Intrinsic capabilities of neural networks in the turtle spinal cord: Selection and generation of motor patterns

Neural networks intrinsic to the turtle spinal cord respond to a tactile stimulus with a goal-directed motor response. Each motor response consists of a distinct motor pattern, i.e., a specific sequence of motor neuron and muscle activities. Intrinsic spinal networks can be examined in the absence of supraspinal networks following complete transection of the spinal cord. Spinal networks in the turtle generate a scratch reflex in response to tactile stimulation of a site on the body surface; during the response, a nearby limb reaches toward and rubs against the stimulated site. There are several forms of scratch reflex; the particular form that is selected depends upon stimulus location. Selection and production of the appropriate scratch motor pattern does not depend upon movement-related sensory feedback; the proper sequence of motor neuron activities during scratch reflex is generated following immobilization of all muscles by neuromuscular blockade. Turtle spinal networks 'decide' which motor pattern is appropriate for each tactile stimulus: these networks have the property of motor pattern selection.