Linguistic and spatial information for action

Motor acts can be triggered according to either semantic or spatial objects attributes, which are thought to predominantly involve the ventral and the dorsal stream of the visual system, respectively, but with different time constraints. To date, no study has specifically addressed the issue of a possible interaction between spatial and semantic information when responding according to linguistic stimuli. In particular, it is not well established whether a motor response to a linguistic stimulus may remain immune to the influence of concurrent spatial information. In this vein, we tested the influence of the presentation of congruent and incongruent spatial information on a right-left motor response made towards a linguistic stimulus, and also the reverse condition. Results showed that the time to respond to a linguistic stimulus was greater than that observed to react to a spatial stimulus. Furthermore, we found an absence of interference of linguistic information on response accuracy and reaction time when responding to spatial stimuli. In fact, a strong interference of spatial information in the form of an increase in reaction time and misdirected responses was observed when responding to the linguistic stimulus, but predominantly for responses with short reaction times (300-500 ms) and in presence of incongruent spatial information. In the latter condition, correct responses showed in addition a tendency to veer away from the distracting spatial stimulus. We conclude that response selection can be influenced by irrelevant visual information. This suggests that information that is processed within the ventral and the dorsal visual streams compete very early under different time constraints, in order to specify the relevant visual signal for action.