latency component (MLC) P50 of the SEPs. METHODS: Twenty-two patients with cortical myoclonus having giant SEPs (patient group) and 15 healthy controls were included in this study. Waveform changes in SEPs before and after perampanel (PER) treatment were evaluated in the patient group. The wide range, time-frequency properties underlying the waveforms were compared between the groups. RESULTS: After PER treatment, SLC was prolonged and positively correlated with PER concentration, whereas MLC showed no correlation with PER concentration. Time-frequency analysis showed a power increase (156 Hz in all patients, 624 Hz in benign adult familial myoclonus epilepsy patients) underlying SLC and a power decrease (156 Hz, 624 Hz) underlying MLC in the patient group. CONCLUSIONS: The high-frequency power increase in SLCs and decrease in MLCs clearly reflected PDS and subsequent hyperpolarization, respectively. This relationship was similar to that of interictal epileptiform discharges, suggesting that giant SEPs evoke epileptic complexes of excitatory and inhibitory components. SIGNIFICANCE: MLCs of giant SEPs reflected inhibitory components.

Heartbeat evoked potentials and autonomic arousal during dissociative seizures: insights from electrophysiology and neuroimaging.

Introduction: Dissociative seizures often occur in the context of dysregulated affective arousal and entail dissociative symptoms such as a disintegration of bodily awareness. However, the interplay between affective arousal and changes in interoceptive processing at the onset of dissociative seizures is not well understood. Methods: Using retrospective routine data obtained from video-electroencephalography telemetry in a university hospital epilepsy monitoring unit, we investigate ictal changes in cardiac indices of autonomic arousal and heartbeat evoked potentials (HEPs) in 24 patients with dissociative seizures. Results: Results show autonomic arousal during seizures with increased heart rate and a shift towards sympathetic activity. Compared with baseline, ictal HEP amplitudes over central and right prefrontal electrodes (F8, Fz) were significantly less pronounced during seizures, suggesting diminished cortical representation of interoceptive information. Significant correlations between heart rate variability measures and HEPs were observed at baseline, with more sympathetic and less parasympathetic activity related to less pronounced HEPs. Interestingly, these relationships weakened during seizures, suggesting a disintegration of autonomic arousal and interoceptive processing during dissociative seizures. In a subgroup of 16 patients, MRI-based cortical thickness analysis found a correlation with HEP amplitudes in the left somatosensory association cortex. Conclusions: These findings possibly represent an electrophysiological hint of how autonomic arousal could negatively impact bodily awareness in dissociative seizures, and how these processes might be related to underlying brain structure.

Unlocking the potential of 'passive' modulation: How sensory stimulation shapes hand and face size.

Knowledge of the body size is intricately tied to multisensory integration processes that rely on the dynamic interplay of top-down and bottom-up mechanisms. Recent years have seen the development of passive sensory stimulation protocols aimed at investigating the modulation of various cognitive functions, primarily inducing perceptual learning and behaviour change without the need for extensive training. Given that reductions in sensory input have been associated with alterations in body size perception, it is reasonable to hypothesize that increasing sensory information through passive sensory stimulation could similarly influence the perception of the size of body parts. The primary aim of this study was to investigate the potential modulatory effects of passive sensory stimulation on the perception of hand and face size in a group of young adults. Passive sensory stimulation effectively modulated the size representation of the stimulated hand, supporting the notion that access to somatosensory and proprioceptive information is prioritised for the hands but may not extend to the face. Increased somatosensory input resulted in a reduction of distortion, providing evidence for bottom-up modulation of size representation. Passive sensory stimulation can induce subjective changes in body size perception without the need for extensive training. This paradigm holds promise as a potential alternative for modulating distorted size representation in individuals with body representational deficits.

Somatosensory game intervention experience among prefrail older adults in the community: A qualitative study.

