Cerebral blood flow regulation under activation of the primary somatosensory cortex during electrical stimulation of the forearm

Coupling of neuronal activity to cerebral blood flow (CBF) is widely accept ed, but the exact mechanism is still under investigation. We assessed the r esponses of CBF coupled with electrical activity over the primary somatosen sory cortex (S-l) during electrical stimulation of the contralateral forear m in cats. CBF in S-l was monitored using laser-Doppler flowmetry (LDF) and electrical activity was recorded with a tungsten microelectrode. The effec ts of varying stimulus intensity and frequency were examined to assess the optimal stimulation parameters. CBF increased within 10 sec after onset of stimulation, sustained the plateau level, and returned to the pm-stimulus l evel after cessation of stimulation. The maximum response was obtained at 4 Hz under a constant intensity. Optimal stimulus intensity at 4 Hz ranged f rom 8 to 10 V. At intensity higher than 10 V, CBF increases reached a near- plateau level, while mean arterial blood pressure (MABP) decreased slightly . Electrical activity was recorded at the same restricted area where CBF in creased. Low frequency components of the power spectrum of electrical activ ity increased as the CBF increase became greater. A tight coupling of CBF i ncreases to neuronal activation is suggested, and CBF regulation may be aff ected by stimulation parameters.