Article

Trial-by-trial relationship between neural activity, oxygen consumption, and blood flow responses.

Department of Radiology, University of Pittsburgh, Pittsburgh, PA, USA.
NeuroImage (impact factor: 5.89). 05/2008; 40(2):442-50. DOI:10.1016/j.neuroimage.2007.12.011 pp.442-50
Source: PubMed

ABSTRACT Trial-by-trial variability in local field potential (LFP), tissue partial pressure of oxygen (PO2), cerebral blood flow (CBF), and deoxyhemoglobin-weighted optical imaging of intrinsic signals (OIS) were tested in the rat somatosensory cortex while fixed electrical forepaw stimulation (1.0-ms pulses with amplitude of 1.2 mA at a frequency of 6 Hz) was repeatedly applied. The changes in the cerebral metabolic rate of oxygen (CMRO2) were also evaluated using a hypotension condition established by our group based on the administration of a vasodilator. Under normal conditions, CBF, PO2, and OIS showed positive signal changes (48%, 32%, and 0.42%, respectively) following stimulation. Over multiple trials, the CBF responses were well correlated with the integral of the LFP amplitudes (sigmaLFP) (Rmean=0.78), whereas a lower correlation was found between PO2 and sigmaLFP (Rmean=0.60) and between OIS and sigmaLFP (Rmean=0.54). Under the hypotension condition the LFP responses were preserved, but the CBF responses were suppressed and the PO2 and OIS changes were negative (-12% and -0.28%, respectively). In this condition, the trial-by-trial variations in PO2 and OIS were well correlated with the variability in sigmaLFPs (Rmean= -0.77 and -0.76, respectively), indicating a single trial coupling between CMRO2 changes and sigmaLFP. These findings show that CBF and CMRO2 signals are more directly correlated with neural activity compared to blood oxygen-sensitive methods such as OIS and BOLD fMRI.

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Keywords

blood oxygen-sensitive methods
 
BOLD fMRI
 
CBF responses
 
cerebral blood flow
 
CMRO2 signals
 
deoxyhemoglobin-weighted optical imaging
 
hypotension condition
 
intrinsic signals
 
LFP amplitudes
 
LFP responses
 
local field potential
 
multiple trials
 
neural activity
 
normal conditions
 
positive signal changes
 
rat somatosensory cortex
 
single trial coupling
 
tissue partial pressure
 
Trial-by-trial variability
 
trial-by-trial variations