Parallel pathways from whisker and visual sensory cortices to distinct frontal regions of mouse neocortex

The spatial organization of mouse frontal cortex is poorly understood. Here, we used voltage-sensitive dye to image electrical activity in the dorsal cortex of awake head-restrained mice. Whisker-deflection evoked the earliest sensory response in a localized region of primary somatosensory cortex and visual stimulation evoked the earliest responses in a localized region of primary visual cortex. Over the next milliseconds, the initial sensory response spread within the respective primary sensory cortex and into the surrounding higher order sensory cortices. In addition, secondary hotspots in the frontal cortex were evoked by whisker and visual stimulation, with the frontal hotspot for whisker deflection being more anterior and lateral compared to the frontal hotspot evoked by visual stimulation. Investigating axonal projections, we found that the somatosensory whisker cortex and the visual cortex directly innervated frontal cortex, with visual cortex axons innervating a region medial and posterior to the innervation from somatosensory cortex, consistent with the location of sensory responses in frontal cortex. In turn, the axonal outputs of these two frontal cortical areas innervate distinct regions of striatum, superior colliculus, and brainstem. Sensory input, therefore, appears to map onto modality-specific regions of frontal cortex, perhaps participating in distinct sensorimotor transformations, and directing distinct motor outputs. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.

Parallel pathways from motor and somatosensory cortex for controlling whisker movements in mice

Carl Petersen, Varun Sreenivasan

Mice can gather tactile sensory information by actively moving their whiskers to palpate objects in their immediate surroundings. Whisker sensory perception therefore requires integration of sensory and motor information, which occurs prominently in the neocortex. The signalling pathways from the neocortex for controlling whisker movements are currently poorly understood in mice. Here, we delineate two pathways, one originating from primary whisker somatosensory cortex (wS1) and the other from whisker motor cortex (wM1), that control qualitatively distinct movements of contralateral whiskers. Optogenetic stimulation of wS1 drove retraction of contralateral whiskers while stimulation of wM1 drove rhythmic whisker protraction. To map brainstem pathways connecting these cortical areas to whisker motor neurons, we used a combination of anterograde tracing using adenoassociated virus injected into neocortex and retrograde tracing using monosynaptic rabies virus injected into whisker muscles. Our data are consistent with wS1 driving whisker retraction by exciting glutamatergic premotor neurons in the rostral spinal trigeminal interpolaris nucleus, which in turn activate the motor neurons innervating the extrinsic retractor muscle nasolabialis. The rhythmic whisker protraction evoked by wM1 stimulation might be driven by excitation of excitatory and inhibitory premotor neurons in the brainstem reticular formation innervating both intrinsic and extrinsic muscles. Our data therefore begin to unravel the neuronal circuits linking the neocortex to whisker motor neurons.

Wiley-Blackwell2015

Long-range connectivity of mouse primary somatosensory barrel cortex

Rachel Aronoff, Céline Matéo, Ferenc Mátyás, Carl Petersen, Bernard Schneider

The primary somatosensory barrel cortex processes tactile vibrissae information, allowing rodents to actively perceive spatial and textural features of their immediate surroundings. Each whisker on the snout is individually represented in the neocortex by an anatomically identifiable 'barrel' specified by the segregated termination zones of thalamocortical axons of the ventroposterior medial nucleus, which provide the primary sensory input to the neocortex. The sensory information is subsequently processed within local synaptically connected neocortical microcircuits, which have begun to be investigated in quantitative detail. In addition to these local synaptic microcircuits, the excitatory pyramidal neurons of the barrel cortex send and receive long-range glutamatergic axonal projections to and from a wide variety of specific brain regions. Much less is known about these long-range connections and their contribution to sensory processing. Here, we review current knowledge of the long-range axonal input and output of the mouse primary somatosensory barrel cortex. Prominent reciprocal projections are found between primary somatosensory cortex and secondary somatosensory cortex, motor cortex, perirhinal cortex and thalamus. Primary somatosensory barrel cortex also projects strongly to striatum, thalamic reticular nucleus, zona incerta, anterior pretectal nucleus, superior colliculus, pons, red nucleus and spinal trigeminal brain stem nuclei. These long-range connections of the barrel cortex with other specific cortical and subcortical brain regions are likely to play a crucial role in sensorimotor integration, sensory perception and associative learning.

Wiley-Blackwell2010

Voltage-sensitive dye imaging of mouse neocortex during a whisker detection task

Matthieu Pierre Auffret, Alexandros Kyriakatos, Alessandro Motta, Carl Petersen, Vijay Sadashivaiah, Yifei Zhang

Sensorimotor processing occurs in a highly distributed manner in the mammalian neocortex. The spatiotemporal dynamics of electrical activity in the dorsal mouse neocortex can be imaged using voltage-sensitive dyes (VSDs) with near-millisecond temporal resolution and similar to 100-mu m spatial resolution. Here, we trained mice to lick a water reward spout after a 1-ms deflection of the C2 whisker, and we imaged cortical dynamics during task execution with VSD RH1691. Responses to whisker deflection were highly dynamic and spatially highly distributed, exhibiting high variability from trial to trial in amplitude and spatiotemporal dynamics. We differentiated trials based on licking and whisking behavior. Hit trials, in which the mouse licked after the whisker stimulus, were accompanied by overall greater depolarization compared to miss trials, with the strongest hit versus miss differences being found in frontal cortex. Prestimulus whisking decreased behavioral performance by increasing the fraction of miss trials, and these miss trials had attenuated cortical sensorimotor responses. Our data suggest that the spatiotemporal dynamics of depolarization in mouse sensorimotor cortex evoked by a single brief whisker deflection are subject to important behavioral modulation during the execution of a simple, learned, goal-directed sensorimotor transformation. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.

SPIE-Intl Soc Optical Eng2017