Task-dependent activation latency in human visual extrastriate cortex.
Event related potentials (ERPs) were recorded from subjects who had to perform either an identification task or a simple detection task on moving visual stimuli. Results showed that the amplitude of the so-called visual "N1" component was larger for identification than for mere detection, replicating previous data obtained with static stimuli. However, we also found that: (i) the onset, peak and offset latencies of the visual N1 to dynamic stimuli were significantly earlier in the detection task than in the identification task, and (ii) in both conditions, the coordinates of the equivalent current dipoles best explaining the visual N1 component were consistent with those of the human motion visual area MT+/V5 in the extrastriate cortex. Altogether, these results indicate that dynamic stimuli may activate (at least partly) different pathways and processes in extrastriate cortex according to the nature of the task required on these stimuli.
Fort
Alexandra
A
INSERM, Unité de recherche U280, Mental Processes and Brain Activation, 151, Cours Albert Thomas, 69424 Lyon, Cedex 03, France. fort@lyon.inserm.fr
Besle
Julien
J
Giard
Marie-Hélène
MH
Pernier
Jacques
J
D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D004192:Discrimination, Psychological / Q000502:physiology*; D004569:Electroencephalography / Q000379:methods; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging; D008297:Male; D009039:Motion Perception / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology*; D014793:Visual Cortex / Q000033:anatomy & histology / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology