title: Altered neurovascular coupling during information-processing states.
abstract: Brain imaging techniques rely on changes in blood flow, volume and oxygenation to infer the loci and magnitude of changes in activity. Although progress has been made in understanding the link between stimulus-evoked neural activity and haemodynamics, the extent to which neurovascular-coupling relationships remain constant during different states of baseline cortical activity is poorly understood. Optical imaging spectroscopy, laser Doppler flowmetry and electrophysiology were used to measure haemodynamics and neural activity in the barrel cortex of anaesthetized rats. The responses to stimulation of the whisker pad were recorded during quiescence and cortical desynchronization produced by stimulation of the brainstem. Cortical desynchronization was accompanied by increases in baseline blood flow, volume and oxygenation. Haemodynamic responses to low-frequency whisker stimuli (1 Hz) were attenuated during arousal compared with that observed during quiescence. During arousal it was possible to increase stimulus-evoked haemodynamics by increasing the frequency of the stimulus. Neural responses to low-frequency stimuli were also attenuated but to a far lesser extent than the reduction in the accompanying haemodynamics. In contrast, neuronal activity evoked by high-frequency stimuli (40 Hz) was enhanced during arousal, but induced haemodynamic responses of a similar magnitude compared with that observed for the same high-frequency stimulus presented during quiescence. These data suggest that there may be differences in stimulus-evoked neural activity and accompanying haemodynamics during different information-processing states.
authors.affiliation: The Centre for Signal Processing in Neuroimaging and Systems Neuroscience, Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TP, UK. m.jones@sheffield.ac.uk
authors.forename: Myles
authors.initials: M
authors.lastname: Jones
authors.forename: Ian M
authors.initials: IM
authors.lastname: Devonshire
authors.forename: Jason
authors.initials: J
authors.lastname: Berwick
authors.forename: Chris
authors.initials: C
authors.lastname: Martin
authors.forename: Peter
authors.initials: P
authors.lastname: Redgrave
authors.forename: John
authors.initials: J
authors.lastname: Mayhew
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D002536:Cerebral Arteries / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004594:Electrophysiology; D005073:Evoked Potentials, Somatosensory / Q000502:physiology; D005260:Female; D017078:Laser-Doppler Flowmetry; D008606:Mental Processes / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D055095:Optics and Photonics; D010465:Perception / Q000502:physiology*; D010812:Physical Stimulation; D051381:Rats; D013003:Somatosensory Cortex / Q000098:blood supply* / Q000502:physiology*; D013057:Spectrum Analysis; D014110:Touch / Q000502:physiology*; D014276:Trigeminal Nerve / Q000502:physiology; D014738:Vibrissae / Q000294:innervation / Q000502:physiology