title: Long-latency reductions in gamma power predict hemodynamic changes that underlie the negative BOLD signal.
abstract: Studies that use prolonged periods of sensory stimulation report associations between regional reductions in neural activity and negative blood oxygenation level-dependent (BOLD) signaling. However, the neural generators of the negative BOLD response remain to be characterized. Here, we use single-impulse electrical stimulation of the whisker pad in the anesthetized rat to identify components of the neural response that are related to "negative" hemodynamic changes in the brain. Laminar multiunit activity and local field potential recordings of neural activity were performed concurrently with two-dimensional optical imaging spectroscopy measuring hemodynamic changes. Repeated measurements over multiple stimulation trials revealed significant variations in neural responses across session and animal datasets. Within this variation, we found robust long-latency decreases (300 and 2000 ms after stimulus presentation) in gamma-band power (30-80 Hz) in the middle-superficial cortical layers in regions surrounding the activated whisker barrel cortex. This reduction in gamma frequency activity was associated with corresponding decreases in the hemodynamic responses that drive the negative BOLD signal. These findings suggest a close relationship between BOLD responses and neural events that operate over time scales that outlast the initiating sensory stimulus, and provide important insights into the neurophysiological basis of negative neuroimaging signals.
authors: Department of Psychology, University of Sheffield, Sheffield S10 2TP, United Kingdom, and L.boorman@sheffield.ac.uk.
authors: Luke
authors: L
authors: Boorman
authors: Department of Psychology, University of Sheffield, Sheffield S10 2TP, United Kingdom, and.
authors: Samuel
authors: S
authors: Harris
authors: Department of Psychology, University of Sheffield, Sheffield S10 2TP, United Kingdom, and.
authors: Michael
authors: M
authors: Bruyns-Haylett
authors: Department of Psychology, University of Sheffield, Sheffield S10 2TP, United Kingdom, and.
authors: Aneurin
authors: A
authors: Kennerley
authors: School of Systems Engineering, University of Reading, Reading RG6 6AY, United Kingdom.
authors: Ying
authors: Y
authors: Zheng
authors: Department of Psychology, University of Sheffield, Sheffield S10 2TP, United Kingdom, and.
authors: Chris
authors: C
authors: Martin
authors: Department of Psychology, University of Sheffield, Sheffield S10 2TP, United Kingdom, and.
authors: Myles
authors: M
authors: Jones
authors: Department of Psychology, University of Sheffield, Sheffield S10 2TP, United Kingdom, and.
authors: Peter
authors: P
authors: Redgrave
authors: Department of Psychology, University of Sheffield, Sheffield S10 2TP, United Kingdom, and.
authors: Jason
authors: J
authors: Berwick
mesh_terms: D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D005544:Forecasting; D065818:Gamma Rhythm / Q000502:physiology*; D006439:Hemodynamics / Q000502:physiology*; D051381:Rats; D013003:Somatosensory Cortex / Q000502:physiology*; D013997:Time Factors; D014738:Vibrissae / Q000502:physiology
keywords: fMRI; gamma power; long latency; negative BOLD; neurovascular coupling; whisker barrel cortex