title: Mechanical restriction of intracortical vessel dilation by brain tissue sculpts the hemodynamic response.
abstract: Understanding the spatial dynamics of dilation in the cerebral vasculature is essential for deciphering the vascular basis of hemodynamic signals in the brain. We used two-photon microscopy to image neural activity and vascular dynamics in the somatosensory cortex of awake behaving mice during voluntary locomotion. Arterial dilations within the histologically-defined forelimb/hindlimb (FL/HL) representation were larger than arterial dilations in the somatosensory cortex immediately outside the FL/HL representation, demonstrating that the vascular response during natural behaviors was spatially localized. Surprisingly, we found that locomotion drove dilations in surface vessels that were nearly three times the amplitude of intracortical vessel dilations. The smaller dilations of the intracortical arterioles were not due to saturation of dilation. Anatomical imaging revealed that, unlike surface vessels, intracortical vessels were tightly enclosed by brain tissue. A mathematical model showed that mechanical restriction by the brain tissue surrounding intracortical vessels could account for the reduced amplitude of intracortical vessel dilation relative to surface vessels. Thus, under normal conditions, the mechanical properties of the brain may play an important role in sculpting the laminar differences of hemodynamic responses.
authors.affiliation: Center for Neural Engineering, Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA 16802, USA; Neuroscience Graduate Program, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Yu-Rong
authors.initials: YR
authors.lastname: Gao
authors.affiliation: Center for Neural Engineering, Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Stephanie E
authors.initials: SE
authors.lastname: Greene
authors.affiliation: Center for Neural Engineering, Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA 16802, USA; Neuroscience Graduate Program, Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, PA 16802, USA; Department of Neurosurgery, Pennsylvania State University, University Park, PA 16802, USA. Electronic address: pjd17@psu.edu.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Drew
mesh_terms: D000818:Animals; D001158:Arteries / Q000033:anatomy & histology / Q000502:physiology; D001160:Arterioles / Q000033:anatomy & histology / Q000502:physiology; D002536:Cerebral Arteries / Q000033:anatomy & histology / Q000502:physiology; D002540:Cerebral Cortex / Q000098:blood supply*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005552:Forelimb / Q000098:blood supply; D006614:Hindlimb / Q000098:blood supply; D007091:Image Processing, Computer-Assisted; D008124:Locomotion / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008959:Models, Neurological; D000069336:Neurovascular Coupling / Q000502:physiology; D012039:Regional Blood Flow; D013003:Somatosensory Cortex / Q000098:blood supply; D014664:Vasodilation / Q000502:physiology*
keywords: Somatosensory cortex; Tissue mechanics; Two-photon microscopy; Voluntary locomotion