Functional significance of the ventral and lateral funiculi in the frog's spinal cord

Abstract

The spinal cord was transected at the level of calamus scriptorius either completely (spinal preparation) or partially (funicular preparation). In the operated frogs and in normal controls cranial and peripheral receptive fields were stimulated by natural stimuli. Results indicated that the information necessary for somatic activation of the protective flight ascends in the dorsolateral funiculus, which can be characterized as an ascending part of the reflex arc of somatotopically guided avoidance behavior. The tectal region is apparently a center of responses. The information necessary for activating different patterns of locomotion adequate to environmental conditions goes unilaterally through the ventral and ventrolateral funiculus. A diminished specificity of these motor patterns observed after injury of the ventrolateral funiculus seems to be related to a reduced feedback from the periphery. Lacking of aquatic pattern of limb movements (even when terrestrial patterns of locomotion were undisturbed), and drowning in water seem to be related to an injury of a vestibulo-spinal system in the ventral funiculus. It is concluded that the ventrolateral area of the frog spinal cord, i.e., the area between median fissure and dorsal root, forms a closed system providing afferent and efferent information sufficient to evoke normal behavior.