title: Early and late stimulus-evoked cortical hemodynamic responses provide insight into the neurogenic nature of neurovascular coupling.
abstract: Understanding neurovascular coupling is a prerequisite for the interpretation of results obtained from modern neuroimaging techniques. This study investigated the hemodynamic and neural responses in rat somatosensory cortex elicited by 16 seconds electrical whisker stimuli. Hemodynamics were measured by optical imaging spectroscopy and neural activity by multichannel electrophysiology. Previous studies have suggested that the whisker-evoked hemodynamic response contains two mechanisms, a transient 'backwards' dilation of the middle cerebral artery, followed by an increase in blood volume localized to the site of neural activity. To distinguish between the mechanisms responsible for these aspects of the response, we presented whisker stimuli during normocapnia ('control'), and during a high level of hypercapnia. Hypercapnia was used to 'predilate' arteries and thus possibly 'inhibit' aspects of the response related to the 'early' mechanism. Indeed, hemodynamic data suggested that the transient stimulus-evoked response was absent under hypercapnia. However, evoked neural responses were also altered during hypercapnia and convolution of the neural responses from both the normocapnic and hypercapnic conditions with a canonical impulse response function, suggested that neurovascular coupling was similar in both conditions. Although data did not clearly dissociate early and late vascular responses, they suggest that the neurovascular coupling relationship is neurogenic in origin.
authors: Department of Psychology, University of Sheffield, Sheffield, UK.
authors: Aneurin J
authors: AJ
authors: Kennerley
authors: Sam
authors: S
authors: Harris
authors: Michael
authors: M
authors: Bruyns-Haylett
authors: Luke
authors: L
authors: Boorman
authors: Ying
authors: Y
authors: Zheng
authors: Myles
authors: M
authors: Jones
authors: Jason
authors: J
authors: Berwick
mesh_terms: D000818:Animals; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004558:Electric Stimulation; D005071:Evoked Potentials / Q000502:physiology*; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006935:Hypercapnia / Q000503:physiopathology*; D020768:Middle Cerebral Artery / Q000503:physiopathology; D009474:Neurons / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013003:Somatosensory Cortex / Q000098:blood supply*; D013057:Spectrum Analysis / Q000379:methods; D013997:Time Factors; D014738:Vibrissae / Q000294:innervation / Q000502:physiology