Mechanisms of attention in touch

A series of experiments demonstrated the role of higher level cognitive pro cesses, such as attention, in tactile perception. The first series of exper iments demonstrated that automatic orienting to a tactile stimulus resulted in inhibition of subsequent stimuli at that body site-inhibition of return (IOR). A possible explanation suggests that inhibition of saccades to a bo dy site can cause the inhibition of subsequent stimuli presented to that sa me site. In contrast, when the subjects strategically oriented attention to the stimulus, the processing of subsequent stimuli at that body site was f acilitated. In both of these experiments the skin received exactly the same test stimuli, (100 Hz sine wave presented for 50 ms), but very different e ffects were observed depending upon attentional strategy. Experimental mani pulations showed that this cannot be due to a peripheral masking of the rec eptors after cue presentation to the target. Rather the results may be expl ained centrally by cognitive, particularly attentional mechanisms. Cross-mo dal interactions suggest that tactile processes are facilitated when vision is oriented to the body site receiving stimulation. Possible explanations come from recent findings of spatiotopic maps of different sensory modaliti es in the superior colliculus of the midbrain and in the parietal lobe. The se are integrated with motor systems that control saccades and head orienta tion towards sensory inputs. Excitatory links among these maps could be the source of the observed facilitation effects.