RT Journal Article
SR Electronic
T1 Estimation of the Timing of Human Visual Perception from Magnetoencephalography
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 3981
OP 3991
DO 10.1523/JNEUROSCI.4343-05.2006
VO 26
IS 15
A1 Kaoru Amano
A1 Naokazu Goda
A1 Shin'ya Nishida
A1 Yoshimichi Ejima
A1 Tsunehiro Takeda
A1 Yoshio Ohtani
YR 2006
UL http://www.jneurosci.org/content/26/15/3981.abstract
AB To explore the timing and the underlying neural dynamics of visual perception, we analyzed the relationship between the manual reaction time (RT) to the onset of a visual stimulus and the time course of the evoked neural response simultaneously measured by magnetoencephalography (MEG). The visual stimuli were a transition from incoherent to coherent motion of random dots and an onset of a chromatic grating from a uniform field, which evoke neural responses in different cortical sites. For both stimuli, changes in median RT with changing stimulus strength (motion coherence or chromatic contrast) were accurately predicted, with a stimulus-independent postdetection delay, from the time that the temporally integrated MEG response crossed a threshold (integrator model). In comparison, the prediction of RT was less accurate from the peak MEG latency, or from the time that the nonintegrated MEG response crossed a threshold (level detector model). The integrator model could also account for, at least partially, intertrial changes in RT or in perception (hit/miss) to identical stimuli. Although we examined MEG–RT relationships mainly for data averaged over trials, the integrator model could show some correlations even for single-trial data. The model predictions deteriorated when only early visual responses presumably originating from the striate cortex were used as the input to the integrator model. Our results suggest that the perceptions for visual stimulus appearances are established in extrastriate areas [around MT (middle temporal visual area) for motion and around V4 (fourth visual area) for color] ∼150–200 ms before subjects manually react to the stimulus.