title: Activity in motor-sensory projections reveals distributed coding in somatosensation.
abstract: Cortical-feedback projections to primary sensory areas terminate most heavily in layer 1 (L1) of the neocortex, where they make synapses with tuft dendrites of pyramidal neurons. L1 input is thought to provide ‘contextual’ information, but the signals transmitted by L1 feedback remain uncharacterized. In the rodent somatosensory system, the spatially diffuse feedback projection from vibrissal motor cortex (vM1) to vibrissal somatosensory cortex (vS1, also known as the barrel cortex) may allow whisker touch to be interpreted in the context of whisker position to compute object location. When mice palpate objects with their whiskers to localize object features, whisker touch excites vS1 and later vM1 in a somatotopic manner. Here we use axonal calcium imaging to track activity in vM1-->vS1 afferents in L1 of the barrel cortex while mice performed whisker-dependent object localization. Spatially intermingled individual axons represent whisker movements, touch and other behavioural features. In a subpopulation of axons, activity depends on object location and persists for seconds after touch. Neurons in the barrel cortex thus have information to integrate movements and touches of multiple whiskers over time, key components of object identification and navigation by active touch.
authors.affiliation: Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia 20147, USA.
authors.forename: Leopoldo
authors.initials: L
authors.lastname: Petreanu
authors.forename: Diego A
authors.initials: DA
authors.lastname: Gutnisky
authors.forename: Daniel
authors.initials: D
authors.lastname: Huber
authors.forename: Ning-long
authors.initials: NL
authors.lastname: Xu
authors.forename: Dan H
authors.initials: DH
authors.lastname: O'Connor
authors.forename: Lin
authors.initials: L
authors.lastname: Tian
authors.forename: Loren
authors.initials: L
authors.lastname: Looger
authors.forename: Karel
authors.initials: K
authors.lastname: Svoboda
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism; D020013:Calcium Signaling; D025461:Feedback, Physiological; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009044:Motor Cortex / Q000166:cytology / Q000502:physiology*; D009046:Motor Neurons / Q000378:metabolism; D009068:Movement / Q000502:physiology; D009434:Neural Pathways; D010812:Physical Stimulation; D013003:Somatosensory Cortex / Q000166:cytology / Q000502:physiology*; D014110:Touch / Q000502:physiology*; D014738:Vibrissae / Q000502:physiology*