Mechanoreceptor synapses in the brainstem shape the central representation of touch

Abstract

Highlights d Disproportionate representation of glabrous skin emerges over postnatal development d Body representation remaps over development through changes at brainstem synapses d Adult mechanoreceptors in or near glabrous skin make stronger central synapses d Regional differences in mechanoreceptor synaptic strength persist absent evoked activity.

Expansion and contraction of resource allocation in sensory bottlenecks

“…Indeed, evidence from non-human primates shows that cortical magnification also critically depends on experience ( Xerri et al, 1996, 1999 ). Similar results have recently been obtained from the brainstem in mice ( Lehnert et al, 2021 ). Empirically reported differences in sizes of receptive fields between the digit-tips and palm have also been recreated from typical contact across the hand during grasping ( Bhand et al, 2011 ), suggesting an influence of hand use statistics.…”

“…Indeed, evidence from non-human primates shows that cortical magnification also critically depends on experience (Xerri et al, 1996(Xerri et al, , 1999. Similar results have recently been obtained from the brainstem in mice (Lehnert et al, 2021). Empirically reported differences in sizes of receptive fields between the digit-tips and palm have also been recreated from typical contact across the hand during grasping (Bhand et al, 2011) Specifically, it would be expected that optic nerves containing a high number of fibers would devote proportionally fewer of them to the fovea than optic nerves containing smaller numbers of fibers (assuming equal receptor densities and numbers in the retina).…”

Focused ultrasound excites action potentials in mammalian peripheral neurons in part through the mechanically gated ion channel PIEZO2

“…Thus, we next asked whether activation of peripheral neurons with sonication requires PIEZO2. We generated Cdx2 Cre ; Piezo2 fl/fl mice, which harbor a deletion of Piezo2 in caudal tissues including peripheral neurons ( 29 , 31 , 32 ). Mechanosensitivity is significantly reduced in A-fiber mechanosensory neurons lacking functional PIEZO2 ( 29 , 30 ); thus, an electrical search method was used to identify A-fiber responses (both Aβ and Aδ fibers) from Cdx2 Cre ; Piezo2 fl/fl and control genotypes ( 33 ).…”

Changes in Sensorimotor Connectivity to dI3 Interneurons in Relation to the Postnatal Maturation of Grasping

“…The receptive fields and thresholds of these nociceptive reflexes are modified, while the amplitude and direction of the evoked motor reflex become greater and more specific (Holmberg and Schouenborg, 1996). Some of these changes may be related to modifications in the connectivity of sensory afferents with their target spinal neurons as sensory afferents in the spinal cord and brainstem undergo a substantial amount of postnatal sensory pruning (Gibson and Clowry, 1999;Granmo et al, 2008;Lehnert et al, 2021). This pruning further supports the idea that maturation of motor control is accompanied by a state of higher regulation of sensory excitability.…”

“…While sensory inputs are the first to extend into the spinal cord, sensory innervation is continually fine-tuned during postnatal development. During the first three postnatal weeks, sensory connections to the central nervous system are refined, including sprouting and eliminating synaptic inputs (Fitzgerald et al, 1994;Granmo et al, 2008;Lehnert et al, 2021). Simultaneously, the circuits that act to gate sensory feedback are also being established.…”