Somatosensory system

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

In vivo voltage-sensitive dye imaging in adult mice reveals that somatosensory maps lost to stroke are replaced over weeks by new structural and functional circuits with prolonged modes of activation within both the peri-infarct zone and distant sites.

Abstract: After brain damage such as stroke, topographically organized sensory and motor cortical representations remap onto adjacent surviving tissues. It is conceivable that cortical remapping is accomplished by changes in the temporal precision of sensory processing and regional connectivity in the cortex. To understand how the adult cortex remaps and processes sensory signals during stroke recovery, we performed in vivo imaging of sensory-evoked changes in membrane potential, as well as multiphoton imaging of dendrite structure and tract tracing. In control mice, forelimb stimulation evoked a brief depolarization in forelimb cortex that quickly propagated to, and dissipated within, adjacent motor/hindlimb areas (<100 ms). One week after forelimb cortex stroke, the cortex was virtually unresponsive to tactile forelimb stimulation. After 8 weeks recovery, forelimb-evoked depolarizations reemerged with a characteristic pattern in which responses began within surviving portions of forelimb cortex (<20 ms after stimulation) and then spread horizontally into neighboring peri-infarct motor/hindlimb areas in which depolarization persisted 300-400% longer than controls. These uncharacteristically prolonged responses were not limited to the remapped peri-infarct zone and included distant posteromedial retrosplenial cortex, millimeters from the stroke. Structurally, the remapped peri-infarct area selectively exhibited high levels of dendritic spine turnover, shared more connections with retrosplenial cortex and striatum, and lost inputs from lateral somatosensory cortical regions. Our findings demonstrate that sensory remapping during stroke recovery is accompanied by the development of prolonged sensory responses and new structural circuits in both the peri-infarct zone as well as more distant sites.

Essential role of POU–domain factor Brn-3c in auditory and vestibular hair cell development

Abstract: The Brn-3 subfamily of POU–domain transcription factor genes consists of three highly homologous members—Brn-3a, Brn-3b, and Brn-3c—that are expressed in sensory neurons and in a small number of brainstem nuclei. This paper describes the role of Brn-3c in auditory and vestibular system development. In the inner ear, the Brn-3c protein is found only in auditory and vestibular hair cells, and the Brn-3a and Brn-3b proteins are found only in subsets of spiral and vestibular ganglion neurons. Mice carrying a targeted deletion of the Brn-3c gene are deaf and have impaired balance. These defects reflect a complete loss of auditory and vestibular hair cells during the late embryonic and early postnatal period and a secondary loss of spiral and vestibular ganglion neurons. Together with earlier work demonstrating a loss of trigeminal ganglion neurons and retinal ganglion cells in mice carrying targeted disruptions in the Brn-3a and Brn-3b genes, respectively, the Brn-3c phenotype reported here demonstrates that each of the Brn-3 genes plays distinctive roles in the somatosensory, visual, and auditory/vestibular systems.

Somatic sensory responses in the rostral sector of the posterior group (POm) and in the ventral posterior medial nucleus (VPM) of the rat thalamus.

Abstract: The rodent barrel field cortex integrates somatosensory information from two separate thalamic nuclei, the ventral posterior medial nucleus (VPM) and the rostral sector of the posterior complex (POm). This paper compares the sensory responses of POm and VPM cells in urethane-anesthetized rats as a first step in determining how cortex integrates multiple sensory pathways. A complete representation of the contralateral body surface was identified in POm. Trigeminal receptive fields (RFs) of POm and VPM cells were mapped by computer-controlled displacement of individual whiskers; responses were quantified by using peristimulus time histograms. Average RF size was similar in POm (5.1 whiskers) and VPM (4.4 whiskers), but evoked responses in the two nuclei differed significantly according to all other measures. VPM cells were maximally responsive to one single whisker--the "center RF." Stimulating this whisker evoked, on average, a response of 1.4 spikes/stimulus at a latency of 7 ms; surrounding whiskers evoked responses of less than 1 spike/stimulus at latencies of greater than 8 ms. In contrast, POm cells were nearly equally responsive to several whiskers. Quantitative criteria allowed us to designate a single whisker as the "center RF" and stimulating this whisker evoked, on average, a response of 0.5 spikes/stimulus at a latency of 19 ms. VPM cells, but not POm cells, were able to "follow" repeated whisker deflection at greater than 5 Hz. We conclude that, when a single whisker is deflected, VPM activates the related cortical barrel-column at short latency--before the onset of activity in POm. The timing of activation could allow POm cells to modulate the spread of activity between cortical columns.