Background matters: Minor vibratory stimulation during motor skill acquisition selectively reduces off-line memory consolidation

- Neuron-level processes sub-serving long-term motor memory formation are triggered by practice.
- Whether these processes will proceed to a successful completion is under strict control (gating).
- Vibratory stimulation during motor sequence training did not affect the acquisition phase gains.
- Off-line, consolidation phase, gains were selectively reduced by stimulation during training.
- A motor training resulting in robust online gains does not necessarily ensure skill consolidation.
- Extra-task vibratory stimulation during acquisition phase may modulate long-term plasticity.
- Exposure to vibration is a counterpart of pharmacologically induced gating of consolidation.

Although a ubiquitous situation, it is not clear how effective is a learning experience when task-irrelevant, sensory noise occurs in the background. Here, young adults were trained on the finger opposition sequence task, in a well-established training and testing protocol affording measures for online as well as off-line learning. During the training session, one group experienced a minor background vibratory stimulation to the trunk by the means of vibrating cushion, while the second group experienced recorded sound vibrations. A control group was trained with no extra sensory stimulation. Sensory stimulation during training had no effect on the online within-session gains, but dampened the expression of the off-line, consolidation phase, gains in the two sensory stimulation groups. These results suggest that background sensory stimulation can selectively modify off-line, procedural memory consolidation processes, despite well-preserved on-line learning. Classical studies have shown that neural plasticity in sensory systems is modulated by motor input. The current results extend this notion and suggest that some types of task-irrelevant sensory stimulation, concurrent with motor training, may constitute a 'gating' factor - modulating the triggering of long-term procedural memory consolidation processes. Thus, vibratory stimulation may be considered as a behavioral counterpart of pharmacological interventions that do not interfere with short term neural plasticity but block long-term plasticity.