Humans have the ability to make motor responses to unpredictable visual stimuli, and do so as a matter of course on a daily basis. We used functional magnetic resonance imaging (fMRI) to examine the neural substrate of this behavior in six cortical motor areas. We found that five of these areas (premotor, cingulate, supplementary motor area, pre-supplementary motor area, and superior parietal lobule) showed increased activation in association with an unpredictable behavior compared to a predictable one; only the motor cortex remained unchanged. There was also a quantitative relation between the response time and functional activation in the premotor and cingulate cortex. There was less activation across all the motor areas with repetition of the motor tasks. With the exception of the pre-supplementary motor area, all areas were significantly lateralized, with a greater volume of activation in the hemisphere contralateral to the performing hand. In addition, a left hemisphere dominance was found in the activation of motor cortex and supplementary motor areas. Our results suggest that activation in motor areas is differentially and quantitatively related to higher order aspects of motor behavior such as movement predictability. Copyright (C) 1998 Elsevier Science Ireland Ltd.
Bibliographical noteFunding Information:
We thank J. Bullis for help with data processing, and A.P. Georgopoulos, A. Verbanov and G. Oehlert for helpful discussion. This work was supported by the National Institute of Health grant NS 32437, the Charles A. Dana Foundation, the Department of Veterans Affairs, and the American Legion Chair in Brain Sciences and P41 RR09079, a National Research Resource (NIH) Grant.
- Motor cortex
- Visually instructed movement