Motor memory - the forgotten aspect of motor adaptation and learning: From after-effects and savings to long-term retention

DELLA MAGGIORE V

Charleston

Congreso; Annual meeting of the Society for the Neural Control of Movement; 2015

NCM

Motor memory ? the forgotten aspect of motor adaptation and learning: From after-effects and savings to long-term retention Chair: Dagmar Sternad, Northeastern University, MA Participants: Nicolas Schweighofer, University of Southern California, CA Valeria Della-Maggiore, University of Buenos Aires, Argentina Gelsy Torres-Oviedo, University of Pittsburgh, PA Abstract: It is widely accepted that learning is only achieved when practice-induced behavioral improvements lead to neuroplastic changes with long-term persistence. Long-term retention of a motor skill has received relatively little systematic study in recent years, even though lasting neuroplasticity is the holy grail of any practice and, more importantly, of any clinical intervention. Although strides have been made toward understanding declarative memory and its neural correlates in humans, long- term memory of sensorimotor skills has been largely neglected. Often regarded as a form of procedural memory, retention of sensorimotor skills is mediated by different processes and brain structures from declarative memory, as seminal studies on the patient HM have suggested. In motor adaptation studies, after-effects following removal of the perturbation, document that the internal representation of the former task has changed. However, these after-effects quickly attenuate and baseline performance reappears. Nevertheless, lasting covert neural changes are reflected in the occurrence of savings, the accelerated re-learning of the same adaptation task. However, any successful clinical intervention requires that behavioral changes persist in scenarios outside the clinic. How can such learning be achieved? The symposium will present four converging lines of research, showing behavioral, modeling, and neuroimaging results, with basic and clinical questions to shed light on the processes of motor memory. Which aspects of a motor skill are retained and which are forgotten? What conditions further long-term retention? What are the time scales of learning and of forgetting? Are adaptation of a known skill and learning of a new skill associated with the same neuroplastic processes? Dagmar Sternad will present three longitudinal studies on practice and retention of a novel motor skill, including self-guided practice and targeted interventions. Detailed quantitative analyses reveal spatio-temporal changes of performances during extensive practice and their remarkable persistence after months and years. Results shed light on time scales of learning and forgetting and conditions that facilitate long-term retention. Nicolas Schweighofer will present a new computational model and supporting data that shed lights on two controversial questions in the retention of motor adaptation: 1) Is savings due to increase in learning rate, or due to recall of previous memories? 2) Is forgetting due to passive decay or due to rapid stochastic decay? In the model, rapid changes in performance during re-adaptation to a second task or during forgetting in error clamp conditions are due to switching among internal models, leaving memories protected. Valeria Della-Maggiore will present functional and anatomical evidence from longitudinal studies conducted at different time scales, indicating that visuomotor adaptation is associated with consolidation and near perfect long-term retention after one year without practice. These studies suggest that adaptation share common features with other forms of learning such as motor skill learning. Gelsy Torres-Oviedo will present learning rates and forgetting in young and old adults when acquiring a new walking pattern on a split-belt treadmill. Based on results that show that healthy aging causes motor memories to be more fragile, she will propose that forgetting may be the cause of the slower learning rates in older populations. Nevertheless, older adults can recall the learned walking pattern, as indicated by faster re-learning after several weeks. These results suggest that forgetting during acquisition and long-term recall might be dissociable processes.