Change Control: Cognitive Mechanisms in Response Adjustment

Imagine that you are about to pass to a teammate when he suddenly darts in another direction, in an attempt to get clear. With some difficulty, you will be able to modify your pass and correctly throw the ball to your teammate's new location. How is this process implemented in the brain? This scenario relies on quick processing of relevant perceptual information in order to modify or interrupt the ongoing motor commands, which itself requires a tight linkage between perception and action - yet another unsolved "binding problem" in cognitive neuroscience (as covered yesterday).

One form of response control is response inhibition - the ability to cancel an ongoing or planned motor movement - but it's not clear whether this differs from other forms of response control. Morein-Zamir et al.'s 2007 new JEP:HPP article examines how the modification of ongoing responses differs depending on whether those responses need to be stopped or accelerated.

To ascertain whether stopping and other forms of response adjustment are similar, the authors manipulated the frequency with which responses needed to be adjusted in the context of a relatively simple task. In the first experiment, 13 subjects were asked to press a force-sensitive key to control the speed of an onscreen object. After 3-5 seconds, the computer emitted one of two tones; if one tone was played, subjects would have to immediately release the key (stopping trials); if the other tone was played, subjects would have to immediately increase the pressure on the key (acceleration trials). The probability of each type of tone was varied in different blocks of trials throughout the experiment.

This experiment, and two slight variants of it, provided some interesting evidence that stopping and other forms of response control are intimately related. First, both types of response control were similarly affected by trial length: longer trials were associated with more efficient response control, particularly for those responses that were less likely. Second, both types of response control were more efficient as they became more probable. Third, the presence of an irrelevant tone effected both forms of response control similarly.

On the other hand, this article also demonstrated one way in which inhibition and acceleration seem to differ: when stopping is being tested simultaneously with other forms of response control in a single task, subjects may that optimize stopping at the expense of other responses. This seems to reflect a difference in cognitive strategies rather than different underlying mechanisms of response control.

In summary, Morein-Zamir et al. provide interesting evidence that similar cognitive mechanisms guide the way that actions can be modified based on new perceptual information, regardless of whether that modification involves stopping.