"Learned Baduse" Limits Recovery of Skilled Reaching for Food After Forelimb Motor Cortex Stroke in Rats: a New Analysis of the Effect of Gestures on Success

Trauma or stroke to motor cortex (MtCx) results in motor impairments that include movements of the contralateral forelimb in reaching for food that is to be placed in the mouth for eating (skilled reaching). In the rat, post-lesion recovery of success is incomplete and achieved using compensatory movements. A striking and puzzling feature of post-lesion performance is an increase in the numbers of reaching attempts. Whereas successful movements, whether normal or compensatory, have been extensively described, there has been no previous analysis of the movements comprising reach attempts, especially those that are unsuccessful. Here, rats pretrained in a single pellet reaching task received MtCx stroke via pial removal contralateral to the preferred-for-reaching forelimb. They then received daily physical rehabilitation and assessment in reaching. In addition to conventional end-point measures of performance, reaching behavior was evaluated by a new measure, gestures, derived from Laban Movement Analysis. Gestural analysis describes all non-weight bearing limb movements and so can document movements not explicitly directed to, or successful in, grasping food. In the acute post-stroke period, MtCx rats made few gestures, but thereafter gesture number escalated with recovery time, and eventually exceeded preoperative levels. Gestures were frequently repetitive and included combinations not used prior to stroke. The escalation in gestures number with recovery training suggests that excessive and inappropriate gestures may represent motor habits that substitute for, and compete with, successful movements. This description of "learned baduse" furthers the understanding of MtCx contributions to skilled movements and could potentially contribute to the modification of rehabilitative strategies for the treatment of stroke.