Tactile input enhances movement activation patterns in human cerebral cortex

Baker JT, Indovina I, Sanes JN (1998) Soc. Neurosci. Abstr., 159.8.  

Prior studies have described tactile input to motor cortical circuits that likely is used to regulate voluntary movement.  Despite neurophysiological evidence that tactile information shapes development and responsiveness of motor related activity, a recent report failed to find tactile modulation of functional MR labeling in human motor cortex (Jansma et al. Neuroreport 9:501; 1998).  We readdressed this issue in the context of motor representation patterns and cerebral asymmetry.

We obtained BOLD MR signals from human cerebral cortex (Siemens Vision, 1.5T) after informed consent was obtained.  Volunteers performed flexion-extension 2Hz fractionated movements of the index, middle and fifth finger using either the dominant or non-dominant hand.  Periods of no movement were used for comparison.  During movements matched for speed and vigor, volunteers either tapped or did not tap the distal portion of the thumb on the same hand.

Functional MR labeling occurred primarily in contralateral primary motor cortex (MI), lateral premotor cortex, and the superior parietal lobule and bilaterally in the medial frontal gyrus.  MI activation patters were patchy and overlapping for the different finger movements.  Finger tapping yielded more activation in all sampled areas independently of the hand used.  In some cases, tapping yielded activation of areas unlabelled by finger movements performed without thumb contact.

These results support prior evidence of tactile input to primary and non-primary motor areas.  While the data do not address the functional significance of tactile enhancement of functional labeling in motor cortical areas, it is likely that tactile inputs modulate movement related responsiveness of neural circuits in these areas.