Simultaneous measurements of microflow and evoked potentials in the somatomotor cortex of the cat brain during specific sensory activation.

The behaviour of both microflow and evoked potentials was investigated in the right somatomotor cortex of the cat (anaesthetized with chloralose) during electrical stimulation of the contralateral left forepaw. Frequency, amplitude, and time of stimulation were varied. Using the local hydrogen clearance method the changes of microflow were continuously monitored in the same cortical area from which the evoked potentials were recorded. The experiments have shown that activation of the somatomotor cortex by somatic stimulation of the contralateral forepaw results in changes of microflow which clearly correlate to the side and amplitude of the primary evoked potentials. An increase in flow as well as in amplitude of the potentials depends on the stimulation parameters. The changes of microflow are limited to a small area of 1--2 mm in diameter. We conclude that a tight coupling of flow to functional activity exists in the microcirculatory range.