Pathway-, layer- and cell-type-specific thalamic input to mouse barrel cortex

Abstract

Mouse primary somatosensory barrel cortex (wS1) processes whisker sensory information, receiving input from two distinct thalamic nuclei. The first-order ventral posterior medial (VPM) somatosensory thalamic nucleus most densely innervates layer 4 (L4) barrels, whereas the higher-order posterior thalamic nucleus (medial part, POm) most densely innervates L1 and L5A. We optogenetically stimulated VPM or POm axons, and recorded evoked excitatory postsynaptic potentials (EPSPs) in different cell-types across cortical layers in wS1. We found that excitatory neurons and parvalbumin-expressing inhibitory neurons received the largest EPSPs, dominated by VPM input to L4 and POm input to L5A. In contrast, somatostatin-expressing inhibitory neurons received very little input from either pathway in any layer. Vasoactive intestinal peptide-expressing inhibitory neurons received an intermediate level of excitatory input with less apparent layer-specificity. Our data help understand how wS1 neocortical microcircuits might process and integrate sensory and higher-order inputs.

Anatomically and functionally distinct thalamocortical inputs to primary and secondary mouse whisker somatosensory cortices

“…Although synaptic integration of thalamocortical inputs in wS1 has begun to be characterized 8,9,11,24,25 , little is known regarding synaptic responses of wS2 excitatory neurons to thalamocortical axonal stimulation. To characterize glutamatergic drive exerted by POm-FO and POm-HO thalamocortical circuits in different layers of wS2, we performed ex vivo whole-cell recordings of membrane potential in parasagittal slices of mice expressing channelrhodopsin-2 in these nuclei ( Fig.…”

“…Sensory information is relayed through parallel modality-specific thalamic nuclei to modality-specific sensory cortices for vision, hearing, taste and touch. For rodents, whisker-related tactile somatosensation provides important information about the structure of their immediate surroundings, and several whisker-related thalamocortical signaling pathways have begun to be characterized [1][2][3][4][5][6][7][8][9][10][11] . In particular, the lemniscal and paralemniscal pathways involve the ventral posterior medial (VPM) nucleus and the posterior medial (POm) group of the thalamus, respectively, with segregated thalamocortical projections [11][12][13][14] .…”

Sensory input drives rapid homeostatic scaling of the axon initial segment in mouse barrel cortex

“…This pathway conveys tactile information from vibrissae on the rodent whisker pad to the barrel field in primary somatosensory cortex (S1BF) in a strictly organized hierarchy and is one of the best-studied sensory systems (reviewed in (Petersen, 2007;Wu et al, 2011)). Thalamic input is largely received by layer IV spiny stellate neurons and propagated to supragranular (layer II/III) neurons; infragranular (layer V) principal neurons also receive direct thalamic input (Sermet et al, 2019). S1BF undergoes activity-dependent maturation with several critical periods during postnatal development (reviewed in (Erzurumlu and Gaspar, 2012;Jamann et al, 2018)), ultimately resulting in a precise somatotopic representation of each whisker in a cortical barrel layer IV (Feldmeyer et al, 2013).…”

An increase in dendritic plateau potentials is associated with experience-dependent cortical map reorganization

“…Here (Figure 3), as in previous work (Gambino et al, 2014), we show that plateau potentials in the barrel cortex depend in part on activity of the POm division of the thalamus. POm neurons send dense axonal projections to L1 in S1 (Ohno et al, 2012;Wimmer et al, 2010b), where they spread out over multiple barrel columns and make synaptic contacts with apical dendrites of numerous L2/3 pyramidal neurons (Bureau et al, 2006;Feldmeyer, 2012;Gambino et al, 2014;Jones, 2000;Jouhanneau et al, 2014;Ohno et al, 2012;Petreanu et al, 2009;Sermet et al, 2019;Zhang and Bruno, 2019). Interestingly, neurons located in this higher-order thalamic nucleus have large receptive fields (Diamond et al, 1992;Jouhanneau et al, 2014;Masri et al, 2008), and the POm input-recipient L2/3 neurons are characterized by large and short-latency responses to multiple whisker deflections (Jouhanneau et al, 2014).…”