Abstract
The time necessary to initiate a goal-directed reaching movement depends on knowing where and when to move. It is well documented that providing advanced information regarding either the spatial location of a target stimulus or its timing of occurrence reduces reaction times (RT). Yet, it remains unclear whether the RT gains attributable to spatial or temporal precueing are subtended by common preparatory dynamics at the neural level. An experiment was designed in which participants (n=21) reached toward appearing visual targets while electroencephalography (EEG) was recorded. In the FullPrecue condition, participants were precued regarding the location (i.e. straight-ahead) and the timing of target onset (TTO) (i.e. 2s post-Precue). In the SpatialPrecue condition, they were precued regarding the location of the target, but its TTO was uncertain (i.e. 1.25, 2 or 2.75s post-Precue). In the TemporalPrecue condition, they were precued regarding the TTO, but its location was uncertain (i.e. left, straight-ahead, right). Results revealed that RTs were significantly faster in the FullPrecue condition (304ms) as compared to the SpatialPrecue (342ms) and TemporalPrecue (334ms) conditions*. Spectral analysis of EEG activity late in the preparatory period showed that spatial precueing was associated with greater synchronization in the theta (3-7 Hz) and alpha (8-13 Hz) frequency bands over midcentral and parietal regions, respectively*. However, temporal precueing was associated with greater desynchronization in the beta-band (20-35 Hz) over contralateral parietal regions*. These results demonstrate that although the RT gains incurred by spatial and temporal precueing are similar, they are subtended by different preparatory dynamics. *p-values <0.05.Acknowledgments: This work was supported by grants from the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Fonds de Recherche du Quebec - Sante (FRQ-S).