No abstract

A cinematographic comparison of treadmill and overground performances by the cat revealed considerable flexibility in the neural control program for locomotion. For the single limb's step cycle, swing duration (time foot is off the surface) was approximately equal in both situations, as has been found previously. Subcomponents of the swing (flexion duration and timings between joints during the transition from flexion to extension) differed, however. Interlimb timings also responded to situation. The interval between touchdown of one hindlimb and the ipsilateral forelimb was reduced for treadmill stepping. An ipsilateral coupling interval also differed that had been previously reported to involve propriospinal activity, the time for onset of extension during the swing phase of the hindlimb to the onset of flexion at the beginning of the swing phase in the forelimb. Segmental afferent input, visual and other suprasegmental inputs, and motivational variables probably all contribute to the separation of treadmill and overground timing profiles.

No abstract

44 hungry rats were tested in a runway once daily for 28 days after a presession consisting of self-stimulation or no stimulation. The goal box reward was food, self-stimulation, or neither. Ss ran well for food and for self-stimulation after priming, but most Ss failed to run for self-stimulation without priming or when run after priming but to no reward. Distributions for running speed and other measures indicated that unprimed rats tend to perform well or not at all for self-stimulation and that priming shifts Ss into the former category. While there was evidence for an energization aspect of self-stimulation, the main aftereffect appeared to be a brief net increase in the rewarding incentive value of intracranial stimulation over an aversive component.

No abstract