Physiological evidence of interaction of first- and second-order motion processes in the human visual system: A magnetoencephalographic study
✍ Scribed by Ayako Sofue; Yoshiki Kaneoke; Ryusuke Kakigi
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- English
- Weight
- 257 KB
- Volume
- 20
- Category
- Article
- ISSN
- 1065-9471
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✦ Synopsis
Abstract
Humans have several mechanisms for the visual perception of motion, including one that is luminance‐based (first‐order) and another that is luminance‐independent (second‐order). Recent psychophysical studies have suggested that significant interaction occurs between these two neural processes. We investigated whether such interactions are represented as neural activity measured by magnetoencephalography (MEG). The second‐order motion of a drifting sinusoidal grating, which is defined by the speed of the dot motion, did not generate a response. Apparent motion (AM) of the square area, defined by the speed of randomly moving dots, evoked a magnetic response whose latency and amplitude changed with the distance that the area moved (a second‐order characteristic), though the response properties were significantly different from those for the first‐order AM. AM, defined by both first‐ and second‐order attributes, evoked an MEG response and the latencies and the amplitudes were distributed between those for the first‐ and second‐order motions. The cortical source of the response was estimated to be around MT+. The results show a distinct difference in the neural processing of the second‐order motion that cannot be explained by the difference in visibility, and they indicate that the interaction of the neural processes underlying first‐ and second‐order motion detection occurs before the MEG response. Our study provides the first physiological evidence of a neural interaction between the two types of early motion detection. Hum. Brain Mapp. 20:158–167, 2003. © 2003 Wiley‐Liss, Inc.