BACKGROUND: Somatosensory game interventions have been used to rehabilitate hospitalized older adults. However, their application in prefrail older adults in the community is poorly understood, hindering the development of effective intervention strategies and exercise diversification. OBJECTIVES: This study aimed to explore the experiences of prefrail Chinese older adults engaging in somatosensory gaming interventions and thus develop tailored intervention frameworks and support strategies. METHODS: We conducted semistructured interviews with 12 prefrail older adults who participated in a 12-week sensory game intervention study from August to September 2022. The interviews were analyzed using Nvivo 11.0 software following Colaizzi's seven-step analysis method. RESULTS: Somatosensory game intervention experiences were classified into four main themes and 11 subthemes: health intervention effects (enhanced limb muscle strength, improved reaction capacity, alleviated negative emotions), positive experiences (enhanced self-achievement, increased exercise motivation, elevated social engagement), negative experiences (frustration from unmet score expectations, initial discomfort), and intervention requirements (sustained interventions, technical support, personalized content). CONCLUSION: The findings have implications for somatosensory game interventions targeting prefrail older adults in the community.

Mesencephalic trigeminal neuron dendritic structures in the macaque.

It is presumed that the unusual central location of mesencephalic trigeminal neurons is a specialization that allows them to receive synaptic input. However, relatively few synaptic terminals were observed on the somata of mesencephalic trigeminal neurons in macaque monkeys via electron microscopy. This leaves the question of dendritic synaptic terminals open. Unlike the pseudounipolar neurons found in the trigeminal ganglion, some mesencephalic trigeminal neurons have been reported to be multipolar cells exhibiting a number of dendritic processes in non-primate species. To examine whether this morphological feature was also present in macaque monkeys, we retrogradely filled these cells with biotinylated dextran amine by injecting it into the trigeminal nerve entry zone. A portion of the mesencephalic trigeminal neurons exhibited short, poorly branched, dendritic processes. They also exhibited very fine, short processes believed to be somatic spines. Thus, primate trigeminal mesencephalic neurons appear to have specializations aimed at increasing the membrane surface area available for synaptic input.

The Effect of Physical Therapy on Somatosensory Tinnitus.

Objective: The objective of this work was to assess the effect of physical therapy in patients with somatosensory tinnitus (ST) and explore the influence of physical therapy on clinical variables obtained before treatment. Methods: A total of 43 patients with ST were randomized to the immediate-start group (n = 20) and delayed-start group (n = 23). All patients received physical therapy for 1 week (seven sessions). Each session lasted 60 min. The Visual Analogue Scale (VAS), Tinnitus Handicap Inventory (THI), and numerical pain rating scale (NPRS) scores were documented at baseline and after treatment (week 1) for all patients. For subjects in the immediate-start group, the THI, VAS, and NPRS scores were measured after therapy (weeks 6, 9, and 12, respectively). Medical history characteristic functional activity scale (HCFA) scores were measured at baseline to assess the association between somatic symptoms and tinnitus. Results: At week 1, VAS, THI, and NPRS scores of patients in the immediate-start group were improved by 1.25 ± 1.59, 11.10 ± 15.10, and 0.95 ± 1.54 points, respectively, and were significantly higher than those in the delayed-start group (p < 0.05). The change in VAS, THI, and NPRS scores in the treatment group was significantly positively correlated with the scores of the HCFA before treatment (r = 0.786, p < 0.001; r = 0.680, p = 0.001; r = 0.796, p < 0.001). There was no significant difference in THI, VAS, and NPRS scores among patients in the immediate-start group between weeks 1, 6, 9, and 12 after treatment (p > 0.05). Conclusions: Although more participants were necessary in the further study, the study implies that physical therapy can reduce physical pain, improve tinnitus symptoms, and quality of life in ST patients without hearing loss, and the short-term curative effect is stable, especially for tinnitus patients with clear somatic symptoms.

Functional Dynamics and Selectivity of Two Parallel Corticocortical Pathways from Motor Cortex to Layer 5 Circuits in Somatosensory Cortex.

