ARLINGTON, Va., March 16, 2004 -- Researchers have identified areas of the brain responsible for disagreements between action and perception, between what you are doing and what you think you are doing.

Andrew Schwartz, Ph.D., of the University of Pittsburgh and his colleagues demonstrated that actual movements are tied to the primary motor cortex of the brain, while the perception of those movements lies in a separate structure, the ventral premotor cortex.

"Now we have a way of identifying perception and differentiating that from reality," said Schwartz, who published the research in a recent issue of the journal Science along with colleagues Daniel Moran of Washington University and Anthony Reina of the University of Pittsburgh.

The researchers first tricked people into drawing circles when they thought they were drawing elipses. The study subjects saw a virtual 3-D image of the figure being drawn but could not see their arms or hands. They were asked to trace an elipse five times and each time saw the virtual representation of an elipse as it was being traced. But the horizontal trajectory of the cursor used to draw the shapes was gradually exaggerated so that the subjects were actually drawing circles during the fifth repetition, even though they were seeing elipses. When asked about the shapes, the subjects said they drew only elipses.

Schwartz's laboratory has developed methods of decoding motor control signals with enough accuracy to successfully predict the shape of a drawn object by monitoring brain activity. Using this technique, the drawing experiments were repeated in monkeys while activity in the motor and ventral premotor areas of the brain was recorded. The researchers could see that the motor control area for the hand was directing that circles be drawn, while the ventral premotor cortex was calling for elipses.

"The main significance is that we can extract signals from the cortex that match and differentiate these movement features," Schwartz said. "We're recording from the brain and predicting the behavior."

The research helps explain how a person can think he or she is moving a certain way when they are not and may lead to more a sophisticated understanding of how the brain directs and monitors the movement of arms and legs.

Schwartz’s laboratory received support through a Whitaker Foundation Special Opportunity Award granted in 1993 to Arizona State University, where Schwartz held a prior academic appointment.

Contact:
Andrew Schwartz, University of Pittsburgh
Frank Blanchard, The Whitaker Foundation