Nonlinear correlation between field potential and local cerebral blood flow in rat somatosensory cortex evoked by changing the stimulus current

The relationship between local cerebral blood flow (LCBF) and field potential (FP) evoked by hindpaw stimulation in rat somatosensory cortex has been investigated while changing stimulus current. The change in LCBF was measured using laser-Doppler flowmetry and the field potential was acquired using a tungsten electrode inserted into the cortex of alpha-chloralose-anesthetized rats. The cortex was activated by electrical stimulation of the hind paw with 5 Hz pulses (0. 1 ms) applied at currents of 1.0, 1.5, 2.0 and 2.5 mA for 5 s. It was found that the summed FP is nonlinear with respect to stimulus current, whereas the integrated LCBF response is linear across the range of currents used in the experiment. This means that the relationship between the summed FP and integrated LCBF is nonlinear as a function of stimulus current. (C) 2004 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.