Open AccessVisual detection of motion speed in humans: spatiotemporal analysis by fMRI and MEG
Author(s) -
Kawakami Osamu,
Kaneoke Yoshiki,
Maruyama Koichi,
Kakigi Ryusuke,
Okada Tomohisa,
Sadato Norihiro,
Yonekura Yoshiharu
Publication year - 2002
Publication title -
human brain mapping
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.005
H-Index - 191
eISSN - 1097-0193
pISSN - 1065-9471
DOI - 10.1002/hbm.10033
Subject(s) - magnetoencephalography , latency (audio) , motion (physics) , functional magnetic resonance imaging , physics , hum , neuroscience , artificial intelligence , computer science , psychology , electroencephalography , telecommunications , art , performance art , art history
Humans take a long time to respond to the slow visual motion of an object. It is not known what neural mechanism causes this delay. We measured magnetoencephalographic neural responses to light spot motion onset within a wide speed range (0.4–500°/sec) and compared these with human reaction times (RTs). The mean response latency was inversely related to the speed of motion up to 100°/sec, whereas the amplitude increased with the speed. The response property at the speed of 500°/sec was different from that at the other speeds. The speed‐related latency change was observed when the motion duration was 10 msec or longer in the speed range between 5 and 500°/sec, indicating that the response is directly related to the speed itself. The source of the response was estimated to be around the human MT+ and was validated by functional magnetic imaging study using the same stimuli. The results indicate that the speed of motion is encoded in the neural activity of MT+ and that it can be detected within 10 msec of motion observation. RT to the same motion onset was also inversely related to the speed of motion but the delay could not be explained by the magnetic response latency change. Instead, the reciprocal of RT was linearly related to the reciprocal of the magnetic response latency, suggesting that the visual process interacts with other neural processes for decision and motor preparation. Hum. Brain Mapping 16:104–118, 2002. © 2002 Wiley‐Liss, Inc.