Somatosensory system

About: Somatosensory system is a research topic. Over the lifetime, 6371 publications have been published within this topic receiving 316900 citations.

Improvement and decline in tactile discrimination behavior after cortical plasticity induced by passive tactile coactivation

Abstract: Perceptual learning can be induced by passive tactile coactivation without attention or reinforcement. We used functional MRI (fMRI) and psychophysics to investigate in detail the specificity of this type of learning for different tactile discrimination tasks and the underlying cortical reorganization. We found that a few hours of Hebbian coactivation evoked a significant increase of primary (SI) and secondary (SII) somatosensory cortical areas representing the stimulated body parts. The amount of plastic changes was strongly correlated with improvement in spatial discrimination performance. However, in the same subjects, frequency discrimination was impaired after coactivation, indicating that even maladaptive processes can be induced by intense passive sensory stimulation.

Local GABAergic signaling within sensory ganglia controls peripheral nociceptive transmission

Abstract: The integration of somatosensory information is generally assumed to be a function of the central nervous system (CNS). Here we describe fully functional GABAergic communication within rodent peripheral sensory ganglia and show that it can modulate transmission of pain-related signals from the peripheral sensory nerves to the CNS. We found that sensory neurons express major proteins necessary for GABA synthesis and release and that sensory neurons released GABA in response to depolarization. In vivo focal infusion of GABA or GABA reuptake inhibitor to sensory ganglia dramatically reduced acute peripherally induced nociception and alleviated neuropathic and inflammatory pain. In addition, focal application of GABA receptor antagonists to sensory ganglia triggered or exacerbated peripherally induced nociception. We also demonstrated that chemogenetic or optogenetic depolarization of GABAergic dorsal root ganglion neurons in vivo reduced acute and chronic peripherally induced nociception. Mechanistically, GABA depolarized the majority of sensory neuron somata, yet produced a net inhibitory effect on the nociceptive transmission due to the filtering effect at nociceptive fiber T-junctions. Our findings indicate that peripheral somatosensory ganglia represent a hitherto underappreciated site of somatosensory signal integration and offer a potential target for therapeutic intervention.

Fine-Grained Nociceptive Maps in Primary Somatosensory Cortex

Abstract: Topographic maps of the receptive surface are a fundamental feature of neural organization in many sensory systems. While touch is finely mapped in the cerebral cortex, it remains controversial how precise any cortical nociceptive map may be. Given that nociceptive innervation density is relatively low on distal skin regions such as the digits, one might conclude that the nociceptive system lacks fine representation of these regions. Indeed, only gross spatial organization of nociceptive maps has been reported so far. However, here we reveal the existence of fine-grained somatotopy for nociceptive inputs to the digits in human primary somatosensory cortex (SI). Using painful nociceptive-selective laser stimuli to the hand, and phase-encoded functional magnetic resonance imaging analysis methods, we observed somatotopic maps of the digits in contralateral SI. These nociceptive maps were highly aligned with maps of non-painful tactile stimuli, suggesting comparable cortical representations for, and possible interactions between, mechanoreceptive and nociceptive signals. Our findings may also be valuable for future studies tracking the time course and the spatial pattern of plastic changes in cortical organization involved in chronic pain.

Viewing the body prepares the brain for touch: effects of TMS over somatosensory cortex.

Abstract: Viewing the body can improve tactile perception. We investigated whether this could be due to a remodeling of somatosensory cortical areas during vision of the body. Single-pulse transcranial magnetic stimulation (TMS) was delivered over the primary and secondary somatosensory areas of subjects who showed clear visual-tactile enhancement while they performed a tactile grating discrimination task. Before the tactile stimulus, subjects viewed either their right index finger through a semisilvered mirror or an object reflected by the mirror and positioned to appear in the same location as the finger. In a first experiment we observed that TMS over primary somatosensory cortex significantly reduced subjects' accuracy whilst viewing the hand. No such reduction was found when subjects viewed a neutral object. In a second experiment, we disrupted the activity of primary and secondary somatosensory areas in different sessions. When stimulating the primary somatosensory cortex, a reduction in accuracy was again found while viewing the hand, but not a neutral object. TMS over secondary somatosensory cortex had no effect in any condition. Our results show that vision of the body may act at an early stage in stimulus elaboration and perception, allowing an anticipatory tuning of the neural circuits in primary somatosensory cortex that underlie tactile acuity.

Plasticity in the barrel cortex of the adult mouse: transient increase of GAD-immunoreactivity following sensory stimulation

Abstract: Sensory experience during perinatal life and adulthood modifies physiological and anatomical characteristics of the central nervous system. So far, this phenomenon has been studied in situations of complete or partial sensory deprivation. We here report that increased sensory stimulation, during four days, of a number of whisker follicles on the face of the adult mouse results in an increased immunoreactivity of glutamic acid decarboxylase (the biosynthetic enzyme of the inhibitory neurotransmitter GABA) in the somatosensory cortex of the adult mouse. Effects were limited to a column of tissue corresponding to the representation of the stimulated follicles and lasted two days beyond stimulation. These findings suggest that sensory stimulation transiently modifies local cortical processing.