In the rodent whisker system, active sensing and sensorimotor integration are mediated in part by the dynamic interactions between the motor cortex (M1) and somatosensory cortex (S1). However, understanding these dynamic interactions requires knowledge about the synapses and how specific neurons respond to their input. Here, we combined optogenetics, retrograde labeling, and electrophysiology to characterize the synaptic connections between M1 and layer 5 (L5) intratelencephalic (IT) and pyramidal tract (PT) neurons in S1 of mice (both sexes). We found that M1 synapses onto IT cells displayed modest short-term depression, whereas synapses onto PT neurons showed robust short-term facilitation. Despite M1 inputs to IT cells depressing, their slower kinetics resulted in summation and a response that increased during short trains. In contrast, summation was minimal in PT neurons due to the fast time course of their M1 responses. The functional consequences of this reduced summation, however, were outweighed by the strong facilitation at these M1 synapses, resulting in larger response amplitudes in PT neurons than IT cells during repetitive stimulation. To understand the impact of facilitating M1 inputs on PT output, we paired trains of inputs with single backpropagating action potentials, finding that repetitive M1 activation increased the probability of bursts in PT cells without impacting the time dependence of this coupling. Thus, there are two parallel but dynamically distinct systems of M1 synaptic excitation in L5 of S1, each defined by the short-term dynamics of its synapses, the class of postsynaptic neurons, and how the neurons respond to those inputs.

Combined Ionizing Radiation Exposure by Gamma Rays and Carbon-12 Nuclei Increases Neurotrophic Factor Content and Prevents Age-Associated Decreases in the Volume of the Sensorimotor Cortex in Rats.

In orbital and ground-based experiments, it has been demonstrated that ionizing radiation (IR) can stimulate the locomotor and exploratory activity of rodents, but the underlying mechanism of this phenomenon remains undisclosed. Here, we studied the effect of combined IR (0.4 Gy γ-rays and 0.14 Gy carbon-12 nuclei) on the locomotor and exploratory activity of rats, and assessed the sensorimotor cortex volume by magnetic resonance imaging-based morphometry at 1 week and 7 months post-irradiation. The sensorimotor cortex tissues were processed to determine whether the behavioral and morphologic effects were associated with changes in neurotrophin content. The irradiated rats were characterized by increased locomotor and exploratory activity, as well as novelty-seeking behavior, at 3 days post-irradiation. At the same time, only unirradiated rats experienced a significant decrease in the sensorimotor cortex volume at 7 months. While there were no significant differences at 1 week, at 7 months, the irradiated rats were characterized by higher neurotrophin-3 and neurotrophin-4 content in the sensorimotor cortex. Thus, IR prevents the age-associated decrease in the sensorimotor cortex volume, which is associated with neurotrophic and neurogenic changes. Meanwhile, IR-induced increases in locomotor activity may be the cause of the observed changes.

Assessment of Temporal Somatosensory Discrimination in Females with Fibromyalgia: Reliability and Discriminative Ability of a New Assessment Tool.

We assessed the test-retest reliability and discriminative ability of a somatosensory temporal discrimination (SSTD) assessment tool for fibromyalgia syndrome (FMS) and determined if pain-related variables were associated with SSTD performance. Twenty-five women with FMS and twenty-five asymptomatic women were assessed during two sessions 7 to 10 days apart. The proportion of correct responses (range 0-100) was calculated. Sociodemographic information was collected for both groups. The participants with FMS also completed the widespread pain index and the Brief Pain Inventory. Test-retest reliability was verified by calculating intraclass correlation coefficients. Discriminative ability was verified by a between-group comparison of scores using a t-test. Associations between SSTD score and pain variables were tested using Pearson or Spearman correlation coefficients. The test-retest reliability of the SSTD score was excellent (ICC > 0.9, CI: 0.79-0.96) for the asymptomatic group and good for the FMS group (ICC: 0.81, 95% CI: 0.62-0.91). The median (Q1-Q3) test session SSTD score differed significantly between the FMS 84.1 (71-88) and the asymptomatic 91.6 (83.4-96.1) groups (p < 0.001). Only pain duration was associated with the SSTD score. In conclusion, the new SSTD test seems reliable for people with FMS and is discriminative. Further studies should examine its sensitivity to change and correlations with other SSTD tests.

