Quantitative and temporal relationship between local cerebral blood flow and neuronal activation induced by somatosensory stimulation in rats

in many studies on functional neuroimaging, change in local cerebral blood flow induced by sensory stimulation (evoked LCBF) is used as a marker fut c hange in cortical neuronal activity, although a full description of the rel ationship between the evoked LCBF and neuronal activity has not been given. The purpose of this study was to estimate the close relationship between t he evoked LCBF and neuronal activity. We measured the field potential using an electrode inserted into the cortex and the evoked LCBF using Laser-Dopp ler flowmetry in alpha -chloralose-anesthetized rats during somatosensory s timulation. Activation of the cortex was carried out by electrical stimulat ion of the hind paw with 1.5 mA pulses (0.1 ms) applied at the Frequencies of 0.2, 1.5 and 10 Hz for a 5 s duration, and at the Frequencies of I and 5 Hz for 2, 5 and 15 s durations. The response magnitude of the evoked LCBF reached the maximum at 5 Hz. During the 5 s stimulation, the pattern of cha nge in the response magnitude of evoked LCBF to various frequencies reflect ed the integrated amplitude of field potentials. During the 15 s stimulatio n, the evoked LCBF at 5 Hz exhibited an initial peak followed by a plateau phase, although there was no initial peak at 1 Hz. These changes in evoked LCBF during the 1 s stimulation reflected change in field potentials, but t hey were delayed during the temporal change in field potentials. These resu lts suggest that the response of evoked LCBF reflects the integrated neuron al activity during the stimulation period, and it is modulated by a tempora l slow function. (C) 2001 Elsevier Science Ireland Ltd and the Japan Neuros cience Society. All rights reserved.