Abstract
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.
Highlights
Interactions between sensory and frontal cortices are likely important for sensory perception and motor control.[1,2,3,4,5] Sensory information is often actively acquired through self-generated movements of sensors to specific locations to gather selected sensory input
Voltage-sensitive dye imaging was carried out using a custom made macroscope, which provided 630 nm excitation light from a 100-W halogen lamp, gated by a shutter (Vincent Associates) under computer control via an ITC18, communicating with custom software running within IgorPro (Wavemetrics)
We investigated the axonal projections from the frontal cortical areas wM1 and Cg-M2 through injecting associated viral (AAV) into these regions
Summary
Interactions between sensory and frontal cortices are likely important for sensory perception and motor control.[1,2,3,4,5] Sensory information is often actively acquired through self-generated movements of sensors to specific locations to gather selected sensory input. Sensory information is typically used to inform motor control allowing precise movements guided by sensory feedback. The mouse whisker and visual systems appear useful for the detailed study of sensorimotor interactions underlying active sensing.[6,7,8,9,10] functional maps in sensory cortices are increasingly becoming understood, much less is known about the organization of mouse frontal cortex.[2,11,12,13] Previous studies of the mouse whisker system have found functionally important projections from primary whisker somatosensory barrel cortex (wS1) to a frontal region, termed the primary whisker motor cortex (wM1).[1,10,14,15,16,17,18] Here, we investigate the functional and anatomical organization of signaling from visual cortex to frontal cortex in comparison to the whisker system through voltage-sensitive dye imaging[19] and anatomical labeling of axonal projections
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