Spatiotemporal dynamics of cortical somatosensory network in typically developing children.

Sense of touch is essential for our interactions with external objects and fine control of hand actions. Despite extensive research on human somatosensory processing, it is still elusive how involved brain regions interact as a dynamic network in processing tactile information. Few studies probed temporal dynamics of somatosensory information flow and reported inconsistent results. Here, we examined cortical somatosensory processing through magnetic source imaging and cortico-cortical coupling dynamics. We recorded magnetoencephalography signals from typically developing children during unilateral pneumatic stimulation. Neural activities underlying somatosensory evoked fields were mapped with dynamic statistical parametric mapping, assessed with spatiotemporal activation analysis, and modeled by Granger causality. Unilateral pneumatic stimulation evoked prominent and consistent activations in the contralateral primary and secondary somatosensory areas but weaker and less consistent activations in the ipsilateral primary and secondary somatosensory areas. Activations in the contralateral primary motor cortex and supramarginal gyrus were also consistently observed. Spatiotemporal activation and Granger causality analysis revealed initial serial information flow from contralateral primary to supramarginal gyrus, contralateral primary motor cortex, and contralateral secondary and later dynamic and parallel information flows between the consistently activated contralateral cortical areas. Our study reveals the spatiotemporal dynamics of cortical somatosensory processing in the normal developing brain.

Spiking networks that efficiently process dynamic sensory features explain receptor information mixing in somatosensory cortex.

How do biological neural systems efficiently encode, transform and propagate information between the sensory periphery and the sensory cortex about sensory features evolving at different time scales? Are these computations efficient in normative information processing terms? While previous work has suggested that biologically plausible models of of such neural information processing may be implemented efficiently within a single processing layer, how such computations extend across several processing layers is less clear. Here, we model propagation of multiple time-varying sensory features across a sensory pathway, by extending the theory of efficient coding with spikes to efficient encoding, transformation and transmission of sensory signals. These computations are optimally realized by a multilayer spiking network with feedforward networks of spiking neurons (receptor layer) and recurrent excitatory-inhibitory networks of generalized leaky integrate-and-fire neurons (recurrent layers). Our model efficiently realizes a broad class of feature transformations, including positive and negative interaction across features, through specific and biologically plausible structures of feedforward connectivity. We find that mixing of sensory features in the activity of single neurons is beneficial because it lowers the metabolic cost at the network level. We apply the model to the somatosensory pathway by constraining it with parameters measured empirically and include in its last node, analogous to the primary somatosensory cortex (S1), two types of inhibitory neurons: parvalbumin-positive neurons realizing lateral inhibition, and somatostatin-positive neurons realizing winner-take-all inhibition. By implementing a negative interaction across stimulus features, this model captures several intriguing empirical observations from the somatosensory system of the mouse, including a decrease of sustained responses from subcortical networks to S1, a non-linear effect of the knock-out of receptor neuron types on the activity in S1, and amplification of weak signals from sensory neurons across the pathway.

Tactile sensory processing deficits in genetic mouse models of autism spectrum disorder.

Altered sensory processing is a common feature in autism spectrum disorder (ASD), as recognized in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). Although altered responses to tactile stimuli are observed in over 60% of individuals with ASD, the neurobiological basis of this phenomenon is poorly understood. ASD has a strong genetic component and genetic mouse models can provide valuable insights into the mechanisms underlying tactile abnormalities in ASD. This review critically addresses recent findings regarding tactile processing deficits found in mouse models of ASD, with a focus on behavioral, anatomical, and functional alterations. Particular attention was given to cellular and circuit-level functional alterations, both in the peripheral and central nervous systems, with the objective of highlighting possible convergence mechanisms across models. By elucidating the impact of mutations in ASD candidate genes on somatosensory circuits and correlating them with behavioral phenotypes, this review significantly advances our understanding of tactile deficits in ASD. Such insights not only broaden our comprehension but also pave the way for future therapeutic interventions.