TIME FOR REORIENTING OF ATTENTION - A PREMOTOR HYPOTHESIS OF THE UNDERLYING MECHANISM

The paradigm of the covert orienting of attention (COA) has shown that the displacement of visual attention may be assessed even in the absence of eye movement. Stimuli correctly cued before their presentation are usually detected faster than uncued stimuli. However, miscued stimuli induce an increased detection time, which has been attributed to the time required for the reorientation of attention from the incorrect to the correct spatial location. Currently, the mechanism of such a displacement of visual attention remains unknown. RIZZOLATTI et al. Neuropsychologia 25, 31-40 (1987) have suggested a premotor hypothesis which suggests that an oculomotor disprograming and reprograming is necessary to reorient visual attention, even if the eye movement is inhibited. Since shifting of auditory attention from one ear to the other does not require any motor control, we further investigated the model of COA in 20 normal subjects who performed two tasks requiring a reorienting of auditory attention: (1) a choice RT task that requires a response readjustment during the auditory reorienting; (2) a simple RT task that does not require a response readjustment during the auditory reorienting. Results indicate that correctly cued stimuli significantly reduce the RT in both tasks and that this reduction is greater in the choice than in the simple RT task. This suggests that a correct cue may produce a pre-programing of the response, in addition to the pre-engagement of the perceptual attention. However, in the case of miscued stimuli, RT is significantly increased in the choice RT task but not in the simple RT task, suggesting that such a delay is mostly attributable to the disprograming/reprograming of the response rather than to the reorienting of attention per se. These results confirm the premotor hypothesis of the COA.