Reversal Phenomenon in a Simple Motor Task: Evidence for an Indirect Model

When we first learn to control a cursor on the screen by means of a computer mouse the brain can either learn the mapping from the brain to the cursor as a whole (direct model) or count on knowledge of the mapping from the brain to hand and augment it with a learned mapping from the hand to the cursor (Indirect model). While the complete direct mapping involves complex nonlinear components arising from the body dynamics, we can set the hand to cursor mapping to be a simple linear transformation. We describe a simple cursor movement task carefully designed to reveal a clear reversal phenomenon in which trials that are a reversal of their predecessor, score higher than non reversal perpendicular trials. We suggest that this phenomenon is evidence of representation and learning of the hand to cursor mapping during the initial stage of learning the task, and discuss implications to brain machine interfaces