Projection of limb venous afferents to the feline motor-sensory cortex.

Previous studies have shown that the cerebral cortex has the capacity to exert a marked influence on the circulatory system. Recently low threshold femoral vein afferent fiber projections to the spinal cord were reported and were found to have powerful reflex connections to motor neurons. The venous afferents appeared to be attractive candidates to provide afferent input to the cortex by the activation of ascending sensory systems. Therefore the experiments described in this report were carried out to determine the existence and functional organization of venous afferent projections to the cerebral cortex in the cat. Femoral and brachial vein afferent fibers were excited in the vein wall by electrical stimulation. Cerebral cortical mapping of cortical evoked potentials revealed that femoral and brachial venous afferent fibers activate ascending sensory systems which activate cortical neurons. The primary projection focus of the hind limb venous afferents lay within the hindlimb 3a--4 gamma motor-sensory cortex on the medial postcruciate gyrus. The forelimb venous afferent primary projection focus lay within the forelimb 3a--4 gamma motor-sensory cortex on the lateral sigmoid gyrus. The venous afferent projection was proposed to be a component of a cortical control system which would facilitate optimal cardiovascular control.