Arrows indicating direction modulate N1 amplitude

Carriero, L.1, Vasile, E.2, Budai, R.3, Weis, L.2, and Battaglini, P. P.2
1Cognitive Neuroscience Sector, I.S.A.S. (S.I.S.S.A.), Trieste, Italy; 2B. R. A. I. N. Center for Neuroscience, University of Trieste, Italy; 3S.ta Maria della Misericordia Hospital, Udine, Italy

It is well documented that N1 amplitude of the visual evoked potentials (ranging from 100 to 200 msec after visual presentation) is sensitive to the orientation and location of a stimulus (O'Donnell et al., 1997). Attention directed to a specific region of the visual filed, also enhances the N1 component elicited by stimuli presented in the same region (Heinze et al. 1990; Rugg et al. 1987). N1 probably reflects the flow of information from V1 to extrastriate cortex (Hillyard et al., 1998). We tested whether spatial attributes of a visual cue modulate early VEP components, namely N1 amplitude. Arrows pointing to the right or to the left were presented lateralized. Subjects had to release, as soon as they could, a right or a left key with the corresponding hand according to the arrow direction, and to ignore its position. In the two control conditions arrows were replaced by non-directional cues or by arrows pointing either upward or downward. Again subjects had to release a key according to specific stimulus features and ignoring their position. Event Related Potentials (ERP) were recorded using a 32-channel system in a modified 10-20 system. Significant shorter RT and greater N1 amplitudes were obtained when arrows were presented instead of controls. We concluded that the efficiency of motor response to spatially oriented stimuli is modulated at early stages of visuomotor processing by N1 component.