Role of auditory-somatosensory corticothalamic circuit integration in analgesia

Abstract

Our sensory environment is permeated by a diverse array of auditory and somatosensory stimuli. The pairing of acoustic signals with concurrent or forthcoming tactile cues are abundant in everyday life and various survival contexts across species, thus deeming the ability to integrate sensory inputs arising from the combination of these stimuli as crucial. The corticothalamic system plays a critical role in orchestrating the construction, integration and distribution of the information extracted from these sensory modalities. In this mini-review, we provide a circuit-level description of the auditory corticothalamic pathway in conjunction with adjacent corticothalamic somatosensory projections. Although the extent of the functional interactions shared by these pathways is not entirely elucidated, activation of each of these systems appears to modulate sensory perception in the complementary domain. Several specific issues are reviewed. Under certain environmental noise conditions, the spectral information of a sound could induce modulations in nociception and even induce analgesia. We begin by discussing recent findings by Zhou et al. (2022) implicating the corticothalamic system in mediating sound-induced analgesia. Next, we describe relevant components of the corticothalamic pathway's functional organization. Additionally, we describe an emerging body of literature pointing to intrathalamic circuitry being optimal for controlling and selecting sensory signals across modalities, with the thalamic reticular nucleus being a candidate mechanism for directing cross-modal interactions. Finally, Ca²⁺ bursting in thalamic neurons evoked by the thalamic reticular nucleus is explored.

Keywords: Auditory-somatosensory integration; Corticothalamic circuits; Sound-induced analgesia; Thalamic Ca(2+) bursting.

Fig. 1.. Points of auditory-somatosensory integration.

Red arrows correspond to somatosensory-auditory connectivity established in the literature and reviewed in the text. Four main pathways have been described and are shown here: A dual L5/L6 projection from the auditory cortex to the somatosensory thalamus, a projection from L5 of somatosensory cortex to LC, projections from Sp5 and DCoN to both the CN and LC, and bidirectional communication between auditory and somatosensory thalamic nuclei via the TRN. Abbreviations: CN = cochlear nucleus, DCoN = dorsal column nuclei, LC = lateral cortex of the inferior colliculus, MGD = dorsal division of the medial geniculate body, MGV = ventral division of the medial geniculate body, PO = posterior medial nucleus of the thalamus, Sp5 = spinal trigeminal nucleus, TRN = thalamic reticular nucleus, VP = ventral posterior nucleus of the thalamus.