This grant has several studies sub-served to it, each of them dealing with a different aspect of motor learning.

Probability detection mechanisms (O.V. Lungu, T. Waechter, T. Liu, D.B. Willingham, J. Ashe)

     People seem very well equipped to automatically detect patterns or regularities in the environment. This feature is central to certain forms of motor learning, which are largely procedural and implicit. However, the rules underlying this detection and the use of the probabilistic information in the perceptual-motor domain are largely unknown.

In this study, we tried to asses the effect of probabilistic information on motor learning when this information was present at cognitive, perceptual or motor level. We conducted two experiments involving a motor learning task with direct and crossed mapping of motor responses in which probabilities were present at the stimulus set level (perceptual), at the response set level (motor), and at the level of stimulus-response (S-R) mapping (cognitive). We manipulated only one level at a time, while controlling for the other two.

     The results showed that probabilities were detected only when present at the S-R mapping and motor levels, but not at the perceptual one (experiment 1), unless the perceptual features have a dimensional overlap with the S-R mapping rule (experiment 2). The effects of probability detection were mostly facilitatory at the S-R mapping, both facilitatory and inhibitory at the perceptual level, and predominantly inhibitory at the response-set level. Our data suggest that both absolute frequencies and transitional probabilities are used in motor learning, but in different temporal orders, according to the probabilistic properties of the environment.

The role of reference frames in the motor learning (T. Liu, O. Lungu, T. Waechter, D.B. Willingham, J. Ashe)

     The question here is to find out of what kind of information subjects use when they learned a motor sequence. Previous work showed that both stimuli and responses are possible components of the representation of the sequence and that learning is dominated by spatial or stimulus location information. Our goal was to investigate the way in which different reference systems are used to form the representation of motor sequence learning.

     In this study subjects were exposed to an 11 elements sequence in a regular pentagonal reference frame, illustrated by an enlarged arrow. After training, either the motor sequence or the arrow or both of them turned 72º clockwise to test the effect of the arrow on the representation of the sequence learning. Subjects were subsequently grouped in two groups based on the amount of explicit knowledge acquired during the task.

     The main results showed that the transfer of the motor sequence for explicit group was affected by the change in the allocentric reference frame, whereas the implicit group was immune to such change. Additionally, the explicit subjects showed a greater transfer as compared with the implicit ones in the situations where they could use the allocentric reference frame; however, they transfer the same as the implicit subjects when the information about the allocentric frame of reference was not available. This suggests that the explicit subjects have two layers of knowledge about the motor sequence, one similar to the implicit group and the other specific to their explicit knowledge.